DOCSLIB.ORG

Population Status and Threat Analysis for the Black-Capped Vireo

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Population Status and Threat Analysis for the Black-Capped Vireo Population Status and Threat Analysis for the Black-capped Vireo Neal Wilkins, Robert A. Powell, April A.T. Conkey and Amy G. Snelgrove Department of Wildlife and Fisheries Sciences Texas A&M University Prepared For U.S. Fish & Wildlife Service, Region 2 May 2006 With contributions from Linda Campbell, David Cimprich, Craig Farquhar, Pat Reardon, Don Petty, Duane Schlitter, Douglas Slack and David Wolfe BCVI Review May 2006 CONTENTS 1.0 Introduction......................................................................................................................... 6 1.1 Objectives ............................................................................................................................ 6 1.2 Approach.............................................................................................................................. 6 1.2.1 Review panel............................................................................................................... 7 1.2.2 External peer review ................................................................................................... 8 2.0 Life History......................................................................................................................... 9 2.1 Introduction..................................................................................................................... 9 2.2 Species Description.........................................................................................................9 2.3 Geographic Range........................................................................................................... 9 2.4 Nesting and Reproduction............................................................................................. 12 2.5 Food Habits and Foraging Behavior............................................................................. 12 2.6 Survivorship and Mortality........................................................................................... 13 3.0 Habitat Characteristics and Availability ........................................................................... 15 3.1 Introduction.................................................................................................................. 15 3.2 Limitations .................................................................................................................... 15 3.3 Habitat Availability at the Landscape Scale ................................................................. 15 3.4 Patch-level Habitat Characteristics............................................................................... 17 3.5 Nest Site Characteristics ............................................................................................... 19 3.6 Factors Influencing Habitat Suitability......................................................................... 20 4.0 Population Status .............................................................................................................. 25 4.1 Introduction................................................................................................................... 25 4.2 Approach....................................................................................................................... 25 4.3 Known Breeding Populations ....................................................................................... 26 4.4 Abundance Patterns ...................................................................................................... 28 5.0 Analysis of Threats ........................................................................................................... 33 5.1 Introduction................................................................................................................... 33 5.2 Habitat Conversion and Land Use Change................................................................... 33 5.2.1 Land use.................................................................................................................... 33 5.2.2 Ownership fragmentation.......................................................................................... 34 5.3 Vegetation Change........................................................................................................ 37 5.3.1 Invasive woody plants............................................................................................... 37 5.3.2 Influence of fire......................................................................................................... 39 5.3.3 Trends in woodland birds as an index of vegetation change. ................................... 40 5.4 Grazing and Browsing .................................................................................................. 48 5.4.1 Grazing on native rangelands.................................................................................... 48 5.4.2 Effect of grazing on grassland birds ......................................................................... 49 5.4.3 Overgrazing as a threat to black-capped vireos ........................................................ 51 5.4.4 Trends in livestock numbers ..................................................................................... 