TERN MIGRATION IN THE SOUTHEAST OF WESTERN SIBERIA(TOM-OB RIVER REGION)

Daily observations of the visible spring migration were conducted at observationposts during 1998-2004. Sterna hirundo, Chlidonias niger, Ch. leucopterus dominatedaccording to the number (in decreasing order). Sterna albifrons was a common species.Sterna paradisaea was a rare species. On the whole territory of the Tom-Ob river regionthe journey annually begins in the 1st or the 2nd decade of May. The common tern camefirst on the 4-20th of May. The black and the little terns appeared 1-19 days later (13-26.V and 13.V-1.VI respectively). The white-winged tern usually arrived 1-9 days laterthan the black tern (17-28.V). There was a natural offset of the arrival dates from southto north. Migration was characterized by low intensity - 0,97 ind./hour. On the whole thehigh-water beds of rivers at the same latitude dont differ in the intensity of the journey.The influence of weather factors on the migration of terns was less important than onother waterfowl birds. The mass flight of the early arriving common tern happens in 1-10 days, on the third day on average, after the appearance of first birds. For the lateflyingmigrants it begins immediately on arrival day. Migration of terns is undulating.There were 3 waves of the journey in the high-water bed of the Tom river and 1 wavewith 3 tops in the floodplain of the Ob river. All waves were registered in a very shortperiod - during the II-III decades of May. There were some flight peaks. Their numberincreased in the high-water bed of the Ob river in comparison with the Tom river (3-5 and 1-3 correspondingly). Migration intensity in such days was up to 10,0 ind./hour. Inthese days up to 100 % individuals of the black and the white-winged terns, 38-83% ofthe little tern and 27-67% of the common tern flew. The congregation of resting birds onlakes and ponds shows that the little tern migrates daytime, the black and the whitewingedterns - at night and the common tern - both day and night. Migration of thewhole tern group lasts 20 days but the common tern flies in 19 days, the black tern -12 days, the white-winged tern - 10 days, the little tern - 14 days (in the floodplain of theTom river). Phenology dates of migrations in the forest-steppe and forest zone of WesternSiberia were similar. However, the journey intensity in the forest zone was smaller. Thecommon terns intensity was 2 times less, the white-winged terns - 10 times. The scaleof the Tom-Ob river region migration was less since more birds stayed nesting in Barabadepression.

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