Landscape dynamics of bird and small mammal communities in sagebrush-

dominated mountain meadows

Tammy L. WilsonMS candidateUSGS Utah Cooperative Fish and Wildlife Research UnitDepartment of Forest, Range, and Wildlife SciencesUtah State University

Committee:John A. BissonetteThomas C. Edwards Jr.James A. MacMahon

Overview

• Status of sagebrush-steppe ecosystems• Species that use sagebrush habitats• Project goals and organization• Methodology• L+1 level analysis

– Pattern and process– What is a landscape?– Thinking outside of the box– Choosing the right scale– Vector analysis

• Brief summary

Knick et al. 2003. Teetering on the edge or too late? Conservation and research issues for avifauna of sagebrush habitats. The Condor. 105:611-634

Status of Sagebrush-steppe ecosystems in the Western United States

excluding Arizona and New Mexico

Sagebrush Obligates of Management Concern (SO)

– Sage Sparrow– Brewer’s Sparrow*– Sage Thrasher– Greater Sage-grouse– Pygmy Rabbit– Sagebrush Vole *– Least Chipmunk*

* Species Observed Greater Sage-grouseUSFWS- Mountain and Prairie Region http://mountain-prairie.fws.gov/species/birds/sagegrouse/

• Species that require sagebrush for some portion of their life history

• Species that commonly use sagebrush but do not require it– 33 species of birds– 19 species of small mammals

Sagebrush Near-Obligates (SNO)

Project Goal• Determine the contribution of high elevation sagebrush

steppe to bird and small mammal species diversity patterns

• Determine whether or not high elevation sagebrush provides a refuge for sagebrush obligate species

Tammy Wilson Jason Robinson, and Joel Ulmer cleaning mammal traps

Beth Johnson, Ruth Kikkert, and Ron Daigle trapping small mammals

Hierarchy TheoryTwo Masters Thesis projects will be divided using a conceptual hierarchy based on the triadic approach

The conceptual hierarchy

– L Project focal level is the animal community within a sagebrush meadow

– L+1 Tammy Wilson is focusing on the influence of meadow arrangement on bird and small mammal diversity and density

– L-1 Beth Johnson is examining the relationship between meadow characteristics and bird and small mammal diversity and density

Objectives

• Assess the influence of meadow arrangement on bird and small mammal diversity and density of selected species (supplementation and complementation processes)

Tammy Wilson collecting Vegetation data

Study Area

Wasatch-Cache National Forest in Northern Utah

Methods

First Tier Randomization

• Designed to reduce pseudoreplication at both levels of observation

• 50 Random points generated within the study area using a dispersion interval of 2500m

Methods• Meadows in an area around the points were digitized

using DOQQs• The meadow closest to the randomly selected point was

chosen as the focal meadow of interest

Methods• Meadows were sampled if they met the following

criteria– on public land– contain at least some sagebrush– within 5km for birds or 1km for mammals of a road– contained within a forested matrix (evaluated using a

6 km2 buffer)– mostly less than 50% slope

• 36 Meadows were sampled for birds and 11 for mammals in the summers of 2003 and 2004

• Each meadow was sampled only once

MethodsSecond Tier Randomization• 2-10 sub-sample points were placed in each

focal meadow– 100 or so Sub-sample points were randomly placed

within the meadow– Points were evaluated in order until no more points fit

in the meadow or 10 points were selected• 250m apart • occur on a slope less than 50%• not in water• not in a group of trees• excess points were deleted

Methods

• Birds and Vegetation were measured at each sub-sample point

• Mammals and soil characteristics were measured at the first 2 sub-sample points in selected meadows

• The bird and mammal data became the response variable for both L+1 and L-1 level analyses

Mammals

• Mammals were trapped using a 50m radius trap web with 8 arms

• Sherman live traps and Victor snap traps were placed at the center, 5m, 10m, 20m, 30m, 40m, and 50m points along each arm of the web

Mammals Trapped1128 Total observations16 Species observed1 SO observed4 SNOs observed

36

22

12

11

722

178

5553

commonDeer MouseLeast ChipmunkUinta ChipmunkGreat Basin pocket mouseRed-Backed VoleMontane VoleLong-Tailed VoleSnowshoe HareUnknown VoleGolden-Mantled Ground SquirrelUinta Ground SquirrelWestern Jumping MouseUnknown MouseUnknownNorthern Pocket GopherShort-Tailed WeaselUnknown Pocket GopherNorthern Flying SquirrelRock SquirrelLong-tailed Weasel

Birds

• Fixed-radius point counts conducted for 8 minutes at each sub-sample point

• The double observer method was used for each point count

• All birds seen or heard were recorded

• Distance and bearing was measured to each bird

Birds Observed3615 Total observations82 Species Observed1 SO observed14 SNOs observed

