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Caldwell Hahn

Research Wildlife Biologist

Contact Info

Short Biography

US Geological Survey, Patuxent Wildlife Research Center, Research Biologist, 1996-present

Rutgers University, Adjunct Faculty, 2007-present



Harvard University, Museum of Comparative Zoology, Post-doctoral Fellow in Sociobiology,

            advisor Bert Holldober

Smithsonian Tropical Research Center, Post-doctoral Fellow in Sociobiology,  advisor

Mary Jane West Eberhard

Rutgers University, Ph.D., Institute of Animal Behavior, behavioral ecology, advisor Colin Beer

Tufts University, M.S.,  animal behavior, advisor, Benjamin Dane

Wellesley College, B.A.

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SELECTED PUBLICATIONS: Hahn, D.C., S.G. Summers, K. Genovese, H. He, M.H. Kogut, 2013. Enhanced innate immune responses in a brood parasitic species: oxidative burst and degranulation. Avian Diseases 57: 285-289. Hahn, D.C. 2011. Patterns of maternal yolk hormones in Eastern screech owl eggs (Megascops asio). General and Comparative Endocrinology 172 (3):423-429. Reisen, W. K. and D. C. Hahn. 2007. Comparison of immune responses of brown-headed cowbird and related blackbirds to West Nile and other mosquito-borne encephalitis viruses. Journal of Wildlife Diseases 43(3):439-449. . Hahn, D.C, N.M. Nemeth, E. Edwards, P.R. Bright, and N. Komar. 2006. Passive West Nile virus antibody transfer from maternal Eastern Screech-Owls (Megascops asio) to progeny. Avian Diseases 50(3): 454-455. Hahn, D. C. and R.J.C. O'Connor. 2002. Contrasting determinants of abundance in ancestral and colonized ranges of an invasive brood parasite, pp. 219-228 in J. Michael Scott, Patricia J. Heglund, Michael L. Morrison, Jonathan B. Haufler, and William A. Wall, editors. Predicting species occurrences : issues of accuracy and scale. Island Press, Washington, DC. xvii, 868 pp. [pdf] Hahn, D. C., R. D. Price, and P. C. Osenton. 2000. Use of lice to identify cowbird hosts. Auk 117(4):943-951. Hahn, D. C., J. A. Sedgwick, I. Painter, and N. Casna. 1999. A spatial and genetic analysis of Cowbird host selection. Pages 204-217 in M. L. Morrison, L. S. Hall, S. K. Robinson, S. I. Rothstein, D. C. Hahn, and T. D. Rich, editors. Research and management of the Brown-headed Cowbird in western landscapes. Studies in Avian Biology 18. 312pp. Hahn, D. C. and J. S. Hatfield. 1995. Parasitism at the landscape scale: Cowbirds prefer forests. Conservation Biology 9(6):1415-1424 . Hahn, D. C. and R. C. Fleischer. 1995. DNA fingerprint similarity between female and juvenile brown-headed cowbirds trapped together. Animal Behaviour 49(6):1577-1580. Hahn, D. C. 1981. Asynchronous hatching in the Laughing Gull: Cutting losses and reducing rivalry. Animal Behavior 29(2):421-427. Burger, J., D. C. Hahn, and J. Chase. 1979. Aggressive interactions in mixed-species flocks of migrating shorebirds. Animal Behaviour 27(2):459-470. Ricklefs, RE, DC Hahn. WA Montevecchi 1978. The relationship between egg size and chick size in the Laughing Gull and Japanese Quail. Auk 95 (1): 135-144. [Download File]


My Science Topics

Science Topic
Ecology and Environmentbiodiversity
Plants and Animalsgenetic diversity
Plants and Animalsinvasive species
Plants and Animalsmigratory species
Plants and Animalswildlife

My USGS Science Strategy Areas

The Role of Environment and Wildlife in Human Health

eco-immunology, host-parasite co-evolution, evolution of immunity

I work on the associations between climate change, wildlife disease, and invasive species.  My work is primarily with birds, and I work with species suited to investigating particular problems.  For studies with West Nile virus, Western equine encephalitis virus, and St. Louis encephalitis virus, we worked with (1) Eastern screech owl; and (2) a genus of parasitic blackbirds, the New World cowbirds (Molothrus spp).  For studies of the evolution of immune defenses studies, we worked with (1)  several species of parasitic cowbird;  (2)  tree swallow;  (3) eastern screech owl; and (4) dabbling ducks, sea ducks, and diving ducks.  For studies of co-evolutionary relationships between parasite and host, we worked with the North American brown-headed cowbird and feather lice (Phthiraptera) associated with the host species that cowbirds exploit.

Honors and Invited Presentations


Invited speaker, Huck Institute of Life Sciences, Penn State University, spring, 2012. "Invasive Species & Climate Change:  the role of immunity"

Invited speaker, Ethological Society Meeting on Cooperation and Conflict, Zurich, 2011

Invited speaker, European Society Evolutionary Biology, Turino, 2009.  "Enhanced Innate Immunity Favored in a Parasite-rich environment"

Invited seminar, Institute for Ecology, University of Bern, Switzerland, 2009

Fellow, American Ornithological Union

Invited seminar, Children’s Hospital, Ludwig-Maximilians University, Munich, 2009.  "The Hygiene Hypothsis Examined in a Model Wildlife Species"

Invited speaker, Jacques Monod Conference “Genetics of Host-Parasite Coevolution”, French National Science Foundation, Roscoff, France, September 2007.

Invited speaker, Dept. Ecology & Evolution, University of Lausanne, Switzerland, 2007

Invited presentation, Symposium on Evolutionary Biology & Human Health, American Institute of Biological Sciences (AIBS), Washington, DC, 2007

 Invited speaker, University of Fribourg, Workshop on Evolution, Switzerland, February, 2002.

Invited Speaker, Conference on Innovation in the Biosciences, Marie Curie Fellowship Association, Bedford, England, 2000.

Invited Speaker, European Science Foundation, Workshop on Host-Parasite Coevolution, Perpignan, France, 1999

1997 Invited speaker, Partners in Flight Symposium on Cowbird Management, Sacramento,

Contact Information

Caldwell Hahn
12100 Beech Forest Road
Laurel, MD 20708
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