Species-of-the-WeekWood Duck (Aix sponsa)

Brink of ExtinctionBy early 1900’s, culminative effects of:

1) wetland drainage (ag. expansion)2) deforestation3) overhunting

Habitat• Wooded swamps &

river bottomlands• Natural tree cavities for

nesting (cypress, sycamore, silver maple, black ash)

• Home range changes with flooding events

Food* In water <18”, feed on:

- seeds of trees (e.g., acorns)

- also field grains

* Young = aquatic insects

ReproductionPairing in late Oct into

spring (Mar-July nest)Clutch size = 6-10 eggsBehavior- Dump nests (up to 30+

eggs in 1 nest) = “egg dumping” behavior = intraspecific brood parasitism

- may decrease hatch rates to 10%

Factors Determining Patterns of Habitat Use

Concept of Habitat Selection

• Wildlife perceiving correct configuration of habitat needed for survival – differences based on age/experience/chance? –

• Niche concept

Concept of Habitat Selection

• Hutchison = n-dimensional hypervolume as explanation of the niche

• Fundamental vs. Realized Niche

Species 1Species 2

Testing the Hutchinsonian Niche Concept of Habitat Selection• James – work with birds in Arkansas…

quantified habitat relationships• How do birds select habitat?

• niche gestalt :

Wildlife Habitat Ecology & Mgt• Habitat from an evolutionary perspective

• Species distribution relative to habitat dist’n• Climatic events

• Pleistocene Epoch & dist’n of modern species

habitat interspersion – Leopold’s Law of Interspersion

Habitat Fragmentation1) gap formation2) decrease patch

size3) increase isolation4) increase edge5) conversion of

matrix

Concepts• Habitat = species-specific resources

available (relative quality)• Habitat Use = manner in which species

use resources• Habitat Selection = hierarchical decision

process (innate & learned) of what habitats to use

• Habitat Preference = based on selection of habitat, which are used more than others (preferred vs. avoided)

Concepts• Habitat Availability = accessibility of

resources• Habitat Quality = positive relation with

fitness (not just density)• Critical Habitat = resources essential to

the species….ESA designation….

Scale Dependence of Habitat Selection

1st Order2nd Order3rd Order4th Order

Macrohabitatvs.

Microhabitat

1st order – innate?

2nd order –decisions

3rd &4th order –decisions

Guild Concept• guild = group of species that exploit the

same class of resources in similar way• community guild = no taxonomic

restrictions; guild members chosen based on investigator-defined resources

• assemblage guild = guild members based on taxonomic relations

Models of Habitat Relationships• Model (assess) habitat for wildlife

species, e.g., USFWS• Habitat Suitability Index (HSI)

models- include top 3 environmental variables related to a species’ presence, distribution, & abundance

HSI = (V1 x V2 x V3)1/3 = 0 to 1

• Yellow Warbler HSI

for different forest conditions

HSI models• useful for representing possible major

habitat factors• true value as hypotheses• Do not provide information on:

- population size or trend- behavioral responses

• single-species approach

Emergence of Landscape Ecology

Equilibrium View

• Constant species composition

• Disturbance & succession = subordinate factors

• Ecosystems self-contained• Internal dynamics shape

trajectory• No need to look outside

boundaries to understand ecosystem dynamics

Structure

Function

?

?

?

?

Emergence of Landscape Ecology

Dynamic View

• Disturbance & ecosystem response = key factors

• Disturbance counter equilibrium

• Ecosystems NOT self-contained

• Multiple scales of processes, outside & inside

• Essential to examine spatial & temporal context

Structure

Function

Scale• What’s the big deal?• Seminal pubs

– Allen & Starr (1982) – Hierarchy: perspectives for ecological complexity

– Delcourt et al. (1983) – Quaternary Science Review 1:153-175

– O’Neill et al. (1986) – A hierarchical concept of ecosystems

Ecological Scaling: Scale & Pattern

• Acts in the “ecological theatre (Hutchinson 1965) are played out across various scales of space & time

