Biologia 71/4: 452—456, 2016 Section Zoology DOI: 10.1515/biolog-2016-0053 Dependence of clutch predation rate of Eurasian reed warbler Acrocephalus scirpaceus on nesting site selection: a model study Marie Kameníková, Josef Navrátil & Josef Rajchard* Faculty of Agriculture, University of South Bohemia, Studentská 13, CZ 370 05, České Budˇ ejovice, Czech Republic; e-mail: rajchard@zf.jcu.cz Abstract: The article is focused on describing a possible way of how biological data can be processed, introduces the procedures used and compares the results gained from a field ornithological study. This was carried out using statistical methods of nonparametric regression with binomial classification and probit function together with the method with forward selection, and presents the most significant outcomes. Some of the interesting findings of this study are as follows: first, a lower level of reed warbler (Acrocephalus scirpaceus Hermann 1804) nest predation by bird predators was proven in the common reed [Phragmites australis (Cavanilles) Trinius 1841] stands growing in shallow waters, compared to nests located in stands growing in deeper waters. For this field research artificial nests containing one egg made of plasticine and one egg of Japanese quail were used. Second, a negative correlation was proven between predation of nests and their distance from the nearest tree, whereas no interdependence was proven either for various nesting-site types (oligotrophic sandpits, ponds with intensive fish-pond management and ponds with extensive use) or monitoring time (during the first, resp. second nesting). Based on the methods applied, 56% of egg predation variability was clarified and last but not least, the efficiency of these statistical methods was proven for practical use in similar field research zoological studies. Key words: artificial nests; sandpit; pond; nonparametric regression; probit function Introduction Like many other animals, waterfowl belong to a group of endangered species and therefore many authors (e.g., Musil 1998, 2000) have been concerned with various aspects of the biology of birds living in aquatic and wetland ecosystems in the Protected Landscape Area Třeboňsko. One of the additional works in this field is a study dealing with nest predation of eggs. A suitable species for this kind of research are species of bird whose abundant occurence can provide enough data. One of such species is the Eurasian reed warbler (Acrocephalus scirpaceus Hermann 1804). It is necessary to mention that during the nest- ing period of reed warbler not only the food variety at their nesting site, but also the safety of their nest and brood against bird predators and parasites are impor- tant. There are various ways of how the birds protect their clutches. As observed, the most common ways of protecting the nests are hanging them on or attaching them to safer sites, and very often in lower quantities. Among others, there are also significant changes in their behaviour depending on more frequent occurrence of predators, such as attacking the predators or (in case of parasitism) removing predators eggs from their nest. Yet the choice of a nesting site still prevails. Due to behaviour, such as for example more ag- gressive behaviour against bird predators during the nesting period, the success rate of reed warbler brood leaving their nests has been increasing (Gill 1996; Neu- dorf 1992). While some bird species tend to prefer nest- ing sites situated close to residential areas in which po- tential bird predators appear only rarely (Golawski & Mitrus 2014), others, on the other hand, build their nests within other bird species communities (Polak 2014). Another strategy is building the nest as hidden as possible (Sieving 1998), or building it at sites with less frequent occurrence of nest predators, as described for example in the Sloan et al. (1998) study. As for nesting, the optimum nesting conditions for reed warbler are both water reeds and terrestrial reeds; the area and spread of reeds are of minor impor- tance. Based on numerous evidence, it was proven that this species tends to search for common reed [Phrag- mites australis (Cavanilles) Trinius 1841] stands with a density of at 40 stalks/m 2 and of minimum height of 120 cm. Its nests can be found in cattail (Typha sp.) stands as well and more rarely also in stands of Urtica dioica, Carex sp., or Salix sp. Common is both indi- vidual nesting and mass nesting in colonies (Šťastný 2006). The nesting period most often falls within May to July, occurs once or twice a year, and a clutch usu- * Corresponding author c 2016 Institute of Zoology, Slovak Academy of Sciences Brought to you by | UCL - University College London Authenticated Download Date | 12/15/16 4:04 PM