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Stopover ecology of autumn-migrating raptors in the central appalachians

Dissertation
Author: Laurie J. Goodrich
Abstract:
In the Central Appalachians, the Kittatinny Ridge is a key autumn migration corridor for eastern raptors. I studied migrating raptors during autumn along the Kittatinny Ridge. My objectives included to assess the frequency of travel and stopover in individual raptors and document behavior during stopover to understand the role and importance of stopover in migration in raptors. I also studied which habitats were used by raptors during stopover and the frequency of use of the Kittatinny Ridge to determine the importance of habitat to raptors and whether a flyway corridor could be identified. In one part of the study, I radio-tagged and followed 34 Sharp-shinned (Accipiter striatus ) and 14 Cooper's Hawks ( A. cooperii ) during autumn migration 2003 and 2004. Birds were trapped on the Kittatinny Ridge, and followed for one to 12 days each through Pennsylvania and neighboring states. Both species spent 1-5 days on stopover between travel periods (mean= 2 d.). Sharp-shinned Hawks spent an average of 33.6% of daylight foraging (+ 24.5 SD) and 32.6% of day roosting (+27.4), and Cooper's Hawks spent 33.8% (+ 6.8) of day foraging and 47.2% (+26.2) roosting. Sharp-shinned Hawks spent less time roosting than Cooper's Hawks; however, neither species differed in behavior by age, except that adults spent more time in non-migrating flight. The ratio of hours in travel to hours on stopover per bird during tracking was 1:7 (including night hours) suggesting that rest and foraging periods are an integral aspect of their migration journey. Forest patch size was one of the most important factors in stopover site selection with both species choosing larger forests more than occurred at random at both the landscape scale and near scale. At a regional scale, both species selected more rural areas for stopover sites, selecting areas with more mixed forest and pasture. Sharp-shinned Hawks avoided suburban areas as well. Hatch-year Sharp-shinned Hawks used contiguous forest, wetlands, and evergreen forest less than adults. Nearly half of all roosts of both species were on the Kittatinny Ridge suggesting either an affinity to large forests or the flyway itself. Both species combined roosted at an average of 6.9 km from the ridge flyway when found within the Ridge and Valley region. Hatch-year birds roosted farther from the ridge than adults in both species and Sharp-shinned Hawks roosted farther from the ridge than Cooper's Hawks. Cooper's Hawks were more selective in their habitat choice during migration than during nesting, choosing large forests in more rural landscapes. The selection of roosts by Sharp-shinned Hawks near wetlands may indicate that the opportunity to drink is important during migration or that wetlands concentrate their songbird prey. Evergreen stands could provide important protective cover to roosting Sharp-shinned Hawks, as they may be more vulnerable to avian predation and more likely to seek out evergreen forest during stopover than the Cooper's Hawk. During road surveys of all raptors on stopover, birds were most abundant within 1 to 6 km of the ridge and less numerous farther from the ridge or on the ridge itself. The lowest abundance was observed at the farthest distance from the ridge, 16 km. The pattern of higher abundance near the base of the ridge remained consistent regardless of changes in forest cover . The abundance near the Ridge indicates that distance to the flyway could be an important factor influencing migrant distribution. Habitat influenced distribution of migrants on stopover as well. Forest raptors were more numerous on the north side where forest cover was more abundant, and open habitat raptors, e.g. Redtailed Hawk and Northern Harrier, were more numerous on the south slope where farmland predominates. Although age influences patterns of migration, no age difference was observed in habitat or distance of migrant raptors surveyed during road surveys. (Abstract shortened by UMI.)

TABLE OF CONTENTS LIST OF FIGURES……………………………………………………………………..xiii LIST OF TABLES……………………………………………………………………….xv ACKNOWLEDGMENTS………..………………………………..………………..….xvii Chapter 1. Stopover ecology of migrating raptors in the Central Appalachians: the background ………………….………………………………………..1

Introduction……………………………….……………………………………...……...1 Feeding on Migration……………………………………………………………...3 Stopover Habitat Selection……………………………………...………………...3 Weather, Migration and Stopover Timing…………………………...……………5 Habitat Conservation…………………………………………………………...…6 Raptor Stopover Ecology Questions…………………………….……………………....7