• To understand these dramas, one must select the appropriate scale

Tem

pora

l Sca

le

Spatial ScaleFine

Shor

t

Coarse

Long

Recruitment

Treefalls

Windthrow

Secondary Succession

Species Migrations

SpeciationExtinction

Fire

Ecological Scaling: Scale & Pattern• Different patterns emerge, depending

on the scale of investigation

Am

eric

an R

edst

art

Least Flycatcher

Am

eric

an R

edst

art

Least Flycatcher

Local Scale(4 ha plots)

Regional Scale(thousands of ha)

Ecological Scaling: Components of Scale• Grain: minimum

resolution of the data– Cell size (raster data)– Min. polygon size

(vector data)

• Extent: scope or domain of the data– Size of landscape or

study area

Ecological Scale

• Scale characterized by:– grain: smallest

spatial resolution of datae.g., grid cell size,

pixel size, quadrat size (resolution)

Fine Coarse

Ecological Scale

• Scale characterized by:– extent: size of

overall study area (scope or domain of the data)

Small Large

Ecological Scaling: Components of Scale

• Minimum Patch Size: min. size considered > resolution of data (defined by grain)

Ecological Scaling: Definitions• Ecological scale & cartographic scale are exactly opposite

– Ecological scale = size (extent) of landscape– Cartographic scale = ratio of map to real distance

Scale in Ecology & Geography

• ecological vs. cartographic scale

Ecology Geography

Small(Fine)

Fine resolutionSmall Extent

Coarse resolutionLarge Extent

Large(Broad)

Coarse resolutionLarge extent

Fine resolutionSmall extent

Scale in Ecology & Geography

• ecological vs. cartographic scale– e.g., map scale

1:24,000 vs. 1:3,000fine vs. coarselarge vs. small extent

1:24,000

1:200,000

Ecological Scaling: Components of Scale• Grain and extent are

correlated• Information content

often correlated with grain

• Grain and extent set lower and upper limits of resolution in the data, respectively.

Ecological Scaling: Components of Scale• From an organism-

centered perspective, grain and extent may be defined as the degree of acuity of a stationary organism with respect to short- and long-range perceptual ability

Ecological Scaling: Components of Scale• Grain = finest

component of environment that can be differentiated up close

• Extent = range at which a relevant object can be distinguished from a fixed vantage point

Fine CoarseScale

ExtentGrain

Ecological Scaling: Components of Scale• From an anthropocentric

perspective, grain and extent may be defined on the basis of management objectives

• Grain = finest unit of mgt (e.g., stand)

• Extent = total area under management (e.g., forest)

Ecological Scaling: Components of Scale• In practice, grain and extent often dictated by scale of

available spatial data (e.g., imagery), logistics, or technical capabilities

Ecological Scaling: Components of Scale• Critical that grain and extent be defined for a study and

represent ecological phenomenon or organism studied.• Otherwise, patterns detected have little meaning and/or

conclusions could be wrong

Scale: Jargon• scale vs. level of organization

Space - Time

Space - Time

Space - TimeIndividual

Population

Community

Ecological Scaling: Implications of Scale• As one changes scale, statistical relationships may

change:– Magnitude or sign of correlations– Importance of variables– Variance relationships

Implications of Changes in Scale

• Processes and/or patterns may change• Hierarchy theory = structural

understanding of scale-dependent phenomena

ExampleAbundance of forest insects sampled at different distance Intervals in leaf litter,

Implications of Changes in Scale

05

1015202530354045

PredatorPrey

Insects sampled at 10-m intervals for 100 m

Implications of Changes in Scale

05

1015202530354045

PredatorPrey

Insects sampled at 2000-m intervals for 20,000 m

Identifying the “Right” Scale(s)

• No clear algorithm for defining • Autocorrelation & Independence • Life history correlates • Dependent on objectives and organisms

• Multiscale analysis!• e.g., Australian leadbeater’s possum

Multiscale Analysis

• Species-specific perception of landscape features : scale-dependent– e.g., mesopredators in Indiana

• Modeling species distributions in fragmented landscapes

Hierarchy Theory

• Lower levels provide mechanistic explanations

• Higher levels provide constraints

Scale & Hierarchy Theory

• Hierarchical structure of systems = helps us explain phenomena–Why? : next lower level–So What? : next higher level

• minimum 3 hierarchical levels needed

Constraints (significance)

Level of Focus (level of interest)

Components (explanation)