Largest of all falcons, and the most northern diurnal raptor, the Gyrfalcon inhabits circumpolar arctic

216 Pages·2010·1.79 MB·English

by  Travis Booms

GYRFALCON BREEDING BIOLOGY IN ALASKA

A

DISSERTATION

Presented to the Faculty
of the University of Alaska Fairbanks

in Partial Fulfillment of the Requirements
for the Degree of

DOCTOR OF PHILOSOPHY

By

Travis L. Booms

Fairbanks, Alaska

August 2010
iii
Abstract
This dissertation addresses specific research needs identified by a panel of experts
on Gyrfalcon biology and conservation convened on 3 September, 2003 at the Raptor
Research Foundation Scientific Conference in Anchorage, Alaska. The first chapter is a
significant update and revision of the 1994 Gyrfalcon Birds of North America (BNA)
species account, using all published papers and available grey literature from 1994 - 2007
and personal expertise from over 3,000 hours of coordinated observations. The second
chapter reports results from a spatially explicit model, based on the best available
compiled data from Alaska, that predicted Gyrfalcon breeding distribution and population
size across Alaska. The model predicted that 75% and 7% of the state had a relative
index of nest occurrence of <20% and >60%, respectively. Areas of high predicted
occurrence primarily occurred in northern and western Alaska. Using environmental
variables, the model estimated the size of the breeding Gyrfalcon population in Alaska is
546 ± 180 pairs. In Chapter 3, I used repeated aerial surveys to estimate detection
probabilities of cliff-nesting raptors from fixed-wing aircrafts and helicopters. Detection
probabilities ranged from 0.79 – 0.10 and varied by species, observer experience, and
study area/aircraft type. Generally, Gyrfalcons had the highest detection probability,
followed by Golden Eagles, Common Ravens, and Rough-legged Hawks, though the
exact pattern varied by study area and survey platform. In the final chapter, I described
for the first time in North America Gyrfalcon nest site fidelity, breeding dispersal, and
natal dispersal using molted feathers as non-invasive genetic tags. Gyrfalcons were
highly faithful to study areas (100% fidelity) and breeding territories (98% fidelity), but
not to specific nest sites (22% fidelity). Breeding dispersal distance averaged 750 ± 870
m, and was similar between sexes. Natal dispersal of three nestlings representing 2.5%
recruitment varied from 0 - 254 km. Mean territory tenure was 2.8 ± 1.4 yrs and
displayed a bimodal distribution with peaks at 1 and 4 years. Mean annual turnover at
one study site was 20%. Gyrfalcons in one study area exhibited low, but significant
population differentiation from the other two study areas.
iv
Table of Contents
Page
Signature Page…………………..……………………………………………………….i
Title Page…………………………………………………………………………………ii
Abstract ............................................................................................................................. iii
Table of Contents ............................................................................................................. iv
List of Figures ................................................................................................................. xiii
List of Tables .................................................................................................................. xiv
Acknowledgements ......................................................................................................... xv
Introduction ....................................................................................................................... 1
Chapter 1. The Gyrfalcon, Birds of North America Species Account. ....................... 4
INTRODUCTION .......................................................................................................... 4
DISTINGUISHING CHARACTERISTICS ................................................................... 5
DISTRIBUTION............................................................................................................. 6
The Americas .............................................................................................................. 6
Breeding Range ....................................................................................................... 6
Winter Range .......................................................................................................... 6
Outside the Americas .................................................................................................. 7
Breeding Range. ...................................................................................................... 7
Wintering Range. .................................................................................................... 7
Historical Changes ...................................................................................................... 7
Fossil History .............................................................................................................. 8
SYSTEMATICS ............................................................................................................. 8
Geographic Variation .................................................................................................. 8
Subspecies and Related Species .................................................................................. 9
MIGRATION ................................................................................................................ 10
Nature of Migration in the Species ........................................................................... 10
Timing and Routes of Migration............................................................................... 10
Migratory Behavior ................................................................................................... 12
v
Control and Physiology............................................................................................. 12
HABITAT ..................................................................................................................... 13
Breeding Range ......................................................................................................... 13
Spring and Fall Migration ......................................................................................... 14
Winter Range ............................................................................................................ 14
FOOD HABITS ............................................................................................................ 15
Feeding ...................................................................................................................... 15
Main Foods Taken ................................................................................................ 15
Microhabitat for Foraging. .................................................................................... 15
Food Capture and Consumption ........................................................................... 15
Diet ............................................................................................................................ 17
Main Foods Taken. ............................................................................................... 17
Quantitative Diet Analysis. ................................................................................... 18
Food Selection and Storage ...................................................................................... 19
Nutrition and Energetics ........................................................................................... 20
Metabolism and Temperature Regulation ................................................................. 21
Drinking, Pellet-Casting, and Defecation ................................................................. 21
SOUNDS....................................................................................................................... 21
Vocalizations............................................................................................................. 22
Development. ........................................................................................................ 22
Vocal Array. .......................................................................................................... 22
Phenology. ............................................................................................................ 24
Daily Pattern of Vocalizing. ................................................................................. 25
Places of Vocalizing. ............................................................................................ 25
Repertoire and Delivery of Calls. ......................................................................... 25
Social Context and Presumed Functions of Vocalizations. .................................. 26
Nonvocal Sounds ...................................................................................................... 26
BEHAVIOR .................................................................................................................. 26
Locomotion ............................................................................................................... 26
vi
Walking, Hopping, Climbing, etc. ........................................................................ 26
Flight. .................................................................................................................... 27
Self-Maintenance ...................................................................................................... 28
Preening, Head-Scratching, Stretching, Bathing, Anting, etc. .............................. 28
Sleeping, Roosting, Sunbathing. ........................................................................... 28