54 5.4.5 Trends in deer numbers............................................................................................. 57 5.5 Brood Parasitism........................................................................................................... 68 5.5.1 Ecology of brood parasitism ..................................................................................... 68 Wilkins et al. 2 BCVI Review May 2006 5.5.2 Relationship between cowbird abundance and parasitism rates............................... 71 5.5.3 Trends in brown-headed cowbird abundance ........................................................... 72 5.5.4 Cowbird parasitism rates........................................................................................... 74 5.5.5 Effects of cowbird parasitism on host populations................................................... 77 5.5.6 Cowbird removal ...................................................................................................... 81 6.0 Management and Recovery Efforts .................................................................................. 91 7.0 Summary and Conclusions ............................................................................................... 93 7.1 Geographic Range......................................................................................................... 93 7.2 Habitat Availability....................................................................................................... 94 7.3 Population Status .......................................................................................................... 95 7.4. Analysis of Threats ....................................................................................................... 96 7.4.1 Habitat conversion and land use change................................................................... 97 7.4.2 Vegetation change..................................................................................................... 98 7.4.3 Grazing and browsing pressures ............................................................................... 99 7.4.4 Brood parasitism ..................................................................................................... 101 7.5 Objectives of Status Review ....................................................................................... 103 7.5.1 Does the black-capped vireo population appear to be declining, stable, or increasing? .......................................................................................................................... 103 7.5.2 Are threats increasing, unchanged, reduced, or eliminated? .................................. 104 7.5.3 Are there any new threats to the species? ............................................................... 106 8.0 Literature Cited ............................................................................................................... 107 9.0 Appendices...................................................................................................................... 138 APPENDIX A. Current known population of black-capped vireos arranged by county and recovery regions...................................................................................................................... 138 APPENDIX B. Museum records of black-capped vireos that were collected in Mexico outside of the breeding season............................................................................................................. 146 Wilkins et al. 3 BCVI Review May 2006 LIST OF FIGURES Figure 2.1. Currently known breeding and wintering ranges for the Black-capped Vireo with recovery regions as suggested for revision by the Population and Habitat Viability Assessment Report (USFWS 1996. Ranges are generalized for all known locations since time of listing. Note:Black outlines in the Texas range of the species represent recovery units………………. 14 Figure 4.1. Current relative population sizes for known occurrences of black-capped vireos throughout the contiguous U.S. breeding range of the species, including areas where the species has been known to occur but has not been documented in the past 10 and 20 years, respectively. Relative population sizes by county are based on figures available
Load more

Recommended publications
  • Bird Checklist
    Gray-cheeked Thrush Catharus minimus Blackburnian Warbler Dendroica fusca Field Sparrow Spizella pusilla Swainson’s Thrush Catharus ustulatus American Redstart Setophaga ruticilla Swamp Sparrow Melospiza georgiana National Park Service Hermit Thrush Catharus guttatus Pine Warbler Dendroica pinus American Tree Sparrow Spizella arborea U.S. Department of the Interior Veery Catharus fuscescens Prairie Warbler Dendroica discolor Grasshopper Ammodramus savannarum Wood Thrush Hylocichla mustelina Palm Warbler Dendroica palmarum Sparrow New River Gorge National River Blue-winged Warbler Vermivora pinus Fox Sparrow Passeralla iliaca Mockingbird and Thrasher Family Yellow Warbler Dendroica petechia Song Sparrow Melospiza melodia (Mimidae) Swainson’s Warbler Limnothlypis swainsonii Vesper Sparrow Pooecetes gramineus Brown Thrasher Toxostoma rufum Worm-eating Helmitheros vermivorus Savannah Sparrow Passerculus sandwichensis Bird Checklist Gray Catbird Dumetella carolinensis Warbler Dark-eyed (“Slate-colored”) Junco hyemalis Northern Mockingbird Mimus polyglottos Tennessee Warbler Vermivora peregrina Junco Wilson’s Warbler Wilsonia pusilla Crow and Jay Family (Corvidae) Hooded Warbler Wilsonia citrina Blackbird and Oriole Family (Icteridae) Blue Jay Cyanocitta cristata Golden-winged Vermivora chrysoptera Rusty Blackbird Euphagus carolinus American Crow Corvus brachyrhynchos Warbler Common Grackle Quiscalus quiscula Common Raven Corvus corax Nashville Warbler Vermivora ruficapilla Red-winged Blackbird Agelaius phoeniceus Kentucky Warbler Oporornis
