A Land Manager’s Guide to Improving Habitat for ... -...

Improving Habitat forScarlet Tanagers and other

Forest-interior Birds

A Land Manager’s Guide to

Improving Habitat forScarlet Tanagers and other

Forest-interior Birds

Published by the Cornell Lab of Ornithology

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Please cite this publication as Rosenberg, K.V., R.W. Rohrbaugh, Jr., S.E. Barker, J.D. Lowe, R.S. Hames,and A.A. Dhondt. 1999. A land managers guide to improving habitat for scarlet tanagers and

other forest-interior birds. The Cornell Lab of Ornithology.

© Copyright 1999 by the Cornell Lab of Ornithology

AcknowledgementsWe wish to thank the National Science Foundation,

National Fish and Wildlife Foundation, Partners in Flight,Archie and Grace Berry Charitable Foundation,

Florence and John Schumann Foundation, Packard Foundation,and participants of Project Tanager for their funding and support of

Project Tanager and the production of this publication.

We also wish to thank the following people for contributing their time and expertise to the preparation of thispublication: Molly Brewton, Annette Finney, John Fitzpatrick, Clayton Grove, Lise Hanners,

Chuck Hunter, Barb Kott, Tony Melchiors, Roger Slothower, and T. Bently Wigley.

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A Land Manager’s Guide toImproving Habitat for Scarlet Tanagers

and other Forest-interior BirdsKenneth V. Rosenberg, Ronald W. Rohrbaugh, Jr., Sara E. Barker,

Ralph S. Hames, James D. Lowe, André A. Dhondt.

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ContentsPreface ................................................................................................................................................................ 4Summary............................................................................................................................................................. 4Introduction ........................................................................................................................................................ 5The Fragmented Forest ........................................................................................................................................ 7

What Is Forest Fragmentation? ...................................................................................................................... 7Area Sensitivity and Isolation Effects ............................................................................................................. 7Brood Parasitism and Nest Predation ............................................................................................................ 8Edge Effects .................................................................................................................................................. 9The Landscape Context ................................................................................................................................. 9

Improving Habitat for Scarlet Tanagers .............................................................................................................. 10General Forest Management Guidelines ..................................................................................................... 10Specific Habitat-area Requirements for Scarlet Tanagers ............................................................................. 12Species Associated with Scarlet Tanagers .................................................................................................... 12Purpose and Use of Minimum-area Tables .................................................................................................. 13

Midwest Region ................................................................................................................................................ 14Atlantic Coast Region ........................................................................................................................................ 16Appalachian Region .......................................................................................................................................... 18Northern Forest Region ..................................................................................................................................... 20Literature Cited ................................................................................................................................................. 22

SidebarsWhat is Partners in Flight? ................................................................................................................................... 6Project Tanager: An innovative approach to studying forest fragmentation ........................................................... 8Estimating Minimum-area Requirements ........................................................................................................... 13Learn More about Scarlet Tanagers .................................................................................................................... 23

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Why the Scarlet Tanager?Why did we choose the Scarlet Tanager for this

set of guidelines? First, this conspicuous speciesrepresents a whole community of forest-dwellingNeotropical migratory birds. Scarlet Tanagers are partof a community of species that share similar habitatrequirements and geographical distributions. Bymeeting the habitat needs of Scarlet Tanagers, we willalso be improving habitat for dozens of other forest-dwelling birds. In addition, several studies show thatScarlet Tanagers are negatively affected by the frag-mentation of mature forests in certain parts of its range.Although Scarlet Tanager populations are not presentlydeclining in many areas, this species is nonethelessvulnerable because so much of its population isconcentrated in forests in the northeastern UnitedStates and eastern Canada. Furthermore, it is vital forthe long-term survival of a species to begin studyingand protecting it while it is still common. For thesereasons, the Cornell Lab of Ornithology conducted athree-year study of four species of North Americantanagers, combining the expertise of Cornell scientistsand hundreds of volunteer “citizen scientists” through-out eastern North America. The results of that study(see Project Tanager sidebar) enable us to makemeaningful recommendations that we believe canbenefit Scarlet Tanagers and other forest-interior birdsover the long-term.

PrefacePurpose and Use of this Guide

This publication is a tool to help improve habitatfor populations of forest-interior birds. These guidelinesare written for two types of land managers: thoseresponsible for large landscapes, such as public landsor entire states; and private landowners who managesmall blocks of forest. We first discuss conceptsassociated with forest fragmentation at both landscapeand smaller habitat scales and provide general man-agement suggestions that benefit many forest-interiorbirds. We then focus directly on the habitat-arearequirements of the Scarlet Tanager: specifically, howmuch mature forest is necessary to sustain a breedingpopulation of this Neotropical migratory songbird?Because habitat requirements for the Scarlet Tanagervary geographically, our specific recommendations aretailored to conditions in four regions of the species’range. Two of these regions, the Midwest and AtlanticCoastal Plain, are sparsely forested, whereas theAppalachian and Northern Forest regions are moreextensively and continuously forested.

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This is the first in a forthcoming series of habitat management guidelines produced by the Cornell Lab ofOrnithology as a tool to help those interested in managing and protecting habitat for birds. These guidelines offera set of “management prescriptions”—descriptions of the kinds and amounts of habitat that are required tosustain healthy bird populations. This guide is for the Scarlet Tanager (Piranga olivacea), a brilliant denizen ofmany mature eastern forests. Providing well-managed habitat for this Neotropical migrant songbird also willbenefit a wide variety of other birds that use mature forest. We first offer a series of general management guide-lines that are applicable throughout the eastern forest region. These include preventing the fragmentation of largeforest tracts, minimizing the creation of edge habitats, establishing forested corridors to reduce isolation of smallpatches, and maintaining structural and plant-species diversity within existing forests. Because habitat require-ments for the Scarlet Tanager vary geographically, our specific recommendations are tailored to conditions infour regions within this species’ range. Two of these regions, the Midwest and Atlantic Coastal Plain, are sparselyforested, whereas the Appalachian and Northern Forest regions are more extensively and continuously forested.In all regions, tanagers show no area sensitivity in landscape blocks that are more than 70% forested; as regionalforest cover is reduced, the minimum area required by tanagers increases. For example, in 2,500-acre (1,000-ha)landscape blocks that are approximately 50% forested, tanagers require 175–300 acres (70–120 ha) of habitat inthe sparsely forested Midwest and Atlantic coastal plain, whereas they require only 70 acres (28 ha) or less in theextensively forested Appalachian and Northern Forest regions. The tables we provide help landowners andmanagers determine the minimum-sized habitat area required to support breeding Scarlet Tanagers in theirregion and determine the relative suitability of existing forest patches in a variety of landscape conditions.

Summary

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Figure 1. Until the late 18th century, most of the 335 million acres of forested land in eastern North Americaexisted as huge expanses of contiguous forest. Photo by Richard E. Bonney, Jr.

IntroductionHumans in eastern North America have been

dependent on forests and their products for thousandsof years. When the first Europeans arrived in NorthAmerica, about 50% of the land or about 1.1 billionacres (445 million ha) were forested (Yahner 1995)(Figure 1). About three-fourths of this forested landoccurred in the eastern half of the continent. Forests inthe eastern United States remained relatively undis-turbed until the late 18th century. Since then, theamount (area), age, size, shape, and structure ofeastern forests have changed dramatically in responseto logging and changing land use. By the 1850s, anestimated 120 million acres (48 million ha) of forest inthe eastern United States had been converted toagriculture, and much of the remaining forest land hadbeen logged at least once. Since the early 20thcentury, the natural reversion of farmland back toforest has increased the amount of forested land in thecoterminous United States by over 20% (Yahner 1995).Furthermore, ecological succession, along withimproved silvicultural practices, have converted manyof the forests harvested in the 19th and early 20thcenturies into sustainable, functioning forests.

