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RESPONDENT
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Brian McCaffery
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SITE NAME
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Old Chevak, Yukon Delta National Wildlife Refuge, 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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Old Chevak Bar-tailed Godwit Breeding Ecology
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Start of survey:
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End
of survey: |
Team
size: |
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26.04
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5.07
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2
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WEATHER
CONDITIONS
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Weather conditions: |
Although spring melt at Old Chevak in 2005 was much later than in either 2003 or 2004, it was still earlier than the 20-year mean. Snow reduced to 50% on flat areas approximately on 1 May. The tundra was > 90% snow-free in the vicinity of the field station by 3 May, and by 15 May, the lowlands were completely free of snow, ice, and melt-water. The Kashunuk River was ice-free by 29 May, 18 days later than in 2004, but not late relative to the long-term mean. Snow flurries occurred on 3 days in the first week of May. Snow fell on 6 days in May, the last being 22 May. A few cm accumulated on the nights of 4-5 May, and 5-6 May; in both cases, fresh snow melted by next afternoon. Additional precipitation (rain and/or drizzle) fell on 7 of 19 days from 13-31 May, and on 10 of 23 days from 8-30 June. No rain fell 1-5 July. Weather during incubation and brood-rearing was generally mild; often warm with light winds. Most days with precipitation involved only occasional showers.
The first mosquito was detected on 28 May, mosquitoes were conspicuous on 30 May, the first major emergence of flying insects (chironomids) was on 2 June (2 weeks later than in 2004), and the first day of major mosquito activity was 8 June (1 week later than in 2004).
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| Date of 50%
snow-cover: |
1.05
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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: |
low
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Breeding conditions:
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As in 2004, small numbers of Long-tailed Jaegers (Stercorarius longicaudus), including pairs, were seen on the study area on a daily basis. Only two pairs nested, and only one definitely completed its clutch (2 eggs); the other nest was depredated one day after being discovered with a single egg on 3 June. During the first three weeks of shorebird laying and early incubation, Arctic Foxes (Alopex lagopus) and Mink (Mustela vison) were seen on 17 and 8 field days, respectively. Up to two Arctic Foxes and up to three Mink were observed simultaneously on the 4 km2 study area. River Otter was rare in the area.
In 2005, we conducted the second year of a study focusing on the breeding ecology of Bar-tailed Godwits on the outer Yukon-Kuskokwim Delta. From 26 April to 5 July, 2-7 people conducted field work on and adjacent to a 4-km2 study area surrounding the Old Chevak field station. The study area is along the Kashunuk River, and is characterized by a diversity of wetlands either embedded in, or surrounding, extensive patches of uplands. Wetlands include tidal sloughs (which make up > 80% of the plot's borders), tidal meadows, freshwater meadows, freshwater marshes, and steep-sided lake basins. The upland tundra was dominated by dwarf shrubs, Carex sedges, lichens, and Sphagnum moss. Nest-searching efforts included focal observations of breeding godwits as well as walking zigzags in sites or habitats suspected of supporting godwit nests.
As in 2004, 12 godwit nests were located on the study area, and an additional 5 nests were located on adjacent tundra. Eight were found during laying, 4 after clutch completion, 2 after depredation events, and the timing of 3 relative to clutch completion was unknown. Final clutch size was determined at 9 nests, with eight 4-egg clutches and one 5-egg clutch. The latter is the third 5-egg clutch on record for this species from the Yukon-Kuskokwim Delta. One egg was markedly different in pattern than the other four, suggesting that it was produced by a second female. Nest initiations ranged from 19 May to 14 June (N = 8), with an average date of 25 May (2 days later than in 2004). At least one egg was collected from 7 nests for contaminants analysis. Following egg collection, adults resumed incubation at > 4 of those nests.
None of the 17 godwit nests hatched. Daily survival rates (DSR) were very low for all classes of nests. DSR during laying and incubation was 0.722 and 0.841, respectively. Overall DSR was 0.797. Based on a comparison of DSR between nests at which we did and did not capture birds (N = 7 and 10, respectively), there was no evidence that capturing, flagging, and outfitting nesting godwits with transmitters affected nest survival rates. This pattern held even when only considering nest histories of impacted birds after the day of capture. In fact, the point estimates for DSR were higher at those nests where we captured adults. Given the absence of a capture effect on DSR, we combined data from our two years to generate an overall DSR for 2004-2005 (N = 22) of 0.815. With an estimated exposure period for successful nests of 27 days, the point estimate for nest success based on this DSR is 0.4%. Comparable data from Black-bellied Plovers at Old Chevak in 2004-2005 (with a DSR of 0.943, estimated exposure period of 29.5 days, and N = 15) yields a nest success estimate of 17.7%. Thus, relative to another large shorebird species with open (i.e., uncovered) nests and aggressive predator-mobbing behaviour, Bar-tailed Godwit nest success at Old Chevak is strikingly low.
Two broods were discovered on or near the main study plot. On 27 June, a pair with 3 chicks (approximately 2 weeks old) was detected in the marsh north of the northwest edge of the plot. This family was not seen subsequently. On 28 June, a pair with a single chick (about 10 days old) was found near the plot's eastern edge. On 29 June, this chick swam across the tidal slough that forms the eastern border of the plot. A reciprocal trip from outside the study area could have preceded our initial detection of this family; thus, we had no conclusive evidence that any nests hatched successfully on our main study plot.
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Rodent dynamics:
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| The last peak in small rodent populations on the Yukon-Kuskokwim Delta occurred in 2000. Since 1984, rodent numbers had peaked every 4 years, so a population high was predicted for 2004, but it did not occur. In 2005, rodents were also rarely seen, except in the immediate vicinity of the field station. After arrived at camp on 26 April 1st vole was seen on 2 May; then seen on 14 dates in May (2-31 May); on 14 dates in June (2-22 June); only once subsequently (3 July) through last day in field (5 July). No capture data.
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Rodent species recorded:
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| Latin | Abundance |
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| Microtus oeconomus | rare |
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Summary
of fauna studies: |
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