Observations of peregrine falcon (Falco peregrinus) migration at the Kekoldi watchsite, Costa Rica

Tilden, Julie
Jon Atwood, PhD
Department of Environmental Studies
Observers at the Kekoldi watchsite, in the Caribbean lowlands of Costa Rica, monitor the highest concentration of autumn, southbound migrant Peregrine Falcons (Falco peregrinus) in the world. Currently little data exist on the migratory behavior of this species in the tropics. During daily observations from 15 August-30 Nov 2005, I counted 2,344 peregrines as they passed within sight of the Kekoldi Reserve. The majority of observations (91%) occurred from 1-21 Oct. Most aged birds were adults. Of the juveniles counted, the most were seen later in the season. Peregrines relied primarily on circle soaring and passed predominantly during midday hours, coinciding with the peak of thermal activity. Flapping occurred most frequently early in the day, decreased through midday, and then increased slightly in the afternoon. The general daily flight path shifted from the coast to inland as wind direction shifted from south to northeast. Flight altitude was greatest during midday. Overall, peregrine movements reflected local weather patterns, and appeared to emphasize flight behavior that maximized efficiency. This preliminary study shows Kekoldi to be a valuable site for long-term monitoring of Peregrine Falcons, and provides a better understanding of how the species behaves as it migrates through the tropics.