Today, the dynamic nature of eastern forestscontinues. Some contemporary forests are being lostand degraded primarily through residential, commer-cial, and industrial development, along with roadconstruction. In addition, some types of timber-harvesting practices, such as clearcutting, can tempo-rarily fragment otherwise contiguous, mature forests.The effects of this new wave of forest loss on birds andother wildlife are potentially greater than even thelarge-scale clearing of the past century, because inmany regions forest loss owing to development ispermanent. How have these historical and contempo-rary changes to eastern forests affected wildlife species,including forest-dependent songbirds?

At the extreme, the Ivory-billed Woodpecker,Carolina Parakeet, and Bachman’s Warbler havebecome extinct, in part, because of deforestation (lossof forest habitat because of conversion to nonforestland uses). The fact remains, however, that most birdspecies in eastern forests are still abundant despiteenormous alterations to their habitats. Several species,such as the Wood Thrush and Cerulean Warbler, aredeclining, but it’s not too late to begin implementing

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Figure 2. The Wood Thrush, which shares habitatrequirements with the Scarlet Tanager, is a commonbut steadily declining species throughout much of itsrange in the United States. In its breeding range, theprimary threats are habitat loss and lowered reproduc-tive success as a result of habitat fragmentation. Photoby Mike Hopiak.

What is Partners in Flight?In response to growing concerns forthe populations of Neotropicalmigratory birds, the National Fish andWildlife Foundation launched a

program in 1990 called Partners in Flight (PIF).The purpose of PIF is to identify decliningpopulations of migratory birds and address theconservation and management needs of speciesbefore they become threatened or endangered.PIF is a cooperative partnership among govern-ment agencies, professional organizations,conservation groups, philanthropic foundations,industry, the academic community, and citizens.

PIF is organized through regional and task-based working groups and operates locally inconjunction with many state or provincialworking groups. Together, these individuals andgroups focus their attention on nongamelandbirds that have historically received lessattention than endangered species and gamebirds.By identifying the most vulnerable species andproviding sound regional conservation plans, PIFcan empower land managers with the toolsnecessary to protect and improve habitat formigratory birds. For more information about PIF,visit their web site at www.PartnersInFlight.org.

habitat conservation plans for these species (Figure 2).If we wait until birds are in serious decline or endan-gered, our conservation efforts will be costly in termsof financial resources and pressures on society. Indeed,the primary objective of the bird-conservation initia-tive, Partners in Flight (see “What is Partners in Flight?”at right) is to keep species from ever reaching thethreatened or endangered lists—that is, to “keepcommon birds common.”

During the 1980s, biologists and birders began tonotice long-term population declines among Neotropi-cal migratory birds—species that breed in temperateregions of North America and migrate to Central andSouth America and to the Caribbean to spend thewinter. Among the declining species were many birdsof grassland and early successional habitats, as well assome birds that depend on mature forests. During thepast 20 years, we have learned a great deal about theprobable causes for the decline of these species. Forexample, we know that deforestation and unregulatedpesticide use threatens birds in Central and SouthAmerica and that collisions with radio towers andglass-covered skyscrapers kill thousands of migratingbirds each year. We also know, however, that land-useand forest-management practices in temperate NorthAmerica profoundly influence the breeding success offorest birds. For many of these species, our greatestopportunity to reverse population declines dependson the way we manage our forests on public andprivate lands.

Not all forests are equally valuable to birds, interms of providing food, cover, or nest sites. Each bird

species has a unique set of habitat requirements basedon its ecology and behavior. Suites of species mayrespond similarly, however, to variation in such forestcharacteristics as tree-species composition (for ex-ample, northern hardwood or Appalachian oak),elevation, hydrology, forest age, patch size, shape, andsurrounding land use. Obviously, some of these charac-teristics, such as forest type and elevation, are not easilymanipulated. On the other hand, through carefulmanagement, many characteristics of forests can bemanipulated to benefit birds.

This is the first publication in a forthcoming seriesof habitat management guidelines that will be producedby the Cornell Laboratory of Ornithology. This particularpublication focuses specifically on mature forests ineastern North America, recognizing that regeneratingforests and other early successional habitats alsoprovide valuable habitat for many bird species. Our aimis to describe the kinds and amounts of forest habitatrequired to sustain healthy forest bird populations. Thisguide focuses on the Scarlet Tanager, a brilliant denizenof many mature eastern forests. Providing adequatehabitat for this Neotropical migrant songbird will alsobenefit a wide variety of other forest birds. It’s now timeto begin applying what we’ve learned to reverse existingpopulation declines and ensure that common speciesremain common.

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Figure 3. During the past 150 years, much of thecontiguous forest land in the United States has beenlost and fragmented by changes in land use. Forestfragmentation occurs when tracts of forest are dividedinto smaller patches by nonforest land use. Photo usedwith permission from PIF and USFS.

The Fragmented ForestWhat Is Forest Fragmentation?

Forest fragmentation occurs when large, contigu-ous forests are divided into smaller patches by residen-tial and commercial development, roads, agriculture,and, in some cases, timber harvesting (Figure 3). Clear-cutting can temporarily fragment mature, contiguousforest until the clear-cut area has regenerated to asuccessional stage in which it no longer poses anecological barrier to forest-interior birds. As matureforests become fragmented, less habitat is available forbreeding birds, and a variety of factors, such asincreased brood parasitism and nest predation, resultin lower reproductive success in the habitat thatremains (Brittingham & Temple 1983; Wilcove 1985;Martin 1988; Robinson et al. 1995). Thus, forestfragmentation not only causes a net loss of habitat, itcan also reduce the suitability of remaining habitat in aregion. Characteristics of a forest that can determine itsquality as bird habitat include the size and shape of aforest patch, how isolated the patch is from otherforests, how much forest remains in the surroundinglandscape, the land-use matrix, and how much edgehabitat exists nearby. Most of these characteristics areinterrelated, so it’s difficult to change one withoutaffecting another.

It is important to distinguish between a forest thatis fragmented by agricultural or urban developmentand a forested landscape composed of a mosaic ofmature and regenerating stands that result from timberharvesting. The first situation typically is more damag-ing to forest bird populations and may representpermanent habitat loss, whereas the latter situationmay only cause a temporary reduction in habitat forforest-interior species that rely on mature forests.Furthermore, early successional forests do providehabitat for many bird species, including some Neotro-pical migrants that are declining. Nevertheless, forest-interior species that require mature forests are affectedby both sources of fragmentation. In most largelandscapes the needs of early successional species canbe met quickly through various sources of disturbance,including timber harvesting. Much more time, how-ever, is required to develop suitable habitat for speciesthat require mature forest. Effective conservationstrategies must focus on maintaining adequateamounts of mature forest at any point in time.

The Scarlet Tanager is one of at least 20 speciesshown to be negatively affected by forest fragmenta-tion in various studies throughout the eastern UnitedStates. For example, Robbins et al. (1989) found that inMaryland the probability of finding a Scarlet Tanagerincreased as the size of a forest patch increased or

became less isolated. Results from the Cornell Lab ofOrnithology’s Project Tanager (see “Project Tanager” onpage 8) also indicate that both forest-patch size anddegree of isolation are important but the way these twofactors affect Scarlet Tanagers varies in a complexfashion across this species’ range (Rosenberg et al.1999). We will take a closer look at these regionaleffects in later sections of this guide.

Area Sensitivity and Isolation EffectsSpecies whose occurrence or reproductive

success is reduced in small habitat patches are referredto as area sensitive. For example, some species willonly establish breeding territories in the interior oflarge forest tracts, far from an edge; these are known asforest-interior specialists. Area-sensitive species mayattempt to nest in small forest patches but are oftenunable to raise young successfully because of highrates of nest predation or brood parasitism. For area-sensitive species, the size and shape of forest tracts arecrucial factors for successful breeding (Whitcomb et al.1981). Forest patches that are too small may not offerenough interior habitat to sustain breeding individuals.Similarly, a forest in the shape of a long corridor orpeninsula does not offer as much interior habitat as acircular or square forest.

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Figure 4. Brown-headed Cowbird nestlings growrapidly, frequently outcompeting the host’s nestlings forfood and parental care. This adult Common Yellow-throat is feeding a cowbird fledgling that’s more thantwice its size. Photo by John Gavin.

