Population biology and migration patterns of North American Peregrine Falcons (Falco peregrinus)


 

The Peregrine Falcon (Falco peregrinus) was extirpated in eastern North America by 1970; however, the population has experienced a substantial recovery over the past two decades due to intensive captive-breeding and release efforts (1).  Much of this population growth has occurred in cities (2).  Despite the increase in numbers, the Peregrine Falcon remains classified as threatened or endangered in many regions, in part due to unanswered questions regarding population dynamics and migratory habits.  The overall objectives of this study are to document the dispersal and migration of Peregrine Falcons in North America, and to evaluate the growth of the eastern population from the perspective of conservation and management implications. 

 

Satellite telemetry has previously been used to document the movements of Peregrine Falcons from western North America and the Arctic (3,4,5).  In the present study, satellite transmitters have been deployed on 27 individuals from Alberta, Ontario, Quebec, New York, and Pennsylvania.  Each bird was classified as being captive-raised or wild, and as urban or rural.  There was considerable variation in the timing of dispersal and distance of travel in all categories.  Overall no significant differences were observed between urban and rural Peregrine Falcons.  Within the urban population, captive-raised juveniles dispersed later and migrated significantly further than their wild counterparts.  Most migrants showed little preference for specific habitats while heading south, but almost all settled in coastal areas for the winter.  Blood and/or tissue samples will be analyzed to evaluate whether migratory behaviour in Peregrine Falcons is linked to their genetic background.  Also underway is a thorough survey of the eastern Peregrine Falcon population, targeting data on productivity, mortality, and nest site characteristics.  In combination with similar efforts in the Midwest (6), this will permit analysis of the interchange between urban and cliff-nesting populations, as well as rates of productivity and mortality within each.  The results of this research are expected to assist with identifying conservation priorities and generating recommendations for future population monitoring.

 

Marcel Gahbauer

Literature cited:

 

1.     Enderson, J.H., W. Heinrich, L. Kiff and C.M. White.  1995.  Population changes in North American

                       peregrines.  Trans. No. Am. Wildl. & Natur. Resour. Conf. 60: 142-161.

2.     Cade, T.J. and D.M. Bird.  1990.  Peregrine Falcons, Falco peregrinus, nesting in an urban environment:

                       a review.  Can. Field-Nat. 104: 209-218.

3.     Fuller, M.R., W.S. Seegar and L.S. Schueck.  1998.  Routes and travel rates of migrating Peregrine

                      Falcons Falco peregrinus and Swainson’s Hawks Buteo swainsoni in the western hemisphere. 

                      J. Avian Biol. 29: 433-440.

4.     Britten, M.W. , P.L. Kennedy and S. Ambrose.  1999.  Performance and accuracy evaluation of small

                      satellite transmitters.  J. Wildl. Manage.  63: 1349-1358

5.     McGrady, M.J., T.L. Maechtle, J.J. Vargas, W.S. Seegar and M.C.P. Pena.  2002.  Migration and ranging

                      of Peregrine Falcons wintering on the Gulf of Mexico Coast, Tamaulipas, Mexico.  Condor 104:

                      39-48

6.     Tordoff, H.B., M.S. Martell and J.S. Castrale.  2002.  Midwest Peregrine Falcon Restoration, 2002

                      Report.  The Raptor Center, University of Minnesota, St. Paul MN.

 

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