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Petra Nováková, Diana Kořanová, Sabine Begall, Erich P. Malkemper, Lukáš Pleskač, František Čapek, Jaroslav Červený, Vlastimil Hart, Veronika Hartová, Václav Husinec, Hynek Burda
Animals use to align their body axis with respect to different cues (e.g. sun position, wind direction, magnetic field lines) and signals (informing about source of interest) in diverse behavioural contexts. Existence of alignment indicates ability to sense such cues or signals and its study can enlighten the mechanism of their sensing. Global cues (sun position, magnetic field) might provide a directional reference (direction/heading indicator) for organization of the mental map and/or for coordinated take-off. The existence of a common direction indicator may be of importance especially in birds living in large colonies and having impeded maneuverability. We measured the direction of the body axis (alignment) in flamingos of four species at 18 localities in zoological gardens and in the wild in altogether eight countries during different seasons of the year and at different times of the day. The measurements were taken from photographs in a blinded way. Flamingos in Europe showed a significant preference to align towards South during all recorded stationary activities (grooming, resting, standing) while those from Kenya tended to head towards North. On the contrary, the distribution of body alignments during locomotor activities (walking, wading, feeding) was random. Under overcast weather, and especially in the morning hours, magnetic South or North were better predictors of heading than sun position. We interpret our findings as evidence for a magnetic alignment in flamingos (depending on the weather condition) and suggest that its main function might be seen in information rather than in energy interaction. Under windless conditions, sun position and magnetic field may provide a common reference direction, i.e. a direction indicator. Visual cues (if available) and vision are in birds probably more dominant in spatial orientation than magnetic cues and magnetoreception. Magnetoreception might be “switched on”, when visual sensing of relevant cues is impeded.
Spontaneous magnetic alignment, in which an animal or group of animals, aligns its body axis in a fixed orientation relative to the geomagnetic field has been observed across a variety of vertebrates. Although a seemingly ubiquitous spatial behaviour, the adaptive significance and sensory mechanisms underlying spontaneous magnetic alignment remain unclear. Here we report another example of spontaneous alignment during feeding behaviour from five corvid species, a well-known and geographically widespread avian taxon. Consistent with previous observational studies of magnetic alignment in free-roaming vertebrates, first- and second-order analyses show that corvids exhibit robust axial alignment corresponding with the north-south magnetic axis. In contrast, when the data is pooled relative to the sun's azimuth, the first-order analysis is indistinguishable from random and the second-order statistics, although statistically significant, are a much weaker predictor of axial orientation compared to the distribution pooled relative to the magnetic field. The magnetic alignment behaviour exhibited by foraging crows reported here is compatible with previous hypotheses proposing that spontaneous magnetic alignment may help to coordinate and structure spatial behaviours in free-living organisms. Clearly, an experimental approach in future studies is needed to help shed light on the functional significance and biophysical mechanisms mediating spontaneous magnetic alignment. These data provide support for spontaneous magnetic alignment in free-roaming corvids, a widespread taxon with exceptional cognitive abilities that may offer unique advantages for future laboratory and field-based studies of magnetoreception.
The aim of this work was to analyse assemblages of wintering birds in three areas of central Europe, that differ in climate: eastern Poland, northern Poland and western Germany in winter in 2003-2009. The severity of winter moderates distinctly from eastern Poland to Germany, so there ought to be more species and larger numbers of birds in Germany. 5445 birds from 73 species were recorded on the 491 transects with a length 500 m. Generalized linear models of the influence of habitat types and localities on the species richness reflected the significant effect of three habitat types and study area location. The species richness was positively affected by the surface area of towns and villages, and negatively by that of grassland areas. The most species were recorded in W Germany, in E Poland, and the fewest in N Poland. While, numbers of birds increased with increasing areas of hedgerows, villages and towns. Most birds wintered in eastern Poland, and reached higher value compared to N Poland; mostly because of large numbers of a few of the most abundant species: yellowhammer, fieldfare, great tit. We can expect that, with warming climate, the wintering areas in central Europe will host increasingly significant bird numbers.
Long-term population decline of the little owl has been recorded in Western Europe and available evidence also suggests severe range restriction in many Central European regions. Using two nationwide volunteer-based monitoring programmes during the years 2009–2016, we investigated distribution, population density and breeding associations of the little owl in the Czech Republic and Slovakia. Across the two countries combined, the average population density of the little owl was 0.19 calling males/10 km2. However, the population density was markedly higher in Slovakia (0.36 calling males/10 km2) than in the Czech Republic (0.09 calling males/10 km2). The overall breeding population of the little owl was estimated at 130 breeding pairs in the Czech Republic and 550 in Slovakia. Compared to the situation two decades ago, those estimates represented a 87–94 % decline in the breeding population in the Czech Republic and a 31–45 % reduction in Slovakia. Our data also revealed marked distributional range contraction of the little owl, indicating rapid local extinctions over the last two decades. The analysis of expected breeding places of the little owl confirmed a strong preference for man-made objects over the original breeding sites in tree cavities. In the light of our present results, we propose urgent preparation and implementation of a species action plan with conservation measures to halt the little owl's steep decline in Central Europe.