Chapter 2. Stopover behavior of Sharp-shinned (Accipiter striatus) and Cooper’s Hawks (A. cooperii) during autumn migration through the Central Appalachians………………………………………………….….…11

Abstract…………………………………………………………………………..11 Introduction……………………………………………………………………....12 Methods………………………………………………………….……………….15 Study Area…………………………………………………………....….15 Trapping……………………………………………………………….…16 Radio-tracking Methods……………………………………………….....17 Behavior of Migrants………………………………………………….....18 Weather Data…………………………………………………………….20 Habitat and Behavior…………………………………………………….22 Stopover Length and Behavior……………………………………….….22 Recent Feeding and Behavior………………………………………..…..23 Statistical Analyses……………………………………………………....23 Results………………………………………………………………………....…25 Daily Rhythm and Behavior Frequency……………………………...….25

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Species and Age Comparisons…………………………………...………28 Migration Travel and Daily Behavior……………………………...…….28 Recent Feeding, Fat, and Behavior……………………………………....29 Stopover and Travel Duration………………………………………..…..29 Seasonal Progression and Behavior…………………………………...…30 Weather and Stopover Behavior………………………………................31 Predicting Travel Days……………………………………………...…...32 Habitat Patch Size and Behavior………………………………………....33

Discussion………………………………………………………….………...…..34

Chapter 3. Flight behavior of autumn-migrating accipiters in the Central Appalachians………………………………………………………………..…..46

Abstract………………………………………………………………………..…46 Introduction…………………………………………………………………........48 Methods……………………………………………………………………..….. 53 Study Area………………………………………………………….....…53 Trapping…………………………………………………………….........53 Radio-tracking……………………………………………….………..….54 Migration Flight…………………………………………..……………...54 Travel Parameters………………………………………………..………55 Weather…………………………………………………………..……....57 Statistical Analyses……………………………………………...……….58 Results……………………………………………………………….………..….59 Travel Direction……………………………………………..……..…….60 Travel Duration……………………………………………………..…....60 Travel Distance……………………………………………………..…....61 Travel Speed…………………………………………………..………....61 Travel within Topographic Regions…………..…………………………62 Weather and Travel…………………………………..…………….…….63 Wind Direction and Speed…………………………..…………...63 Thermals…………………………………………………..……..65

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Cloud Cover………………………………………………..…….65 Days since Cold Front Passage………………………..…………66 Discussion……………………………………………………..……………..…..66 Migration Direction………………………………………………..…….67 Travel Distance, Duration, and Speed………………………………..….70 Regional Patterns………………………………………………..…….…71 Weather and Migration Travel…………………………………..…….…72

Chapter 4. Stopover habitat use by migrating Sharp-shinned and Cooper’s hawks in the central Appalachians………………………………………….....84

Abstract……………………………………………..……………………….…...84 Introduction………………………………………………..…………………......85 Methods…………………………………………………………..…………...….89 Study Area……………………………………………………..……..….89 Trapping…………………………………………………………..…..….89 Radio-tracking……………………………………………..……….….…89 Roost Identification………………………………………..…………......89 Locating Roosts and Available Habitat Points……………..………..…..90 Patch Size Analysis………………………………………..…………..…91 Distance to the Flyway……………………………………..……….…....92 Habitat Sampling…………………………………………………..….…92 Habitat Analysis………………………………..……………….……..…93 Results………………………………………………………..….…………….....96 Characteristics of Stopover Sites…………………………..………….…97 Distance to the Kittatinny Ridge…………………..…………..…97 Habitat Cover……………………………………………..……...98 Habitat Selection – Sharp-shinned Hawk………………………..…..…..98 Regional Scale……………………………..………………...…..98 Landscape Scale…………………………………..………….…..99 Near Scale………………………………………………..……...99 Selection by Age……………………..…………………..….…...99

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Habitat Selection – Cooper’s Hawk………………..…………………..100 Regional Scale……………………………………..…..……….100 Landscape Scale…………………………………………..…….100 Near Scale…………………………..……………………….….100 Selection by Age…………………………..……………………101 Stopover Habitat and Scale……………………………..………………101 Forest Patch Size………………………..…………………………..…..102 Discussion……………………………………………..…………..…………....103