Project Tanager: Aninnovative approach tostudying forestfragmentation

Studying the rangewide effects of land-scape features and habitat fragmentation onwidespread species such as Scarlet Tanagers isnot a simple task. In fact, no single researcher orteam of researchers could adequately coverenough territory during a short breeding seasonto conduct such a study. For this reason, theCornell Lab of Ornithology developed ProjectTanager, a partnership between amateur birdersand professional scientists, with support from theNational Science Foundation and the NationalFish and Wildlife Foundation. By employing thisvolunteer, citizen-scientist workforce, Cornellresearchers could be “everywhere at once.”From 1993 to 1996, more than 1,000 trainedvolunteers studied tanagers at more than 2,000study sites across North America—amassingperhaps the largest dataset ever collected onforest fragmentation and birds.

Project Tanager participants followed asimple but rigorously tested protocol thatincluded selecting suitable study sites, visitingthese sites at least twice during the breedingseason to search for tanagers and look forevidence of breeding, measuring a suite ofhabitat variables, and returning data to Cornellfor analysis. Many land managers contributed tothe project as active participants and site coordi-nators, helping volunteers with landscapemeasurements, obtaining maps, or gainingaccess to study sites. The management guide-lines presented here are a direct result of thismassive study.

Tim

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erThe degree of isolation, or the distance between

a patch and the surrounding forest, may also beimportant in determining the long-term persistence ofbird populations. For nonmigratory species, such asmany woodpeckers, the ability of young birds todisperse and establish new territories is greatly re-duced when the habitat is isolated. Forested corridorsconnecting isolated patches may be critical for thesepopulations. Also, if fragments are separated byagriculture or regenerating forest, the possibility fordispersal may be greater than between fragments thatare separated by residential or commercial develop-ment where movement is limited.

Brood Parasitism and Nest PredationAmong the primary causes of lowered reproduc-

tive success of forest-interior birds in fragmentedhabitats are increased rates of both brood parasitismand nest predation. Brood parasites, notably Brown-headed Cowbirds (Molothrus ater), are birds that donot build nests or raise young on their own; instead,they lay eggs in a host bird’s nest (Figure 4 ). Thecowbird nestling generally hatches first, outcompetesthe host’s nestlings for food, and receives the majorityof the parental care. As cowbirds expanded theirhistoric range from midwestern prairies into newlycreated agricultural land and fragmented forests in theEast, they encountered many new potential hostspecies (Robinson et al. 1995). Forest birds that havehad no long-term exposure to cowbirds often do nothave mechanisms for rejecting cowbird eggs and are

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A. Regional-sized forest (10,000+ acres) withsome natural fragmentation• Local diversity is low because few edge

species are present.

• Regional diversity is high because regionsupports many area-sensitive species.

B. Regional forest becomes more fragmented• Local diversity increases because edge species

are added to fragmented areas.

• Regional diversity remains nearly constant asgains in edge species offset losses of somearea-sensitive species.

C. Regional forest becomes extensivelyfragmented• Local diversity remains constant, but edge

species are distributed over a wider geo-graphical area.

• Regional diversity declines because no newedge species are added, but many area-sensitive species are lost.

Figure 5. Thumbnail sketches of regional forest showhow increasing fragmentation leads to more edgehabitat and lowered, regional avian diversity. Illustra-tions by Keila Sydenstricker.

particularly vulnerable to parasitism. Researchersbelieve that parasitism by Brown-headed Cowbirds is asignificant factor contributing to declining numbers ofmany songbirds in North America (Robinson et al.1995).

In addition to parasitic cowbirds, nest predatorssuch as jays, crows, raccoons, and domestic and feralcats that are not usually found in extensive forests gainaccess to the interior of forest patches via roads,power-line cuts, and other openings. Studies consis-tently show that nest predators have a greater affect onthe reproductive success of forest birds in forestfragments than in contiguous forest (Wilcove 1985,Small and Hunter 1988).

Edge EffectsThe plight of many forest-nesting songbirds has

brought into question the benefits of certain traditionalwildlife management techniques. For example,historically land managers were trained to “develop asmuch ‘edge’ habitat as possible because wildlife is aproduct of the places where two habitats meet” (Giles1971). Creating edges increases local diversity byattracting game species such as rabbits and deer, aswell as a variety of nongame bird species such as SongSparrows and Northern Cardinals. We now know,however, that forest-interior species may disappearfrom areas that contain extensive edge habitat. Gatesand Gysel (1978) proposed the idea that edges mayserve as “ecological traps” for some breeding birds byproviding a variety of attractive habitat characteristics,while at the same time subjecting the birds to higherrates of nest predation and parasitism. Evidence fromnumerous studies indicates that the detrimental effectsof an edge can extend from 150–300 feet (45–90 m)into the forest interior.

The Landscape ContextIf all lands were managed to enhance local

diversity by creating edges, diversity at a larger re-gional scale might actually decline because area-sensitive species would disappear from the largerlandscape (Figure 5). As long as large habitat blockscontinue to be managed in this manner, forest-interiorspecies will continue to decline, leaving only edgespecialists; those birds that can tolerate disturbancefrom predators, or those that reject Brown-headedCowbird eggs. One goal of current conservationplanning is to reach a balance between supportingdesirable edge species locally, while protecting theregional and global populations of the more vulner-able forest-interior birds. This is best accomplished byconsidering the landscape context of local forestpatches.

More and more, land managers and conserva-tionists are taking into account the importance of

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managing habitat at large landscape scales (Freemarket al. 1995). For example, the value of an individual100-acre (40 ha) woodlot to birds varies greatly,depending on whether it is part of an extensivelyforested landscape or the only woodlot for miles.Similarly, decisions to fragment large forested areasmay be influenced by the importance of these areas toregional bird populations. By managing habitat at the

landscape scale, managers can contribute to the healthof regional populations through their own local actionson the ground. The forest-management guidelines weprovide below explicitly consider how landscapefeatures such as amount of surrounding forest, degreeof isolation, and amount of edge affect the suitabilityof mature forest habitats for one high-profile focalspecies, the Scarlet Tanager.

Improving Habitat for Scarlet TanagersGeneral Forest Management Guidelines

The following general guidelines present astrategy for conserving populations of birds, such asthe Scarlet Tanager, that depend on mature, contiguousforest throughout eastern North America. Theseguidelines, combined with the specific guidelines weprovide for the Scarlet Tanager, provide a powerful toolfor improving forest-bird habitat. Many of thesegeneral guidelines were adapted from two recentpublications on habitat management in Illinois(Herkert et al. 1993) and Maryland (MD PIF 1997).Those excellent resources contain additional detailedinformation for these states.

Regional Forest Conservation• Whenever possible, avoid fragmenting large con-

tiguous forest tracts; these areas have the ability tosupport the largest number of forest-interior birdsand will also be more likely to provide habitat forarea-sensitive species. Also, it ismuch easier to protect existingforest than to “create” newforested areas. The Marylandguidelines suggest that blocks ofat least 7,500 acres (3,000 ha) ofmature forest should be pre-served. In the Midwest, land-scapes that remain at least 70%forested tend to minimizeadverse effects of fragmentation,especially hampering intrusionby Brown-headed Cowbirds.

• Develop a long-range forestmanagement plan at as large ascale as possible. Plan to desig-nate tracts that will be mature ateach stage in the managementplan and maintain connections(corridors) between regeneratingforests and mature tracts tofacilitate repopulation by birds.

• In regions where public lands contain the majorityof contiguous or large forest tracts, the most benefi-cial management strategies for these forests mayinvolve protection or minimal disturbance, tocompensate for habitat loss and fragmentation onadjacent lands.

Local Forest Conservation• Attempt to concentrate disturbance (buildings,

roads, campgrounds, other development) along theedges and not within the interior of forest blocks.

• In areas with little forest or high levels of distur-bance, preserve or restore even the smallest of forestfragments in an effort to provide some habitat forforest specialists and to provide important stopoversites for Neotropical migrants. Riparian bottomlands(along rivers, streams), ravine bottoms, and patchesalong lakeshores and coastlines are particularlyimportant (Figure 6).