    [Show full text]
  • Buckingham Trails Preserve Wildlife Species List
    Wildlife Species List for Buckingham Trails Preserve Designated Status Scientific Name Common Name FWC FWS FNAI MAMMALS Family: Dasypodidae (armadillos) Dasypus novemcinctus nine-banded armadillo * Family: Leporidae (rabbits and hares) Sylvilagus floridanus eastern cottontail Family: Felidae (cats) Felis silvestris domestic cat * Family: Procyonidae (raccoons) Procyon lotor raccoon Family: Suidae (old world swine) Sus scrofa feral hog * Family: Mephitidae (skunks) Spilogale putorius eastern spotted skunk BIRDS Family: Anatidae (swans, geese and ducks) Subfamily: Anatinae Aix sponsa wood duck Anas fulvigula mottled duck Family: Odontophoridae (new world quails) Colinus virginianus northern bobwhite Family: Ciconiidae (storks) Mycteria americana wood stork E E G4/S2 Family: Anhingidae (anhingas) Anhinga anhinga anhinga Family: Ardeidae (herons, egrets, bitterns) Ardea herodius great blue heron Ardea alba great egret G5/S4 Egretta thula snowy egret SSC G5/S3 Egretta caerulea little blue heron SSC G5/S4 Egretta tricolor tricolored heron Bubulcus ibis cattle egret Butorides virescens green heron Family: Threskiornithidae (ibises and spoonbills) Subfamily: Threshiornithinae Eudocimus albus white ibis Family: Cathartidae (new world vultures) Coragyps atratus black vulture Cathartes aura turkey vulture Family: Accipitridae (hawks, kites, accipiters, harriers, eagles) Elanoides forficatus swallow-tailed kite G5/S2 Rostrhamus sociabilis plumbeus Everglades snail kite E E G4G5T3Q/S2 Accipiter cooperii Cooper's hawk G5/S3 Hailaeetus leucocephalus
    [Show full text]
  • Warbling Vireo (Vireo Gilvus)
    Warbling Vireo (Vireo gilvus) NMPIF level: Species Conservation Concern, Level 2 (SC2) NMPIF assessment score: 14 NM stewardship responsibility: Low National PIF status: No special status New Mexico BCRs: 16, 34, 35 Primary breeding habitat(s): Mixed Conifer Forest, Montane Riparian Other habitats used: Spruce-Fir Forest, Ponderosa Pine Forest, Middle Elevation Riparian Summary of Concern Warbling Vireo is a generally stable and widespread species, but local population trends are uncertain. In New Mexico, it is associated with highland riparian and aspen communities which may be sensitive to disturbance or changes in forest structure. It may also be sensitive to nest parasitism by cowbirds and loss of winter habitat. Associated Species Dusky Grouse (BC2), Northern Goshawk (BC2), Red-naped Sapsucker (SC2), Purple Martin, Violet-green Swallow (SC2), American Robin, Orange-crowned Warbler, Black-headed Grosbeak Distribution Warbling Vireo is very broadly distributed across almost the entire United States and western Canada, excluding the southeast and Gulf Coast regions. Breeding populations also extend south in the Sierra Madre Occidental to central Mexico. The species winters along the Pacific slope of Mexico (Gardali and Ballard 2000). In New Mexico, Warbling Vireos breed in upper elevation forests and woodlands statewide, and also occur in lowland riparian areas. Ecology and Habitat Requirements Across its large range, this species occupies many different woodland and forest vegetation types. It is generally associated with riparian areas and mature, mixed deciduous woodlands. In many locations, it is strongly associated with cottonwood-dominated riparian forests, which provide favored habitat structure of large trees with a semi-open canopy. In New Mexico, it also shows a preference for aspen and spruce-aspen communities.
    [Show full text]
  • Red-Eyed Vireo Vireo Olivaceus
    Red-eyed Vireo Vireo olivaceus Folk Name: Preacher, Hanger, Red-eyed Swinging Bird Status: Breeder Abundance: Common to Very Common Habitat: Hardwood forests and mixed pine hardwood forests The Red-eyed Vireo is our most common and best known member of the vireo family. It is also the largest of our vireos, averaging 6 inches in length. Adults have a blue-gray head with a distinctive bright red eye and a white eyebrow outlined in black. Its body is olive green above and white below and it has no wing bars. Like our other vireos, this bird is more often heard than seen. It repeats its song over and over all day long, often while perched high up in a tree. This is why many local folk have called it “Preacher” or the “Preacher Bird.” One early interpretation of this bird’s call was: “You see it, you know it, do you hear me? Do you believe it?” last bird leaving during fall migration on 18 September of In June 1919, Charlotte businessman and birder C. M. that year. McIlwaine had two arrive in Charlotte on April Carson published this poem with a different interpretation 14, 1930, and his last was seen on 24 September. Charlie of the song of the Red-eyed Vireo: Sellers reported a departure date of 13 October in 1939 and an early return date of 11 April in 1941. What little bird is it that’s up so soon, from early Grace Anderson of Statesville published this morn to sleepy moon? He is calling his dearie all anthropomorphic but eloquent account of the nesting day long, as he hops from limb with his pretty song.
