44 Years of Peregrine Falcon Studies


44 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 14,724. 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 45th annual study at Assateague was conducted on the northern (MD) portion of the island. Observations and captures by unit effort were the 2nd and 3rd highest, respectively for this long-term study. Between 26 September and 18 October the survey team expended 219 man-hours in the field, recording 480 sightings of Peregrines and capturing 136 different individuals. Five of the falcons captured were previously banded. The 480 sightings included 158 observations and seven recaptures of individuals previously captured during the survey. We also obtained 133 blood samples from Peregrines of all ages and 115 feather samples from immature falcons for collaborative studies.  See our report for full details. 2014 Assateague Report

During the 2014 spring survey period at South Padre Island (SPI) from 8-26 April, we expended 196 survey hours in the field, recording 549 sightings and capturing 51 individual Peregrines.  Of those captured; 9 (17.65 %) were previously banded Padre returns and 42 (82.35 %) were first banded during the survey.  After second year (ASY) Peregrines comprised 80.39 % of the captured sample.  The seasonal sighting rate of 28.01 peregrines/10 survey hours is the highest recorded during the spring season, significantly higher than the 20 year SPI mean of 18.28 (±4.66).  Not included in the totals above are 10 seasonal recaptures of Peregrines, whose minimum average staging time on SPI is 2.00 days.  Durations range from a few hours to 7 days.

In autumn 2014, we surveyed SPI from 1 to 24 October, expending 358 survey hours in the field, recording 585 Peregrine observations and capturing 114 individuals.  Of those captured; 3 (2.63 %) were previously banded and 111 (97.37%) were first banded this season.  Previously banded captured include 1 foreign banded falcon and two Padre returns. The seasonal sighting rate of 16.34 birds/10 survey hours is below, yet consistent with our 21 year mean of 18.65 (+ 4.18) on SPI only.  Adults comprised 29.47 % of the age determined sightings (n=492) and 14.04 % of captured Peregrines. Not included in the above totals, we recorded 38 sightings of Peregrines color marked this season and recaptured 8.  The minimum average stopover duration of recaptures on SPI was 3.00 days, ranging from a few hours to 7 days. See our report for full details. 2014 Padre Report