Daily Time Budget. ............................................................................................... 29
Agonisitic Behavior .................................................................................................. 29
Physical Interactions. ............................................................................................ 29
Communicative Interactions – Threat Displays. ................................................... 29
Appeasement Displays. ......................................................................................... 30
Spacing ...................................................................................................................... 30
Nature and Extent of Territory. ............................................................................. 30
Manner of Establishing and Maintaining Territory. ............................................. 31
Interspecific Territoriality. .................................................................................... 31
Winter Territoriality. ............................................................................................. 32
Dominance Hierarchies. ........................................................................................ 32
Individual Distance. .............................................................................................. 32
Sexual Behavior ........................................................................................................ 33
Mating System and Sex Ratio. .............................................................................. 33
Displays at the Nest Ledge. .................................................................................. 33
Aerial Displays...................................................................................................... 34
Food Transfers. ..................................................................................................... 35
Copulation; Pre- and Postcopulatory Displays. .................................................... 36
Duration and Maintenance of Pair Bond. ............................................................. 37
Extra-Pair Copulations. ......................................................................................... 37
Social and Interspecific Behavior ............................................................................. 37
Degree of Sociality. .............................................................................................. 37
Play. ...................................................................................................................... 37
Interactions with Members of Other Species. ....................................................... 37
vii
Predation ................................................................................................................... 38
BREEDING .................................................................................................................. 38
Phenology ................................................................................................................. 38
Pair Formation. ..................................................................................................... 38
Nest-Building. ....................................................................................................... 39
First/Only Brood per Season. ................................................................................ 39
Second Brood per Season. .................................................................................... 40
Nest Site .................................................................................................................... 40
Selection Process. ................................................................................................. 40
Microhabitat, Nest-Site Characteristics. ............................................................... 40
Nest ........................................................................................................................... 41
Construction. ......................................................................................................... 41
Structure and Composition. ................................................................................. 41
Dimensions. .......................................................................................................... 41
Microclimate. ........................................................................................................ 41
Maintenance or Reuse of Nests, Alternate Nests. ................................................. 42
Nonbreeding Nests. ............................................................................................... 42
Eggs........................................................................................................................... 42
Shape. .................................................................................................................... 42
Size and Mass. ...................................................................................................... 42
Color. .................................................................................................................... 43
Eggshell Thickness. .............................................................................................. 43
Egg-Laying. .......................................................................................................... 43
Incubation ................................................................................................................. 43
Onset of Broodiness and Incubation in Relation to Laying. ................................. 43
Incubation Patches. ............................................................................................... 44
Incubation Period. ................................................................................................. 44
Parental Behavior. ................................................................................................. 44
Hardiness of Eggs ................................................................................................. 45
viii
Hatching .................................................................................................................... 45
Preliminary Events and Vocalizations. ................................................................. 45
Shell-Breaking and Emergence. ............................................................................ 45
Parental Assistance and Disposal of Eggshells. .................................................... 46
Young Birds .............................................................................................................. 46
Condition at Hatching. .......................................................................................... 46
Growth and Development. .................................................................................... 47
Parental Care ............................................................................................................. 47
Brooding. .............................................................................................................. 47
Feeding. ................................................................................................................. 48
Nest Sanitation. ..................................................................................................... 49
Cooperative Breeding ............................................................................................... 50
Brood Parasitism ....................................................................................................... 50
Fledgling Stage ......................................................................................................... 50
Immature Stage ......................................................................................................... 50
DEMOGRAPHY AND POPULATIONS .................................................................... 51
Measures of Breeding Activity ................................................................................. 51
Age at First Breeding. ........................................................................................... 51
Clutch. ................................................................................................................... 51
Annual and Lifetime Reproductive Success. ........................................................ 51
Life Span and Survivorship ...................................................................................... 52
Disease and Body Parasites ...................................................................................... 52
Causes of Mortality ................................................................................................... 53
Range ........................................................................................................................ 54
Initial Dispersal from Natal Site. .......................................................................... 54
Fidelity to Breeding Site and Winter Home Range. ............................................. 54
Dispersal from Breeding Site. ............................................................................... 54
Home Range.......................................................................................................... 55
Population Status ...................................................................................................... 55
ix
Numbers. ............................................................................................................... 55
Trends. .................................................................................................................. 57
Population Regulation ............................................................................................... 57
