Why they occur here but not there - a case study of Great Spotted Woodpeckers in the city of Munich

Abstract

O_LIMany animal species can occur in the urban environment. The factors determining whether a particular species can live in a particular place in the city are, however, often not known. Such knowledge is needed to be able to design a built environment that is suitable for species. C_LIO_LIThe Great Spotted Woodpecker, Dendrocopos major, breeds in self-made cavities in trees and regularly occurs in cities. Here, we used a number of approaches to elucidate the factors that influence the occurrence of woodpeckers in the build-up area of the city. C_LIO_LIWe studied the occurrence of D. major on 103 squares in Munich, Germany and linked their presence to a number of square features such as square size, position in the city, tree occurrences, and a number of other variables. We also observed the presence of woodpecker cavities and undertook behavioural observations to study tree use. C_LIO_LIWoodpeckers were observed on 60% of the squares. A random forest model showed that the number of humans on squares negatively affected woodpecker occurrence, while a number of tree-related variables, such as tree density, tree diversity, the number of old trees (>60 cm DBH), and the sum of DBH of trees on the square, positively affected occurrence. Some other variables were also important, such as the amount of green in the surroundings and the distance to the city centre. C_LIO_LINests were found only in trees with a DBH>20 cm, and there was a distinct preference for larger trees, whereby a range of species was accepted. Behavioural observations showed that woodpeckers used a wide variety of trees, including small ones. Particular species and trees with a DBH>20 cm are preferred. C_LIO_LIOur study shows that humans can design public places for the presence of the Great Spotted Woodpecker by providing a locally high abundance of trees of different species with total DBH close to 25m. Trees in the surroundings and the presence of softwood trees with >40 cm will make it more likely that woodpeckers will use such sites in the city. C_LI Statement on inclusionOur study brings both established scientists with permanent faculty positions with Ph.D.-students and students of the 2nd year of their B.Sc.-studies or 1st or 2nd year of their M.Sc.-studies for whom this work is the first experience in the publication of scientific results. Students were particularly encouraged to contribute to question and hypothesis development as well as analysis and interpretation.