Chapter 5. Behavior, Abundance and Distribution of autumn-migrating Raptors along a key migration corridor, the Kittatinny Ridge, Pennsylvania\…………………..123

Abstract………………………………………………..…………………...…...123 Introduction………………………………………..……………………….…...124 Methods…………….……………………………………..…………………….128 Study Area……………………………………………..……………….128 Road Survey Methods………………………………………..…….…...129 Habitat Cover……………………………………………….……..……131 Raptor Density………………..…………………………………...……132 Raptor Abundance…………………..…………….……………..……..133 Avian Prey Abundance……………………………..……………………..……134 Results…………………………………..………………..…………………..…135 Habitat Cover………………………………………….………………..136 Raptor Behavior…………………………………………..……….……136 Raptor Density………………………………………..…………..….…138 Raptor Abundance……………………………………….……….…….139 Age Distribution………………………………………….…….……….140 Avian Prey Abundance……………………………..……….……….....140 Avian Prey and Raptor Abundance Patterns…………………..……….141 Discussion……………………………………………………..…………..……141

Chapter 6. Stopover Ecology of Migrating Raptors and Conservation………..………153

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Literature Cited.……………………..………………………………………………….158

Appendix A1. Migration paths taken by individual Sharp-shinned Hawks during autumn 2003 and 2004 (only birds tagged at Little Gap Raptor Research station that traveled for more than 40 km)…………………………..…….....171

Appendix A2. Migration paths taken by individual Cooper’s Hawks during autumn 2003 and 2004 (only birds tagged at Little Gap Raptor Research station that traveled for more than 40 km)…………………………..…….....................180

Appendix B: Stopover behavior of autumn-migrating accipiters in Central Appalachians.……….…….…………………………………………………………….184

Appendix C. Migration behavior of autumn-migrating accipiters in the Central Appalachians………………………………………………………………..…………..186 . Appendix D. Stopover habitat use by migrating accipiters in the Central Appalachians….................…..……………………………………………………..…...187

Appendix E. Stopover behavior and distribution of raptors along the Kittatinny Ridge in Central Appalachians during autumn 2003 and 2004………….....195

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LIST OF FIGURES

Figure 2.1a. Mean proportion of day (+ SD) Sharp-shinned Hawks spent in different behaviors when migrating and not migrating in autumn 2003 and 2004 (n=29 birds, 107 days)…………………………………….……….……42

Figure 2.1b. Mean proportion of day (+ SD) that Coopers Hawks spent in different behaviors when migrating and not migrating in autumn 2004 (n=11 birds, 62 days)………………………………… ….….……...…42

Figure 2.2. Mean (+ SE) % cloud cover on non-travel days (N) and travel days (Y) for migrating Cooper’s and Sharp-shinned hawks (CH: t=2.362, p=0.02; SS: t=4.591, p=0.000)………....…..….…43

Figure 3.1. Migration tracks of radio-tagged Sharp-shinned Hawks (n=32) through Central Appalachians and areas south during autumn 2003 and 2004 (dots=estimated locations, lines = estimated track between subsequent locations)………………… ……....……....76

Figure 3.2. Migration tracks of radio-tagged Cooper’s Hawks (n=14) through Central Appalachians and areas south during autumn 2004 (dots=estimated locations, lines = estimated track between subsequent locations)…………………… …….………..….77

Figure 3.3. The mean direction of migration (º) of 10 Sharp-shinned and 32 Cooper’s (B) hawks using the Central Appalachian corridor in autumn migration through Pennsylvania in 2003 and 2004 (line shows the mean & 95% CI)……..…………………… ……..….…78

Figure 3.4a. Mean (SD) mid-flight travel rate (km/h) under differing winds for migrating Cooper’s and Sharp-shinned hawks in Central Appalachians during autumn 2003 and 2004……………….…………...….…..79

Figure 3.4b. Mean (SD) daily travel rate (km/h) under differing winds for migrating Cooper’s and Sharp-shinned hawks in Central Appalachians during autumn 2003 and 2004 (n=59 days)……….…………..79

Figure 3.5. Mean (SD) distance traveled per day (km) under differing winds by migrating Cooper’s and Sharp-shinned hawks in Central Appalachians during autumn 2003 and 2004 (n=59 days).… …..……….…..80

Figure 3.6. Mean (SD) daily rate of travel (km/hr) by species in relation to cold front passage during autumn migration in the Central Appalachians in 2003 and 2004 (days 0 to 3 only, n=38 days)… …….………..80 .

