Investigating a seabird hotspot : factors influencing the distribution of birds in the southern Baltic Sea

• Main Author: Sonntag, Nicole
• Other Authors: Garthe, Stefan, Bork, Hans-Rudolf
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2009
• Subjects: ddc:590; thesis; seabirds; distribution; habitat selection; Baltic Sea; Arctic
• Online Access: https://nbn-resolving.org/urn:nbn:de:gbv:8-diss-47672; https://macau.uni-kiel.de/receive/diss_mods_00004767; https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/dissertation_derivate_00003097/Sonntag_diss_2009.pdf

The southern Baltic Sea in northeastern Europe has been described as one of the most important areas for seabirds in the Western Palaearctic, based on extraordinary high numbers of birds occurring in the area particularly during the winter half-year. Most studies, however, only comprise information about the distribution of birds, while the factors and mechanisms causing the observed distribution patterns are only seldom addressed. Prey distribution and abundance and foraging strategies are certainly the most decisive factors determining the distribution and habitat choice of seabirds at sea, but diet preferences are unknown for many species. However, an extensive understanding of the functionality between seabirds and their marine environment is essential not only to be able to assess natural changes in numbers and distribution, but to evaluate the risks posed by anthropogenic activities as human pressure on marine ecosystems has increased enormously over the last decades. This thesis overcomes the lack of comprehensive knowledge about the ecology of birds in the brackish environment of the southern Baltic Sea and provides basic information on bird-habitat-relationships, on interspecific interactions and on diet preferences of selected species. Furthermore, set net fisheries as a particularly high threat to birds in the southern Baltic Sea are exemplarily outlined in this thesis. The methods to address the study objectives comprise ship-based Seabirds at Sea surveys to reveal spatial and temporal distribution patterns, mathematical modelling to analyse these patterns with regard to habitat parameters and species’ interactions, analyses of stomach contents for dietary studies and the development of an approach to evaluate the conflict between birds and human impacts. The avifauna of the brackish Baltic Sea strongly differs from truly marine systems: while pelagic species are only represented by auks, the bird community is dominated by species that breed in (arctic) freshwater habitats and occur in the southern ...