Cape May Raptor Banding Project40+ Years of Conservation through Banding

Cape May Raptor Banding Project, Inc.Cape May, NJ, U.S.A.CapeMayRaptors.org

September 24, 2010

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IntroductionWe have operated a raptor banding station every year since 1967 near Cape May, New Jersey, U.S.A. In 1999 we incorporated as the Cape May Raptor Banding Project, Inc. (CMRBP), a 501c3 non-profit organization run entirely by volunteers. As of 2009 the project had captured about 132,000 diurnal raptors of 16 species during fall migration in the months of September, October and November. This makes CMRBP the largest raptor banding project in North America and one of the largest in the world.

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Location of the Cape May Raptor Banding Project

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Methods From one to five banding stations have been operated annually at CMRBP using a combination of bow traps, mist nets and dho-gaza traps employing live rock pigeons, starlings and house sparrows as lures. Trapping methods have been described previously (Clark 1970, 1976, 1981). Habitats at stations range from agricultural fields and meadows to scrub-shrub to tidal and non-tidal wetlands. Blinds and trap/net arrays are generally oriented towards the north and/or east to take advantage of typical flight lines at Cape May.

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Overall Banding ResultsDatasets maintained by the project include birds first banded at Cape May (bandings), Cape May-banded birds that return to Cape may in subsequent years (returns), encounters elsewhere of birds originally banded at Cape May (recoveries), and birds originally banded elsewhere that are encountered at Cape May (foreign recoveries). Most raptors captured at Cape May have been unbanded; fewer than 300 of the total of 132,000 have been foreign recoveries, and only about 45 captures have been returns.

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Slightly more than half of the birds captured at Cape May have been Sharp-shinned Hawks (Accipiter striatus). Cooper’s Hawk (A. cooperii) and American Kestrel (Falco sparverius) together constitute another 30% of the total; no other single species represents more than 7%.

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Bandings by Species Species Percent of Total (n = 131,717)

Sharp-shinned Hawk 52.9 (n = 68,892)

Cooper’s Hawk 16.3 (n = 22,452)

American Kestrel 13.7 (n = 17,760)

Merlin 6.4 (n = 8,474)

Red-tailed Hawk 5.8 (n = 7,644)

Northern Harrier 2.8 (n = 3,644)

Peregrine Falcon 1.2 (n = 1,694)

Red-shouldered Hawk 0.3 (n = 390)

Northern Goshawk 0.3 (n = 375)

Broad-winged Hawk 0.2 (n = 316)

Golden Eagle <0.1 (n = 21)

Swainson’s Hawk <0.1 (n = 18)

Osprey <0.1 (n = 17)

Rough-legged Hawk <0.1 (n = 9)

Bald Eagle <0.1 (n = 6)

Eurasian Kestrel <0.1 (n = 1) 7

Annual totals for all species have topped 5,000 birds on five occasions, the last time occurring in 1987. The decline in annual totals since the 1970’s and 1980’s is due to sharp decreases in numbers of Sharp-shinned Hawks and American Kestrels.

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Highlights include the second North American record of Eurasian Kestrel (F. tinnunculus) (Clark 1974a), and confirmation of the occurrence of Swainson’s Hawk (Buteo swainsonii) in New Jersey (Clark 1974b).

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Long Term TrendsLong term trends in banding numbers at Cape May show a variety of patterns. These may indicate actual changes in populations, but could also reflect shifts in migration pathways. Such shifts could result from year-to-year irregularities in weather, the influence of natural succession or increased residential development on the Cape May Peninsula, or other factors.

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Banding numbers have been demonstrated to correlate closely with similar trends in Cape May Hawk Watch counts for Northern Harrier (Schultz 1996). Numbers of birds banded appear to track Cape May count trends for other species too, including declines in Sharp-shinned Hawk and American Kestrel since the 1970’s and 1980’s, and increases in Cooper’s Hawk and Peregrine Falcon (Falco peregrinus) over the last 30-35 years (Bildstein, et al 2008).

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Age and sex ratiosOf those that could be aged, 94% of birds banded were aged by plumage as juveniles (hatch year), while only 0.6% were definitively aged as full adults (after second year). Sex ratios frequently deviate from 1:1, with some species, such as Cooper’s Hawk, Northern Goshawk and Northern Harrier, showing ratios of nearly 2:1. Sex ratios of recoveries vary from those of bandings, with no discernable relationship between the two.