10 M

ost c

omm

on s

peci

esLe

ss c

omm

on S

NO

sCommon Name

Green-tailed Towhee Unknown BirdAmerican RobinBrewer's Sparrow Chipping SparrowRuby-crowned KingletDark-eyed Junco Mountain ChickadeeHermit ThrushDusky FlycatcherWhite-crowned Sparrow Vesper Sparrow MacGillivray's WarblerYellow WarblerOrange-crowned WarblerBrewer's BlackbirdWestern MeadowlarkSong SparrowWilson's WarblerSwainson's ThrushGrasshopper SparrowGray Flycatcher

117

110

98

441

419

324245

243

198

139

Objectives

• Assess the influence of meadow arrangement on bird and small mammal diversity and density of selected species

Tammy Wilson collecting bird data

• Our study area contains sagebrush patches within a forested matrix

• Habitat obligates can exist in patchy landscapes through complementation and/or supplementation of resources (Dunning et al. 1992)

Dunning, J. B., B. J. Danielson, and H. R. Pulliam. 1992. Ecological processes that affect populations in complex landscapes. Oikos. 65:169-175

Linking Pattern and Process

• Complementation– If non-substitutable resources

are located in different patches, “the presence of resources in one patch is complemented by the close proximity of the resources in a second patch.”

• Supplementation– If habitat patches are too small

to support a population or individual, then necessary resources can be supplemented by using adjacent patches.

A

B

A

B

Figures adapted from Dunning et al. 1992

Elements of complementation and supplementation

• Proximity of adjacent meadows– Supplementary or complementary resources

will have to be near enough for use by the individual or population

• Size of focal meadow and adjacent meadows– The amount of resources contained within

adjacent patches will be a function of their size

What is a Landscape?

• Landscape metrics are typically calculated on a classified satellite imagery with a fixed grain, using an arbitrary extent

• Organisms scale allometrically to their surroundings, so choice of right scale resolution and extent is important

• We intend do detect many organisms, making it difficult to use any one species life history to define scale parameters

• Without modification, these problems may limit our ability to detect important ecological phenomena

Effects of decreasing landscape extent• Large patches are

truncated and edge effects are magnified

• Rare classes are reduced or lost

• Landscape metrics will change making them difficult to interpret

Thinking outside of the box

• By eliminating the ‘landscape’ with a fixed grain and extent, we tend to eliminate the problems associated with the box and the image simultaneously– We already have a vector coverage of our digitized

meadows– Patch size and distance to nearest, next, 3rd, 4th, 5th…

nearest meadows can be measured directly with a vector analysis

– Results are much easier to interpret, because scale-related problems are reduced

Vector analysis• Create centroids in each

adjacent polygon• Measure distance to the

adjacent polygons of interest

• Create logistic regression relating presence/absence of selected SO or SNO species to distance and size of adjacent meadows

• Extract amazing story about patch arrangement and ecological processes of supplementation and/or complementation

12

3 4

Thinking outside of the boxPart 2

• But we don’t get to ignore scale effects altogether because we still need to know how close a meadow needs to be in order to affect ecological process– J. Bowman related territory size and dispersal

distance of birds and small mammals– Others, including C. S. Holling, related body size and

territory size– C. S. Holling also noticed that body sizes tended to be

clumped– Maybe there is a way to use this to get at the proper

scale (extent) to use for our analysis

Choosing the right scale

• Published data on our most commonly observed species can be analyzed using Bowman’s equations

• The accuracy of these equations can be checked where we have both home range and dispersal data

• The robustness of these equations can be tested by adding our species and re-running Bowman’s analysis

• These relationships can be used to guide scale extent choices if there is a reasonable amount of overlap amongst species.

Summary• Preliminary observations

– Only 2 or maybe 3 of 7 SOs and 18 of 52 SNOs were observed

– Preliminary results suggest that small mammal diversity is lower (16 observed vs. 22 SO/SNO), and bird diversity higher (82 observed vs. 37 SO/SNO) in montane sagebrush patches than in contiguous low-elevation sagebrush

• Future analyses– Linking patch arrangement to species diversity and

habitat-specialist presence/absence– Analysis of published body mass, home range, and

dispersal data to determine the scale important to detected species

Acknowledgements

• Beth Johnson• Committee

– John Bissonette– Tom Edwards– Jim MacMahon

• Technicians– Ron Daigle – Ruth Kikkert – Jason Robinson– Joel Ulmer– Mark Johnson– Dave Johnson– Robert lloyd Morris

• Funding– United States Forest

Service– USGS Utah Cooperative

Fish and Wildlife Research Unit

Questions…