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Figure 3.7. Mean daily distance (+ SD, km) traveled by accipiters during autumn migration compared by days since cold front passage (day 0 to 3 only, n=38 days).………… …………………………….…..…………….....81

Figure 3.8. Mean (SD) daily rate of travel (km/h) by age class of accipiters in relation to cold front passage during in autumn migration in 2003 and 2004 (day 0 to 3 only, n=38 days)…………… …..…………..…81

Figure 4.1 Flight paths of migrant accipiters (black lines, n= 44) from release point (white circle) compared to regional habitat sample points (grey dots, n=79) and the physiographic boundaries (grey wavy line separating the Ridge and Valley region north of line and Piedmont and Coastal Plain regions, south of line)……………………...……...…121

Figure 4.2. Proportion of accipiter roosts, random points, and regional habitat samples located in forest patches of differing sizes during autumn migration, 2003-2004 (Cooper’s and Sharp-shinned hawks pooled).………………………………………...………………..122

Figure 5.1. Density of open habitat raptors (mean + SE) on roadside transects in low, moderate, and high forest cover on and near the Kittatinny Ridge in Central Pennsylvania during autumn 2002 and 2003 (density estimated using Distance 4.1; high cover>70%, low<40%)...……………………………………………………..…...152

Figure 5.2. Mean abundance of raptors on stopover (+ SE, birds/km) on transects with low, moderate, and high forest cover within four distance categories from the Kittatinny Ridge in autumn 2002, 2003 (>70% cover=high forest cover, <40%=low’, 40-70%=moderate)……..…………...…152

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LIST OF TABLES

Table 2.1. Proportion of day migrant accipiters spent in different activities during autumn, 2003-2004……………………………………………………….………44

Table 2.2. Periodicity of travel and stopover in migrants tracked for more than five days, in autumn 2003, 2004……………………………...…………………....45

Table 3.1. Migration parameters of Sharp-shinned and Cooper’s hawks using The Central Appalachians during autumn 2003 and 2004 compared by age and species…………………………………………………………………….…………..….82

Table 3.2. Mean daily migratory travel parameters of accipiters flying on the Kittatinny Ridge and within three different Central Appalachian regions during autumn 2003 and 2004……………………………………………......….83

Table 4.1. Forest patch size associated with stopover roost sites of migrating accipiters in the central Appalachians during autumn 2003 and 2004 (% of total roosts)………………………………………………… ……..….109

Table 4.2. Mean % habitat cover surrounding migrant accipiter roost sites, random and regional points in autumn 2003 and 2004………………………….…......110

Table 4.3. Top-ranked logistic regression models distinguishing migrant accipiter roosts and regional sample points (10 km radius sample)…...……....111

Table 4.4. Model-averaged parameter estimates for migrant accipiter habitat selection at a regional scale (including models with ∆QAIC C < 2)………….….112

Table 4.5. Case-control logistic regression models distinguishing migrant accipiter roosts and random sites at landscape scale (10 km radius sample)…………………………………………………………………..113

Table 4.6. Model-averaged parameter estimates distinguishing roosts and random points at landscape scale (habitat cover at 10 km radius)…………114

Table 4.7. Top-ranked case-control logistic regression models distinguishing land cover surrounding roost sites from random points at near scale (0.5 km radius, only models where ∆AICc < 2)…………………..…..…..115

Table 4.8. Model-averaged parameter estimates distinguishing habitat surrounding migrant accipiter roosts and random points at near-scale (0.5 km radius)…………………………………………………..………..116

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Table 4.9. Mean % habitat cover at near scale (0.5 km radius) for stopover sites of adult and hatch-year accipiters during autumn migration, in the Central Appalachians 2003 and 2004………..………………………………….117

Table 4.10. Competing models from case-control logistic regression distinguishing migrant accipiter stopover sites from random points by age at near scale (0.5 km radius) in central Appalachians..………………………....118