A small population of otter and mink coexist on the Isle of Sálvora, off the coast of Galicia, a region in northwest Spain. The aim of this study was to analyse the feeding habits of both species (taxa and type of prey) and their degree of trophic overlap. In order to analyse which habitat features best define otter and mink trophic preferences, fish preys were defined according to three criteria: substrate preference, position in the water column, and tidal zones. A total of 178 otter spraints and 158 mink scats were collected and analysed between May and October 2007. The relative frequency of occurrence and the biomass of each taxon were calculated. Mink consume mainly rabbits in spring, seagulls in summer, and rodents and shrews in autumn. The frequency of rabbits and gulls in mink diet was related to the abundance of both prey on the island. Otters were basically feeding upon fish throughout the study period. Their main prey was garfish (pelagic fish) during spring and summer, and Bleniidae and Gobiidae (benthic fish of rocky bottom pools) in autumn. These fishes are also consumed by mink during late summer, when the diet overlap between both species is higher (August diet overlap of 43.5 %, mean diet overlap of 16.4 %).
Sexual segregation has been found among many vertebrate species. Argali, like other sexually dimorphic Capridae, form sexually segregated groups outside the breeding season. The degree of sexual segregation and its seasonal changes have never been examined and quantified in Asiatic species of wild sheep. In this paper we are considering seasonal fluctuation in the degree of sexual segregation and check the activity budget hypothesis to explain this phenomenon in the Darwin's wild sheep (Ovis ammon darwini), a subspecies of argali sheep (Ovis ammon). The activity budget hypothesis states that sexually size-dimorphic males and females segregate into different groups due to incompatibilities in activity budgets and movement rates. We collected data on activity budgets in the argali sheep from 2015 to 2016, in the Mengluoke Mountains of Xinjiang Province, and used Conradt's segregation coefficient (SC) to measure the degree of sexual segregation outside and during the rutting seasons. Our results showed that the SC value was highest outside the rutting season (0.98), when argalis were almost completely segregated. During the rutting period, the segregation coefficient dropped more than twofold (0.43) compared to the non-rutting season. In addition, our data supported the activity budget hypothesis: female and male argali had different behavioural activity patterns during the non-rutting season. Female argali spent more time feeding, followed by resting, standing, moving, and other behaviours, while males spent most of their time resting, followed by feeding, standing, other behaviours, and moving. Female argali spent significantly more time feeding than males, while males spent significantly more time resting and in other behaviours than females. Activity synchronization indices for both female groups and male groups were significantly higher than in mixed-sex groups. Sexual segregation is the best behavioural strategy for sexually dimorphic ungulates and the activity budget hypothesis explained this phenomenon well in Darwin's wild sheep.
Trade-offs such as the ones between reproduction and longevity or present and future reproduction are believed to shape reproductive patterns. We here used zoo data to investigate trade-offs and life histories in four taxa of Asiatic (Equus hemionus ssp.) and African wild asses (Equus africanus ssp.). All taxa showed even in captivity peak birth rates during the periods of highest food availability in their natural environments. Sex-specific survival rates with females living longer than males were evident in kulan and onager but not in kiang and Somali wild ass, pointing towards different life-history strategies even among closely related taxa. Females achieved their highest reproductive output earlier in life than males, which is typical for polygynous mating systems. Offspring number and longevity were positively rather than negatively correlated. Taken together evidence for reproductive trade-offs was weak, though the length of the reproductive period was negatively related to birth rates within the reproductive period. Birth intervals increased with female age, probably reflecting detrimental effects of senescence. Despite several limitations, zoo data seem to be useful to better understand the reproductive biology of endangered, rare or cryptic species.
The wildcat is a rare and elusive mammal species, with a broad feeding spectrum. We collected 34 scats of wildcat in the surroundings of a reproductive site to assess the diet of juvenile wildcats and relevant parents in a rural area of Central Italy. The Brillouin diversity index suggested that our sample was large enough to assess the seasonal diet of both age classes. Wood mice were the most preyed species (59.4 %), followed by bank voles (12.5 %). No significant difference was observed between adult and juvenile diet compositions. Birds were rarely consumed and mostly present in the diet of adult individuals, with the exception of the red-legged partridge, observed only in juvenile scats.
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