ARCTIC PROGRAM UPDATE – June 2005, Kangerlussuaq/ Søndre Strømfjord, West Central Greenland
— 1 July 2005
— in Arctic Program - Greenland
For your possible interest, last week Kurt Burnham and I completed a survey of all known Gyrfalcon nest sites in the Kangerlussuaq/Søndre Strømfjord, west-central Greenland study area. All 74 sites visited were nesting locations found to have been occupied by breeding Gyrfalcons one or more times since 1972. Some are on cliffs with raven nests, possibly used by Gyrs for only a single season, while other nest sites probably have been used for hundreds of years (one site at least 2,500 years) and have thick fecal buildup. This year we found only nine (12%) of the 74 locations to be occupied. Geographically, this is quite a large area and a helicopter must be used. At occupied locations we climbed into the eyries, banded nestlings, and collected DNA samples (feathers and blood) and data related to the nest site. While surveying known sites we also visited other suitable-appearing cliffs along the way but found no additional Gyrfalcons. This is the first time we surveyed 100% of the known Gyrfalcon nest sites. The previous six years we surveyed between 50 to 88% of the known locations, finding between 18 (26%) and 6 (13%) annually occupied. In any given year, the largest number of occupied sites ever known since 1972 was in 1991 when 22 (31%) of the sites checked had Gyrfalcons present.
Nest sites used for hundreds of years
What does this mean? It is difficult to know for certain as Gyrfalcon populations elsewhere in the world are shown to fluctuate somewhat based on prey availability, and in particular ptarmigan populations. In the early spring when Gyrfalcons arrive at breeding sites, having ptarmigan (and in some areas lemming and other small mammals) available may determine whether they even attempt to breed. Lemming or other small mammals do not exist along the entire west coast of Greenland. At the nine 2005 Gyrfalcon nesting locations, at only one was there what could probably be considered an abundance of prey remains in and/or below the eyrie. At that site there were four robust, approximately 35-day-old young and a minimum of 55 different ptarmigan breast bones on the nest ledge, plus the remains from three ducks. Much of the prey remains, although picked clean of most meat, were not consumed to the degree found at the other eight eyries. At the other sites the prey remains were more limited and even the bones were almost totally eaten. For whatever reason (possibly an exceptionally good adult male hunter and provider), the one pair/eyrie appeared to have an abundance of prey while the other pairs/eyries were having difficulty finding enough food to raise their young.
Although it cannot yet be proven, it seems likely that the Gyrfalcon population in this part of Greenland has declined. Why? The influence of a greatly expanded Peregrine Falcon population on ptarmigan may be a factor, as could be climate change. Only through continued investigation will we be able to answer these questions. In mid-July we will begin the work in northwest Greenland where Peregrines are also increasing and Gyrfalcon density is low.
Other items of possible interest—the female Gyrfalcon that appears on our webpage and 2004 fall/winter newsletter is at her eyrie again this summer and with what we believe is the same mate. They have three young that we banded. Also, we captured a female Peregrine that was banded and had a backpack satellite-monitored transmitter (PTT) attached in 2003. She was incubating four eggs and in good health when we caught her and removed the PTT.
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