Figure 6. Riparian forests typically have a high diversity of plant speciesand foods, such as insects and fruits, that combined provide excellentbreeding and migratory stopover habitat for many forest-dwelling birdspecies. Photo by Bill Evans.

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Figure 7. The shape of a forest patch affects the amount of edge and forest-interior habitat that is present. Roundand square patches have less edge and more forest interior than long narrow-shaped patches. Illustrations byKeila Sydenstricker.

• When managing individual forest tracts for birds,consider the patch’s shape, degree of isolation,vegetation structure, age structure, and status ofadjacent forests.

Shape of Forested Area• Attempt to manage for forest shapes that create the

least amount of edge. Circular plots are the best atmaximizing forest interior, whereas square orrectangular plots are better than long, narrow strips(Figure 7). Circular forest plots offer less access tothe interior for predators and nest parasites whilemaximizing habitat for area-sensitive species.Research shows that area-sensitive species tend touse forested areas that are at least 330 feet (100meters) from an edge.

Isolation Effects• Minimize isolation of forest patches by promoting

reforestation of gaps between disconnected foresttracts. Forest birds generally have higher reproduc-tive success in forest that is either connected to or inclose proximity to other forest patches. This alsofacilitates dispersal and territory establishment.

Forest Structure and Age• Maintain a well-developed woody and herbaceous

understory. Many forest-interior birds depend on the

cover, food, and nest sites provided by a diverse andwell-developed understory. Monitoring or control-ling livestock grazing and browsing by white-taileddeer may be desirable or necessary.

• Uneven-aged forests with a well-developed, butbroken, canopy usually provide the best habitat forforest birds.

• Where possible, preserve existing old-growth standsand provide for the development of future oldgrowth by leaving areas undisturbed or unharvestedfor 150 years or more.

• Avoid loss or change in tree-species diversity andfitness by minimizing “high-grading” (the removal ofonly the most valuable species and the moststructurally superior trees).

Reforestation• Promote reforestation of artificial forest openings,

areas surrounding forest peninsulas, gaps betweenisolated forest tracts, and riparian corridors to createmore forest interior for area-sensitive species.Reforestation can be achieved by succession,essentially leaving the area untouched for a numberof years, or by planting native trees.

• Avoid planting monocultures, especially of exoticspecies; these are less attractive to most forest birds.Monitor forested plots for nonnative, invasiveplants, and devise a removal plan if necessary.

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Work Within Your Community• Work with your neighbors and adjoining landown-

ers to conserve adjoining forest to maintain contigu-ously forested areas. Consider creating a landown-ers association, or work with a land trust or forestmanager to produce guidelines for people withinyour community who wish to maintain the commer-cial value and ecological integrity of their forests.Take part in your state or regional Partners in FlightWorking Group (see regional summaries section).

Specific Habitat-area Requirements forScarlet Tanagers

The following sections provide specific informa-tion about the habitat requirements of Scarlet Tanagersin four geographic regions. These guidelines are baseddirectly on the results of Project Tanager and focus onthe effects of forest fragmentation. They tell us theminimum area required to provide the most suitablehabitat for breeding tanagers, as well as the chances ofattracting tanagers to less-suitable habitats. For infor-mation on improving other aspects of habitat suitabil-ity, such as forest structure and age, see the “GeneralForest Management Guidelines” and the suggestedreadings referenced in the regional summaries of thispublication.

Results from Project Tanager confirm that breed-ing Scarlet Tanagers respond negatively to forestfragmentation; that is, tanagers are much less likely toattempt breeding in small or isolated forest patches,especially in landscapes already largely deforested bydevelopment or agriculture. The degree to whichScarlet Tanagers are affected by forest fragmentation(their area sensitivity) differs geographically withintheir range (see Rosenberg et al. 1999). Therefore, wedivided the tanager’s range into four regions, theMidwest, Atlantic Coastal Plain, Appalachian, andNorthern Forest to assess more accurately the effects offorest fragmentation and provide guidelines that areaccurate within various portions of the range.

In each regional profile we provide informationdesigned to help land managers evaluate and improvehabitat for Scarlet Tanagers in their region. Eachregional profile includes

• a map and description of available forest types

• Project Tanager results of forest types used byScarlet Tanagers

• estimates of the minimum habitat area required tosupport breeding Scarlet Tanagers

• a list of associated forest birds that may also benefitfrom habitat improvement for Scarlet Tanagers

• a regional summary that briefly presents the mostimportant management strategies for that region

Figure 8. Although not a high-priority species forconservation, the Red-eyed Vireo is more likely to befound with Scarlet Tanagers than any other specieswithin the tanager's range. Photo by Mike Hopiak.

Within each region, the likelihood that a forestpatch of a given size will attract tanagers varies basedon the amount of forest remaining in the surroundinglandscape and how close the forest patch is to thenearest large forest (more than 100 acres). For ex-ample, a 20-acre (8-ha) woodlot may be unlikely tosupport tanagers if it is surrounded by agriculturalland, but a similar woodlot that is close to a large,extensively forested state park may be almost as likelyto have tanagers as the park itself.

Because the probability of finding tanagers in aforest patch of a given size depends on the proportionof forest in the surrounding landscape, we offer arange of minimum-area estimates for landscapes withdifferent proportions of forest. For this purpose, wedefine a landscape as a 2,500-acre (1,000-ha) blocksurrounding each forest patch. If a landscape blocksurrounding a 50-acre forest patch is mostly forested(say, 70%), then it may be much more likely to supporttanagers than the same sized patch in a landscapeblock that is only 20% forested. Where appropriate,we also give a range of minimum areas that might beaffected by the degree of isolation, or distance to thenearest large forest (more than 100 acres). Finally,because in many areas remaining forest patches maynot reach our calculated minimum-area requirements,we provide a range of patch sizes that do have signifi-cant—even if lower—chances of attracting tanagers.

Species Associated with Scarlet TanagersAlthough Scarlet Tanagers are still common and

are not considered to be of conservation concern inmany areas, they do share habitat requirements withother forest birds that are of higher conservationpriority. Priority status for each species is determined

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on a regional basis by Partners in Flight. We used PIFconservation priority designations and Breeding BirdCensus (BBC) data to determine the species andconservation status of the birds that are most likely tobenefit from habitat improvement for Scarlet Tanagers.We used BBC data to determine which forest birdspecies were frequently associated with ScarletTanagers in each region (Figure 8). In the regionalprofiles that follow, we list those species that occurredon at least 75% of BBC plots with Scarlet Tanagers, aswell as additional forest species that are identified ashigh priority in regional PIF plans and the nationalWatch List.

Purpose and Use ofMinimum-area Tables

The minimum-area tables can be used in avariety of ways to help improve habitat for breedingScarlet Tanagers. The tables can be used as follows:

• In conjunction with topographical maps, aerialphotos, and Geographic Information Systems (GIS) toremotely identify forest patches with a high probabil-ity of supporting breeding tanagers. Identifying forestpatches remotely allows managers to maximize theirinventory and management efficiency by first focusingtheir efforts on sites with the greatest need for protec-tion and management.

• To predict the impacts of proposed managementactions or land-use changes on the suitability ofhabitat for breeding tanagers.

• To determine the degree of habitat enhancement(reforestation) needed to increase the probability ofattracting tanagers to a given forest patch.

• To develop long-term management plans at local,state, and regional levels.

• To make planning and mitigation decisions whenhabitat loss and fragmentation are unavoidable.

In the minimum-area tables provided with eachregional profile, acreage estimates are listed for threelevels of habitat suitability. These are defined asfollows:

• High Suitability: Habitats of this size have the sameprobability of supporting breeding tanagers as anunfragmented forest.

• Moderate Suitability: Habitats of this size are 25%less likely to support breeding tanagers relative tounfragmented forest.

• Low Suitability: Habitats of this size are 50% lesslikely to support breeding tanagers relative tounfragmented forest.

To use the minimum-area tables, first estimate thepercentage of forested land occurring in a roughly2,500-acre (1,000-ha) block surrounding your area ofinterest. Then, read across the row to determine theminimum area required to achieve a desired suitabilityfor tanagers. You can also use the tables to determinethe suitability of your particular forest patch based onits size.

