Bird Feeder Explorers Are Not Attracted by the Seeds of Invasive Weeds in Winter

Abstract

Winter feeding of birds is one of the most widespread forms of human influence on animals in the world. Urban areas, however, contain many other food sources apart from the contents of feeders, including contaminated food and seeds of invasive plants. This research aimed to investigate whether birds exploring urban food select it, giving up potentially toxic or unknown seeds, or whether they use every available food. In the winter of the year 2022, an experiment was carried out with 18 feeders in two city parks in Kraków, Poland, which was based on feeding birds using sunflower seeds with various admixtures of the invasive Caucasian hogweeds Heracleum sp. seeds. Despite the detection of pecking marks on the hogweed seeds, only a small part of them disappeared from the feeders compared to the intensive feeding of birds on sunflower seeds. This result shows that not every new food source in the city can be used by birds. Urban explorers remain selective when choosing food, which keeps their behaviour close to non-urban populations.