Table 4.11. Model-averaged parameter estimates from case-control logistic regression comparing habitat surrounding migrant stopover sites and random points by age class at near-scale (0.5 km radius) in Central Appalachians…...……………………………………………………………………….119

Table 4.12. Habitat parameters influencing stopover site selection in migrating Sharp-shinned and Cooper’s hawks during autumn 2003, 2004 (‘+’ = odds ratio >1.0; ‘-‘= odds ratio<0.99, blank= odds ratio=1.0.)…...……...……..120

Table 5.1. Mean density of raptors on stopover (birds/ha, SD) and % habitat cover along road transects across and adjacent to the Kittatinny Ridge, in central Appalachians during autumn migration 2002, 2003……………………………………………………………………………………..148

Table 5.2. Proportion of raptors exhibiting different behaviors on roadside surveys along the Kittatinny Ridge during autumn 2002, 2003…..………149

Table 5.3. Percent of raptor sightings within different habitat types during roadside surveys in autumn 2002 and 2003………..…..………………………150

Table 5.4. Mean abundance of raptors on roadside surveys (birds/km) and their songbird prey on point counts (mean birds/point) (+ SD) during autumn stopover along the Kittatinny Ridge in Pennsylvania compared distance from ridge in autumn 2002, 2003…………………….…………………..…..151

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ACKNOWLEDGMENTS I especially thank my advisor Margaret C. Brittingham, and my committee, Duane Diefenbach, George S. Young, Christopher Goguen, and Richard Yahner for their guidance, assistance, and abundant patience. Data analysis, and habitat and migration mapping, was conducted with assistance from Duane Diefenbach, Joe Bishop, Chris Farmer, David Barber, Scott Morrison, and Glenn Stauffer. David Barber assisted with GIS mapping and remapping ‘above and beyond the call of duty’. Sue Guers, Shealyn Marino and Beth Swartzentruber were instrumental in organizing the field data and providing initial compilations. Sue Guers, Shealyn Marino, Melissa Cunningham, Corey Kanuckel, Beth Swartzentruber, Scott Morrison, Tray Biasiolli, Zack Rowe, Ben Vang- Johnson, Cheryl Calustro, Kim Van Fleet, Philip Campbell, Darryl and Jackie Speicher, David Hastings, and Jason Ryan assisted with field data collection and entry. Tracking assistance was given by Marshall Allen, Patti Barber, Todd Bauman, Eugenia Becker, Michael Hendricks, Jim Morris, Brad Silfies, Dale Wilsey, and Hawk Mountain interns as well as personnel from Bake Oven Knob, Lehigh Gap Nature Center and Waggoner’s Gap, Audubon Pennsylvania. Radio-tracking by air was facilitated by American Flight Services, particularly Dan Siegle, Dan Wynen, and Ken Highley. Todd Bauman, Ryan Marino, and Allen Koch designed and maintained the telemetry vehicle’s equipment. Funding was provided by the U.S. Fish and Wildlife Service through the State Wildlife Grants Program Grant T-2, administered through the Pennsylvania Game Commission and Pennsylvania Fish and Boat Commission. Additional support was provided by the Gloria M. Young Ornithological Fund of the Philadelphia Foundation, Hawk Mountain Sanctuary Association, Deb and Ralph Siefkin, and in-kind contributions were provided by Little Gap Raptor Banding Station, Waggoner’s Gap and Audubon Pennsylvania, Bake Oven Knob and the Lehigh Gap Nature Center, and Hawk Mountain Sanctuary and its staff, interns, and volunteers.

I thank Cynthia R. Lenhart, Keith L. Bildstein, Lee Schisler, and the Hawk Mountain board of directors and staff for their support throughout this endeavor. Several friends and colleagues provided encouragement when it was needed the most including Margaret, Todd, Jim, Bill P., Sue W., Jane and family, Jack, Dave C., Chris, Steve, Ernesto, Dave H., Annie, Scott, Sally, Merry, Jeremy, Anna, Shea, Sue G., my sisters Kim and Tara and their families, my father and step-mother, and many others from the Hawk Mountain family. The faith and confidence of these people kept me on course and moving forward. Thank you one and all. I dedicate my dissertation to my mother for setting me on this journey, for believing in me, and for not letting me delay, even for a few days more with her.