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Migration TimingGenerally, falcon captures peak in late September; accipiters, with the exception of Northern Goshawk (A. gentilis), in mid-October; and buteos, chiefly Red-tailed Hawk (B. jamaicensis), in early November.

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Within most species, seasonal timing of captures differs noticeably by age class, with juveniles peaking before adults. The statistical significance of this difference at Cape May has been confirmed for Northern Harrier (Circus cyaneus) (Bildstein et al 1984) and holds true for other species as well.

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Differences in timing by sex are less consistent. Analysis of Cape May data shows that females migrate earlier than males for Merlin (Falco columbarius) (Clark 1985). This is partially or completely true for Sharp-shinned Hawk, Cooper’s Hawk and American Kestrel as well. However, this tendency is reversed for Northern Harrier (Bildstein et al 1984), where males migrate first.

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28 September

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Summary of RecoveriesAbout 2,500 Cape May-banded birds (2%) have been encountered subsequently at other locations throughout the Americas at all times of the year. Most recoveries are from the Eastern U.S. and the Canadian Maritimes, although there are some records from the West Indies and Central and South America.

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Recoveries of Cape May-banded birds

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Encounter frequencies differ from capture rates in most species, with larger species encountered relatively more often than smaller species. This is probably the result of an increased probability of detection of larger birds.

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MovementsMapping of encounter locations shows that summer ranges – and therefore, presumably, breeding areas – for many species are primarily northeast of Cape May.

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Summer recoveries of Sharp-shinned Hawk

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Summer recoveries of Cooper’s Hawk

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Summer recoveries of Red-tailed Hawk

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Summer recoveries of Merlin

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Summer recoveries of American Kestrel

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Mapping also demonstrates possible seasonal differences in migration pathways, and possible differences between sexes in breeding and wintering ranges, for some species. For example, Sharp-shinned Hawks and Cooper’s Hawks appear to migrate further inland in the spring than in the autumn, and female Cooper’s Hawks winter further south, on average, than males.

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Spring and Autumn recoveries of Sharp-shinned Hawk

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Spring and Autumn recoveries of Cooper’s Hawk

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Winter recoveries of Cooper’s Hawk

37.98°

39.17°

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Finally, about 6% of recoveries were made north or west of Cape May within several weeks of the banding date, indicating that fall migration does not always progress steadily southward.

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Same-season recoveries north of Cape May

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LongevityLongevity records for raptors banded at Cape May, derived from recoveries, include 24 yrs for Red-tailed Hawk, 15 yrs for Northern Harrier, Sharp-shinned Hawk and Cooper’s Hawk, and nearly 14 yrs for Broad-winged Hawk (B. platypterus).

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Longevity Records by SpeciesSpecies Longevity

Red-tailed Hawk 24 yrs

Sharp-shinned Hawk 15 yrs, 6 mos

Cooper’s Hawk 15 yrs, 3 mos

Northern Harrier 15 yrs

Broad-winged Hawk 13 yrs, 10 mos

Peregrine Falcon 11 yrs

Merlin 10 yrs, 9 mos

American Kestrel 7 yrs, 6 mos

Red-shouldered Hawk 5 yrs, 5 mos

Northern Goshawk 3 yrs, 11 mos

Golden Eagle 2 yrs, 2 mos

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MortalityOf encounters listing a specific cause of mortality, collisions with moving vehicles account for about 30% and collisions with stationary objects about 25%.

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MorphometricsMorphometric data – primarily mass and wing chord – have been collected for tens of thousands of individuals. Comparison with measurements from other raptor migration banding stations shows regional variations within some species, with many western birds having lower mass but longer wings and/or tails than eastern conspecifics (Smith et al 1990).

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AbnormalitiesAlthough the vast majority of birds captured at Cape May appear entirely normal, various abnormalities have been noted. These include supernumerary flight feathers (Clark et al 1988), and assorted injuries and deformities.

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Merlin with 13 tail feathers, one more than the normal 12

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Collaborative ResearchCMRBP has long made captured birds available to other researchers. Collaborators have studied local movements, parasites, contaminants and taxonomy. Among their findings are support for the counting methodology used by the Cape May Hawk Watch (Holthuijzen and Oosterhuis 1985); the presence of hematozoans in nearly 60% of birds examined (Kirkpatrick and Lauer 1985); and genetic confirmation of subspecies classification in Red-tailed Hawk (Pearlstine 2004). Current research projects include levels of mercury contamination in various species and population genetics of Merlin subspecies.

