2005 Autumn Capture and Release of Gyrfalcons in East Greenland
— 15 November 2005
— in Arctic Program - Greenland
The Peregrine Fund biologists Bill Heinrich, Cal Sandfort, and Jim Willmarth departed the United States arriving in East Greenland in early September 2005. The immediate objective of the trip was to capture, measure, collect blood/DNA, and band as many falcons as possible. The secondary and longer term objective was to determine if we can monitor the conservation status and population numbers and fluctuations of Gyrfalcons in northeast Greenland through annual and eventually periodic capture of autumn migrants. Since the Gyrfalcons depend importantly on numbers of ptarmigan and lemming as prey in northeast Greenland, both of which fluctuate over years, the Gyrfalcon population most probably responds likewise. To achieve this objective we must be able to capture sufficient numbers of falcons to detect trends and allow for comparisons over time, not only of total numbers of birds captured but between ratios of immature to adults caught, and even sexes. For example, changes in the juvenile to adult ratio can be an indicator of reproduction (more adults to juveniles suggests lower reproduction). The effect of near and long term weather/climate can also be examined.
The location where the capture/trapping occurred was Kap Tobin/Uunarteq, a seasonally (autumn and winter) deserted village about 7.5 km from Scoresbysund/Illoqqortoormiut, the primary village in central and north Greenland (~600 people). In 1928 about 250 Gyrfalcons were shot for museum collections in this area during the autumn and lesser numbers in other years. In 2004 we accomplished the first capture and release effort in this area, establishing trapping stations both at Kap Tobin and Constable Point, the latter being an airstrip and buildings mostly constructed by ARCO while exploring for oil in the area. We captured a total of 38 different Gyrfalcons at these two sites in 2004.
Adult Gyrfalcon in net.
This year our biologists attempted to capture falcons for a total of 379.5 hours from 11 September through 17 October at Kap Tobin. They caught and released 87 Gyrfalcons and one immature female Peregrine Falcon, one new falcon caught for every 4.3 hours of trapping. This does not count the many falcons that were captured multiple times. Of the Gyrfalcons, 81 were 2005 hatch-year birds. Their best day they caught 11 different Gyrfalcons. The plumage of all but two of the Gyrfalcons was white. When the biologists departed Kap Tobin, Gyrfalcons were still moving through the area. Hopefully next year we can have a team there to capture falcons through mid-November.
What do these results mean? First, it does appear we can capture a sufficiently large number of Gyrfalcons to monitor for population trends over time. It also appears there remains a fairly large breeding population of Gyrfalcons in northeast Greenland. There were questions whether that was the case. Questions remaining or raised, however, are why we did not capture more adults, how many of these young were siblings, the number of wild nests/pairs represented, and much more. Through use of genetic analysis of the blood taken we can look at relatedness between the falcons, including which ones are siblings, and how many pairs/nest sites are represented. More difficult to determine is why we did not capture more adults. Possibly they migrated later in the season after we departed.
Cal Sandfort and gray Gyrfalcon
Beyond the capture and collection of considerable information about Gyrfalcons, also significant is the capture of a Peregrine Falcon. This was a first as Peregrines have never been known to breed in this part of Greenland. As with the species in West Greenland, it appears to be extending its range to the north.
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