Ongoing Projects

Our ongoing, 45-year study on dispersal patterns and population productivity in Red-shouldered and Red-tailed Hawks in southwestern California continues to yield intriguing and informative results. One fascinating finding is that productivity in the two raptor species shows predictable synchronous oscillations that we think are predominately influenced by weather patterns. We also have detected declines in territory occupancy, suggesting declines in population numbers or dispersal to new breeding areas. Currently, we are seeking funding to further explore how our productivity data relate to temporal changes in local and regional weather, including weather patterns influenced by El Niño Southern Oscillation and climate change.  We also hope to secure funding to conduct research to determine if declining territory occupancies can be explained by declines in population numbers and, if so, if the population declines are caused by inclement or changing weather patterns, habitat alterations or loss, exposure to contaminants (e.g., rodenticides), or increased susceptibility to infectious diseases (e.g., West Nile Virus).

In  addition we are working towards acquiring satellite transmitters as well, so that we can track and better understand the atypical movement patterns of fledgling Red-tailed and Cooper’s Hawks in southern latitude populations. Publishing results from BRI’s innovative scientific research program is ongoing and we continue to publish independent research conducted by Peter Bloom on raptor ecology, raptor population status, population threats, conservation and management needs, and efficacy of conservation actions.



Peter Bloom Ph.D.

Selected Publications


Doyle, Jacqueline M., T.E. Katzner, G.W. Roemer, J.W. Cain, III, B. Milsap, C. McIntyre, S.A. Sonsthagen, N. Fernandez, M. Wheeler, Z. Bulut, P.H. Bloom, and J.A. DeWoody.  Genetic structure and viability selection in the Golden Eagle (Aquila chrysaetos), a vagile raptor with Holarctic distribution.  Conserv Genet (2016). doi:10.1007/s10592-016-0863-

Clark, W.S., and P.H. Bloom (in press).  Plumages by sex of Adult and Basic III Rough-legged Hawks.  Wilson Journal of Ornithology.

Poessel, S.A., P.H. Bloom, M.A. Braham, T.E. Katzner.  2016.  Age-and season-specific variation in local and long-distance movement behavior of golden eagles.  European Journal of Wildlife Research.  62:377-393.

Singh, N.J., E. Moss, T. Hipkiss, F. Ecke, H. Dettki, P. Sandstrom, P.H. Bloom, J.W. Kidd, S.E. Thomas, B. Hornfeldt.  2016.  Habitat selection by adult Golden Eagles Aquila chrysaetos during the breeding season and implications for wind farm establishment.  Bird Study.   

Thomsen, S.K., C.E. Kroeger, P.H. Bloom, and A.L. Harvey. (in press). Space Use and Home Range Size of Barn Owls on Santa Barbara Island. Monographs of the Western North American Naturalist 7:xx–xx.

Bloom, P.H., J.W. Kidd, and S.E.Thomas, T. Hipkiss, B. Hornfeldt, M. Kuehn, 2015.  Trapping Success Using Carrion with Bow Nets to Capture Adult Golden Eagles in Sweden.  Journal of Raptor Research.

Bloom, P.H., M.D. McCrary, J.M. Scott, J.M. Papp, K.J. Sernka, S.E. Thomas, J.W. Kidd, E.H. Henckel, J.L. Henckel, and M.J. Gibson 2015.  Northward Summer Migration of Red-Tailed Hawks Fledged from Southern Latitudes.  Journal of Raptor Research. 

Moss, E.H.R., T. Hipkiss, E. Frauke, H. Dettki, P. Sandstrom, P.H. Bloom, J.W. Kidd, S.E. Thomas, B. Hornfeldt.  2014.  Home-range Size and Examples of Post-nesting Movements for Adult Golden Eagles (Aquila chrysaetos) in Boreal, Sweden.  Journal of Raptor Research. 48 (2):93-105.

Doyle, J.M., T.E. Katzner, P.H. Bloom, Y. Ji, B.K. Wijayawardena, J.A. DeWoody.  2014.  The Genome Sequence of a Widespread Apex Predator, the Golden Eagle (Aquila chrysaetos).  Plos One. 9 (4):1-11.

Chiang, S.N., P.H. Bloom, A.M. Bartuszevige, and S.E. Thomas. 2012. Home Range and Habitat Use of Cooper's Hawks in Urban and Natural Areas. In C.A. Lepczyk and P.S. Warren (editors). Urban bird ecology 45: 1-16

Bloom, P.H., J.M. Scott, J.M. Papp, S.E. Thomas and J.W. Kidd. 2011. Vagrant Western Red-shouldered Hawks: Origins, Natal Dispersal Patterns, and Survival. The Condor 113: 538-546

Houston, C.S. and P.H. Bloom. 2005. Turkey Vulture Marking History: The Switch From Leg Bands to Patagial Tags. North American Bird Bander 30: 59-64

Clark, W.S. and P.H. Bloom. 2005. Basic II and Basic III Plumages of Rough-legged Hawks. Journal of Field Ornithology 76: 83-89

P.H. Bloom and W.S. Clark. 2001. Molt and Sequence of Plumages of Golden Eagles, and a Technique for In-Hand Ageing. North American Bird Bander 26: 97-116

Collins, C.T. and P.H. Bloom. 2000. The Status of Harlan's Hawk in Southern California. Western Birds 31: 200-202

Goldstein, M.I., P.H. Bloom, J.H. Sarasola, and T.E. Lacher. 1999. Post-migration Weight Gain of Swainson's Hawks in Argentina. Wilson Bulletin 111: 428-432

Tietje W.D., P.H. Bloom, and J.K. Vreeland. 1998. Characteristics of Red-tailed Hawk Nest Sites in Oak Woodlands of Central California. Proceedings of a Symposium on Oak Woodlands: Ecology, Management, and Urban Interface Issues 0: 365-372

Hall, L.S., M.S. Morrison, and P.H. Bloom. 1997. Population Status of the Endangered Hawaiian Hawk.Journal of Raptor Research 31: 11-15

Bloom, P.H. and M.D. McCrary. 1996. The Urban Buteo: Red-shouldered Hawks in Southern California.In: Raptors in Human Landscapes, Adaptations to Built and Cultivated Environments. D.M. Bird, D.E. Varland, and J.J. Negro, eds. Academic Press 0: 31-39

Woodbridge, B., K.K. Finley and P.H. Bloom. 1995. Reproductive Performance, Age Structure and Natal Dispersal of Swainson's Hawks in the Butte Valley, California. Journal of Raptor Research 29: 187-192

Bloom, P.H.. 1994. The Biology and Current Status of the Long-eared Owl in Coastal Southern California. Bulletin of the Southern California Academy of Sciences 93: 1-12

Garrison, B.A. and P.H. Bloom. 1993. Natal Origins and Winter Site Fidelity of Rough-legged Hawks Wintering in California. Journal of Raptor Research 27: 116-118

Bloom, P.H., M.D. McCrary, and M.J. Gibson. 1993. Red-shouldered Hawk Home Range and Habitat use in Southern California. Journal of Wildlife Management 57: 258-265