"Provident Fathers" "Influence of Nest-Building Behaviour on the Breeding Success of Common Whitethroat Sylvia Communis" JUSTYNA CHACHULSKA, LESZEK JERZAK University of Zielona Gora, Faculty of Biological Sciences, Department of Nature Conservation prof. Z. Szafrana 1 PL 65-516 Zielona Góra e-mail: chachulska.j@gmail.com Collecting nest material in the spring rain

Description popularizing the research project

There are people who have an extraordinary gift. They have ideas for nifty interior decor, they can design spectacular clothes or cook a delicious dish. In this attractive way they stand out from the crowd, unable to answer the question they bare asked "How you do it?". Apparently, it is all in the genes and the talent is inherited after their ancestors. Then, jumping to conclusions, it means a beautiful open-concept kitchen design or a delicious roast have something to do with genes and are inherited from parents and grandparents. If the far-fetched assumption were true, it would mean that man-made objects do contribute to preserving our species. As the evolution and the selection of species work the same for all living creatures, it would imply that among other species than Homo sapiens, creations of beak, claws and wings mean reproductive success.
In the world of fauna we will find a lot of evidence that certain skills may be crucial in the most important life issue of every individual: passing on the genes to the offspring. The best example are creations of claws, beaks, wings or other specialized organs: burrows dug underground, laboriously curved out tree hollows, nests or weaved cocoons. Instinctively, the construction is not only to provide shelter for themselves and the younglings. It is also subject to an instinctive and unforgiving evaluation made by a potential sexual partner - parent of their offspring. It is particularly evident in case of birds' nests, which, within the same species, differ in size and ornaments. The bird most famous for the ornamented bowers is Australian bowerbird. Also in Polish gardens and shrubs we can find a minute bird, the common whitethroat, whose males try to best one another in their instinctive creativity while building nests, and females decide where they will lay the eggs.
For the preservation of a species, the appearance of nests built by males of the common whitethroat is as important as the tail for a peacock. It signals attractive genetic material, just like unique skills of Homo sapiens.

Abstract

In recent years many studies have indicated that birds' nests play a role not only in protection of eggs and chicks but also in communication between individuals. A nest as an extended phenotype may constitute a signal to potential competitors and members of the opposite sex about social status of the builder, his capacity to deter the rivals, experience, age, genetic quality. Males of common whitethroat Sylvia communis build a few cock nests in their territory before pairing. If female chooses a male, she starts laying eggs in one of his nest. In part of the nests, beside the typical grassy nest material, there occur also arthropod cocoons and vegetal fluff, of still unknown functions. Building multiple nests- and nest ornamentation are not common among birds, however such behaviours occur in all species of genus Sylvia. There are very few available descriptions of this behaviour of Sylvia warbler species. Researchers suspect that building multiple nests and nest ornamentation are under sexual selection pressure and they may be essential for females in choosing a partner. Research on breeding biology of common whitethroat was carried out in years 2014 - 2016 on the outskirts of Wrocław. The research area consisted of meadows, bushy patches of willow and hawthorn and fallows. Males were individ-ually marked with a combination of metal and colour rings put on tarsus. Measurements of individuals included physical condition (haemoglobin level) and morphometric features. Nests measurements were made no later than at the incubation stage and, to avoid the mechanical deformations, the nests were collected right after fledging. After drying, the nests were weighted and the ornaments were counted. High diversity in male nest-building behaviour was found in the study population. Males built a few (1-3) cock nests in their territories. The nests varied in morphology and a number of ornaments. Most males used the arthropod cocoons and vegetal fluff to ornament their nests (94% nests with ornaments). The number of ornaments per nest fluctuated between 1 and 40. The most ornamented nests were built by males with long wings and in good physical condition. Pairing period was shorter in males with more orna-mented nests. Our results suggest that a high variability in nests morphology and in the level of ornamentation may reflect quality of a male, and thus may influence real breeding success. Further research is necessary.

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