    [Show full text]
  • Stephens Forest
    Field Checklist for Stephens Forest ___Warbling Vireo* ___Kentucky Warbler* * = confirmed or likely area breeder ___Red-eyed Vireo* ___Common Yellowthroat* Iowa Wildlife Action Plan Migratory Species of Greatest ___Hooded Warbler* Stephens Forest Conservation Need ___Blue Jay* ___American Redstart* Iowa Wildlife Action Plan Nesting Species of Greatest ___American Crow* ___Cerulean Warbler* Conservation Need ___Northern Parula* ___Horned Lark* ___Magnolia Warbler ___Greater White-fronted Goose ___Ring-billed Gull ___Bay-breasted Warbler Bird Conservation ___Snow Goose ___Purple Martin* ___Blackburnian Warbler ___Cackling Goose ___Rock Pigeon* ___Tree Swallow* ___Yellow Warbler* ___Canada Goose* ___Eurasian Collared-Dove* ___N. Rough-winged Swallow* ___Chestnut-sided Warbler* Area ___Wood Duck* ___Mourning Dove* ___Bank Swallow* ___Blackpoll Warbler ___Gadwall ___Cliff Swallow* ___Yellow-rumped Warbler ___American Wigeon ___Yellow-billed Cuckoo* ___Barn Swallow* ___Yellow-throated Warbler ___Mallard ___Black-billed Cuckoo* ___Black-throated Green Warbler ___Blue-winged Teal ___Black-capped Chickadee* ___Canada Warbler ___Northern Shoveler ___Barn Owl ___Tufted Titmouse* ___Wilson’s Warbler ___Hooded Merganser ___Yellow-breasted Chat* Belted Kingfisher ___Common Merganser ___Eastern Screech-Owl* ___Red-breasted Nuthatch USFWS ___Great Horned Owl* ___White-breasted Nuthatch* ___Eastern Towhee* ___Northern Bobwhite* ___Barred Owl* ___American Tree Sparrow ___Ring-necked Pheasant* ___Long-eared Owl ___Brown Creeper ___Chipping Sparrow* ___Ruffed
    [Show full text]
  • Birds of Tahquamenon Falls State Park
    Birds of Tahquamenon Falls State Park LOONS SANDPIPERS SWALLOWS SPARROWS ___Red-throated Loon ___Greater Yellowlegs ___Tree Swallow ___Rufous-sided Towhee ___Common Loon ___Lesser Yellowlegs ___N. Rough-winged Swallow ___American Tree Sparrow GREBES ___Solitary Sandpiper ___Bank Swallow ___Chipping Sparrow ___Pied-billed Grebe ___Spotted Sandpiper ___Cliff Swallow ___Clay-colored Sparrow ___Horned Grebe ___Whimbrel ___Barn Swallow ___Vesper Sparrow ___Red-necked Grebe ___Ruddy Turnstone CHICKADEES ___Savannah Sparrow ___Eared Grebe ___Sanderling ___Black-capped Chickadee ___Le Conte's Sparrow PELICANS ___Dunlin ___Boreal Chickadee ___Fox Sparrow ___American White Pelican ___Semipalmated Sandpiper NUTHATCHES ___Song Sparrow CORMORANTS ___Least Sandpiper ___Red-breasted Nuthatch ___Lincoln's Sparrow ___Double-crested Cormorant ___Common Snipe ___White-breasted Nuthatch ___Swamp Sparrow BITTERNS AND HERONS ___American Woodcock CREEPER ___White-throated Sparrow ___American Bittern GULLS AND TERNS ___Brown Creeper ___White-crowned Sparrow ___Great Blue Heron ___Bonaparte's Gull WRENS ___Dark-eyed Junco VULTURES ___Ring-billed Gull ___Winter Wren ___Snow Bunting ___Turkey Vulture ___Herring Gull ___Sedge Wren CARDINAL, GROSBEAK GEESE AND DUCKS ___Caspian Tern KINGLETS ___Northern Cardinal ___Canada Goose DOVES ___Golden-crowned Kinglet ___Rose-breasted Grosbeak ___Mute Swan ___Rock Dove ___Ruby-crowned Kinglet ___Indigo Bunting ___Trumpeter Swan ___Mourning Dove GNATCATCHER BLACKBIRDS ___Tundra Swan CUCKOOS ___Blue-gray Gnatcatcher ___Bobolink
    [Show full text]
  • The Endemic Vireo of Fernando De Noronha {Vireo Gracilirostris)
