Spatial Habitat Use and Behavior of Birds in Forests Infected with Beech Bark Disease

Ravyn A. NevilleSUNY College of Environmental Science and Forestry, Syracuse, NY

Final Report to the Edna Bailey Sussman Foundation, 2018

Introduction

The introduction of non-native organisms into new habitats can present a significant threat to biodiversity (Loo 2009, Lovett et al. 2006). Exotic pathogens may have direct and indirect effects on native species. While direct effects (e.g. forest composition) have been the primary foci of research, the indirect impacts that disease can have on native faunal communities are significant. Exotic pathogen invasions can cause changes in habitat structure that may alter the species assemblage, species interactions, and habitat quality for wildlife species of interest. Therefore, the broader consequences of biological invasions to wildlife communities are an area of ecological concern.The Cryptococcus fagisuga-Nectria scale- fungus complex causes Beech Bark Disease (BBD) affecting American beech (Fagus grandifolia) throughout the northeastern U.S. and Canada. Trees infected with BBD produce prolific root suckers and thus produce numerous saplings that shade out diverse understory growth. Consequently, BBD alters overall forest structure and species composition in ways that may affect habitat availability and quality for wildlife species (Cale et al. 2013). Despite BBD’s long history in the region, little progress has been made to understand wildlife responses in this context. Wildlife habitat use and habitat quality are influenced by forest structure. The physical structure of the forest can affect availability and access to resources (Hilden 1965, Robinson and Holmes 1982, 1984, Vanhooydonck et al. 2000). Forest composition, or floristics, is known to play a role in habitat selection for birds. Physiognomy, or the physical structure of the forest, is also influential in determining the success of many forest birds. This is because birds rely on environmental cues to inform important survival decisions (e.g. foraging, shelter, nesting locations, and foraging tactics (Martin, 1987; Hutto, 1990)). Assessing foraging behavior and habitat use among vegetation types may serve as an indicator of resource availability and resulting habitat quality (Rotenberry and Wiens, 1980; Lovette and Holmes, 1995; Ghosh et al., 2011). At a smaller scale, differential resource availability across vegetation strata (e.g., Robinson and Holmes, 1982) and plant species (e.g., Keane and Morrison, 1999) also influence avian foraging behavior. These relationships with vegetative habitat contribute to patterns in avian demographics and success. Vertical habitat structure is defined as the bottom-to-top configuration of aboveground vegetation on a site (Brokaw and Lent 1999). Vegetative structure provides opportunities and limitations that determine how and where birds locate and capture prey (Holmes 1990). Consequently, birds tend to forage in specific tree species at specific heights (Holmes and Robinson 1981, Gabbe et al. 2002). Additionally, songbird survival and productivity rates are limited by the time and energy required to locate food (Martin 1987). For instance, when a bird needs to travel far distances to obtain food it leaves its nest unattended and at risk of being depredated. Foraging behavior is an area of growing exploration (Morrison et al. 1990), as it has

been shown to reflect food availability and variation (Robinson and Holmes 1982) as well as habitat structure and quality (Robinson and Holmes 1982, Dobbs et al. 2007). Knowledge of the placement of these behaviors in space can enhance our understanding of niche differentiation (Cunha and Vieira 2004), habitat selection and use, and interspecific and intraspecific competition (Belant et al. 2012). Through studying the location at which certain behaviors occur within the forest strata we obtain a more in depth knowledge of habitat use and interactions. The impact that BBD has on forest structure may influence the overall composition of bird communities. Dissimilar avian foraging guilds respond to forest structure alterations differently (Young and Schlesinger 2014). Structural diversity provides different opportunities to birds with different spatial preferences or survival strategies. Through understanding how birds of different guilds utilize space, management efforts can focus on providing for the vegetative needs of local birds while strengthening the resiliency of the habitat.The goal of this study is to understand 1) how birds are utilizing American beech 2) how birds are utilizing different forest strata, and 3) how and which bats are using affected forests.Despite the long history of BBD in the northeastern forest system, little is known about how different taxa utilize these forests. The knowledge gained about how avian and bat communities respond to the local effects of BBD can be used to help predict potential impacts of forest change, which can guide management for conservation and biodiversity.

MethodsStudy sites:

This study will take place on two sites within the Adirondack Park, NY. The primary site is a 404-acre area, separated into 14 blocks, within the Huntington Wildlife Forest (HWF). The site is colloquially known as the “Electric Fence” (EF) area (Fig 1). The second site is located on an adjacent property owned by F&W Forestry (FW). This site is separated into 3 plots, averaging 15 acres each (Fig 2.). Each study site has a significant presence of shrubby American beech and BBD-infected trees.

