NESTING PECULIARITIES AND INTERLAY VARIABILITY OF THE STERNIDAE FAMILY BIRDS’ EGGS IN THE PRIPYAT RIVER MIDDLE STRECH FLOODPLAN

Abstract

Purpose: to analyze the nesting features of birds of the Sternidae family living in the floodplain meadow of the Pripyat River.

Methodology. For research, the route method was used, in which bird nests were identified during direct examination of the territory of the floodplain meadow. Hard-to-reach areas of the meadow were surveyed from a boat. To assess the morphological parameters of the eggs of birds of the Sternidae family, the eggs were measured using a caliper. The length (L) and diameter of the eggs (B) were measured. Based on the measurements, the index of intra-laying variability (i_v) was determined. During the study period, 245 eggs of birds of the Sternidae family were measured, of which 88 eggs were in the Common tern, 60 eggs in the Little tern, 51 eggs in the White-winged tern and 46 eggs in the Whiskered tern.

Scientific novelty. It has been established that the formation of multispecies colonies of birds of the Sternidae family makes it possible to qualitatively use territories favorable for nesting and provides protection of nests from raptors to accompanying bird species. The smallest intra-laying variability of the studied egg parameters was found in the common and barnacle tern, which is an indicator of the birds’ adaptability to nesting conditions.

Conclusions. The nesting of White-winged black and Whiskered tern is directly dependent on floodwater level. A gradual decrease in the level of floodwaters leads to the drying up of the floodplain meadow and the impossibility of building nests, since these species build nests on aquatic plants or floating bogs.

Nesting of Little and Common tern is limited by biotic factors, such as predation by Corvidae birds and other animals, as well as anthropogenic factors - people resting on the shore, fishermen and locals visiting the meadow, which in turn creates a disturbance factor for the birds.

Among the bird species considered, the maximum value of the index of intra-variability of eggs laying in egg diameter (i_v) was found for White-winged black tern (i_v = 4.10 ± 0.52). The minimum value of this index is observed in Whiskered tern (i_v = 3.41 ± 0.39). It should be noted that differences in this index among Common tern are less pronounced than among Marsh tern

The maximum value of the index of intra-variability of eggs laying (i_v) was found for Little Tern (i_v = 5.42 ± 0.65). The minimum value of this indicator was found in Common tern (i_v = 3.90 ± 0.44). For Marsh tern (Whiskered and White-winged black tern), the value of the index of intra-variability of eggs laying length (i_v) does not differ significantly.