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Based on Travis Booms’ thesis research, we
investigated gyrfalcon (Falco rusticolus) food habits in Central West
Greenland near Kangerlussuaq, Greenland in 2000 and 2001. Our research was
funded primarily by The National Science Foundation, The Peregrine Fund, Inc.,
and the Boise State University Raptor Research Center. We were assisted by many
persons but especially in the field collecting data: Ryan Blaedow, Gregg Doney,
Catherine Wightman, Jim Mussell, Kurt Burnham, Bill Burnham, Alberto Palleroni,
and Ron Vander Velden. We thank Bent
Brodersen, Robin Abbot, Tom Quinn, Diana Garcia-Novick, Ed Stockard,
Kangerlussuaq International Science Support, and VECO Polar Resources for
invaluable logistics support. Dotty
Douglas, Bill Mattox, and Bob Rosenfield provided very helpful reviews and
comments in preparing manuscripts.
We used three sources of data: time-lapse video (3 nests), prey remains (22 nests), and regurgitated pellets (19 nests) to study food habits. These sources provided different information describing the diet during the nesting period. Gyrfalcons relied heavily on rock ptarmigan (Lagopus mutus) and arctic hares (Lepus arcticus). Combined, these species contributed 79–91% of the total diet, depending on the data used. Passerines were the third most important group. Prey less common in the diet included waterfowl, arctic fox pups (Alopex lagopus), shorebirds, gulls, alcids, and falcons. All rock ptarmigan were adults, and all but one arctic hare were young of the year. Most passerines were fledglings. We observed two diet shifts, first from a preponderance of ptarmigan to hares in mid-June, and second to passerines in late June. The video-monitored gyrfalcons consumed 94–110 kg of food per nest during the nestling period, higher than previously estimated. Using a combination of video, prey remains, and pellets was important to accurately document gyrfalcon diet, and we strongly recommend using time-lapse video in future diet studies to identify biases in prey remains and pellet data. For details see:
Booms, T.L., and M.R. Fuller. 2003. Gyrfalcon diet in central West Greenland during the nesting period. Condor 105:528-537 [Full Text]
From
the time-lapse video cameras installed at three nests, we recorded 2677.25 hours
of nestling video. Ptarmigan delivered to
nests were usually plucked prior to delivery and included the breast and
superior thoracic vertebrae. Arctic hare
leverets were rarely plucked and often delivered in parts.
The most commonly delivered leveret part was the hind legs attached to
the lower back. Passerines were rarely
plucked and usually delivered whole. After
feeding, adults removed 20.9% of prey items including those with and without
obvious muscle still attached. Prey
delivery rates were similar among nests and increased as nestlings aged.
Prey delivery frequency peaked in the morning and evening, with a
distinct lull in the late evening and early morning hours.
Male and female adults delivered a similar number of prey, though males
typically delivered smaller prey than females. Gyrfalcons
cached and re-delivered at least 9.1% of all items delivered and cached some
items multiple times. For details see:
Booms,
T.L., and M.R. Fuller. 2003b. Gyrfalcon feeding behavior during the nestling
period in central West Greenland. Arctic 56:341-348.
We
used solar-powered time-lapse video photography to document food deliveries and
feeding behavior at the nest. The
2,677.25 h of videotape from three nests, represented 94, 87, and 49% of
the nestling period at each nest. The
video recorded 921 deliveries of 832 prey items.
We placed 95% of the items into prey categories.
The image quality was good but did not reveal enough detail to identify
most passerines to species. We found no
evidence that gyrfalcons were negatively affected by the video system after the
initial camera set-up. The video system
experienced some mechanical problems but proved reliable.
The system likely can be used to effectively document the food habits and
nesting behavior of other birds, especially those delivering large prey to a
nest or other frequently used site. For
details, see:
Questions and comments regarding the Raptor Research Center: mark_fuller@usgs.gov
Questions and comments regarding this website:
kbledsoe@boisestate.edu
This page was last reviewed on 20 March 2007.