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Chapter 1. Stopover Ecology of Autumn-migrating Raptors in the Central Appalachians: background.

INTRODUCTION Migration, the regular journey of birds between their breeding grounds and non- breeding grounds (Dingle 1996), occurs in 183 of 292 species (62%) of birds of prey worldwide (Zalles and Bildstein 2000). Many species aggregate in large numbers along established corridors during migration with concentrations ranging from thousands of birds to millions at some locations (Bildstein 2006, Newton 2008). Migration behavior is a product of natural selection and varies widely among species and populations (Alerstam 1990, Berthold 1996, Alerstam et al. 2003). Most North American migratory raptors are partial migrants in which a portion, but not all members, of the species migrates (Kerlinger 1989, Bildstein 2006). Attributes of migration behavior, e.g., timing and distance, may vary within a species, among populations, by age, and by sex (Kerlinger 1989). Individuals also may vary their migration patterns among years, affecting their annual survival and reproduction (Newton 2008). Late-arriving individuals in the spring may have less time to prepare for nesting and produce less young, and be relegated to lower-quality territories. Early arriving birds may be subject to stress of severe weather and reduced foraging opportunities but can have better choice of breeding territories. The timing and pace of the migration journey and the choices made during the journey can have immediate consequences on survival (Berthold 1999, Alerstam et al. 2003).

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Choices about when to fly and when to not fly during migration are poorly understood, particularly for raptors. Weather suitability for migration and seasonal timing are suggested to influence individual decisions (Kerlinger 1989); however, a bird may also be influenced by need to refuel or replenish food stores and rest (Alerstam and Lindstrom 1990, Carmi et al. 1992, Moore et al. 1995). The challenges of migration represent a significant selective force which has shaped behavioral strategies of raptor populations (Kerlinger 1989, Moore et al. 1995, Bildstein 2006, Newton 2008). Migrants can face water crossings, inclement weather, long journeys over unfamiliar terrain, predators, and many other hazards (Moore et al. 1995, Hutto 2000). Recent research suggests that much of the adult mortality in songbirds occurs during the migration and not during breeding and wintering periods (Sillett and Holmes 2002, Newton 2008). Mass mortality of migrant songbirds has been documented during water crossings (Kerlinger 1989) and at radio towers and other lighted structures (e.g., Shire et al. 1999). Some raptors are reported to arrive at migration roost sites emaciated and near death, and mortality at water crossings numbering over 1,000 birds has been noted (Smith et al. 1986, Kerlinger 1989). If migration is challenging for raptors, then finding adequate migration stopover habitat and opportunities to rest and feed could be pivotal to their survival. Moore et al. (1995) posit that the lack of suitable stopover habitat, or “areas with the combination of resources and environmental conditions that promotes occupancy by individuals of a given species and allows those individuals to survive during passage” could result in substantial population declines as migration places birds at their physiological limit in an unfamiliar landscape.

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Feeding on Migration Food supply can influence patterns of migration within and between years (Newton 1979). In partial migrants, e.g., the Red-tailed Hawk (Buteo jamaicensis) some individuals may not migrate if the winter is mild and prey are plentiful (Craighead and Craighead 1969). Food resources and feeding opportunities along the migration route may be as critical in shaping migration patterns and behavior en route as it is in non- breeding periods, however very little research has been conducted on foraging or food requirements of raptor migrants. Although long-distance migrants e.g., the Broad-winged Hawk (Buteo platypterus) and Swainson’s Hawk (B. swainsoni) build up fat prior to migration and may not need to forage regularly, anecdotal observations suggest most raptors forage consistently during migration at northern latitudes (Shelley and Benz 1985, Nicoletti 1997). Even long-distance migrants forage during migration, as 6 to 15% of Broad-winged Hawks had distended crops as they migrated past Hawk Mountain Sanctuary during three autumns (Shelley and Benz 1985, HMS unpubl. data). In shorebirds, researchers have found that migration is timed to maximize feeding opportunities during stopover, e.g., Red Knot at Delaware Bay, New Jersey (Kerlinger 1995). The timing of migration of some raptor species, e.g., American Kestrel (Falco sparverius) and Sharp-shinned Hawk, has been hypothesized to be coordinated with the timing of the migration of their prey as well (Kerlinger 1989, Nicoletti 1997). Stopover Habitat Selection How migrants select stopover habitat is still unclear. Moreover, what types of habitats are important and how individuals locate them is relatively unstudied (Moore and Aborn 2000). Migrant songbirds appear to select habitats for stopover based on

