Climatic conditions and prevalence of melanistic snakes-contrasting effects of warm springs and mild winters.

Climate change is one of the greatest challenges that wildlife is facing. Rapid shifts in climatic conditions may accelerate evolutionary changes in populations as a result of strong selective pressure. Most studies focus on the impact of climatic conditions on phenologies and annual cycles, whereas there are fewer reports of empirical support for climate-driven changes in the phenotypic variability of free-living populations. We investigated whether climatic variables explain the prevalence of colour polymorphism in a population of the grass snake (Natrix natrix) with two morphotypes, the melanistic and non-melanistic ones, in the period 1981-2013. We found that the prevalence of the black phenotype was negatively related to spring temperature and winter harshness, expressed as the number of snow days. According to the thermal melanism hypothesis, a high predation rate during warmer springs may override relaxed thermal benefits and vice versa, i.e. black individuals may perform better than typical ones when thermal conditions in spring are unfavourable. In turn, because they are smaller, melanistic individuals may be exposed to a higher risk of winter mortality, particularly during longer winters. We highlight the need for more studies on the effects of climatic conditions on temporal variation in melanism prevalence in other populations and species as well as in various geographic regions.

A Unified Approach to Analysis of Body Condition in Green Toads.

Body condition is increasingly used to assess the status of populations and as a proxy for individual fitness. A common, quick and non-invasive approach is to estimate condition from the relation between body length and mass. Among the methods developed for this purpose, the Scaled Mass Index (SMI) appears best suited for comparisons among populations. We assembled data from 17 populations of European green toads (Bufotes viridis) with the aim of devising a standard formula applicable for monitoring this species. The mean value of the exponents describing length-mass allometry in these samples was 3.0047. Hence, we propose using 3 as a scaling coefficient for calculating the SMI in green toads. From the contrast of SMI values for both sexes within populations, estimated with either the population-specific or the standard coefficient, we conclude that applying the standard formula not only facilitates comparisons among populations but may also help to avoid misinterpretation of variation within populations.

Melanism, body size, and sex ratio in snakes-new data on the grass snake (Natrix natrix) and synthesis.

It is postulated that melanism in ectotherms is adaptive by enhancing thermoregulation, subsequent resource acquisition, and growth. Such effects may differ between the sexes as a result of the differential costs of self-maintenance and reproduction, but empirical support for the sex-specific consequences of melanism remains inconsistent. We studied the effects of melanism on body size and sex ratio in a population of the European grass snake (Natrix natrix) in SE Poland and also carried out a systematic review of the literature on the consequences of melanism in terrestrial snakes. Melanistic grass snakes of both sexes appeared to be smaller than the typical phenotype, which indicates higher predation pressure and minimal thermal benefits for black individuals. A female-biased sex ratio was observed in the typical phenotype, but not in melanistic snakes, suggesting that the costs for females and/or benefits for males are higher in melanistic individuals. In conjunction with earlier studies, our data indicate that the consequences of melanism may be related to the reproductive mode of species. In viviparous species, melanism tends to improve growth and/or body size and is more frequent in females, whereas the opposite holds for oviparous snakes. Further studies on melanism should examine a wider array of species with different reproductive strategies and traits beyond the usual thermal benefits.

Effects of interspecific coexistence on laying date and clutch size in two closely related species of hole-nesting birds.

