The use of a drone to count the flock sizes of 33 species of waterbirds during the breeding and non‐breeding periods was investigated. In 96% of 343 cases, drone counting was successful. 18.8% of non‐breeding birds and 3.6% of breeding birds exhibited adverse reactions: the former birds were flushed, whereas the latter attempted to attack the drone. The automatic counting of birds was best done with ImageJ/Fiji microbiology software – the average counting rate was 100 birds in 64 s. Machine learning using neural network algorithms proved to be an effective and quick way of counting birds – 100 birds in 7 s. However, the preparation of images and machine learning time is time‐consuming, so this method is recommended only for large data sets and large bird assemblages. The responsible study of wildlife using a drone should only be carried out by persons experienced in the biology and behavior of the target animals.

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 ScaupAythya marila, Tufted DuckA. fuligula, Common PochardA. ferina, Common GoldeneyeBucephala clangulaand Eurasian CootFulica atra), and two are piscivores (SmewMergellus albellusand GoosanderMergus 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.

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 19^th 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.

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... RESUMEN La construcción del nicho puede llevar a episodios de coevolución y mayor especialización y puede tener implicancias para la evolución de la diversidad biológica, por lo que entender cómo los individuos ajustan sus comportamientos a otros individuos de la misma especie y de diferentes especies en gradientes sociales y ambientales cambiantes representa un desafío interesante de investigación. El objetivo de este trabajo fue evaluar la hipótesis de que las bandadas mixtas de gaviotas y patos buceadores se congregan como resultado de una interacción por alimentos entre ellos. Los patos son vectores que transportan Mejillones Cebra desde el fondo de los cuerpos de agua hacia arriba, y las gaviotas consumen este tipo de alimento. Investigamos tres patos bentívoros– Aythya marila, A. ferina, A. fuligula – en la Laguna Szczecin, Polonia. Encontramos que la presencia de las gaviotas en las bandadas de patos estuvo estrechamente asociada con el forrajeo de los patos. 84% de las bandadas de patos que forraj...

This research was carried out in north-eastern Poland, where Whooper Swan Cygnus cygnus is a sparse breeder. Whooper Swan is timid and exhibits a tendency to hide in emergent vegetation. A drone was used to improve the effectiveness of research into its breeding success and offspring productivity. The breeding density of Whooper Swan in the study area in 2022 was 10 pairs/100 km². The number of breeding birds detected at the beginning of the breeding season did not differ according to the method used (drone vs ground). The breeding productivity of the sample of swans studied (N = 36) was 2.19 cygnets per breeding pair using the ground method, but 3.71 per pair with the drone, a significant difference (p-value of the Wilcoxon test = 0.0148). The traditional method showed that 50% of the pairs had bred successfully, whereas with the drone this figure was 79%. The birds either did not react to the drone’s presence or else moved slowly away. The drone study of Whooper Swan breeding productivity was considerably faster (9 min per site vs 1–2 h ground survey), more precise, and less invasive for the birds than a traditional ground survey.