Marcin Antczak

The Food Composition of Immature and Non-breeding White Storks in Poland

Abstract The food of immature White Storks (Ciconia ciconia) feeding in meadows in Poland was studied by pellet analysis. The most important food items by numbers were insects, mainly beetles, which constituted 83% of all prey items (N = 5,958 items) and were found in all pellets (N = 163). However, by biomass, 58% of food consisted of small mammals, mainly voles Microtus sp. Insects (22%) and earthworms (11.5%) were secondary resources. Literature on White Stork diet in Europe also showed that voles, insects and earthworms were the dominant food of breeding White Storks. Their roles changed with latitude, habitat, time, as well as method of data analysis. Generally, the diet of non-breeding storks was similar to breeding birds, but more of the prey was obtained in dry habitats.

Settling Decisions and Heterospecific Social Information Use in Shrikes

Animals often settle near competitors, a behavior known as social attraction, which belies standard habitat selection theory. Two hypotheses account for these observations: individuals obtain Allee benefits mediated by the physical presence of a competitor, or they use successfully settled individual as a source of information indicating the location of high quality habitat. We evaluated these hypotheses experimentally in two species of shrikes. These passerine birds with a raptor-like mode of life impale prey to create larders that serve as an indicator of male/habitat quality. Thus, two forms of indirect information are available in our system: a successfully settled shrike and its larder. Typically these two cues are associated with each other, however, our experimental treatment created an unnatural situation by disassociating them. We manipulated the presence of larders of great grey shrikes and examined the settling decisions of red-backed shrikes within and outside the great grey shrike territories. Male red-backed shrikes did not settle sooner on plots with great grey shrikes compared to plots that only contained artificial larders indicating that red-backed shrikes do not use the physical presence of a great grey shrike when making settling decisions which is inconsistent with the Allee effect hypothesis. In contrast, for all plots without great grey shrikes, red-backed shrikes settled, paired and laid clutches sooner on plots with larders compared to plots without larders. We conclude that red-backed shrikes use larders of great grey shrikes as a cue to rapidly assess habitat quality.

Ecological character displacement in the face of gene flow: evidence from two species of nightingales.

BackgroundEcological character displacement is a process of phenotypic differentiation of sympatric populations caused by interspecific competition. Such differentiation could facilitate speciation by enhancing reproductive isolation between incipient species, although empirical evidence for it at early stages of divergence when gene flow still occurs between the species is relatively scarce. Here we studied patterns of morphological variation in sympatric and allopatric populations of two hybridizing species of birds, the Common Nightingale (Luscinia megarhynchos) and the Thrush Nightingale (L. luscinia).ResultsWe conducted principal component (PC) analysis of morphological traits and found that nightingale species converged in overall body size (PC1) and diverged in relative bill size (PC3) in sympatry. Closer analysis of morphological variation along geographical gradients revealed that the convergence in body size can be attributed largely to increasing body size with increasing latitude, a phenomenon known as Bergmanns rule. In contrast, interspecific interactions contributed significantly to the observed divergence in relative bill size, even after controlling for the effects of geographical gradients. We suggest that the divergence in bill size most likely reflects segregation of feeding niches between the species in sympatry.ConclusionsOur results suggest that interspecific competition for food resources can drive species divergence even in the face of ongoing hybridization. Such divergence may enhance reproductive isolation between the species and thus contribute to speciation.

Disperse or Stay? Exceptionally High Breeding-Site Infidelity in the Red-Backed Shrike Lanius collurio

Nesting in the same breeding area in successive years provides information to help understand the cues used by birds in habitat selection. Moreover, such information may also be an important tool for the conservation and management of endangered species. Based on the ringing results of 122 adult and 1245 nestling Red-backed Shrike Lanius collurio in the years 1996–2005, we studied philopatry of the species in two different populations: in western and in eastern Poland. Moreover we analysed all Polish Red-backed Shrike ring recoveries since 1996 (n = 3102 ringed birds). We noted that both natal and breeding philopatry in the populations were almost entirely absent. This is surprising in comparison with other studies, especially those including shrikes. Comparisons with other populations suggest that the lack of philopatry is not related to the breeding success of local birds and/or the size of the study area. In contrast, we suggest that low philopatry is an effect of and/or an adaptation to a relatively high population density at the land-scape scale, where many breeding areas and potential nesting sites still remain vacant.

Breeding Biology of the Great Grey Shrike Lanius excubitor in W Poland

Abstract. A Great Grey Shrike population was studied in two large plots (220 km2 and 176 km2) in western Poland in 1999–2003. During the study period densities varied from 11.4 to 14.1 breeding pairs/100 km2 but numbers were stable. In all, 180 Great Grey Shrike nests were found — 114 (63.3%) in conifers, 66 (36.7%) in deciduous trees. This populations reproductive parameters were relatively high in comparison to those of other European populations: mean clutch size — 6.6, hatching success — 92.5%, mean brood size — 5.72, mean number of fledglings per pair — 4.1, mean number of fledged young per successful pair — 5.25. Eggs (mean 27.1 × 19.9 mm) were found to be larger than reported in the literature. Nesting success was similar in both study plots, but there was slight seasonal variability: 41.0%–52.6% from 99 nesting attempts in the first plot, 42.1%–43.7% from 37 nests in the second. Predation was the main cause of nest losses. Plastic string used as nesting material appeared to be the most important cause of partial failures: 13 (8.2%) of a total of 147 nestlings surviving to fledging perished as a result of becoming tangled up in it. Nestlings rarely starved. Nests in linear habitats suffered significantly higher breeding losses (78.6%) than those in non-linear habitats (50%). The high fitness values obtained from this population were probably due to traditional farming practices, the sparing use of pesticides and the good potential food source.