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EducationTens of thousands of people have attended educational programs, featuring banded raptors, that emphasize natural history and conservation. The audience is given an introduction to the history and operation of the banding project, and to the raptor migration phenomenon at Cape May. Key facts and figures about project statistics and findings are also related. Finally, the biology, ecology and conservation status of each species present are discussed and the birds are then released in front of the audience.

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Golden Eagle at an educational program

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Acknowledgements •Many raptor banders and helpers, especially Chris Schultz, Sam Orr and Ray Miller•Marlene Miller for data entry•Cape May Bird Observatory/New Jersey Audubon, National Wildlife Federation and U.S. Fish & Wildlife Service for support during the initial stages of the project

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References Cited and Other Literature Utilizing CMRBP DataAnderson, D., A.M.A. Holthuijzen, and L. Oosterhuis. 1980. A pilot telemetry study on the migration movements of female Sharp-shinned Hawks at Cape May, New Jersey. Technical Report, Department of Fisheries and Wildlife Sciences. Virginia Polytechnic Institute and State University, Blacksburg.

Bildstein, K.L., W.S. Clark, D.L. Evans, M. Field, L. Soucy, and E. Henckel. 1984. Sex and age differences in fall migration of Northern Harriers. J. Field Ornithology 55:143–150.

Bildstein, K.L., J.P. Smith, E. Ruelas I., and R.R. Veit (eds). 2008. State of North America’s Birds of Prey. Nuttall Ornithological Club and American Ornithologists Union Series in Ornithology No. 3. Cambridge, Massachusetts, and Washington, D.C. 466 pp.

Bolgiano, N.C. 2006. Was the rise and fall of eastern Sharp-shinned Hawk migration counts linked to the 1970s spruce budworm infestation? Hawk Migration Studies 31: 9-14. 60

Clark, W.S. 1969. Migration trapping of hawks at Cape May, N.J. – second year. EBBA News 32:69-76.

Clark, W.S. 1970. Migration trapping of hawks (and owls) at Cape May, N.J. - third year. EBBA News 33: 181-190.

Clark, W.S. 1972. Migration trapping of hawks (and owls) at Cape May, N.J. - fifth year. EBBA News 35: 121-131.

Clark, W.S. 1973. Cape May Point raptor banding station - 1972 results. EBBA News 36: 150-165.

Clark, W.S. 1974. Second record of the Kestrel (Falco tinnunculus) for North America. Auk 91: 172.

Clark, W.S. 1974. Cape May Point raptor banding station - 1973 results. EBBA News 37: 51-64.

Clark, W.S. 1974. Occurrence of Swainson's Hawk substantiated in New Jersey. Wilson Bulletin 86: 284-285.

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Clark, W.S. 1976. Cape May Point Raptor Banding Station - 1974 Results. North American Bird Bander 1:5-13.

Clark, W.S. 1981. A modified dho-gaza trap for use at a raptor banding station. J. Wildlife Management 45: 1043-1044.

Clark, W.S. 1985. Migration of the Merlin along the coast of New Jersey. J. Raptor Research 19:85–93.

Clark, W.S. 1985. The migrating Sharp-shinned Hawk at Cape May Point: banding and recovery results. Pages 137-148 in M. Harwood, ed. Proceedings of hawk migration conference IV. Hawk Migration Association of North America, Washington Depot, CT U.S.A.

Clark,W.S., K. Duffy, E. Gorney, M. McGrady, and C. Schultz. 1988. Supernumerary primaries and rectrices in some Eurasian and North American raptors. J. Raptor Research 22: 53-58.

Clark, W.S., C. Schultz, and O. Allen. 2000. Conservation of migrating raptors through banding; results of over 30 years of the Cape May Point Raptor Banding Project. In: Raptors at Risk. World Working Group on Birds of Prey, London and Berlin.

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Dunne, P.J. and W.S. Clark. 1977. Fall hawk movement at Cape May Point, New Jersey - 1976. Occasional Paper No. 130, New Jersey Audubon 3: 114-124.

Henny, C. J., and W.S. Clark. 1982. Measurements of fall migrant Peregrine Falcons from Texas and New Jersey. J. Field Ornithology 53: 326-332.

