Habitat selection of seabirds in a highly dynamic coastal sea: temporal variation and influence of hydrographic features

• Main Author: Markones, Nele
• Other Authors: Garthe, Stefan, Bork, Hans-Rudolf
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2007
• Subjects: ddc:590; thesis; seabirds; Black-legged Kittiwake; habitat choice; hydrography; SE North Sea; seasonality; activity budgets; variability; Seevögel; Dreizehenmöwe; Habitatwahl; Hydrografie; südöstliche Nordsee; Saisonalität; Aktivitätsbudgets; Variabilität; rissa tridactyla
• Online Access: https://nbn-resolving.org/urn:nbn:de:gbv:8-diss-26015; https://macau.uni-kiel.de/receive/diss_mods_00002601; https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/dissertation_derivate_00002278/Markones_2007.pdf

In the German Bight (south-eastern North Sea), recent high efforts of at-sea studies have led to an increasing knowledge of key hotspots and general distribution patterns of the most common seabird species. Distribution patterns were shown to undergo temporal variation, in particular at the order of seasons. So far, less attention was paid to variability of distribution patterns at smaller time scales. Variability of seabird distribution complicates conservation and management efforts as it constrains the ecological evaluation of specific areas, the calculation of total numbers, and the assessment of population trends or shifts in distribution. The next step on our way to a thorough picture of the life of seabirds at sea has thus to be the understanding of factors and processes driving the observed patterns. This thesis consequently focused on habitat choice of seabirds in the German Bight and on temporal variability of seabird distribution patterns. Study objectives were addressed by analysing dedicated seabirds at sea surveys and long-term survey data. Small scale temporal variability of seabird distribution patterns was found to be substantial at the order of days. However, several factors and mechanisms influencing distribution patterns and their temporal variation at the order of seasons and days were identified. A significant influence was revealed for large scale hydrographic structures, i.e. water masses, small scale hydrographic structures such as fronts, tidal stage, wind speed and fishing activity. Most of these factors represent direct or indirect indicators of food availability for seabirds. The connecting link between hydrographic features and seabird distribution was addressed in one case study dealing with the diet of Black-legged Kittiwakes Rissa tridactyla in the study area. Their main prey was found to be juvenile Whiting Merlangius merlangus. These fish concentrate in frontal areas of the North Sea. Accordingly, Kittiwakes showed a significant association with fronts in the German Bight in ...