Interaction of climate change with effects of conspecific and heterospecific density on reproduction

We studied the relationship between temperature and the coexistence of great titParus majorand blue titCyanistes caeruleus, breeding in 75 study plots across Europe and North Africa. We expected an advance in laying date and a reduction in clutch size during warmer springs as a general response to climate warming and a delay in laying date and a reduction in clutch size during warmer winters due to density-dependent effects. As expected, as spring temperature increases laying date advances and as winter temperature increases clutch size is reduced in both species. Density of great tit affected the relationship between winter temperature and laying date in great and blue tit. Specifically, as density of great tit increased and temperature in winter increased both species started to reproduce later. Density of blue tit affected the relationship between spring temperature and blue and great tit laying date. Thus, both species start to reproduce earlier with increasing spring temperature as density of blue tit increases, which was not an expected outcome, since we expected that increasing spring temperature should advance laying date, while increasing density should delay it cancelling each other out. Climate warming and its interaction with density affects clutch size of great tits but not of blue tits. As predicted, great tit clutch size is reduced more with density of blue tits as temperature in winter increases. The relationship between spring temperature and density on clutch size of great tits depends on whether the increase is in density of great tit or blue tit. Therefore, an increase in temperature negatively affected the coexistence of blue and great tits differently in both species. Thus, blue tit clutch size was unaffected by the interaction effect of density with temperature, while great tit clutch size was affected in multiple ways by these interactions terms.Peer reviewe

Variation in clutch size in relation to nest size in birds

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Foraging Eurasian Jays (Garrulus glandarius) prefer oaks and acorns in central Europe

The Eurasian Jay (Garrulus glandarius) is considered as the most important factor in the dispersal and spread of oak species. We conducted studies in oak stands in four countries (Poland, Hungary, Romania, Ukraine) in the autumn of 2015 and 2016. To identify the preferences of Jays for both acorns and trees, we compared the size of acorns and tree characteristics between each selected tree and the closest unused oak. We found that acorns from selected oaks were smaller (narrower) than those from unused trees. We found no differences in the characteristics of selected and unused oaks. These results indicate that the size of acorns can be an important indicator determining the choices of foraging birds. The Jays’ preferences for specific trees may influence the composition of oak populations. Trees with certain phenotypic and genomic characteristics may be favoured and dominate in the ecosystem

Productivity of the Great Egret (Ardea alba) and Grey Heron (A. cinerea) in mixed heronries in Poland and behavioral response of fledglings to a drone

Productivity of avian populations provides important demographic information helpful in understanding population dynamics and processes involved during species expansions. We tested the hypothesis that the productivity of the two species of ecologically similar herons that breed together in mixed heronries is related to their expansion status. We expected the expansive species, colonizing the new area and increasing in numbers, to outperform the native species, whose abundance is stable. We studied the breeding success of two herons in mixed colonies in eastern Poland in 2018: Great Egret (Ardea alba) (an expansive species, increasing breeding range and population size), and the Grey Heron (Ardea cinerea) (a native species, stable breeding population). Mean productivity (number of young per nest) was similar for Great Egret and Grey Heron and appeared correlated to each other in mixed heronries. Productivity of both species was unrelated to the colony size, but Grey Heron tended to have higher productivity as the proportion of Great Egret nests in the colony increased. Similar productivity of both species can be explained by the sufficient food resources coupled with the low level of competition. The two species differed significantly in their response of young to the approaching drone: the mean probability of a young Great Egret adopting an upright display was 0.47 compared to only 0.18 in a young Grey Heron (P=0.025). This was unlikely an age-related difference as the fledglings of both species were at a similar stage of development, but may represent some kind of a species-specific trait. Our research once again shows that UAVs allow a quick and non-invasive study of the size of the breeding populations and reproductive performance of herons, egrets and other wading birds

Observations of waterbirds on migration along two rivers in northern China during August 2010

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Urban habitats and feeders both contribute to flight initiation distance reduction in birds

© The Author 2014. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. Animals respond to approaching predators by taking flight at a distance that optimizes the costs and benefits of such flight. Previous studies have shown that urban populations of birds have shorter flight initiation distances than rural populations of the same species, that this difference is partly explained by differences in the community of predators, and that a longer history of urbanization implies a greater reduction in flight initiation distance in urban populations. The use of birdfeeders may be an additional factor reducing flight initiation distance not only in cities but also elsewhere by among other effects increasing body condition, increasing availability and reliability of food, and hence reducing the relative cost of flight. Here, we tested the prediction that urban habitats and presence of feeders independently accounted for reductions in flight initiation distance using extensive samples from different cities in Poland. We found independent significant effects of urban habitat and presence of feeders on flight initiation distance. These findings suggest that different factors have contributed to the >tameness> of urban birds.Peer Reviewe