Understanding Minimum-area RequirementsCalculating minimum-area requirements for each region required two steps. In the first step, we used

results from Project Tanager to determine the probability of finding breeding tanagers in suitable,unfragmented habitats in each of the four regions. In the second step, we used logistic regression analysisto predict the chances of finding breeding tanagers across a complete range of forest-patch sizes in land-scapes with different percentages of forest cover.

We then calculated the minimum-sized forest patch required to achieve the same probability ofsupporting tanagers as a suitable, unfragmented forest. Patches greater than or equal to this minimum areaare defined as having High Suitability for tanagers in the minimum-area tables. We defined ModerateSuitability patches as those that have a 25% lower probability of supporting tanagers, relative tounfragmented forest, and determined the minimum area required to achieve that lowered probability.Similarly, we calculated the minimum area of Low Suitability patches, which are 50% less likely to supporttanagers relative to unfragmented forest. Because minimum areas are dependent on the amount of forest inthe surrounding 2,500-acre (1,000-ha) landscape, a range of minimum areas is presented for each level ofsuitability. Note that a reduction in habitat suitability is defined here only in terms of the effect of forestfragmentation and otherwise assumes that forest type and structure are favorable for breeding tanagers.

14

DescriptionThe Midwest region

is defined as the portionof the Scarlet Tanager’srange that is west of theAppalachian Mountainsand south of the GreatLakes. It stretches fromthe southern shore ofLake Ontario in the east,across the southern partsof Ontario, Michigan,and Wisconsin, intosouthern Minnesota. Theregion extends south toinclude the northern edgeof Alabama in the east,and to the northeastcorner of Oklahoma in the west. The western andsouthern boundaries of this region are defined by thelimits of the Scarlet Tanager’s range.

Relatively small forest patches located within alargely agricultural landscape characterize much of theregion. More heavily forested areas are located incentral Tennessee, southeastern Missouri, and westernArkansas. Because the region has less precipitationthan areas to the east, the broadleaf deciduous forestsof the Midwest tend to include more of the drought-tolerant oak-hickory association (Bailey 1995). Forestsin the northern and eastern parts of the Midwest regioncontain more maples, American beech, and basswood,whereas the western part becomes savanna-like as itgradually gives way to prairie. Oaks and hickoriesdominate upland forests in the prairie region, whereasfarther west, floodplain forests contain cottonwood,willows, and elms (Bailey 1995). The more mountain-ous areas of Arkansas support oak-hickory forests thatinclude coniferous trees, especially pines.

Forest Types and Tree SpeciesEighty-six percent of Project Tanager study sites

were located in deciduous forest and 14% occurred inmixed deciduous/coniferous forests. Scarlet Tanagersdid not show any preference between these two foresttypes. The most common tree species present ontanager-occupied sites in the Midwest were oaks (80%of sites), maples (58%), and hickories (35%).

Minimum-area RequirementsIn the Midwest region, tanagers are predicted to

occur in virtually any size forest patch within land-scape blocks that are more than 70% forested; that is,

the birds do not show area sensitivity in extensivelyforested landscapes. In a block that is 70% forested,roughly 66 acres (26 ha) are required to achieve HighSuitability (Table 1). As the amount of forest in thesurrounding block decreases, the minimum arearequired by tanagers increases sharply, roughlydoubling for every 10% reduction in surroundingforest. Note that in sparsely forested landscapes, theminimum areas required for high and moderatesuitability are sometimes impossible to achievebecause the area of forest required exceeds theamount (%) of forest available in the 2,500-acre(1,000-ha) block.

Midwest Region

Table 1. Minimum area required to provide high,moderate, or low habitat suitability for ScarletTanagers based on analysis of 298 study sites inthe Midwest region (see page 13 for definitionsof habitat suitability).

Percentage Minimum area (acres)of Forest in Required for2,500-acreblock High Moderate Low

70 66 11 160 141 23 350 292 47 640 605 97 1230 NAa 208 2720 NA 481 6210 NA NA 173a Not Available—acreage values exceed the amount of forestin the 2,500 acre block

0–33% forest 34–66% forest 67–100% forest

Pixel size = 1 km2

Map generated from USFS forest-density map.

15

Scarlet Tanager AssociatesTwelve bird species of high conservation priority

are associated with Scarlet Tanagers in the Midwestregion. Most notably, the Eastern Wood-Pewee andWood Thrush were found at more than 90% of BBCplots that also contained tanagers (Figure 9). Therewere seven high-priority species that occurred withtanagers at more than 25% of BBC plots (Table 2). Inaddition, we found that Scarlet Tanagers were presentat 35% (9 of 26 plots) of BBC plots that reportedCerulean Warblers and 86% (6 of 7 plots) of plots thatreported Worm-eating Warblers. These data suggestthat appropriate management actions for ScarletTanagers will certainly enhance populations of EasternWood-Pewees and Wood Thrushes and are likely toimprove habitat for these other high-priority forestbirds as well.

Figure 9. The Eastern Wood-Pewee is listed as a high-priority species in the Midwest region by PIF. Althoughstill common in most areas, Breeding Bird Survey datasuggest that this species declined by 36% from 1966to 1993 (Price et al. 1995). Eastern Wood-Pewees werepresent at 91% of BBC plots that also supportedScarlet Tanagers. Photo by Mike Hopiak.

Regional SummaryThe Scarlet Tanager is not considered a high

conservation priority by PIF in the Midwest region.According to the Breeding Bird Survey, Scarlet Tanagerpopulations in that region have remained stable duringthe past 30 years. With the exception of a few heavilyforested areas (see “Description” section on page 14),the Midwest region is sparsely forested and theremaining forest is heavily fragmented. As a conse-quence, the best strategies to sustain populations ofScarlet Tanagers are to protect existing forests andpromote the establishment of forested corridors toreconnect isolated forest patches. In addition, whenappropriate, large areas of forest could be reestab-lished via the reclamation of abandoned farms, surfacemines, and landfills. For more information on improv-ing habitat for Scarlet Tanagers in the Midwest region,consult Herkert et al. 1993 and Hamel 1992; orcontact the PIF Midwest Regional Coordinator. PIFcontact information can be found atwww.PartnersInFlight.org.

Table 2. These species may also benefit fromhabitat improvement for Scarlet Tanagers in theMidwest region. Species shaded with the darkercolor were included in the list because theyoccurred with Scarlet Tanagers on at least 75%of 34 Breeding Bird Census plots from 1932 to1990. The remaining species were includedbecause they are considered by PIF to be of highconservation priority in this region.

ConservationSpecies % Plots Priority

Eastern Wood-Pewee 91 HighWood Thrush 91 High, WLa

Red-eyed Vireo 82 LowBlue Jay 82 LowNorthern Cardinal 82 LowDowny Woodpecker 79 LowGreat Crested Flycatcher 76 HighAcadian Flycatcher 41 HighYellow-billed Cuckoo 35 HighRed-headed Woodpecker 29 High, WLKentucky Warbler 26 High, WLCerulean Warbler 23 High, WLLouisiana Waterthrush 18 HighWorm-eating Warbler 15 High, WLWhip-poor-will 12 HighHooded Warbler 12 Higha WL—Also considered a Watch List species of globalconservation concern (Carter et al. 1996)

16

DescriptionThe Atlantic Coast region includes all of the area

between the Appalachian Mountains and the AtlanticOcean. It stretches from the southern edge of Mainesouth to the boundary of the Scarlet Tanager’s breedingrange in Virginia and North Carolina. Relatively smallforested areas located within a largely urban andsuburban landscape characterize much of the region.This is especially true in the corridor between Bostonand Washington, D.C. Some extensively forested areasoccur in central Massachusetts, southern New Jersey,and Virginia. The forests of the northern part of theregion are mostly deciduous, especially the Appala-chian oak association. The dominant species are whiteoak and northern red oak. Pine-oak forests (pinebarrens) are also found in dry sandy locations that arefrequently exposed to naturally occurring fires (Bailey1995). Oaks, hickories, sweetgum, blackgum, redmaple, and winged elm are also common. Along thesouthern coast, evergreen oaks, laurels, and magnoliasare common, while gum and cypress dominate coastalswamps. Savannas of pine forests with an understoryof grasses and sedges (Bailey 1995) historicallycovered most upland areas in the southern portionof the region.

