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RESPONDENT
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Brian McCaffery
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SITE NAME
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Kanaryarmiut Field Station, Yukon Delta National Wildlife Refuge, Alaska, USA
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| Contact details
(phone/fax//e-mail//address): |
| 907-543-1014/907-543-4413(f) // brian_mccaffery@fws.gov // U.S. Fish and Wildlife Service, Yukon Delta National Wildlife Refuge, P.O. Box 346, Bethel, AK, 99559, USA
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PROJECT DETAILS |
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Project name:
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Western Sandpiper (Calidris mauri) demography on the central Yukon-Kuskokwim Delta
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Start of survey:
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End
of survey: |
Team
size: |
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1.05
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14.09
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2
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WEATHER
CONDITIONS
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| Date of ice-break on
rivers: |
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| Date of final loss of
snow: |
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BIOTIC
CONDITIONS
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| Rodents abundance evaluation: |
high
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Breeding conditions:
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Abundant rodents supported atypically high local nesting densities of Short-eared Owls on the central Delta. The southern Delta supported unusually high numbers of Snowy Owls in late summer and early fall. By the fourth week of August, up to 220 Snowy Owls were estimated in a study area of 2,444 sq.km. Despite the presence of aerial surveys and ornithological field camps on the Delta for more than three decades, similar concentrations of Snowy Owls have not been previously reported by ornithologists on the Delta over that interval. Red and Arctic Foxes are both uncommon in the area, but skuas and mink are fairly common.
We studied the breeding ecology of the Western Sandpiper from 1998 through 2000 at a permanent field site. The density of nesting pairs in 1999 and 2000 was 2.95/ha. and 3.01/ha., respectively, among the highest densities recorded for this species. Mayfield nest success on a 16 ha. plot from 1998 to 2000 was 0.56, 0.24 and 0.35, respectively. Fledging success, defined as a nest fledging one or more young, was 75% (12 of 16 hatched nests) in 1999 and 68% (19 of 28 hatched nests) in 2000. Chicks were observed to fledge as soon as day 13, but often required up to 18 days to achieve sustained flight. Among 12 and 19 broods observed in 1999 and 2000, respectively, males tended broods a mean of 11.75 days and 13.2 days after hatch, while mean female attendance was 8 and 6.4 days in those two years. Males and females did not differ significantly in the length of attendance in 1999, but males remained with broods significantly longer than females in 2000. Males demonstrated significant seasonal declines in duration of attendance in both years, while females exhibited significant seasonal declines only in 2000. Finally, survival estimates based on resightings of banded adults were extremely low for females relative to males at our study site, as well as to breeding female survival estimates from other studies. Of 21 females banded in 1998, only 5 (23.8%) were resighted in 1999, only 1 (4.7%) of which was subsequently resighted again in 2000. Of 31 males banded in 1998, 23 (74.2%) were resighted in 1999, and 20 (64.5%) were again resighted in 2000. Despite finding a combined 99 nests on an additional 35 ha. area surrounding our core study plot in 1999 and 2000, we observed no additional banded females. Further, females who bred successfully in 1998 were less likely to be resighted in both 1999 and 2000 than unsuccessful females. We therefore suspect that the low survival estimate is primarily the result of mortality rather than emigration.
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Rodent dynamics:
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| On the Yukon-Kuskokwim Delta, arvicoline rodent numbers (particularly Tundra Voles) have peaked every 4 years since 1984. Although widespread, these highs are often somewhat patchy due to local variation in storm tides, amount of winter snowfall, and patterns of mid-winter melting, thawing and re-freezing. This environmental variation results in geographic variation in the amplitude of the Delta's rodent highs. The year 2000 was no exception. For the first time in many years, rodent numbers in the coastal zone of the Delta were quite high, probably a function of the absence of storm tides in both fall 1999 and spring 2000.
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Rodent species recorded:
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| Latin | Abundance |
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| Microtus oeconomus | abundant |
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Summary
of fauna studies: |
| Overall project objectives include documenting population trends and determining the factors on the breeding grounds which contribute to variation in the population growth rate, including: 1) seasonal variation in reproductive output, 2) age-related variation in reproductive output, and 3) variation in brood survival as a function of variation in parental attendance.
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