43 Years of Peregrine Falcon Studies


43 Years of Peregrine Falcon Studies

Earthspan principals conduct long-term studies on migrating peregrines at Assateague Island, MD/VA (autumn since 1970) and Padre Island, TX (autumn and spring since autumn 1977). We have expended more than 50,000 man-hours of survey time in observing over 63,000 peregrines and capturing 14,588. The tundra Peregrine has made a significant recovery and has been removed from the list of endangered species, yet continued monitoring of populations is imperative. Because of the continuity and standard method for data collection these surveys have become an essential tool in that effort.  Our database at Assateague includes sightings of every other raptor we have observed on the Island since 1970. Over 90% of all observations there have been recorded by three experienced individuals, who have also conducted springtime studies at Padre Island. At Padre a more diverse cast of highly qualified individuals has participated.

Our work in these studies with satellite-received telemetry allows us to continue elucidating previously undescribed aspects of the tundra Peregrine’s wintering biology and continental migration and to identify critical habitats. Given available technologies, Assateague and Padre remain ideal laboratories in which to study and address present and future issues of concern to Peregrines, other Neotropical migrants, and humans. In recent years we have studied emerging infectious pathogens such as West Nile Virus and Avian Influenza in partnership with U.S. Government entities, and currently address contaminants through studies related to the 2010 Gulf oil spill.

In 2008 our database allowed us to provide an Expert Declaration on the Draft Environmental Assessment and Management Plan for Take of Migrant Peregrine Falcons in the United States for Use in Falconry. Among other points, we concluded that the standardized average number of migrating Peregrines we observed at Assateague over the preceding 29 years was essentially the same as that seen more than six decades ago (1939-1944), before DDT had serious adverse effects on the reproductive potential of the Peregrine in North America. Our work at Assateague and Padre Islands represents the bulk of tundra Peregrine Falcons banded within the continental United States since the establishment of the Bird Banding Laboratory by the Department of the Interior.  Furthermore, our overall database constitutes the most significant and longest continuous monitoring study on this falcon in the Americas. Long-term studies such as ours are essential to monitoring the stability of wildlife populations, particularly in light of rapid changes that may occur due to contaminants, infectious diseases, habitat loss, climate change and other factors. By the long-term and standardized nature of our studies, we have established levels of observation in stable populations that will quickly raise future concerns if not achieved over a several year period.

The 2013 Assateague survey commenced on 28 September and was suspended on 1 October by loss of access to the study area as a result of the U.S. Government shutdown. Earthspan’s team remained on site, poised to resume operations if Congress resolved the impasse. That did not happen in time to salvage any meaningful 2013 results, as the bulk of migrating falcons were south of Assateague by then. The survey team was able to expend only 28.8 man-hours in the field, recording nine sightings of Peregrines and capturing five different individuals. One of the falcons captured was previously banded. The nine sightings included three observations of individuals previously captured during the survey. We obtained blood samples from Peregrines of all ages and feather samples from immature falcons for collaborative studies. The inability to conduct the standardized survey as in the previous 43 years leaves an irreplaceable gap in our data base, and we hope 2014 will see a return to normal operations. See our report for full details. 2013 Asstateague Report

During the spring 2013 survey period at Padre (11-25 April), we expended 144 hours, 55 minutes in the field, recording 319 sightings and capturing 42 individual peregrines.  Of those captured; 4 (9.52%) were previously banded Padre returns and 38 (90.48%) were first banded during the survey.  The seasonal sighting rate of 22.01 peregrines/10 survey hours is among the highest in recent years.  Adult peregrines comprised 66.67 % of the captured sample.  Not included in the totals above are 11 seasonal recaptures of peregrines, whose minimum average staging time on South Padre Island was 1.81 days.  Durations range from a few hours to 12 days.

In autumn 2013, we surveyed from 26 September to 24 October.  During this period we expended 532 survey hours in the field, recording 1028 peregrine falcon observations and capturing 212 individuals.  Of those captured; 18 (8.49%) were previously banded and 194 (91.51%) were first banded this season.  The seasonal sighting rate of 19.32 birds/10 survey hours was slightly above the 19 year seasonal mean of 18.73 on South Padre only.  Adult composition of migrants was among the highest recorded, including 43.77% of the age determined sightings (n=786) and 36.79% of captured peregrines.  Not included in the above totals, are 74 sightings of color marked falcons and 29 seasonal recaptures.  The minimum average stopover time of recaptures on South Padre was 4.00 days, ranging from a few hours to 12 days. We collected 232 blood samples and 189 feather samples from individual peregrines for collaborative studies of Padre migrants. See our report for full details. 2013 Padre Report