    THE WILSON BULLETIN A QUARTERLY MAGAZINE OF ORNITHOLOGY Published by the Wilson Ornithological Society VOL. 106, No. 1 MARCH 1994 PAGES 1-188 Wilson Bull, 106(1), 1994, pp. 1-17 THE ENDEMIC VIREO OF FERNANDO DE NORONHA {VIREO GRACILIROSTRIS) STORRS L. OLSON' ABSTRACT.•The Noronha Vireo (Víreo gracilirostris) is endemic to the small oceanic island of Fernando de Noronha off the easternmost tip of Brazil. Although derived from the Red-eyed Vireo (F. olivaceus) complex, the Noronha Vireo is differentiated strongly in coloration, plumage pattern, and morphology and fully merits recognition as a distinct species. It is a smaller bird with a much more rounded wing, longer, more slender bill and a more elongated tail and tarsus. These appear to be specializations for gleaning small insects from foliage, particularly the undersides of leaves. The birds are abundant where appropriate habitat is maintained. The few available data on reproductive and molt cycles, nesting, and vocalizations in V. gracilirostris are summarized. Received 11 November 1992, accepted 24 March 1993. The archipelago of Fernando de Noronha is the easternmost extension of land in the Neotropics, lying 345 km east of the eastern tip of mainland Brazil (3°50'S, 32°25'W). It consists of one main island with a string of minor rocks and islets at its northeastern end and various other scattered stacks. The total land area is 18.4 km^. The island is volcanic in origin and before its discovery in 1503 probably was almost entirely forested. The avifauna consists of the usual complement of tropical seabirds, an as yet undescribed extinct flightless rail (Olson 1982), the Eared Dove (Zenaida auriculatá), and the easternmost populations in the world of tyrant flycatcher (Tyrannidae) and vireo (Vireonidae).
    [Show full text]
  • A Conservation Blueprint for Neotropical Migratory Birds in Western Colorado
    A Conservation Blueprint for Neotropical Migratory Birds in Western Colorado Michelle Fink, David Hanni, David Klute, John Sovell, and Renée Rondeau December 2007 Photo by Dave Menke, Photo Courtesy of U. S. Fish and Wildlife Service. Final report submitted to the United States Fish and Wildlife Service (Neotropical Migratory Bird Act). Executive Summary The purpose of this project was to incorporate land use, policy, and biological inputs to define areas representing the most important opportunities for conservation of Neotropical migratory birds in coniferous and aspen forest habitats in Western Colorado and to understand the current status and requirements for maintaining viable populations of these migratory birds within the project area. To that end, we used NatureServe Vista, a decision-support software, and SPOT, a conservation portfolio optimization software, to analyze information about bird distribution, abundance, conservation priorities, quantitative conservation goals, threats to ecosystem stability, and current landscape integrity in order to identify conservation needs and opportunities for birds in aspen and conifer forests in western Colorado. Twenty-two forest-based bird species were used as conservation targets. Multi-year survey data from the Rocky Mountain Bird Observatory was combined with data from the Colorado Natural Heritage Program’s Biodiversity Tracking and Conservation System (BIOTICS) database in addition to modified Southwest Regional GAP vertebrate models for the target species. We used available statewide spatial data to determine general landscape integrity for these species, current and future predicted land use, and policy mandated protection status. This information was then input in NatureServe Vista and SPOT projects and evaluated against varying conservation goal sets for the target species.