More secluded places for extra-pair copulations in the great grey shrike Lanius excubitor

Summary Extra-pair copulations (EPCs) are prominent features of avian mating systems. EPCs can be costly for both sexes, especially if extra-pair encounters are discovered by a social partner. The threat of extra-pair fertilization of the social partner could potentially result in physical punishment, reduced parental investment or divorce. In order to reduce the costs of EPCs, natural selection may favour behaviour that reduces the likelihood of detection of EPC by a social partner. Moreover, habitat structure may influence the efficiency of male paternity guards and, therefore, the possibilities of seeking and obtaining EPCs. We tested this hypothesis with the great grey shrike Lanius excubitor, a socially monogamous passerine bird, living in semi-open landscapes. We have found that 1) extra-pair and within-pair copulations (WPCs) occurred in different places, and 2) individuals of both sexes chose more secret places for extra-pair than for within-pair copulations.

Costly replacement: how do different stages of nest failure affect clutch replacement in the red- backed shrikes Lanius collurio?

Re-nesting is costly and strongly stage- and time-related in the redbacked shrike. We tested whether failure which occurred at more costly developmental stages of the first clutches influenced the characteristics of replacement clutches in red-backed shrike Lanius collurio. Field work was conducted in the breeding seasons 1999–2006 at three study plots in Poland. During nest visits, standard data on breeding biology were collected, including clutch size, eggs measurements, laying date, and number of nestlings. We found significant differences in the clutch size of replaced clutches according to the failure phase of first clutches. Pairs which experienced brood failure at the nestling phase produced smaller replacement clutches than pairs whose nest was destroyed at the egg laying stage. There were no differences in the nesting success of replaced cluches relative to the stage where the first clutch was lost. However, pairs which failed during the nestling phase of the first clutch significantly more often skipped further reproduction in that season than those which failed during other phases. For breeding red-backed shrikes the best strategy is to initiate clutches as early as possible because it gives a more time for possible re-nesting.

Blood parasites in two co-existing species of lizards (Zootoca vivipara and Lacerta agilis)

We investigated the occurrence of blood parasites of two lizard species: the common or viviparous lizard (Zootoca vivipara) and the sand lizard (Lacerta agilis) in western Poland. Selected traits of lizard body morphology were studied with respect to the presence and intensity of haematozoan infection in blood samples collected from 218 adult lizards; 88 of the common lizard and 130 of the sand lizard. Haemogregarinid blood parasites were found to be the common parasite of both lizard species in studied locality with prevalence 39.8 (95% CL, 29.5–50.8) for Z. vivipara and 22.3 (95% CL, 15.5–30.4) for L. agilis. Incidence of parasitemia did not differ between sexes and was not correlated with morphological traits or presence of ectoparasites—Ixodes ricinus ticks. However, a significant difference between the two species of lizards was a greater frequency of haemogregarinid parasitism in Z. vivipara.

A Large Scale Survey of the Great grey shrike Lanius excubitor in Poland: Breeding Densities, Habitat use and Population Trends

The great grey shrike Lanius excubitor is declining in western Europe but relatively stable, or even increasing populations still exist in central and eastern Europe. It is a medium-sized passerine living in diverse, low-intensity farmland. Being a predatory bird, it is especially susceptible to any changes in farming practices that affect its prey. In this paper, we provide estimates of density, national population size and trends and generate a habitat-use model; information which is all necessary for effective conservation. We used data gathered during 71 censuses made in the years 1978–2005 to document the past and present status of the great grey shrike population in Poland. The mean population density has more than doubled from 4.5 in the early period of the study (1978–1995) to 11.3 pairs/100 km2 in the later period (1996–2005). The habitat use model shows that the great grey shrike avoids intensive arable fields and coniferous forests and prefers areas of extensively used farmland. We estimate the current size of the Polish breeding population to be 22 000–25 000 breeding pairs. Our results show that the Polish breeding population of the great grey shrike is still healthy. This can be attributed to high habitat heterogeneity and fragmentation, a slow rate of change in agricultural landscapes and recent mild winters which have had a positive effect on survival. We believe that our results can help to establish an effective conservation strategy for the species.

Structural heterogeneity of linear habitats positively affects Barred Warbler Sylvia nisoria, Common Whitethroat Sylvia communis and Lesser Whitethroat Sylvia curruca in farmland of Western Poland

Capsule Structural heterogeneity was the most important factor influencing the distribution of Barred Warbler Sylvia nisoria, Common Whitethroat S. communis and Lesser Whitethroat S. curruca in linear habitats in farmland of Western Poland. Aims To investigate the occurrence of three species of Sylvia warblers in relation to the spatial structure of linear habitats in the agricultural landscape of Western Poland where, in contrast to Western Europe, field boundaries are not managed in terms of their size or spatial structure. Methods In 2008, the distribution of breeding territories of Sylvia warblers in linear habitats was estimated in farmland of Western Poland. Redundancy detrended analysis was used to assess the relationship between bird abundance and seven linear habitat variables in ninety-four 150 m sections. Results Sylvia warblers differed in habitat requirements, however heterogeneity affected their distribution to the greatest extent. In addition, Barred Warbler preferred high shrub volume and wider sections, whereas Common Whitethroat was attracted by brambles and nettles and Lesser Whitethroat favoured shrubs. All species avoided a high proportion of low vegetation. Conclusion Structural heterogeneity resulted in highly preferred linear habitats for Sylvia warblers. Thus, maintaining or increasing structural heterogeneity of linear habitats may be a very effective tool for the conservation of farmland bird populations.