Forest Types and Tree SpeciesFifty-eight percent of Project Tanager study sites

were located in deciduous forests with the remainder(42%) in mixed deciduous/coniferous forests. Thedistribution of sites with breeding Scarlet Tanagers wasthe same: 58% deciduous and 42% mixed deciduous/coniferous. The most common tree species present onProject Tanager study sites were oaks (76% of sites),maples (64%), and pines (32%). Similarly, oaks,maples, and pines were present at 79%, 67%, and30% of sites with breeding tanagers, respectively.

Minimum-area RequirementsIn the Atlantic Coast region, tanagers are pre-

dicted to occur in virtually any size forest patch withinlandscape blocks that are more than 70% forested; thatis, the species does not show area sensitivity inextensively forested landscapes. As the amount offorest in the surrounding landscape block decreasesbelow 70%, the minimum area required by tanagersincreases (Table 3). For example, as the amount offorest in a landscape is reduced from 50% to 40%, theminimum area required increases from 170 acres (68ha) to 475 acres (190 ha). Note that in sparselyforested landscapes, the minimum areas required forhigh, moderate, or low suitability are sometimes

Atlantic Coast Region

Table 3. Minimum area required to provide high,moderate, or low habitat suitability for ScarletTanagers based on analysis of 136 study sites inthe Atlantic Coast region (see page 13 fordefinitions of habitat suitability).


70 21 4 160 62 11 250 172 31 540 476 86 1430 NAa 249 4020 NA NA 12910 NA NA NAa Not Available—acreage values exceed the amount of forestin the 2,500 acre block

impossible to achieve because the area of forestrequired exceeds the amount (%) of forest available inthe 2,500-acre (1,000-ha) block.

Another way of assessing the suitability of aparticular forest patch for tanagers is in terms of itsisolation, or distance from larger tracts of contiguousforest. The suitability of small forest patches (less than100 acres) increases if they are relatively close tolarger tracts of contiguous forest (Table 4). For ex-ample, a 100-acre (40 ha) patch that is within one-halfmile of the nearest large forest would be more than70% as likely to support tanagers as an unfragmentedforest. If the same patch, however, was greater than


Pixel size = 1 km2


17

two miles from the nearest large forest, it would haveless than a 40% chance of supporting tanagers whencompared to an unfragmented forest.

Scarlet Tanager AssociatesEight bird species of high conservation priority

are associated with Scarlet Tanagers in the AtlanticCoast region (Table 5). Of these, the Wood Thrush andEastern Wood-Pewee are the species most likely tobenefit from management for Scarlet Tanagers, as theyoccur at more than 60% of BBC plots that also supporttanagers. Even though they are present at a lower

Table 4. Probability of finding breeding ScarletTanagers in small forest patches (less than 100acres) in relation to distance from nearest largeforest in the Atlantic Coast region.

Probability ofDistance From Finding TanagersSmall Patch to Relative toLarge Forest Unfragmented Forest

100 yards 1.001/4 mile 0.881/2 mile 0.701 mile 0.552 miles 0.405 miles 0.28≥ 10 miles 0.20

Figure 10.The Yellow-throated Vireo is listed as a high-priority species in the Atlantic Coast region by PIF. Thisspecies is sometimes associated with forest edgehabitat; however, breeding pairs require large blocks offorest or high percentages of regional forest cover tobreed successfully. Yellow-throated Vireos were presentat 22% of BBC plots that also supported ScarletTanagers. Photo by Mike Hopiak.

Table 5. These species may also benefit fromhabitat improvement for Scarlet Tanagers in theAtlantic Coast region. Species shaded with thedarker color were included in the list becausethey occurred with Scarlet Tanagers on at least75% of 59 Breeding Bird Census plots from1932 to 1990. The remaining species wereincluded because they are considered by PIF tobe of high conservation priority in this region.

ConservationSpecies % Plots Priority

Ovenbird 85 LowWood Thrush 83 High, WLa

Red-eyed Vireo 80 LowTufted Titmouse 75 LowEastern Wood-Pewee 63 HighAcadian Flycatcher 41 HighKentucky Warbler 30 High, WLLouisiana Waterthrush 25 HighYellow-throated Vireo 22 HighCerulean Warbler 7 High, WLWhip-poor-will 3 Higha WL—Also considered a Watch List species of globalconservation concern (Carter et al. 1996)

percentage of plots, the Acadian Flycatcher, KentuckyWarbler, Louisiana Waterthrush, and Yellow-throatedVireo should also be considered when developinghabitat management strategies for Scarlet Tanagers inthis region (Figure 10). It’s also worth noting thatScarlet Tanagers were present at 67% (4 of 6 plots) ofBBC plots that reported Cerulean Warblers and 56%(10 of 18 plots) of plots that reported Worm-eatingWarblers.

Regional SummaryAccording to the Breeding Bird Survey, Scarlet

Tanagers have declined significantly during the past 30years in the Mid-Atlantic Coastal Plain and SouthernNew England. The Scarlet Tanager is considered amoderate conservation priority by PIF in these regions.The Atlantic Coast region, like the Midwest region, issparsely forested and heavily fragmented. Unlike theMidwest region, however, much of the fragmentationin the Atlantic Coast region is caused by development.Fragmentation caused by development, as opposed toagriculture, seems to be more detrimental to forest-dwelling birds. Furthermore, it’s very difficult toestablish forest corridors and restore forest habitat inextensively developed landscapes. The best strategy forsustaining populations of Scarlet Tanagers in thisregion is to protect existing forest through careful,long-term management that limits development inforested areas. In more rural areas, establishingforested corridors and restoring forest land might alsoprove beneficial. For more information on improvinghabitat for Scarlet Tanagers in the Atlantic Coastregion, consult Bushman and Therres (1988), Hamel(1992), and Maryland Partners in Flight (1997); orcontact the PIF Northeastern or Southeastern RegionalCoordinators. PIF contact information can be found atwww.PartnersInFlight.org.

18

Appalachian RegionDescription

The Appalachian region stretches from theHudson River Valley of New York to northern Alabama.Most of Pennsylvania and all of West Virginia areincluded in this region. Also included are the westernparts of Maryland, Virginia, and North Carolina, theeastern parts of Ohio, Kentucky, and Tennessee, andthe northern edge of Georgia. The eastern half of theregion is characterized by mountainous ridges andvalleys, while the western half is composed of plateausand rolling hills. The northernmost hills are of glacialorigin. The region is heavily forested throughout, but alittle less so in southwestern Pennsylvania and easternOhio.

In the mountainous areas, tree species composi-tion changes with elevation. The valleys have mixedoak-pine forests, above which are mostly oak forests.At higher elevations the composition includes birches,American beech, maples, elms, oaks, and basswood,with some eastern hemlock and white pine. Finally,spruce-fir forests and meadows can be found on thehighest peaks in some areas. The local topography andsoils further complicate the pattern of vegetation, thusmaking it difficult to generalize across the region(Bailey 1995). The western, less-mountainous areashave mixed deciduous forests with great diversity.Common species include beech, tuliptree, basswood,maples, buckeye, oaks, and hemlock.

Forest Types and Tree SpeciesProject Tanager study sites were almost equally

distributed between deciduous forests (48% of sites)and mixed deciduous/coniferous forests (49%). Theremaining 3% of the study sites were in coniferousforests. The distribution of sites with breeding ScarletTanagers was similar: 47% deciduous, 51% mixeddeciduous/coniferous, and 2% coniferous. The mostcommon tree species present on Project Tanager siteswere maples (74% of sites), oaks (66%), Americanbeech (22%), Eastern hemlock (21%), and pines (20%).Trees found at sites with breeding Scarlet Tanagerswere similar: maples (75% of sites), oaks (71%),American beech (21%), Eastern hemlock (20%), andpines (21%).

