| Rodents abundance evaluation: |
low
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Breeding conditions:
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Despite conditions being over 2 weeks later than in 2004, however, shorebird migration was the earliest in a quarter century of record-keeping. Fourteen species regularly occur here during spring migration, 9 common local breeders, 2 species that are primarily migrants (with low numbers of local breeders), and 3 that are exclusively migrants. Among those 14 species in 2005, 6 set or tied the previous early arrival record, and 4 others arrived on the second-earliest dates yet recorded in this region. Prior to 2005, 2004 was the earliest year for shorebird arrival. 2005 arrival dates for 5 species were earlier than in 2004, and 6 other species arrived on the same date in both years. Among the 11 locally-breeding species, arrival dates preceded the long-term mean by 4-12 days, and averaged a week earlier than the species-specific long-term means. By the time all 9 commonly-breeding species had arrived (2 May), upland areas had 30-40% snow-cover, and lowland meadows were > 80% snow-covered.
Shorebird clutch initiations at KFS were not well correlated with the remarkably early arrival dates. In 2004, the earliest Rock Sandpiper nest was initiated on 4 May (11 days after arrival), and five of nine nests on the study plot in were initiated on or before 11 May. In contrast, in 2005, the earliest Rock Sandpiper clutch was not initiated until 14 May (17 days after arrival). In 2004 and 2005, both Western Sandpipers and Dunlin arrived on 30 April. In 2004, the first Western Sandpiper nest was initiated on 11 May, and > 10 nests had been initiated prior to 15 May. In 2005, the earliest nest was not initiated until15 May, which is only about 1 day earlier than the mean initiation date over the preceding 7 years. Similarly, the first Dunlin nest was initiated on 12 May in 2004, but not until 15 May in 2005. In both 2004 and 2005, the first Red-necked Phalarope clutches were initiated late in the third week of May. The earliest nest in 2005 was found with 5 eggs on 27 May, and hatched on 8-9 June. We do not know if all 5 eggs were produced by a single female.
In 2005, the combined frequency of all mammalian predator observations (i.e., Arctic Fox, Red Fox, and Mink) was the highest during the study. In fact, mink observations alone exceeded the highest previous total for the three major mammalian predators. During 3 months of study at KFS, Arctic Fox, Red Fox, and Mink were observed on 17, 6, and 61 days, respectively. As in past years, however, there was no correlation between the frequency of predator observations and wader nest success. Despite high numbers of predator observations in 2005, Western Sandpiper nest success was near the long-term average, and the point estimates of nest success for both Western Sandpipers and Dunlin were higher than in 2004.
Western Sandpiper Study. Basic methodologies (1998-2005) included two observers surveying a 36 ha study plot daily from early May through late July for banded birds, nests, and broods. Adults and chicks were banded with unique color combinations at the nest, and the location and behavior of banded birds was recorded daily. The locations of discovered nests were mapped and nests were monitored through hatch, predation, or abandonment. After hatch, Western Sandpiper parent(s) and broods were resighted (brood location mapped, parent and chick behaviors recorded) once (1998-2002) or twice (2003-2005) daily through fledging, predation, or abandonment.
In 2005, we located and monitored a total of 94 nests, 81 of which were on the 36 ha plot. Seventy-one nests were initial nesting attempts, and for four nests we were unable to determine whether this represented an initial nesting attempt because neither attending adult was banded. Nineteen males and 13 females attempted reproduction after losing their first clutch (i.e., re-nested) in 2005, and one pair attempted reproduction a third time after losing their second clutch of the season. Following initial clutch loss, 32% of renesting males paired with a new mate, whereas all renesting females retained their mate during secondary nesting attempts. Based on initial nesting attempts, the apparent density of Western Sandpipers on the study plot in 2005 was 1.8 pair/ha.
We regularly monitored 85 nests to estimate reproductive success in the area. Apparent nest success (i.e., percent of known nests successfully hatching >1 chick) among first nests in 2005 was 28% (Mayfield nest success = 0.29 [95% CI = 0.25-0.35, n = 67]), and pairs at 52% of successful nests fledged at least one chick. Mayfield nest success for all nests, including renesting attempts, was 0.31 (95% CI = 0.27-0.36, n = 85), which was similar to the preceding seven years (1998-2004, mean ñ SE Mayfield nest success all nesting attempts = 30.6 ñ 3.3). Readers should note that these figures are not directly comparable to past results for this site reported in previous issues of "Arctic Birds", which summarized nest success data only for a core 16-ha plot.
Rock Sandpiper study. During 2005, we resighted 11 of 17 Rock Sandpipers that were previously banded at our study site (1999-2000, n = 4; 2003-2004, n = 13). We banded three additional pairs of Rock Sandpipers in 2005. A female that we banded at her nest in 2003 was resighted in Prince William Sound on 13 April 2005. We subsequently detected this bird on our study plot on 12 May 2005. We discovered her partially consumed body on the plot the next day. In past years, this bird attempted reproduction four times with the same mate. She successfully fledged young from her second nesting attempt in 2003, but failed to hatch any offspring during two attempts in 2004.
During 2005, we located and monitored 11 nests and one additional brood from 10 pairs in a 48 ha area in and around KFS (0.21 pair/ha). Two pairs re-nested after initial clutch loss. One of the 11 nests successfully hatched young (second nesting attempt), and another nest was of unknown fate. We observed a mink (Mustela vison) depredating one of the 9 nests known to have failed.
Dunlin study. This was the second field season of a Ph.D. project examining parental investment in Pacific Dunlin. Every 1-2 days we surveyed 58 hectares of wet meadow habitat for breeding Dunlin. Nests were found by territory mapping and behavioural observations. Once a nest was found we identified the parents and if not banded, they were trapped and individually colour-banded. Twenty-seven territorial males were banded in 2004, and 21were detected back in the study area in 2005. Nests were visited, at a minimum, every 3 days to determine whether they were still active. Once hatched, broods were banded and located daily to determine parental roles and desertion dates.
We found 57 Dunlin nests on 38 territories - 33 of these nests were first attempts, 21 were first renests, and 3 were second renest attempts. Nest completion dates ranged from 18 May to 1 July. The overall Mayfield estimate for nesting success was 46.7% and for fledging success was 41.1% (proportion of hatched nests that fledged at least one chick). We suspected, but could not confirm, that mink were the primary nest predator, while the primary chick predators were apparently Sandhill Cranes. Eight birds produced a second clutch after hatching their first clutch. One pair and a divorced, re-mated male initiated second clutches after failing to fledge their first brood, and five other birds produced and/or tended clutches after leaving their first brood in the care of the other parent.
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