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availability of food and protective cover (Hutto 1985, Moore and Yong 1991, Moore et al. 1995, Keller et al. 2009). If a stopover site is unsuitable a migrant may depart with less fat reserves than needed, and risk mortality or require additional stops which could lead to late arrival to the breeding or non-breeding sites or poor condition (Moore and Yong 1991). Some migratory songbirds may seek out certain habitats during migration stopover (Moore et al. 1990, Rodewald and Brittingham 2004). Habitat area or size may contribute to suitability for migration stopover and the ability for replenishing fat stores (Moore et al. 1995, Petit 2000, Buler et al. 2007, Keller et al. 2009). The habitat used, however, may vary from the habitat used during the breeding season. Forest-nesting birds have been found concentrated along edges or in shrubland, perhaps because invertebrate prey were more abundant in such habitats (Rodewald and Brittingham 2004). Birds may also vary their habitat choices geographically suggesting stopover site selection may be complicated by ecological and physiological requirements that may vary with migration progress and landscapes (Petit 2000). Birds in need of sleep may also seek out flocks to take advantage of others alertness to predators during their rest period (Nemeth 2009). Migrants with fat stores may select different habitats than lean birds (Petit 2000). In the few studies of migrant raptor habitat use that have been conducted, birds appear to seek out habitats similar to their breeding habitat types. A study of 34 radio- tagged Sharp-shinned Hawks (Accipiter striatus) during migration stopover in Cape May, New Jersey, suggested that this woodland raptor selected woodlands on migration over other habitat types (Holthuijzen et al. 1985). Niles et al. (1996) found that raptors in

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Cape May flew over habitats similar to their breeding habitats as they moved along the Cape May Peninsula. Selecting habitat similar to familiar habitats may assist migrants in finding prey, however because prey abundance and habitat components may vary, some flexibility in selection could be an appropriate strategy (Moore and Aborn 2000). Sampling of habitats or sites in the first hours of stopover within a landscape may be important mechanisms birds use to select certain stopover sites (Petit 2000, Moore and Aborn 2000). However, time spent searching may need to be minimized when fat stores are depleted. Distances raptors travel from their migration corridor or flyway in search of suitable stopover sites is unknown. If suitable habitat is rare near migration pathways, migrants may be forced to settle in less suitable sites or expend energy seeking appropriate habitat. Young birds on migration may be particularly challenged when habitat is limited, with some species exhibiting differences in foraging behavior and fat stores by age (Yong and Moore 1993, Woodrey 2000). First-year raptors suffer high rates of mortality post- fledging (70%) presumably because learning to capture live prey is difficult (Newton 1979). Foraging in unfamiliar terrain and habitats along migration routes may be particularly challenging for inexperienced, immature hawks. Longer stopover periods by immature age classes have been noted for several wading birds and Steller’s Eagle (Haliaeetus pelagicus) and could reflect lower foraging efficiency or possibly a reduced migration urgency compared to adults (Newton 2008). Weather, Migration, and Stopover Timing Stopover behavior of individual birds may be influenced by an individual’s internal conditions (i.e., need for feeding and resting, migration urgency) as well as

