Dariusz Wysocki

Urbanization affects neophilia and risk-taking at bird-feeders

Urban environments cover vast areas with a high density of humans and their dogs and cats causing problems for exploitation of new resources by wild animals. Such resources facilitate colonization by individuals with a high level of neophilia predicting that urban animals should show more neophilia than rural conspecifics. We provided bird-feeders across urban environments in 14 Polish cities and matched nearby rural habitats, testing whether the presence of a novel item (a brightly coloured green object made out of gum with a tuft of hair) differentially delayed arrival at feeders in rural compared to urban habitats. The presence of a novel object reduced the number of great tits Parus major, but also the total number of all species of birds although differentially so in urban compared to rural areas. That was the case independent of the potentially confounding effects of temperature, population density of birds, and the abundance of cats, dogs and pedestrians. The number of great tits and the total number of birds attending feeders increased in urban compared to rural areas independent of local population density of birds. This implies that urban birds have high levels of neophilia allowing them to readily exploit unpredictable resources in urban environments.

Who started first? Bird species visiting novel birdfeeders.

Adapting to exploit new food sources may be essential, particularly in winter, when the impact of food limitation on survival of individuals is critical. One of the most important additional sources of food for birds in human settlements is birdfeeders. At a large spatial scale, we experimentally provided birdfeeders with four different kinds of food to analyze exploitation and use of a novel food supply provided by humans. Nine species started foraging at the new birdfeeders. The species that exploited the new feeders the fastest was the great tit. Use of novel food sources was faster in urban habitats and the presence of other feeders reduced the time until a new feeder was located. Urbanization may be associated with behavioural skills, technical innovations and neophilia resulting in faster discovery of new food sources. This process is accelerated by the experience of feeder use in the vicinity, with a strong modifying effect of the number of domestic cats.

Winter Bird Assemblages in Rural and Urban Environments: A National Survey

Urban development has a marked effect on the ecological and behavioural traits of many living organisms, including birds. In this paper, we analysed differences in the numbers of wintering birds between rural and urban areas in Poland. We also analysed species richness and abundance in relation to longitude, latitude, human population size, and landscape structure. All these parameters were analysed using modern statistical techniques incorporating species detectability. We counted birds in 156 squares (0.25 km2 each) in December 2012 and again in January 2013 in locations in and around 26 urban areas across Poland (in each urban area we surveyed 3 squares and 3 squares in nearby rural areas). The influence of twelve potential environmental variables on species abundance and richness was assessed with Generalized Linear Mixed Models, Principal Components and Detrended Correspondence Analyses. Totals of 72 bird species and 89,710 individual birds were recorded in this study. On average (±SE) 13.3 ± 0.3 species and 288 ± 14 individuals were recorded in each square in each survey. A formal comparison of rural and urban areas revealed that 27 species had a significant preference; 17 to rural areas and 10 to urban areas. Moreover, overall abundance in urban areas was more than double that of rural areas. There was almost a complete separation of rural and urban bird communities. Significantly more birds and more bird species were recorded in January compared to December. We conclude that differences between rural and urban areas in terms of winter conditions and the availability of resources are reflected in different bird communities in the two environments.

Weather conditions and breeding season length in blackbird (Turdus merula)

Abstract. The timing of egg laying by songbirds is known to be strongly affected by local climate, with temperature and precipitation being the most influential factors. However, most research to date relates only to the start of the breeding season: later records and the duration of the whole have not been taken into consideration. In the case of multibrooded species, productivity usually depends on the length of the breeding season. In this work we analysed climatic factors affecting breeding season length of an urban blackbird (Turdus merula) population. The study was conducted in two parks in the city of Szczecin, north-western Poland, spanning 14 breeding seasons since 1997. We found that over the study period, the breeding season became shorter as a result of colder springs and possibly because of warmer June-July temperatures. Our study revealed a positive relationship between breeding season length and the mean and mean minimum temperatures in April. Total precipitation in April-July also positively influenced breeding season length. The present survey confirms the influence of temperature and precipitation on the breeding season length of blackbird.