Focal species:

I expect birds of different foraging guilds to respond uniquely to American beech presence and treatment. Therefore, I chose focal species carefully to have at least one representative of three foraging guilds; ground, mid-story, and canopy. Each species is relatively abundant throughout the Adirondacks sites (McNulty et al. 2008).

Ground: Ovenbird (Seiurus aurocapillus), Hermit thrush (Catharus guttatus), Swainson’s thrush (Catharus ustulatus)

Mid-story: Black-throated Blue Warbler (Setophaga caerulescens), Scarlet Tanager (Piranga olivacea)

Canopy: Red-eyed vireo (Vireo olivaceus)

Bark-gleaners: Hairy woodpercker (Leuconotopicus villosus)

Behavioral Survey:

In mid-May we identified potential territories by walking the stand and listening for any singing males beginning their territory establishment. Behavioral surveys were conducted at each site from late-May until early-August to describe habitat use. We used an instantaneous focal follow technique (Altmann 1974) similar to Smith-Hicks et al. (2016), recording bird behavior every 30 seconds for at least 5 minutes and no more than 40 minutes. When an individual detected a focal species, they recorded species, time of survey start, and took a GPS point. After every thirty second beep of an interval watch, the observed recorded the behavior (Resting, foraging, vocalizing, locomotion, aggression, pair-bonding, or out of sight), if the bird was on an American beech tree (yes or no) and height (estimated to nearest m). Observations were spoken into a voice recorder and scribed at the end of the field day. Each collection of continuous observation were one survey “bout” (Wiens et al. 1970). If the bird is not seen at a beep, but we know it is still present, we recorded that observation as “out of sight,” while continuing the survey. To prevent repeating observational sessions of the same species we alternated focal species surveyed, and made sure we are at least 200 m away from the most previously observed individual of that species before repeating it.

Bat survey:

I used Sonobat SM4BAT FS (Wildlife Acoustics, Maynard, MA) detectors to record acoustic calls from bats. Each sampling site was surveyed for at least two consecutive nights for two rotations. The first rotation occurred during the maternity season 1 June 2017 through 10 July 2017. The second rotation was during the volant season when pups are starting to fly, 11 July 2017 through 10 August 2017. Overall there was at least four survey nights for each sampling site. I programed the SM4BAT FS to capture echolocation calls within the frequency range of northeastern bat species. Microphones were attached to the top of ½ inch 10ft tall PVC poles that where secured into the ground about 1ft. To increase the chances of recording the most amount of bat calls the mics were pointed in the direction with the least amount of clutter or stem obstructions and oriented towards potential bat flying routes.

Acoustic Call Classification:

I used SonoBat software (version 4.0.6 nE) to manually ID all of the echolocation calls based on the minimum, maximum, characteristic frequencies, and slope of calls (O’Farrell et al. 1999). A bat call sequence was identified if it has at least two discrete echolocation pulses (Burns et al. 2015).

Vegetation Survey:

We measured vegetative habitat features for each site. Vegetation plots were chosen where focal birds were present. We measured dbh (<4.5in) and calculated the basal area.

ResultsBirdsDuring the 2018 field season, we obtained a total of 3,036 avian observations. 2,205 observations were in EF, and 831 were in FW. BTBW’s were observed the most often, with SWTH being the most rare across sites, and FW not having any SCTA’s. There were many out of sight observations, mainly because every bout ended with a string of out of sight’s before the bout ended. Vocalizing was the most frequent behavior, followed by resting, foraging, locomotion, pair-bonding, and then aggression.

Height and behavior distributions varied for each species (Figs. 3 and 4). For the black-throated blue warbler (BTBW), proportionally, foraging was more likely to occur in non-beech trees, across all species (Fig. 5). Out of all BTBW occurrences in non-beech trees, the most common strata was at 21 m. Resting occurred significantly more in at higher strata for BTBW (Fig 6).

BatsThere were 26 bat sampling locations (13 individual locations with 2 rotations. A total of 872 sounds were recorded. After vetting, about 800 have been determined to be potential bat calls.

VegetationEach stand had a majority American beech (AMBE) across the stand. Sugar maple (SUMA) were the co-dominate tree with an average dbh of 13.6, yet occurring 4 times less than AMBE (Table 1). The average dbh of AMBE was only 8.8, with most AMBE occurring in the understory in the form of thickets. Other species occurred rarely compared to AMBE and SUMA.

Future Analysis

Further analyze behavior and strata relationship for each species and each guild. Also, we hope to add a vigilance behavior category for birds. Additional 3D modelling in GIS will allow us to visualize the occupancy and behavior patterns across sites. An ANOVA will be used to determine the differences between avian abundance and richness across forest conditions.

The bat calls will be manually ID’d to species and an ANOVA will be used to determine differences in species abundance across forest conditions.

