| Rodents abundance evaluation: |
low
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Breeding conditions:
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Arctic Fox numbers were low to average across the island. Density on the study plot was average - 0.29 fox/sq.km. Apart from breeding animals (62%) the plot was inhabited by territorial singles (23%) and non-territorial juveniles (15%, n=13). Five broods were found in 12 dens in the sutdy plot and its vicinity, while den occupation generally on the island was 32% (n=50), which is considerably lower than in 2003. Mean brood size did not differ between areas of the island, and was 5.5 (n=12, range 3-8) which is close to 2003 value.
Pomarine Skuas were not observed on the island with the exception of 2 breeding pairs found by V.V. Baranyuk in the lower reaches of the Neizvestnaya River. Long-tailed Skuas had low to average numbers and highly uneven distribution with density varying by a factor of 10 across the island. Most birds bred, but nest success was very low due to heavy predation and low lemming numbers. Only 4 broods with flying juveniles were observed in August. Nest density was 0.33 nest/sq.km on the study plot, which is close to 2003 value. Two from 14 nests were successful and chicks fledged by 10.08. Long-tailed Skuas started gathering in flocks on 18.07, and began to leave territories by the end of July.
Numbers of Snowy Owls were very low, and they occurred at a density 0.23 bird/km (n=253 km). Proportion of females was record low in 2004: 1:2.5 on the study plot and 1:2.76 elswhere on the island. All females bred, while 70% of males hold territories, but failed to find mates. Density of Snowy Owls and their nests on the study plot was 0.30 bird/sq. km and 0.07 nest/sq. km, respectively, which is record low for the periods of observations from 1990-1995 and from 1998-2004. Nesting density was also low elsewhere on the island, and average distance to closest nests was 3.17 km (n=9) in the valley of the Neizvestnaya River. From 14 nests with known fate 3 were deserted, 2 failed, while 1-3 chicks survived to fledging in 9 nests. One of the deserted nests was situated on the slope inhabited by large flock of reindeers and 3 wolverines, and another was very late. Mean size of clutch was 5.25 (n=8), and did not differ between areas. Chicks hatched from 52% of eggs (n=42), and 19% of chicks survived to fledging. Low reproductive performance was in all known cases associated with the deficiency of food.
Combined density of rodent-specialists was 0.59 animal/sq. km. Proportion of birds in diet of breeding Snowy Owls was 28.8% (n=52), including Snow Goose (1.9%), Common Eider (7.7%), Brent Goose (1.9%), wader chicks (5.8%) and Long-tailed Skuas (7.7%). This portion of alternative to lemmings prey indicates pronounced deficiency of rodents. Accordingly predation pressure on birds was significant despite low density of predators.
Approximately 300 nests of Snowy Geese were found in 11 colonies associated with 12 nests of Snowy Owls. One colony was destroyed almost completely by grazing musk-ox male, and at least 30 nests were destroyed by skuas and Glaucous Gulls. Actic Foxes, 5 Glaucous Gulls and 2 Arctic Skuas destroyed less than 25% of nests in two colonies, although nests of owls had already been deserted. Remains of a Snowy Goose were found near single owl nest which indicates considerably lowere level of predation of owls on geese than in 2003. Mean clutch size of geese was 4.83 (n=29, range 2-9), while nest success was approximately 61% (n=201). Breeding conditions for geese near nests of Snowy Owls were poor in 2004 due to low numbers of owl females and low numbers of lemmings.
Common Eider nests (n=108) were found in the vicinity of 5 from 12 nests of Snowy Owls, while only 3 eider nests were found isolated. Mean clutch size was 5.72 (n=65, range 2-11), while three found broods contained 5, 3 and 3 chicks. Nest success was 2.7 % (n=111), and 3.7 % (n=108) of females were captured by Snowy Owls. Large eider colony of at least 100 nests was established in traditional area near the Neizvestnaya River. This area was protected by a territorial owl male from Arctic Foxes and Glaucous Gulls, and predation on nests in the colony was not recorded until start of hatching. However, owl nest was deserted after the storm just before 10.07 on the first day of hatching of chicks in eiders. All but one eider nests in the colony were destroyed then during one day by a male Arctic Fox, 6 Glaucous Gulls and 2 Arctic Skuas. All three females of eiders were killed by owls near one of the owl nests, while owls from another nest failed to catch a single eider female which nest survived to hatching. Weather conditions were favourable for nesting of Common Ediers and extremely low nest succuss was due to low lemming numbers.
A female Brent Goose nesting 30-40 m from a nest of Snowy Owl was captured by owl female in the period of adverse weather from 7-8.07, while another Brent Goose nest (1.5 m from owl nest) was apparently successful, with at least 4 chicks hatching, based on egg-shell remains in the nest.
Grey Plovers (4 pairs), Turnstones (6 pairs), Red Knots (2 pairs), Dunlins (3 pairs), Pectoral Sandpipers (1 pair) and Redpolls (3 birds and 1 pair) were observed on a transect 3 km long in the study plot vicinity. Numbers of Pectoral Sandpipers and Dunlins increased compared with 2003. A nest of Redpolls was predated by Arctic Fox, but at least two broods were seen in the filed camp vicinity in August. Wader broods were rarely seen in August, which indicates low reproductive success.
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