Survival and Site Fidelity of Urban Blackbirds Turdus merula — Comparison of Cormack-Jolly-Seber and Barker Models

Abstract. Studies dealing with the individual survival of birds in open populations usually estimate survival according to capture-recapture models like the Cormack-Jolly-Seber (CJS). In fact, these models estimate local apparent survival (ϕ), which is a combination of the probabilities of true survival (S) and site-fidelity (F), i.e. death and emigration are confounded. These S and F parameters can be estimated by using ‘robust’ models (e.g. Barkers model), which use additional resighting and dead reports data. We aim to compare the results (and associated biological implications) obtained by analysing juvenile and adult survival in a Polish urban population of Blackbirds Turdus merula using both the CJS and Barker models. Our CJS models estimated high ϕ values for both juvenile and adult birds (0.48 and 0.62, respectively). The lower scores for juveniles could be interpreted as low juvenile overwintering survival. By fitting Barker models to the same dataset we determined that juvenile site fidelity was lower than that of adults (0.91 and 0.93, respectively), so natal dispersal was slightly greater than breeding dispersal. The high fidelity causes similarity between apparent survival and true survival parameters (S: 0.51 for juveniles, 0.64 for adults). The results are comparable with data from other urban populations. Thus, using robust models certainly allows one to reduce the noise of movements confounding and/or masking survival probabilities, but one can also determine the individual or environmental variables affecting any of them separately.

The Importance of Non-Native Prey, the Zebra Mussel Dreissena polymorpha, for the Declining Greater Scaup Aythya marila: A Case Study at a Key European Staging and Wintering Site.

The European population of Greater Scaup Aythya marila has experienced an alarming, ~60% decline in numbers over the last two decades. The brackish lagoons of the Odra River Estuary (ORE) in the south-western Baltic Sea, represent an important area for the species during the non-breeding season in Europe. The lagoons regularly support over 20 000 Scaup, with peaks exceeding 100 000 (38%–70% of the population wintering in NW Europe and the highest number recorded in April 2011–105 700). In the ORE, Scaup feed almost exclusively on the non-native Zebra Mussel Dreissena polymorpha. This mussel was present in the ORE already in the 19th century and continues to be superabundant. Using the results of 22 Scaup censuses (November to April 2002/2003 to 2013/2014) from the whole ORE (523 km2 of water), we show that Scaup flocks follow areas with the greatest area of occurrence and biomass of the Zebra Mussel, while areas with low mussel densities are ignored. The numbers of Scaup in the ORE are primarily related to the area of Zebra Mussel occurrence on the lagoon’s bottom (km2) in a non-linear fashion. Zebra Mussels were absolutely prevalent (97% of biomass) in the digestive tracts of birds unintentionally by-caught in fishing nets (n = 32). We estimate that Scaup alone consume an average of 5 400 tons of Zebra Mussels annually, which represents 5.6% of the total resources of the mussel in the ORE. Our results provide a clear picture of the strong dependence of the declining, migratory duck species on the non-native mussel, its primary food in the ORE. Our findings are particularly important as they can form the basis for the conservation action plan aimed at saving the north-western European populations of Scaup.

Factors affecting nest size in a population of Blackbirds Turdus merula

Capsule We examined intraspecific variation in the nest size of open cup nesting Blackbirds Turdus merula and found that of seven variables considered, nest size variation was determined by the length of the nest construction period, nest height and the experience of the building female. Aims We tested seven hypotheses to investigate the influence of the following factors on nest size: (A) speed of construction: smaller nests are constructed faster; (B) nest height: nests placed higher up are smaller; (C) experience: inexperienced females construct smaller nests; (D) predation pressure: predation is less on smaller nests; (E) clutch size: larger nests contain larger clutches; (F) nest placement: nests constructed in open areas are larger than those situated in well-concealed sites and (G) incubation: larger and thicker nests are constructed during colder periods. Methods We used data from 54 Blackbird females nesting (73 nests) in two urban parks. Results Our data supported the speed, nest height and experience hypotheses. With respect to predation pressure, our data indicated that breeding failure occurred later in smaller nests. We found no evidence for the placement and incubation hypotheses. Conclusion Nest size may be determined by predator avoidance and the energy used during building. The negative relationship between nest size and time of nest failure suggests that nest size parameters are adjusted to avoid predation.

