ИСТИНА

Based on data collected in 2010-2013 in vicinity of Meinypilgyno, southern Chukotka, waders are breeding with very low densities there. Mapping of pairs, nests and broods on the best surveyed areas (7.5 km2 for most species and 90 km2 for Spoon-billed Sandpiper Eurynorhynchus pygmeus) revealed the following densities (pairs/km2): 0.8-1.9 in Ringed Plover Charadrius hiaticula, 1.5-2.1 in Lesser Sand Plover Ch. mongolus, 1.1-1.2 in Red Knot Calidris canutus, and 0.1 in Spoon-billed Sandpiper. The densities were most stable between years in the latter two species and were increasing in Ringed Plover being doubled in last three years. At the same time, densities of Lesser Sand Plover were fluctuating with the highest obtained value in 2011 and the lowest one in 2013. It is found with help of individual colour-marking that the higher return rates probably reflecting survival rates are typical for three monogamous species: 82% in Red Knot males (n=33), 77% in Ringed Plover males (n=13) and 63-67% in Spoon-billed Sandpiper of both sexes in former years (Tomkovich 1994; Zöckler et al. 2010). The lowest return rate to the area between years is recorded in Lesser Sand Plover (50% in males, n=20). There are indications that some Lesser Sand Plovers can be successively polygamous and move large distances in search for mates or following them, which explains their both lower return rate and density fluctuations.