Coexistence between great tits Parus major and blue tits Cyanistes caeruleus, but also other hole-nesting taxa, constitutes a classic example of species co-occurrence resulting in potential interference and exploitation competition for food and for breeding and roosting sites. However, the spatial and temporal variations in coexistence and its consequences for competition remain poorly understood. We used an extensive database on reproduction in nest boxes by great and blue tits based on 87 study plots across Europe and Northern Africa during 1957-2012 for a total of 19,075 great tit and 16,729 blue tit clutches to assess correlative evidence for a relationship between laying date and clutch size, respectively, and density consistent with effects of intraspecific and interspecific competition. In an initial set of analyses, we statistically controlled for a suite of site-specific variables. We found evidence for an effect of intraspecific competition on blue tit laying date (later laying at higher density) and clutch size (smaller clutch size at higher density), but no evidence of significant effects of intraspecific competition in great tits, nor effects of interspecific competition for either species. To further control for site-specific variation caused by a range of potentially confounding variables, we compared means and variances in laying date and clutch size of great and blue tits among three categories of difference in density between the two species. We exploited the fact that means and variances are generally positively correlated. If interspecific competition occurs, we predicted a reduction in mean and an increase in variance in clutch size in great tit and blue tit when density of heterospecifics is higher than the density of conspecifics, and for intraspecific competition, this reduction would occur when density of conspecifics is higher than the density of heterospecifics. Such comparisons of temporal patterns of means and variances revealed evidence, for both species, consistent with intraspecific competition and to a smaller extent with interspecific competition. These findings suggest that competition associated with reproductive behaviour between blue and great tits is widespread, but also varies across large spatial and temporal scales.

Haemoparasites of the pied flycatcher: inter-population variation in the prevalence and community composition.

The prevalence and community composition of haemoparasites can substantially differ among avian host populations, which may lead to different selection pressures. Therefore, information about these parameters is crucial for understanding, e.g. the inter-population variation in host life history traits. Here, we molecularly screened a population of a long-distance migrant, the pied flycatcher Ficedula hypoleuca, from central Poland for the presence of three genera of blood parasites: Haemoproteus, Plasmodium and Trypanosoma. The infection rate in this population was the highest for haemosporidians (86·8%) and one of the highest for trypanosomes (39·7%) among the thus far screened breeding populations of this species. The haemosporidian community was composed of six Haemoproteus/Plasmodium lineages, and the trypanosome community - 4 species and a parasite assigned to genus level. Trypanosomes were dominated by T. culicavium, a recently described species, corroborating the prediction that insectivorous songbirds are vertebrate hosts of this parasite. Host sex and age did not explain variation in infection incidence except for the higher trypanosome infection rates in males. A comparison of the study population with three other breeding populations previously screened molecularly for haemosporidians showed some geographic differences. This study confirms the importance of examining local parasite communities across a host distribution range.

Effect of spatial resolution of soil data on predictions of eggshell trace element levels in the Rook Corvus frugilegus.

Although a considerable research effort has gone into studying the dietary pathways of metals to the bodies of laying female birds and their eggs in recent years, no detailed investigations have yet been carried out relating the properties of the biogeochemical environment at large spatial scales to eggshell trace element levels in typical soil-invertebrate feeding birds under natural conditions. We used data from a large-scale nationwide monitoring survey of soil quality in Poland (3724 sampling points from the 43 792 available) to predict levels of five trace elements (copper [Cu], cadmium [Cd], nickel [Ni], zinc [Zn] and lead [Pb]) in Rook Corvus frugilegus eggshells from 42 breeding colonies. Our major aim was to test whether differences exist in the explanatory power of soil data (acidity, content of elements and organic matter, and particle size) used as a correlate of concentrations of eggshell trace elements among four different distances (5, 10, 15 and 20 km) around rookeries. Over all four distances around the rookeries only the concentrations of Cu and Cd in eggshells were positively correlated with those in soil, while eggshell Pb was correlated with the soil Pb level at the two longest distances (15 and 20 km) around the rookeries. The physical properties of soil (primarily the increase in pH) adversely affected eggshell Cd and Pb concentrations. The patterns and factors governing metal bioaccumulation in soil invertebrates and eggshells appear to be coincident, which strongly suggests a general similarity in the biochemical pathways of elements at different levels of the food web. The increasing acidification of arable soil as a result of excessive fertilisation and over-nitrification can enhance the bioavailability of toxic elements to laying females and their eggs.

Interspecific variation in the relationship between clutch size, laying date and intensity of urbanization in four species of hole-nesting birds.