    [Show full text]
  • Northern Argentina Tour Report 2016
    The enigmatic Diademed Sandpiper-Plover in a remote valley was the bird of the trip (Mark Pearman) NORTHERN ARGENTINA 21 OCTOBER – 12 NOVEMBER 2016 TOUR REPORT LEADER: MARK PEARMAN Northern Argentina 2016 was another hugely successful chapter in a long line of Birdquest tours to this region with some 524 species seen although, importantly, more speciality diamond birds were seen than on all previous tours. Highlights in the north-west included Huayco Tinamou, Puna Tinamou, Diademed Sandpiper-Plover, Black-and-chestnut Eagle, Red-faced Guan, Black-legged Seriema, Wedge-tailed Hilstar, Slender-tailed Woodstar, Black-banded Owl, Lyre-tailed Nightjar, Black-bodied Woodpecker, White-throated Antpitta, Zimmer’s Tapaculo, Scribble-tailed Canastero, Rufous-throated Dipper, Red-backed Sierra Finch, Tucuman Mountain Finch, Short-tailed Finch, Rufous-bellied Mountain Tanager and a clean sweep on all the available endemcs. The north-east produced such highly sought-after species as Black-fronted Piping- Guan, Long-trained Nightjar, Vinaceous-breasted Amazon, Spotted Bamboowren, Canebrake Groundcreeper, Black-and-white Monjita, Strange-tailed Tyrant, Ochre-breasted Pipit, Chestnut, Rufous-rumped, Marsh and Ibera Seedeaters and Yellow Cardinal. We also saw twenty-fve species of mammal, among which Greater 1 BirdQuest Tour Report: Northern Argentina 2016 www.birdquest-tours.com Naked-tailed Armadillo stole the top slot. As usual, our itinerary covered a journey of 6000 km during which we familiarised ourselves with each of the highly varied ecosystems from Yungas cloud forest, monte and badland cactus deserts, high puna and altiplano, dry and humid chaco, the Iberá marsh sytem (Argentina’s secret pantanal) and fnally a week of rainforest birding in Misiones culminating at the mind-blowing Iguazú falls.
    [Show full text]
  • Date/Weather/Start Time Species Number of Surveyors Anatidae:Swans,Duck,Geese Black-Bellied Whistling-Duck Wood Duck American Wi
    THE ARBORS PRESERVE BIRD LIST Date/Weather/Start time 3/26/2017 3/31/2017 4/7/2017 4/21/2017 Sunny 12:30 Sunny Sunny Partly cloudy 3/6/2017 pm 8:30 9:30 am 8:30 a.m. Species 29 3 18 15 23 Number of surveyors 2 2 2 2 3 Anatidae:Swans,Duck,Geese Black-bellied whistling-duck Wood duck American wigeon Mallard Northern Shoveler Gadwall Blue-winged teal Green-winged teal Redhead Ring-necked duck Lesser scaup Odontophoridae:Quail Northern bobwhite Phasianidae: Pheasant-like birds Wild Turkey Podicipedidae:Grebes Pied-billed grebe Phalacrocoracidae:Comorants Double-crested cormorant Ardeidae:Herons,Egrets, and Bitterns Great egret 1 Great blue heron 1 3 Green heron Cathartidae:Vultures Black vulture 4 2 7 5 Turkey vulture 3 3 4 5 Accipitridae:Hawks, Eagles, and Kites Missisiippi Kite Osprey Sharp-shinned hawk 1 Cooper's hawk 1 Red-shouldered hawk 3 1 Swainson's hawk Zone-tailed hawk Red-tailed hawk 1 1 Accipitor sp. Rallidae: Rails, Gallinules, Coots American Coot Gruidae: Cranes THE ARBORS PRESERVE BIRD LIST Sandhill crane Charadriidae: Plovers and Lapwings Killdeer 1 1 2 Scolopacidae: Sandpipers and Phalaropes Greater yellow legs Columbidae: Pigeons and Doves Rock pigeon Inca dove Common ground dove White wing dove 4 4 Mourning dove 1 1 2 Eurasian collared dove 1 Cuculida: Cuckoos, Roadrunners and Anis Yellow-billed cuckoo Greater Roadrunner Tytonidae and Strigidae: Owls Eastern Screech owl Great horned owl Caprimulgidae: Nightjars and Allies Common nighthawk Common poorwill Chuck-will's Widow Apodidae: Swifts Chimney swift Family Trochilidae:
    [Show full text]
  • Two Subspecies of Warbling Vireo Differ in Th!:.!R Rfponses to Cowbird Egc
