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RESPONDENT
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Irina Menyushina
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SITE NAME
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Neizvestnaya River upper reaches, Wrangel Island, Russia
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| Contact details
(phone/fax//e-mail//address): |
| (495)687-06-57 // v.n.ira@mail.ru // Prospect Mira, 103-109, Moscow, 129085, Russia
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PROJECT DETAILS |
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Start of survey:
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End
of survey: |
Team
size: |
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28.04
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15.09
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WEATHER
CONDITIONS
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Weather conditions: |
| The breeding conditions were unfavourable for birds in 2008. The summer was very cold and wet. Frequent rains and snowfalls were accompanied in June and July by strong wind and air temperatures below freezing. The start of breeding by birds was interrupted on 2-5 June by a heavy snowstorm with wind reaching 10-25 m/s and air temperatures dropping to -10°Ñ. Southerly winds resulted in icing of all surfaces during the last 2 days of this period. The next rapid drop of temperatures occurred from 24 to 29 June. Some snow banks in the Neizvestnaya River valley and in the Central Mountains did not melt until 10 September due to the cold summer.
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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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Numbers of Arctic Foxes were low everywhere on the island in 2008. Counts of snow tracks in spring indicated that most animals had left the island in winter, and then returned to breeding territories in the second half of May. This was probably caused by low lemming abundance and low availability of prey due to the icing. The density of Arctic Foxes was 0.1 pairs/km2 in the monitoring area of 45 km2. Only half of the pairs in this area bred, and many of them did not use dens (presumably, due to predation pressure by Wolves and Wolverines), which made the assessment of pair status and litter size difficult. Mean litter size was 5.6 young.
Death of Arctic Foxes after attacks by Wolves and Wolverines became more common. Numbers of Wolverines increased on the island, but their impact on tundra birds (with the exception of Snowy Owls) is difficult to evaluate. We found 2 downy chicks of Grey Plovers near a den of Wolves in the Gusinaya River valley. Based on the damage to the chick's bodies we concluded that Wolves had crushed the chicks with their paws but had not eaten them.
Numbers of Snowy Owls were extremely low, and considerably fewer birds than usual arrived to the island by the start of the breeding season. The distribution of owls across the island was typical, and optimal territories in the Northern Mountains and in the Gusinaya River valley were occupied first. The maximum density of owls in the monitoring area of the upper Neizvestnaya River was 0.4 birds/km2, below average. Non-breeding owls arrived later, and were relatively evenly distributed across the island, usually having no permanent territories. Many breeding pairs failed in the very beginning of the season, and the proportion of breeding pairs was determined only for the upper Neizvestnaya River monitoring area. Nesting density (0.2 nests/km2) was below the long-term average there, and was even lower elsewhere on the island.
In total there were 33 breeding records of owls in 2008. Clutch size varied from 3-9 eggs, with the mean 6.2 eggs (n=15). Breeding success was extremely low in Snowy Owls due to adverse weather conditions and low food supply. Approximately 25% of nests were deserted by Snowy Owls during the snowstorm in early June. Brood size after fledging was a maximum of 2 chicks at the end of summer. Lemmings were the main diet of breeding owls (85%): other prey items included Snow Goose, Common Eider, Eider eggs, chicks of Long-tailed Skuas and Snow Buntings, and waders.
Pomarine Skuas arrived to the study area on 28 May, and departed from inland parts of the island on 20 June, making no breeding attempts. On the upper Neizvestnaya River monitoring area (45 km2) the maximum density of Pomarine Skuas was recorded at the end of the first one third of June, when it was still low, 0.4 birds/km2. The proportion of dark birds was 12.5%.
Long-tailed Skuas arrived to the study area on 28 May and started breeding on 16 June. Average density was 0.3 nests/km2 on the upper Neizvestnaya River monitoring area. The abundance of breeding Long-tailed Skuas was average in all areas of the island where counts were conducted, with the exception of the Northern Plain. Breeding success was extremely low, as most clutches were destroyed or failed due to weather conditions. A single chick of Long-tailed Skuas was found among prey items of Snowy Owls. Long-tailed Skuas started to leave breeding territories in late July, with a few families with young remaining. Most adult skuas left the island by mid August, and we recorded only 5 families with fledglings during counts in different parts of the island in the second half of August.
Numbers of waders were lower than usual in the inland parts of the island due to the mass departure of birds during the snowstorm in early June and mortality in some of the remaining waders and passerines. Bodies of 3 Turnstones, 3 Snow Buntings and 2 Redpolls were found in the vicinity of two research stations in the Neizvestnaya River valley.
The number of nests of Common Eiders halved compared with 2007 (52 vs.102). Their clutches contained 3-6 eggs, with a mean of 4.3 eggs (n=12). The proportion of successful nests was 79% for females nesting in the vicinity of Snowy Owl nests (n=47); nest success was not known for eiders not associated with owls. Owls captured 12.8% of incubating eider females (n=47). Numbers of Snowy Geese were unusually low during the nesting period outside of the main colony. Most geese gave up breeding due to adverse weather conditions and the scarcity of nesting Snowy Owls.
Breeding success was extremely low in Kittiwakes and Guillemots as well. We observed chicks only in nests of cormorants during the survey of the western seabird colonies from the sea in ideal weather conditions on 16 August.
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Rodent dynamics:
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| Contrary to expectations populations of Collared Lemmings and Siberian Lemmings had decreased yet at a stage of growth, before reaching peak abundance. This deviation from the expected population cycle was probably due to heavy icing in autumn and winter 2007/2008, caused by abundant and prolonged rains in September 2007. The overall abundance of lemmings was low on the island in 2008, and apparently insufficient for the successful breeding of rodent specialists. The linear density of undersnow nests of lemmings was 0.9 per 1 km of transect.
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Rodent species recorded:
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| Latin | Abundance |
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| Lemmus sibiricus | rare |
| Dicrostonyx torquatus | rare |
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Summary
of fauna studies: |
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