Newly demonstrated foraging method of Herring Gulls and Mew Gulls with benthivorous diving ducks during the nonbreeding period

ABSTRACT Niche construction can lead to coevolutionary episodes and greater specialization, and can have implications for the evolution of biological diversity, so understanding how individuals adjust their behavior to conspecifics and heterospecifics over changing social and environmental gradients presents an interesting research problem. The objective of our study was to test the hypothesis that mixed flocks of gulls and diving ducks congregate as a result of interacting over food. Ducks are vectors that carry zebra mussels (Dreissena polymorpha) up from the bottom of a water body, and gulls consume this type of food. We investigated the interactions of 2 gull species with 3 benthivorous duck species—Common Pochard (Aythya ferina), Tufted Duck (A. fuligula), and Greater Scaup (A. marila)—in the Szczecin Lagoon, Poland. We found that the presence of gulls in duck flocks was closely correlated with foraging by ducks. Eighty-four percent of foraging duck flocks (>5% of the flock members were foraging) and 52% of nonforaging duck flocks (<5% of the flock members were foraging) were accompanied by gulls (Fishers exact test, P = 0.008). The odds ratio showed that every 10% increase in the number of foraging ducks doubled the chance of gulls being present (odds ratio of 10% unit change = 2.058). We defined the relationship between the size of the foraging duck flock and the number of gulls present in it; the number of gulls rose with increasing numbers of ducks in the flock. All our findings confirmed that this gull–duck co-occurrence was the result of interaction over food (commensalism or interspecific kleptoparasitism). We showed that the diet of gulls in the Szczecin Lagoon changed dramatically when Aythya ducks made their appearance; after duck arrival, gull pellets contained almost exclusively mussels. Our results reveal that the trophic relationship between zebra mussels and the studied bird species is not just a straightforward one between predator and prey.

Ducks change wintering patterns due to changing climate in the important wintering waters of the Odra River Estuary

Some species of birds react to climate change by reducing the distance they travel during migration. The Odra River Estuary in the Baltic Sea is important for wintering waterfowl and is where we investigated how waterbirds respond to freezing surface waters. The most abundant birds here comprise two ecological groups: bottom-feeders and piscivores. Numbers of all bottom-feeders, but not piscivores, were negatively correlated with the presence of ice. With ongoing global warming, this area is increasing in importance for bottom-feeders and decreasing for piscivores. The maximum range of ice cover in the Baltic Sea has a weak and negative effect on both groups of birds. Five of the seven target species are bottom-feeders (Greater Scaup Aythya marila, Tufted Duck A. fuligula, Common Pochard A. ferina, Common Goldeneye Bucephala clangula and Eurasian Coot Fulica atra), and two are piscivores (Smew Mergellus albellus and Goosander Mergus merganser). Local changes at the level of particular species vary for different reasons. A local decline of the Common Pochard may simply be a consequence of its global decline. Climate change is responsible for some of the local changes in the study area, disproportionately favoring some duck species while being detrimental to others.

Blackbirds Mate Choice: Dependence of Male Social Status on Age and Morphology in an Urban Population of the European Blackbird, Turdus merula L.

ABSTRACT The differences in morphology and age between single and paired males of an urban population of the European Blackbirds (Turdus merula) were studied in Żeromski park in the city of Szczecin (NW Poland) spanning 11 breeding seasons since 1998. The proportion of single to paired males in different age groups was established. Also, morphology features like the length of tail, wing and tarsus of 45 single males and 475 paired males were collected. We found that old males (after second year of life) formed pair bonds more often than the young males (in their second year of life). The probability of being a paired male in case of young males increased along with the tarsus length.