Minimum-area RequirementsIn the Appalachian region, tanagers are predicted

to occur in virtually any size forest patch withinlandscape blocks that are at least 50% forested; that is,tanagers do not show area sensitivity in moderately orheavily forested landscapes. As the amount of forest inthe surrounding landscape block decreases below

50%, the minimum area required by tanagers in-creases (Table 6). In this region, even small patches ofroughly 25 acres located in landscapes that are only30% forested provide moderately suitable habitat forbreeding tanagers. As landscapes become highlydeforested (less than 20% forest cover), however, forestpatches of even low suitability are generally impos-sible to find because the area of forest requiredexceeds the amount (%) of forest available in the2,500-acre (1,000-ha) block.

Another way of assessing the suitability of aparticular forest patch for tanagers is in terms of itsisolation, or distance from larger tracts of contiguousforest. The suitability of small forest patches (less than100 acres) increases if they are relatively close to

Table 6. Minimum area required to provide high,moderate, or low habitat suitability for ScarletTanagers based on analysis of 89 study sites inthe Appalachian region (see page 13 for defini-tions of habitat suitability).


70 Any size Any size Any size60 Any size Any size Any size50 Any size Any size Any size40 25 4 Any size30 148 26 420 NAa 185 2610 NA NA NAa Not Available—acreage values exceed the amount of forestin the 2,500 acre block


Pixel size = 1 km2


19

larger tracts of contiguous forest (Table 7). For ex-ample, a 100-acre patch that is more than one milefrom the nearest large forest is 50% less likely tosupport breeding tanagers than an unfragmentedforest. A similar patch, however, that is within one-quarter mile of the nearest large forest is 80% as likelyto have tanagers as an unfragmented forest.

Scarlet Tanager AssociatesEight bird species of high conservation priority

are associated with Scarlet Tanagers in the Appala-chian region (Table 8). Of these, only the Wood Thrushand Eastern Wood-Pewee occur at more than 50% ofBBC plots with Scarlet Tanagers. Aside from the WoodThrush, there are three national Watch List species—Worm-eating Warbler, Cerulean Warbler, and Black-throated Blue Warbler—that occur with tanagers on at

Figure 11. The Black-throated Blue Warbler is listed asa high-priority species in the Appalachian region by PIFand is a national Watch List species of global conserva-tion concern. This species is area sensitive and typi-cally occurs only in forest tracts larger than 100 ha.Black-throated Blue Warblers were present at 20% ofBBC plots that also supported Scarlet Tanagers. Photoby Bill Dyer.

Table 7. Probability of finding breeding ScarletTanagers in small forest patches (less than 100acres) in relation to distance from nearest largeforest in the Appalachian region.

Probability ofDistance From Finding TanagersSmall Patch to Relative toLarge Forest Unfragmented Forest

100 yards 1.001/4 mile 0.801/2 mile 0.641 mile 0.492 miles 0.385 miles 0.25≥ 10 miles 0.19

Table 8. These species may also benefit fromhabitat improvement for Scarlet Tanagers in theAppalachian region. Species shaded with thedarker color were included in the list becausethey occurred with Scarlet Tanagers on at least75% of 158 Breeding Bird Census plots from1932 to 1990. The remaining species wereincluded because they are considered by PIF tobe of high conservation priority in this region.

Conser-vation

Species % Plots Priority

Red-eyed Vireo 89 LowWood Thrush 68 High,WLa

Eastern Wood-Pewee 54 HighWorm-eating Warbler 25 High, WLCerulean Warbler 22 High, WLBlack-throated Blue Warbler 20 High, WLKentucky Warbler 19 High, WLLouisiana Waterthrush 15 HighCanada Warbler 11 Higha WL—Also considered a Watch List species of globalconservation concern (Carter et al. 1996)

least 20% of BBC plots (Figure 11). Furthermore, in aslightly different analysis, we determined that ScarletTanagers were present at 61% (41 of 67 plots), 58%(29 of 50 plots), and 55% (32 of 58 plots) of BBC plotsthat reported Cerulean Warblers, Black-throated BlueWarblers, and Kentucky Warblers, respectively. TheseWatch List species are of global conservation concernand should be considered when developing habitatmanagement plans for the Scarlet Tanager in this region.

Regional SummaryThe Scarlet Tanager is considered a moderate

conservation priority by PIF throughout the Appala-chian region. According to the Breeding Bird Survey,this species has declined significantly during the past30 years in parts of the Appalachian region, includingthe Allegheny Plateau and Blue Ridge Mountains;however, it has increased significantly in the Ridge andValley and Cumberland Plateau areas. Because muchof the Appalachian region is extensively forested, themost effective strategy for sustaining populations ofScarlet Tanagers is to prevent landscape blocks frombecoming too fragmented (in other words, maintain atleast 50% forest), rather than managing the size ofindividual forest patches. This means devising long-term management plans that consider the landscapecontext and future sources of fragmentation. For moreinformation on improving habitat for Scarlet Tanagersin the Appalachian region, contact the Northeastern orSoutheastern PIF Regional Coordinators. PIF contactinformation can be found at www.PartnersInFlight.org.

20

DescriptionThe Northern Forest region includes the area

around most of the Great Lakes, the Adirondacks ofNew York, northern New England, and the CanadianMaritime Provinces. It covers the area between thesouthern deciduous forests and the northern borealspruce-fir forest. This region is at the northern limit ofthe Scarlet Tanager’s distribution, and the species isgenerally less abundant here than in other regions.

The region is heavily forested throughout. Thearea surrounding the Great Lakes and along theAtlantic coast is characterized by relatively little reliefwith many rolling hills, most of glacial origin. Forestsof this region are transitional between southerndeciduous forests and the northern boreal spruce-firforest. Deciduous forests tend to occur on favorablesites with good soils whereas coniferous forests arefound on less-favorable sites with poor soils. Commontree species are yellow birch, sugar maple, Americanbeech, white pine, and eastern hemlock (Bailey 1995).The mountainous areas of New York and New Englandhave a vertical zonation of tree species. The valleyshave deciduous forests of sugar maple, yellow birch,beech, and some hemlock. The lower slopes havemixed forests of spruce, fir, maple, beech, and birch.Finally, pure stands of balsam fir and red spruce can befound above the mixed-forest zone (Bailey 1995).

Forest Types and Tree SpeciesSixty-six percent of Project Tanager study sites

were located in mixed deciduous/coniferous forestswith the remainder in deciduous forests (32%) and

Northern Forest Region

coniferous forests (2%). The distribution of sites withbreeding Scarlet Tanagers was similar: 60% mixeddeciduous/coniferous, 39% deciduous, and 1%coniferous. The most common trees present on ProjectTanager study sites were maples (66% of sites), oaks(55%), and pines (41%). Trees located at sites withbreeding Scarlet Tanagers were similar but with slightlymore oaks: maples (65% of sites), oaks (66%), andpines (38%).

Minimum-area RequirementsIn the Northern Forest region, tanagers are

predicted to occur in virtually any size forest patchwithin landscape blocks that are more than 70%forested; that is, the birds do not show area sensitivityin extensively forested landscapes. As the amount offorest in the surrounding landscape block decreasesbelow 70%, the minimum area required by tanagersincreases (Table 9). Because of the large amount offorest throughout this region, minimum areas requiredby tanagers and other species are generally smallerthan in other regions. For example, only in landscapesthat are less than 40% forested are patches more than100 acres (40 ha) necessary to achieve high suitabilityfor tanagers, and high-suitability habitats are attainablein landscape blocks with less than 20% forest.

Scarlet Tanager AssociatesNine bird species of high conservation priority

are associated with Scarlet Tanagers in the NorthernForest region (Table 10). Of these, the Veery, Black-and-white Warbler, Rose-breasted Grosbeak, and


Pixel size = 1 km2

Map generated from USFS forest-density map and Canada Centre for Remote Sensing land cover map.

21

Yellow-bellied Sapsucker are the species most likely tobenefit from habitat management for Scarlet Tanagers,as they occur at more than 50% of BBC plots that alsosupport tanagers. Even though they are present at alower percentage of plots, the Blackburnian Warbler,Wood Thrush, Canada Warbler, and Black-throatedBlue Warbler also should be considered when devel-oping habitat management strategies for ScarletTanagers in this region (Figure 12). Finally, in a slightlydifferent analysis, we found that Scarlet Tanagers werepresent at 35% (9 of 26 plots) of BBC plots thatreported Black-throated Blue Warblers.