Acknowledgements This project was funded by the Edna Bailey Sussman Foundation, USDA McIntire Stennis Program, and the Northern New York Audubon. Thank you to the ESF Adirondack Ecological Center for housing and for lending my team gear. S. Farrell, S. McNulty, and G. McGee provided guidance and encouragement throughout the planning process. T. Tripp of F&W Forestry for supervising my internship. O. Bernardo and J. Levi collected and entered the data.

Literature CitedAltmann, J. 1974. Observational Study of Behavior: Sampling Methods. Behaviour 49:227-267. Brokaw, N. V., and R. A. Lent. 1999. Vertical structure. Pages 373–399 in Maintaining

Biodiversity in Forest Ecosystems (M. L. Hunter, Jr., Ed.). Cambridge University Press, Cambridge, United Kingdom.

Burns, L. E., J. L. Segers, and H. G. Broders. 2015. Bat Activity and Community Composition in the Northern Boreal Forest of South-Central Labrador, Canada. Northeastern Naturalist 22:32–40.

Cale, J., S. McNulty, S. Teale and J. Castello. 2013. The impact of beech thickets on biodiversity. Biological Invasions 15:699-706. DOI:10.1007/s10530-012-0319-5.

Dobbs, R. C., T. S. Sillett, N. L. Rodenhouse, and R. T. Holmes. 2007. Population density affects foraging behavior of male black-throated blue warblers during the breeding season. Journal of Field Ornithology 78(2): 133-139.

Gabbe, A. P., S. K. Robinson, and J. D. Brawn. 2002. Tree-species preferences of foraging insectivorous birds: Implications for floodplain forest restoration. Con Bio 16:462-470.

Holmes, R. T. and S. K. Robinson. 1981. Tree species preferences of foraging insectivorous birds in a northern hardwoods forest. Oecologia 48: 31-35.

Loo JD.2009. Ecological impacts of non-indigenous invasive fungi as forest pathogens. Biol Invasions 11:81–96

Lovett GM, Canham CD, Arthur MA, Weathers KC, Fitzhugh RD (2006) Forest ecosystem responses to exotic pests and pathogens in eastern North America. Bioscience 56: 395–405.

Morrison, M. L., C. J. Ralph, J. Verner, and J. R. Jeiil Jr., EDS. 1990. Avian Foraging: theory, methodology, and applications. Studies in Avian Biology no. 13.

O’Farrell, M. J., B. W. Miller, and W. L. Gannon. 1999. Qualitative Identification of Free-Flying Bats Using the Anabat Detector. Journal of Mammalogy 80:11–23.

Robinson, S. K. and R. T. Holmes. 1982. Foraging behavior of forest birds: the relationships among search tactics, diet, and habitat structure. Ecology 63:1918–1931.

Robinson, S. K. and R. T. Holmes. 1984. Effects of plant species and foliage structure on the foraging behavior of forest birds. Auk 101: 672-684.

Rodewald, P. G. and K. G. Smith. 1998. Short-term effects of understory and overstory management on breeding birds in Arkansas oak-hickory forest. Wildl. Manage. 62(4):1411-1417.

Smith-Hicks, K. N., J. C. Newnam, M. R. Colon, A. M. Long, and M. L. Morrison. 2016. Golden-cheeked warbler behavior in relation to vegetation characteristics across their breeding range. Am. Midl. Nat. 176:81-94.

Wiens, J. A., S. G. Martin, W. R.Holthaus, AND F. A. Iwen. 1970. Metronome timing in behavioral ecology studies. Ecology 51:350–352.

Young, L. and C. Schlesinger. 2014. Habitat use and behaviour of birds in areas invaded by buffel grass (Cenchrus ciliaris L.) and in restored habitat. Wildlife Research 41: 379–394.

Figures and Tables

Figure 1. Location of the Electric Fence (EF) site within HWF.

Figure 2. Location of FW sampling areas (Gray, Pink, Yellow) within FW property.

Figure 3. Height distribution for each species. This data excludes out of sight observations.

Figure 4. Behavior distribution for each species. This data excludes out of sight observations.

Figure 5. Behavior distrution on AMBE and non-AMBE for the Black-throated Blue Warbler. This data excludes out of sight observations.

Figure 6. Height distrution of each behavior for the Black-throated Blue Warbler. This data excludes out of sight observations.

AMBA AMBE EAHE HOPH PABI RESP STMA SUMA WHAS YEBI

Number of Trees

10 456 9 20 2 9 7 188 31 78

Number of Snags

1 91 0 1 0 3 2 14 3 6

Average DBH (in)

12.7 8.8 21.4 7.8 10.4 9.4 5.7 13.6 12.2 10.1

Table 1. Canopy vegetative data across all species >4.5 in dbh. This data is representative of only EF sites.