Breeding birds in the Wadden Sea at risk due to poor breeding results

Breeding birds in the Wadden Sea do not raise enough offspring to keep the population in a healthy condition. This is the conclusion of a review published today by the Common Wadden Sea Secretariat and the Joint Monitoring Breeding Bird Group (JMBB). The report conducted an analysis of the breeding success among birds in the Wadden Sea over the years 2009–2012. It found that especially typical Wadden Sea bird species, like the oystercatcher, the avocet and the arctic tern, were hardly able to raise any young. The black-headed gull, the lesser black-backed gull, the herring gull and the common tern also showed poor breeding results at many breeding sites across the Wadden Sea.

These results apply to the international Wadden Sea, in Denmark, Germany and the Netherlands, but correspond to previous results from a long-term monitoring project in the Dutch Wadden Sea, which also showed that low breeding success was an important driver for the decline of most breeding bird species.

“The number of birds of several species in the Wadden Sea has continuously declined over the past 20 years. A report published in June 2015 revealed that 15 out of 26 breeding bird species showed a negative trend. This does not mean that adult birds have a higher mortality rate. We now know that poor breeding success is the main factor that explains the decline,” says Gerold Lüerßen of the Common Wadden Sea Secretariat (CWSS), who coordinates the Trilateral Monitoring Migratory and Breeding Bird Group.

The review discusses several factors that might explain this poor breeding success. Especially along the mainland coasts and on islands that are connected with barrier dams to the mainland, breeding birds suffer from a high risk of predation by animals like foxes and martens. Moreover, on several Wadden Sea islands, predator species like hedgehogs have been introduced. Sea level rise and climate change constitute another negative factor. Summer storms are increasingly flooding nests on salt marshes, beaches and other breeding sites exposed to the sea. Finally, several species also suffer from food shortage, which contributes to the poor survival rate of the young.

In order to improve the breeding conditions for breeding birds, the Joint Breeding Bird Monitoring Group has developed a framework for action. This includes habitat restoration, improvement of the existing breeding habitats, predation management, and visitor management.

About the monitoring of breeding success in the Wadden Sea

Monitoring of breeding success in the Wadden Sea has been part of the Trilateral Monitoring and Assessment Programme (TMAP) since 2009–2010. It is, like the chemical analysis of breeding bird eggs, an important addition to the monitoring of abundance and distribution, as it allows detection of the causes for changes in numbers and can be more directly linked to management measures.
 

Report details:

Title: Breeding success in the Wadden Sea 2009-2012. A review.
Authors: Ole Thorup and Kees Koffijberg.
Publisher: Common Wadden Sea Secretariat, Wilhelmshaven (Germany).
Download: www.waddensea-secretariat.org/WSE36-Breb_success.pdf
More information: Kees Koffijberg, Sovon Vogelonderzoek, Netherlands
Office: +49 2855 30499 55. E-mail: kees.koffijberg@t-online.de