The increase in size of human populations in urban and agricultural areas has resulted in considerable habitat conversion globally. Such anthropogenic areas have specific environmental characteristics, which influence the physiology, life history, and population dynamics of plants and animals. For example, the date of bud burst is advanced in urban compared to nearby natural areas. In some birds, breeding success is determined by synchrony between timing of breeding and peak food abundance. Pertinently, caterpillars are an important food source for the nestlings of many bird species, and their abundance is influenced by environmental factors such as temperature and date of bud burst. Higher temperatures and advanced date of bud burst in urban areas could advance peak caterpillar abundance and thus affect breeding phenology of birds. In order to test whether laying date advance and clutch sizes decrease with the intensity of urbanization, we analyzed the timing of breeding and clutch size in relation to intensity of urbanization as a measure of human impact in 199 nest box plots across Europe, North Africa, and the Middle East (i.e., the Western Palearctic) for four species of hole-nesters: blue tits (Cyanistes caeruleus), great tits (Parus major), collared flycatchers (Ficedula albicollis), and pied flycatchers (Ficedula hypoleuca). Meanwhile, we estimated the intensity of urbanization as the density of buildings surrounding study plots measured on orthophotographs. For the four study species, the intensity of urbanization was not correlated with laying date. Clutch size in blue and great tits does not seem affected by the intensity of urbanization, while in collared and pied flycatchers it decreased with increasing intensity of urbanization. This is the first large-scale study showing a species-specific major correlation between intensity of urbanization and the ecology of breeding. The underlying mechanisms for the relationships between life history and urbanization remain to be determined. We propose that effects of food abundance or quality, temperature, noise, pollution, or disturbance by humans may on their own or in combination affect laying date and/or clutch size.

Variation in clutch size in relation to nest size in birds.

Nests are structures built to support and protect eggs and/or offspring from predators, parasites, and adverse weather conditions. Nests are mainly constructed prior to egg laying, meaning that parent birds must make decisions about nest site choice and nest building behavior before the start of egg-laying. Parent birds should be selected to choose nest sites and to build optimally sized nests, yet our current understanding of clutch size-nest size relationships is limited to small-scale studies performed over short time periods. Here, we quantified the relationship between clutch size and nest size, using an exhaustive database of 116 slope estimates based on 17,472 nests of 21 species of hole and non-hole-nesting birds. There was a significant, positive relationship between clutch size and the base area of the nest box or the nest, and this relationship did not differ significantly between open nesting and hole-nesting species. The slope of the relationship showed significant intraspecific and interspecific heterogeneity among four species of secondary hole-nesting species, but also among all 116 slope estimates. The estimated relationship between clutch size and nest box base area in study sites with more than a single size of nest box was not significantly different from the relationship using studies with only a single size of nest box. The slope of the relationship between clutch size and nest base area in different species of birds was significantly negatively related to minimum base area, and less so to maximum base area in a given study. These findings are consistent with the hypothesis that bird species have a general reaction norm reflecting the relationship between nest size and clutch size. Further, they suggest that scientists may influence the clutch size decisions of hole-nesting birds through the provisioning of nest boxes of varying sizes.

Residues of chromium, nickel, cadmium and lead in Rook Corvus frugilegus eggshells from urban and rural areas of Poland.

We examined the concentrations of chromium (Cr), nickel (Ni), cadmium (Cd) and lead (Pb) in Rook Corvus frugilegus eggshells from 43 rookeries situated in rural and urban areas of western (=intensive agriculture) and eastern (=extensive agriculture) Poland. We found small ranges in the overall level of Cr (the difference between the extreme values was 1.8-fold; range of concentrations=5.21-9.40 Cr ppm), Ni (3.5-fold; 1.15-4.07 Ni ppm), and Cd (2.6-fold; 0.34-0.91 Cd ppm), whereas concentrations of Pb varied markedly, i.e. 6.7-fold between extreme values (1.71-11.53 Pb ppm). Eggshell levels of these four elements did not differ between rural rookeries from western and eastern Poland, but eggshells from rookeries in large/industrial cities had significantly higher concentrations of Cr, Ni and Pb than those from small towns and villages. Our study suggests that female Rooks exhibited an apparent variation in the intensity of trace metal bioaccumulation in their eggshells, that rapid site-dependent bioaccumulation of Cu, Cr, Ni and Pb occurs as a result of the pollution gradient (rural

Trace-element interactions in Rook Corvus frugilegus eggshells along an urbanisation gradient.