Figure 12. The Veery is listed as a high-priority speciesby PIF in the Northern Forest region. Breeding BirdSurvey data suggest that this species declined by 1.0%annually from 1966 to 1991. Veeries were present at76% of BBC plots that also supported Scarlet Tanagers.Photo by Mike Hopiak.

Table 9. Minimum area required to provide high,moderate, or low habitat suitability for ScarletTanagers based on analysis of 66 study sites inthe Northern Forest region (see page 13 fordefinitions of habitat suitability).


70 41 21 960 54 28 1250 70 36 1540 90 46 2030 118 61 2620 158 82 3510 228 117 51

Regional SummaryBecause the Northern Forest region

is extensively forested, the most effectivestrategy for sustaining populations ofScarlet Tanagers is to prevent landscapeblocks from becoming too fragmented(in other words, maintain at least 70%forest), rather than managing the size ofindividual forest patches. For moreinformation on improving habitat forScarlet Tanagers in the Northern Forestregion, contact the PIF NortheasternRegional Coordinator. PIF contactinformation can be found atwww.PartnersInFlight.org.

Table 10. These species may also benefit fromhabitat improvement for Scarlet Tanagers in theNorthern Forest region. Species shaded with thedarker color were included in the list becausethey occurred with Scarlet Tanagers on at least75% of 51 Breeding Bird Census plots from1932 to 1990. The remaining species wereincluded because they are considered by PIF tobe of high conservation priority in this region.

Conser-vation

Species % Plots Priority

Red-eyed Vireo 98 LowOvenbird 88 LowVeery 76 HighBlack-capped Chickadee 80 LowBlack-and-white Warbler 61 HighRose-breasted Grosbeak 53 HighYellow-bellied Sapsucker 53 HighBlackburnian Warbler 45 HighWood Thrush 31 High, WLa

Canada Warbler 29 HighBlack-throated Blue Warbler 22 High, WLBay-breasted Warbler 10 Higha WL—Also considered a Watch List species of globalconservation concern (Carter et al. 1996)

22

Bailey, R.G. 1995. Description of the ecoregions of theUnited States. 2d ed. rev. and expanded (1st ed.1980). Misc. Publ. No. 1391 (rev.), Washington,DC: USDA Forest Service. 108 p. with separate mapat 1:7,500,000.

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Brittingham, M.C., and S.A. Temple. 1983. Havecowbirds caused forest songbirds to decline?Bioscience 33:31–35.

Bushman, E.S. and G.D. Therres. 1988. Habitatmanagement guidelines for forest interior breedingbirds of coastal Maryland. Maryland Department ofNatural Resources, Wildlife Tech. Publ. 88–1. 50p.

Carter, M., G. Fenwick, C. Hunter, D. Pashley, D. Petit,J. Price, J. Trapp. 1996. For the future (Watch List1996). Audubon Field Notes 50(3).

Freemark, K.E., J.B. Dunning, S.J. Hejl, and J.R. Probst.1995. A landscape ecology perspective for research,conservation, and management. Pages 381–427 inMartin, T.E., and D.M. Finch, (editors). Ecology andmanagement of Neotropical migratory birds. OxfordUniversity Press.

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Giles, R.H., ed. 1971. Wildlife Management Tech-niques. 3rd edition (revised). The Wildlife Society,Washington D.C. 623 pp.

Hamel, P.B. 1992. The land manager’s guide to thebirds of the South. The Nature Conservancy. ChapelHill, North Carolina. 367 pp.

Herkert, J.R, R.E. Szafoni, V.M. Kleen, and J.E.Schwegman. 1993. Habitat establishment, enhance-ment and management for forest and grassland birdsin Illinois. Natural Heritage Technical publication#1, Illinois Department of Conservation, pp. 1–20.

Martin, T.E. 1988. Habitat and area effects on forestbird assemblages: is nest predation an influence?Ecology 69:74–84.

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Robbins, C.S., D.K. Dawson, and B.A. Dowell. 1989.Habitat area requirements of breeding forest birds ofthe middle Atlantic states. Wildlife Monographs103, The Wildlife Society, pp. 1–34.

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Rosenberg, K.V., J.D. Lowe, and A.A. Dhondt. 1999.Effects of forest fragmentation on breeding tanagers:a continental perspective. Conservation Biology13568–583.

Small, M.F. and M.L. Hunter. 1988. Forest fragmenta-tion and avian nest predation in forested land-scapes. Oecologia 76:62–64.

The Birds of North America (A. Poole, P. Stettenheim,and F. Gill, Eds.). Philadelphia: The Academy ofNatural Sciences; Washington, D.C.: The AmericanOrnithologists’ Union.

Whitcomb, R.F., C.S. Robbins, J.F. Lynch, B.L.Whitcomb, M.K. Klimkiewicz, and D. Bystrak.1981. Effects of forest fragmentation on avifauna ofthe eastern deciduous forest. Pp. 125–206 in: R.L.Burgess and D.M. Sharpe, eds. Forest island dynam-ics in man dominated landscapes. Springer-Verlag,New York.

Wilcove, D.S. 1985. Nest predation in forest tracts andthe decline of migratory songbirds. Ecology66:1211–1214.

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Literature Cited

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a.

female

breedingmale

moltingmale

wintermale

DistributionThe Scarlet Tanager breeds in Eastern North

America, from extreme southern Canada to thenorthern portions of the Gulf states. It winters primarilyin South America, along the eastern base of the Andesand western Amazonia from Panama to northwesternBolivia. It is infrequently observed and poorly knownin its winter range.

DescriptionMale: Flaming scarlet, withjet-black wings and tail.During late summer and fall,male shows splotchy green andred as he molts to yellow-greenwinter plumage.Female: Dull greenish above,yellowish below, with dark brownishor blackish wings.

VocalizationsSong: A series of short up-and-down phrases, with araspy or gravelly quality. Robin-like but hoarse,suggesting a “robin with a sore throat.”Call: Sharp chip, followed by a lower, buzzy note,CHIP-burr. Sometimes the chip is given alone. Callsare given by either sex when there is any disturbance,and at other times, such as early in the morning or latein the evening, when no disturbance is evident.Disputes over territorial borders usually cause males tosing shorter songs more rapidly and to intersperse thesongs with chip and CHIP-burr calls.

DietPrimarily insectivorous during the breeding

season; common prey include caterpillars, moths,bees, wasps, and beetles. They usually forage in mid-canopy and often sally into the air for flying insects.From late summer through winter, diet includes manyberries and other fruit, which may be especiallyimportant for fat deposition before fall migration.

Breeding HabitatInhabits a variety of deciduous forests; also

occurs in pine-oak woodland, parks, orchards, andlarge shade trees in suburban areas. In areas where thebreeding ranges of Scarlet Tanagers and SummerTanagers overlap, Scarlet Tanagers tend to occur inareas with significantly higher and denser canopycover, a larger variety of tree species, a smaller per-centage of ground cover, and higher densities of 9–12”diameter trees than those of the Summer Tanager.

Nest SiteIn a deciduous tree, occasionally conifer, 20'–30'

above ground (6'–75' possible). The nest is placed on ahorizontal limb, well out from the trunk—usually morethan half of the branch’s length. The nest is usuallybuilt at the junction of two or more smaller branches

with the main horizontalbranch. Almost all ScarletTanager nests have four nestsite characteristics in com-mon. Nests are placed (1) in aleaf cluster, or at least withseveral leaves shading the nest(2) on a nearly horizontalbranch (3) with a clear,unobstructed view to theground below; (4) with clearopen flyways from adjacenttrees to the nest.

This publication was published in cooperation withThe National Fish and Wildlife Foundation and Partners in Flight

Graphic design by Diane L. Tessaglia-HymesCover Photos by Lang Elliott

© Copyright 1999 by the Cornell Lab of Ornithology

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