On the basis of field studies conducted in 1973–2000 it was found for four species of Phylloscopus warblers breeding in the taiga zone of NW Russia that their northern marginal populations, more remote from wintering grounds, have considerably shorter period of staying in the breeding region as compared with southern populations (because of later arrival and earlier departure), shorter interval between male and female arrival and lower population densities. It determines the regional features of their behavior during pre-nesting period: reduction of time of its first phase (before female’s arrival) and more “peaceful” delimiting of nesting territories. The “companionship” stage (according to D. May) is absent as the warblers from northern populations arrive in the nesting sites being physiologically readier for breeding. Although socially monogamous pairs dominate, the cases of facultative polygamy occur, especially in Willow Warbler. The molecular-genetic analysis has shown that in this species the frequency of polygyny (5–17 %) is much lower than the frequency of polyandry (68,4 %), i.e. in majority of Willow Warbler’s nests the bastard nestlings (15,3 % of total nestling number) are found. This is obviously conditioned by the excess of adult males, which is quite typical for all Phylloscopus species. Refs 31.
Acoustic playback techniques involve broadcasting of various sound stimuli to simulate the presence of a certain species. In this article, we applied a variation of the method using automatic sound-reproducing stations (ASRS), which imitate the daily vocal activity of birds that is close to natural. We investigated whether acoustic playback experiments help to examine the role of social cues for bird settlement decisions, as well as to detect the presence of rare and low-density species. Using this method, we were able to increase the local density of the rustic bunting Ocyris rusticus Pallas, 1776 (Emberizidae) – species, which is currently listed in the Red Book of the Russian Federation (2001). The findings of our study show that rustic buntings preferred to settle on plots where the song imitating the presence of conspecifics was broadcasted by ASRSs. In addition, the playback method was used to examine the social structure of the population of the wood warbler Phylloscopus sibilatrix Bechstein, 1793 (Sylviidae), a small species that lives here on the northern periphery of the range. The wood warbler songs were broadcasted by ASRSs before the arrivals of the first conspecifics to the breeding area. Songs with different acoustic activity (2 or 6 trills per min) were used to create a difference between the social environments on plots. The gathered data showed a display of two different behavioral responses of individuals (males) to different song types broadcasted on plots. Based on this observation, the main hypothesis is about the existence of both conservative and opportunistic male reproductive strategies of the wood warbler. The results demonstrate the possibility of using acoustic playback techniques to study the role of acoustic signals in territorial behavior and social structure of a bird population. Understanding the ways birds make settlement decisions is essential for the development of conservation practices.
A finding of conspecific brood parasitism (CBP) in willow warblers, Phylloscopus trochilus, breeding in western Russia is presented. The data set consists of 41 broods and 214 chicks, and the results are based on an analysis of the willow warbler microsatellites Phtr1, Phtr2, and Phtr3. Two chicks (1%, two chicks of 214) were in broods where they were unrelated to both social "parents," and these two chicks were in two different broods (5%, two broods of 41). In each case, the clutch comprised six eggs, one of which had been laid in by a parasitic female. In both nests, chicks hatched out of all eggs and fledged successfully. There is no information about the possible relatedness of the parasitic females to the hosts. In addition, the paper reviews other reports of CBP in the genus Phylloscopus, based on brood size, the morphological characteristics of eggs, and observation data. Such reports are considered to be insufficient for CBP confirmation. Currently, the only reliable evidence for CBP is the data obtained by genetic methods.
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