    TWO SUBSPECIES OF WARBLING VIREO DIFFER IN TH!:.!R RFPONSES TO COWBIRD EGC SPENCER G. SEALY, Departmentof Zoology,University of Manitoba,Winnipeg, Manitoba R3T 2N2, Canada ALISON J. BANKS, Montana CooperativeWildlife Research Unit, Universityof Montana, Missoula,Montana 59812 JAMESON F. CHACE, Departmentof Environmental,Population, and Organismic Biology,University of Colorado,Boulder, Colorado 80309-0334 ABSTRACT: Using real cowbirdeggs, we experimentallyparasitized 41 nestsof the WarblingVireo (Vireo gilvus), three each in BritishColumbia and Colorado, five in Montana, and 30 in Manitoba, and recordedwhether the cowbirdeggs were acceptedor rejected.Cowbird eggs were acceptedat all neststested in British Columbia and Colorado, but both acceptanceand rejectionwere recordedin Montana.In Manitoba,all cowbirdeggs were rejected(29 by puncture-ejection,one bydesertion). The resultssuggest acceptance by a westernsubspecies of the Warbling Vireo, V. g. swainsonii,and rejectionby the easternsubspecies, V. g. gilvus. The geographicvariability in acceptance/rejectionagrees with suggestedtaxonomic differencesfor the WarblingVireo, i.e., that there are two speciesand that neither appearsto vary in responseto the presenceof cowbirdeggs in its nests. Speciesof birdsthat sufferreduced reproductive success when parasitized by Brown-headedCowbirds (J•olothrus ater) shouldevolve strategies that reduceor eliminatethe costsof parasitism,especially because cowbird eggs are distinguishablefrom the eggsof most host species.Adaptations for rejectionof parasiticeggs from nests have evolved in somespecies, but most speciesaccept cowbirdeggs (Rothstein1975, 1990). Why only a few speciesreject cowbird eggs has been attributed to the durationof exposure to the selectivepressure of cowbirdparasitism (Rothstein 1975) or con- straintson the abilityof smallhosts to eject cowbirdeggs from the nest (Rohwerand Spaw 1988). Amongthe ejecterspecies, the largerones grasp and remove cowbirdeggs with their bills, whereasthe smallerspecies puncture-ejectthem (Rohwerand Spaw 1988).
    [Show full text]
  • Territory Switching Behavior in a Sedentary Tropical Passerine, the Dusky Antbird (Cercomacra Tyrannina)
    Behavioral Ecology Vol. 11 No. 6: 648–653 Territory switching behavior in a sedentary tropical passerine, the dusky antbird (Cercomacra tyrannina) Eugene S. Morton,a Kim C. Derrickson,b and Bridget J. M. Stutchburyc aConservation and Research Center, National Zoological Park, 1500 Remount Road, Front Royal, VA 22630, USA, bDepartment of Biology, Loyola College, 4501 North Charles Street, Baltimore, MD 21210, USA, and cDepartment of Biology, York University, Toronto, Ontario M3J 1P3, Canada Demographic data from an 8-year study of a marked population showed that switching territories and mates is common in both genders of dusky antbirds (Cercomacra tyrannina), a sedentary neotropical passerine with year-round territories and pairbonds. We conducted 22 experimental removals and followed six natural disappearances to examine territory switching. Antbirds quickly abandoned territories and mates to move to openings created by experimental removals. Pairing with the resident on a new territory was rapid. Unmated birds attracted new mates by singing a gender-specific song that differed from songs given by mated birds. There were no gender differences in replacement time or rate. Some vacancies, experimental and natural, were not filled, suggesting that floaters were rare. Territory and mate switching were not related to immediate enhancement of reproductive success because the probability of reproducing successfully was equally poor on all territories. Territory switching may be an overlooked but common tropical form of territoriality that increases individual survivorship during periods of low food abundance (dry season). We suggest that switching is favored when low annual reproductive success enhances selection for a long lifespan as the primary means to increase reproductive success.
    [Show full text]