Holthuijzen, A.M.A . and L. Oosterhuis. 1981. Migration patterns of female Sharp-shinned Hawks (Accipiter striatus) at Cape May Point, New Jersey. Technical Report, Department of Fisheries and Wildlife Sciences. Virginia Polytechnic Institute and State University, Blacksburg.

Holthuijzen, A.M.A., and L. Oosterhuis. 1985. Implications for migration counts from telemetry studies of Sharp-shinned Hawks (Accipiter striatus) at Cape May Point, New Jersey. Pages 305-312 in M. Harwood (ed.). Proc. Hawk Migration Conference IV, Hawk Migration Association of North America, Lynchburg, VA.

Holthuijzen, A.M.A ., L. Oosterhuis, and M.R. Fuller. 1985. Habitat used by migrating Sharp-shinned Hawks (Accipiter striatus) at Cape May Point, New Jersey, U.S.A. In I. Newton and R.D. Chancellor, eds. Conservation Studies on Raptors. Based on the Proceedings of the Second World Conference on Birds of Prey, held in Thessaloniki, Greece, April 1982. International Council for Bird Preservation Technical Publication No. 5.

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Hull, J.M. and D.J. Girman. 2005. Effects of Holocene climate change on the historical demography of migrating Sharp-shinned Hawks (Accipiter striatus velox) in North America. Molecular Ecology 14:159-170.

Kirkpatrick, C.E. and D.M. Lauer. 1985. Hematozoa of raptors from southern New Jersey and adjacent areas. J. Wildlife Disease 21: 1-6.

Kirkpatrick, C.E. and V.P. Trexler-Myren. 1986. A survey of free-living falconiform birds for Salmonella. J. Amer. Veterinary Medical Assoc. 189:997-998.

Mueller, H.C., N.S. Mueller, D.D. Berger, G. Allez, W. Robichaud, and J.L. Kaspar. 2000. Age and sex differences in the timing of fall migration of hawks and falcons. Wilson Bull. 112:214–224.

Pearlstine, E.V. 2004. Variation in mitochondrial DNA of four species of migratory raptors. J. Raptor Research 38:250-255.

Pearlstine, E.V., and D.B. Thompson. 2004. Geographic variation in morphology of four species of migratory raptors. J. Raptor Research 38:34-342.

Schultz, C.W. 1994. Osprey captures tethered rock dove. North American Bird Bander 19:56-57. 64

Schultz, C.W. 1994. AFR: Cape May Raptor Banding Project - 1993 Yearly Report. North American Bird Bander 19:34-35.

Schultz, C.W. 1996. Cape May Raptor Banding Project 1995 Yearly Report. North American Bird Bander 21:35-37.

Schultz, C.W. 1996. Migration trend and morphometric characteristics of Northern Harriers during autumn migration at Cape May Point, New Jersey. M.S. Thesis, Utah State University, Logan, 90pp.

Schultz, C. and W.S. Clark. 2009. A Bander's Guide to Aging and Sexing Common Eastern North American Raptors During Autumn Migration. Unpubl. Ms. Cape May Raptor Banding Project in conjunction with Cape May Bird Observatory, New Jersey Audubon Society. 20 pp.

Smith, J.P., S.W. Hoffman, and J.A. Gessaman. 1990. Regional size differences among fall-migrant accipiters in North America. J. Field Ornithology 61:192-200.

Struve, S. and L. Goodrich. 1992. Distribution of band recoveries for sharp-shinned hawks banded in the eastern Appalachian flyway. Unpubl. Rep. Hawk Mountain Sanctuary, Kempton, PA, U.S.A.

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Viverette, C., L. Goodrich, and M. Pokras. 1994. Levels of DDE in eastern flyway populations of migrating Sharp-shinned Hawks and the question of recent declines in numbers sighted. HMANA Hawk Migration Stud. 20(1):5-7.

Viverette, C.B., S. Struve, L.J. Goodrich, and K.L. Bildstein. 1996. Decreases in migrating Sharp-shinned Hawks at traditional raptor-migration watchsites in eastern North America. Auk 113: 32-40.

Wood, P.B., C. Viverette, L.J. Goodrich, M. Pokras and C. Tibbott. 1996. Environmental contaminant levels in Sharp-shinned Hawks from the eastern United States. J. Raptor Research 30: 136-144.

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