CONSERVATION AND MANAGEMENT ................................................................ 59
Effects of Human Activity ........................................................................................ 59
Management .............................................................................................................. 62
APPEARANCES .......................................................................................................... 63
Molts ......................................................................................................................... 63
Prejuvenile (First Prebasic) Molt. ......................................................................... 63
Preformative Molt. ................................................................................................ 64
Second Prebasic Molt. .......................................................................................... 64
Definitive Prebasic Molt. ...................................................................................... 64
Plumages ................................................................................................................... 65
Natal Down. .......................................................................................................... 66
Juvenal Plumage. .................................................................................................. 67
Second Basic Plumage. ......................................................................................... 68
Definitive Basic Plumage. .................................................................................... 68
Bare Parts .................................................................................................................. 69
Bill......................................................................................................................... 69
Iris. ........................................................................................................................ 70
Legs and Feet. ....................................................................................................... 70
MEASUREMENTS ...................................................................................................... 70
Mass .......................................................................................................................... 70
Linear ........................................................................................................................ 71
PRIORITIES FOR FUTURE RESEArCH ................................................................... 72
ACKNOWLDEGEMENTS .......................................................................................... 73
ABSTRACT ................................................................................................................ 100
INTRODUCTION ...................................................................................................... 101
METHODS ................................................................................................................. 103
x
Environmental Layers ............................................................................................. 103
Training Data .......................................................................................................... 104
Modeling Approach ................................................................................................ 104
Model Evaluation .................................................................................................... 106
Evaluation with Internal Training Data .................................................................. 106
Independent Spatial Data ........................................................................................ 106
General Methods ..................................................................................................... 109
RESULTS ................................................................................................................... 109
DISCUSSION ............................................................................................................. 111
ACKNOWLEDGEMENTS ........................................................................................ 116
LITERATURE CITED ............................................................................................... 124
Chapter 3. Detection Probability of Cliff-nesting Raptors During Helicopter and
Fixed-wing Aircraft Surveys in Western Alaska. ..................................................... 133
ABSTRACT ................................................................................................................ 133
INTRODUCTION ...................................................................................................... 134
METHODS ................................................................................................................. 135
General Survey Design ........................................................................................... 136
Study Design by Study Area ................................................................................... 139
Kilbuck Mountains.............................................................................................. 139
Volcanoes ............................................................................................................ 139
Data Analysis .......................................................................................................... 140
Model development ................................................................................................ 142
RESULTS ................................................................................................................... 143
DISCUSSION ............................................................................................................. 144
Species Differences ................................................................................................. 144
Observer Experience Differences ........................................................................... 147
Study Area/Aircraft Differences ............................................................................. 148
Implications for Future Surveys.............................................................................. 148
ACKNOWLEDGMENTS .......................................................................................... 150
xi
LITERATURE CITED ............................................................................................... 155
Chapter 4. Direct and Indirect Estimates of Gyrfalcon Nest Site Fidelity and
Breeding and Natal Dispersal using Non-invasive Genetic Sampling...................... 160
Abstract ....................................................................................................................... 160
INTRODUCTION ...................................................................................................... 161
METHODS ................................................................................................................. 163
Study Area .............................................................................................................. 163
Definitions of Terminology .................................................................................... 165
Sample Collection ................................................................................................... 166
Microsatellite DNA Genotyping and Molecular Sexing ........................................ 167
Data Processing ....................................................................................................... 168
Genetic Diversity .................................................................................................... 168
Individual Identification and Relatedness ............................................................... 169
Population Differentiation ...................................................................................... 170
Statistical Analysis .................................................................................................. 170
RESULTS ................................................................................................................... 171
Feather and Blood Samples .................................................................................... 171
Microsatellite Loci and Relatedness ....................................................................... 171
Fidelity and Population Differentiation .................................................................. 172
Breeding Dispersal .................................................................................................. 172
Natal Dispersal ........................................................................................................ 173
DISCUSSION ............................................................................................................. 173
Fidelity and Population Differentiation .................................................................. 174
Breeding Dispersal .................................................................................................. 175
Natal Dispersal ........................................................................................................ 176
Potential Biases ....................................................................................................... 176
Implications............................................................................................................. 177
ACKNOWLEDGEMENTS ........................................................................................ 179
LITERATURE CITED ............................................................................................... 188