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BOU Register of Avian Thesis Abstracts

Jochen Bellebaum

Influence of predators on the breeding success of meadowbirds in Brandenburg

Institution: University of Osnabrück, Germany
Supervisors: H-H Bergmann, H Hötker (Univ. Kiel)
Details: Ph. D. 2002 (Completed)

Current Address: Institute for Applied Ecology Ltd, Alte Dorfstrasse11, D – 18184 Neu Broderstorf (Sep 2006)
Email: Jochen.Bellebaum @ t-online.de(remove spaces)

Subject Keywords: Vulpes vulpes, breeding success, predation

Species Keywords: Northern Lapwing Vanellus vanellus, Yellow Wagtail Motacilla flava

Abstract:

Predation as a threat to ground breeding birds has received a growing attention during the 1990s. I studied densities and breeding success of Northern Lapwing simultaneously with number and distribution of Red Foxes several years after rabies vaccination in two East German wetlands. The study areas were situated in the Havel and Oder valleys.
Since c. 1995 Red foxes Vulpes vulpes inhabit Eastern German wetlands at similar densities like open farmland (3 – 4.6 litters per 10 km²) except a part of the Lower Oder valley which is flooded every spring (1.5/10 km²). They selected for dry places when excavating dens but in wet meadows along the river Havel increasing numbers of dens closer to ground water suggested a recent immigration. Foxes regularly preyed upon birds in spring but only formed one part of a diverse guild of mammalian predators inhabiting wetlands. Thus at low fox densities other mammals like mustelids became more important as predators. Increasing ground-water tables and removing artificial dry places can help to make wetlands less attractive for foxes.
Conservation management has created attractive habitats for several meadowbird species in both areas. Nest losses due to farming activities were of relatively low importance but throughout the study period losses due to predation were usually high and productivity was insufficient to maintain local populations. Carnivores formed the majority of the predators identified and especially Red Foxes played an important role. The only exception was a hatching success of 66 % for one year in one area which is subject o regular flooding and where area mustelids appeared to be the most important predators. This occurred in 1998 after the catastrophic Oder flood of 1997 which probably led to a crash of local small mammal and mustelid populations. Thus neither culling of corvids nor attempts to control only foxes can be expected to effectively lower predation rates and future management should identify the factors limiting the entire mammalian predator guild.
Lapwing chick survival showed a decrease during summer and was strongly dependent on the availability of water and wet soils in the parents’ territories. Water therefore still seems to be the most important environmental factor in wet grassland management.
Predation on Yellow Wagtail nests in the Oder valley was no important threat. Without additional losses due to mowing and grazing the local population would be self-sustaining. Similar results were obtained in other German studies and a review revealed two general patterns. Mainly large and medium-sized species of ground breeders suffered from high predation rates while songbirds are mostly unaffected. Carnivores have been identified as important predators in virtually all recent thorough studies while birds (including the regularly suspected corvids) were of minor importance.

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