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RESPONDENT
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Raymond Klaassen
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SITE NAME
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Uboynaya River mouth, Taimyr, Russia
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| Contact
details (phone/fax//e-mail//address): |
| +31 294 239 319 // raymond.klaassen2@gmail.com // Kloosterstraat 67, 6562AV Groesbeek, the Netherlands |
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PROJECT DETAILS
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Project name:
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Expedition to the Uboynaya river |
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Start of survey:
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End
of survey:
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Team
size:
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27.06 |
18.07 |
5 |
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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: |
average |
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Breeding conditions:
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We found in total 3 active fox dens in an area of about 60 km2. Foxes were seen in the study area, but not regularly. Roughly, every 3 field days 1 fox was observed. One Polar fox was observed carrying a dead Ptarmigan female towards a den. In one of the pipes of a den 3 dead Siberian lemmings were observed.
Rough legged buzzards (Buteo lagopus) bred, but only had small clutch sizes (2.8 eggs, SD=1.1, n=5). In our study area of about 80 km2 4 Snowy owl nests with eggs were found. Three nests contained 5 eggs, one nest only had 3 eggs. Hatching started at 10th of July. The Snowy owl nest without Brent geese nests in the vicinity was surprisingly predated by an Arctic fox.
After a week of frequently displaying Pomarine skuas (Stercorarius pomarinus) started to breed. In a plot of 8 km2 a total number of 18 Pomarine skua nests were found (2.25 nests/km2). From in total 50 individuals only 14 % represented the dark morph. Almost all pairs had two eggs. Only 2 out of 30 nests contained 1 egg. Long-tailed skuas (Stercorarius longicaudus) also bred in the area, but at much lower densities. For comparison, only three nests of Long-tailed skua were found in the 'skua plot'.
Brent geese were rather scarce (29 nests were found) and clutch sizes were small (3.6 eggs, SD=1.2 , n =20 ). Brent geese nests were found mainly in the vicinity of Snowy owl nests. From in total 29 nest, only 5 nests were not directly related to a Snowy owl nest. Around four different Snowy owl nests 13, 7, 4 and 0 Brent geese nests were found.
All Brent geese nests unrelated to Snowy owl nest were predated by Pomarine skuas or Polar foxes. Brent geese nests nearby Snowy owl nests were heavily predated, although 46 % of all nests around Snowy owls were not predated at the time we left (after about 2 weeks of incubation). Most nests were predated by Pomarine skuas (72% of all predated nests).
In total 15 nests of Little stint and 3 nests of Curlew sandpiper were found within a small 0.33 km2 plot where wader nests were searched for. Nest success of Little stint nests was calculated using the Mayfield method (23 nests, 235 nestdays). The probability that a nest hatches is 78 %, which is high compared to other years. Only one nest was predated by a skua. Two other nests were left before eggs hatched. At the time we left the area the first eggs hatched.
It is hypothesized that wader nests escaped from predation because lemming densities were (just) high enough to make searching for wader nests less profitable than searching for lemmings. However, because Brent goose nests attain a higher reward to the predator, Brent geese nests did not escape from predation, because searching for Brent goose nests was favorable over searching for lemmings. |
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Rodent dynamics:
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| The abundance of Siberian (Lemmus sibericus) and Collared lemming (Dicrostonyx torquatus) was determined by trapping them using 25 traps placed near lemming burrows or at lemming tracks for three successive days. Two habitat types (grassy tundra as found in valleys and patchy tundra as found on hills) were sampled twice. In total 9 lemmings were caught during 300 trapnights. Lemmings clearly were most abundant in wet, grassy tundra. Both lemmings caught in the patchy-tundra habitat were Collared lemmings, all other lemmings caught were Siberian lemmings. Contrary to our expectations, 2002 was not a lemming peak year, but a typical intermediate year at the Uboynaya study site.
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Rodent species recorded:
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| Latin | Abundance |
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| Lemmus sibiricus | common |
| Dicrostonyx torquatus | rare |
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Summary
of fauna studies: |
| An area of about 80 km2 was surveyed for the presence of Brent goose nests, Snowy owl and Rough legged buzzard nests as well as Polar fox dens. Lemming abundance was determined according to a standard trapping protocol. |
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