Concentrations of seven trace elements [arsenic (As), chromium (Cr), nickel (Ni), lead (Pb), copper (Cu), zinc (Zn), and cadmium (Cd)] in the eggshells of Rooks Corvus frugilegus, a focal bird species of Eurasian agricultural environments, are increased above background levels and exceed levels of toxicological concern. The concentrations of Cr, Ni, Pb, Cu, and Zn are greater in eggshells from urban rookeries (large cities) compared with rural areas (small towns and villages) suggesting an urbanisation gradient effect among eggs laid by females. In the present study, the investigators assessed whether the pattern of relationships among the seven trace elements in eggshells change along an urbanisation/pollution gradient. Surprisingly, we found that eggshells with the greatest contaminant burden, i.e., from urban rookeries, showed far fewer significant relationships (n = 4) than eggshells from villages (n = 10), small towns (n = 6), or rural areas (n = 8). In most cases, the relationships were positive. As was an exception: Its concentration was negatively correlated with Ni and Cd levels in eggshells from small town rookeries (where As levels were the highest), whereas eggshells from villages (with a lower As level) showed positive relationships between As and Cd. Our findings suggest that at low to intermediate levels, interactions between the trace elements in Rook eggshells are of a synergistic character and appear to operate as parallel coaccumulation. A habitat-specific excess of some elements (primarily Cr, Ni, Cu, As) suggests their more competitively selective sequestration.

Can starling eggs be useful as a biomonitoring tool to study organohalogenated contaminants on a worldwide scale?

Large-scale international monitoring studies are important to assess emission patterns and environmental distributions of organohalogenated contaminants (OHCs) on a worldwide scale. In this study, the presence of OHCs was investigated on three continents (Europe, North America and Australasia), using eggs of starlings (Sturnus vulgaris and Sturnus unicolor) to assess their suitability for large-scale monitoring studies. To the best of our knowledge, this is the first study using bird eggs of the same species as a biomonitor for OHCs on an intercontinental scale. We found significant differences in OHC concentrations of the eggs among sampling locations, except for hexachlorocyclohexanes (HCHs). Mean concentrations of sum polychlorinated biphenyls (PCBs) in eggs ranged from 78±26 ng/glipid weight (lw) in Australia to 2900±1300 ng/g lw in the United States. The PCB profile was dominated by CB 153 and CB 138 in all locations, except for New Zealand, where the contribution of CB 95, CB 101 and CB 149 was also high. The highest mean sum polybrominated diphenyl ether (PBDE) concentrations were found in Canada (4400±830 ng/g lw), while the lowest mean PBDE concentrations were measured in Spain (3.7±0.1 ng/g lw). The PBDE profile in starling eggs was dominated by BDE 47 and BDE 99 in all countries, but in Belgium, the higher brominated PBDEs had a higher contribution compared to other countries. For the organochlorine pesticides (OCPs), dichlorodiphenyltrichloroethanes (DDTs) ranged from 110±16 ng/g lw in France to 17,000±3400 ng/g lw in New Zealand, while HCHs and hexachlorobenzene were generally in low concentrations in all sampling locations. Chlordanes were remarkably high in eggs from the United States (2500±1300 ng/g lw). The OCP profile in all countries was largely dominated by p,p'-DDE. In general, the worldwide trends we observed in starling eggs were in accordance with the literature on human and environmental OHC data, which suggests that there is potential for using starling eggs as a biomonitoring tool on a large geographical scale.

Parasites of chaffinch (Fringilla coelebs) population. Part II. Blood parasites.

Blood parasites of Chaffinches caught from June to October near Luknajno Lake (Mazurian Lakeland) were studied. Only parasites belonging to the genera Haemoproteus were found. A decrease in prevalence as the season progressed was observed. No differences in blood parasite infections in relation to the sex of the birds were found. Also males body weight was not affected by the presence of parasites.