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environmental conditions, i.e., habitat, weather, prey availability, date (Wlasberg 1990, Alerstam and Lindstrom 1990). Most studies of raptor migration have examined when birds are seen migrating in relation to weather or seasonal progression (Kerlinger 1989, Titus and Mosher 1982). For example, pulses of raptor migration at migration watch- sites in the eastern United States have been correlated to the passage of cold fronts and northerly winds (Broun 1939, Richardson 1978, Titus and Mosher 1982, Allen et al. 1996, Maransky et al. 1997). During rain and snow, migrants are suspected to roost and wait for clearer conditions, although satellite-telemetry techniques have revealed a few species may migrate even during inclement conditions (Newton 2008). Because most studies of raptor migration have focused on ground-based counts, our understanding of weather and migration behavior may be biased (Titus and Mosher 1982, Kerlinger 1989). Weather can enhance or inhibit conditions for migration and may have considerable influence over stopover decisions by an individual as well. Observations on individual birds during both stopover and travel periods can provide more complete and unbiased data on migration choices and patterns in response to different weather conditions. Habitat Conservation Availability of roosting and foraging habitat along the migration pathway may directly affect migrant survival. Biologists suggest that large, undeveloped areas with a diverse habitat array may be needed along key migration corridors although small patches in urbanized landscapes are also important (Moore et al. 1995, Hutto 2000, Mehlman et al. 2005). The Kittatinny or Blue Mountain, is the eastern-most ridge of the central Appalachians, and has been recognized as a major migration corridor for southbound

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Abstract: In the Central Appalachians, the Kittatinny Ridge is a key autumn migration corridor for eastern raptors. I studied migrating raptors during autumn along the Kittatinny Ridge. My objectives included to assess the frequency of travel and stopover in individual raptors and document behavior during stopover to understand the role and importance of stopover in migration in raptors. I also studied which habitats were used by raptors during stopover and the frequency of use of the Kittatinny Ridge to determine the importance of habitat to raptors and whether a flyway corridor could be identified. In one part of the study, I radio-tagged and followed 34 Sharp-shinned (Accipiter striatus ) and 14 Cooper's Hawks ( A. cooperii ) during autumn migration 2003 and 2004. Birds were trapped on the Kittatinny Ridge, and followed for one to 12 days each through Pennsylvania and neighboring states. Both species spent 1-5 days on stopover between travel periods (mean= 2 d.). Sharp-shinned Hawks spent an average of 33.6% of daylight foraging (+ 24.5 SD) and 32.6% of day roosting (+27.4), and Cooper's Hawks spent 33.8% (+ 6.8) of day foraging and 47.2% (+26.2) roosting. Sharp-shinned Hawks spent less time roosting than Cooper's Hawks; however, neither species differed in behavior by age, except that adults spent more time in non-migrating flight. The ratio of hours in travel to hours on stopover per bird during tracking was 1:7 (including night hours) suggesting that rest and foraging periods are an integral aspect of their migration journey. Forest patch size was one of the most important factors in stopover site selection with both species choosing larger forests more than occurred at random at both the landscape scale and near scale. At a regional scale, both species selected more rural areas for stopover sites, selecting areas with more mixed forest and pasture. Sharp-shinned Hawks avoided suburban areas as well. Hatch-year Sharp-shinned Hawks used contiguous forest, wetlands, and evergreen forest less than adults. Nearly half of all roosts of both species were on the Kittatinny Ridge suggesting either an affinity to large forests or the flyway itself. Both species combined roosted at an average of 6.9 km from the ridge flyway when found within the Ridge and Valley region. Hatch-year birds roosted farther from the ridge than adults in both species and Sharp-shinned Hawks roosted farther from the ridge than Cooper's Hawks. Cooper's Hawks were more selective in their habitat choice during migration than during nesting, choosing large forests in more rural landscapes. The selection of roosts by Sharp-shinned Hawks near wetlands may indicate that the opportunity to drink is important during migration or that wetlands concentrate their songbird prey. Evergreen stands could provide important protective cover to roosting Sharp-shinned Hawks, as they may be more vulnerable to avian predation and more likely to seek out evergreen forest during stopover than the Cooper's Hawk. During road surveys of all raptors on stopover, birds were most abundant within 1 to 6 km of the ridge and less numerous farther from the ridge or on the ridge itself. The lowest abundance was observed at the farthest distance from the ridge, 16 km. The pattern of higher abundance near the base of the ridge remained consistent regardless of changes in forest cover . The abundance near the Ridge indicates that distance to the flyway could be an important factor influencing migrant distribution. Habitat influenced distribution of migrants on stopover as well. Forest raptors were more numerous on the north side where forest cover was more abundant, and open habitat raptors, e.g. Redtailed Hawk and Northern Harrier, were more numerous on the south slope where farmland predominates. Although age influences patterns of migration, no age difference was observed in habitat or distance of migrant raptors surveyed during road surveys. (Abstract shortened by UMI.)