Migratory birds are counted along their migration route every three years. The observations also provide information about influences on their habitats. Researchers are concerned about climate change.

According to a study, the consequences of the changing global climate are threatening the habitats of some migratory birds along their East Atlantic migration routes.

In north-western Europe, the rising sea level is already one of the main burdens, the Joint Wadden Sea Secretariat in Wilhelmshaven recently announced when the investigation report was published. The Wadden Sea off the coasts of Denmark, Germany and the Netherlands is considered the hub of East Atlantic bird migration. Millions of birds eat up food reserves for their onward flight between Africa and the Arctic in the UNESCO-listed wetland.

Climate change is having an impact on most coastal areas, said Kristine Meise, Program Manager Migration and Biodiversity at the Wadden Sea Secretariat. In the Wadden Sea, for example, in addition to the rise in sea level, extreme weather events such as heavy rain and storms are increasingly affecting the birds when resting and breeding. The consequences of climate change, for example through erosion on the coasts for migratory birds, are already being felt in the main wintering area off West Africa, said Meise. According to the study, other factors such as overfishing, shipping traffic and logging have an even greater influence there.

Count since 2014

The assessments of habitat pollution are part of the investigation report published at the end of April. The project has been counting migratory bird populations along the East Atlantic bird migration every three years since 2014. More than 13,000 people in 36 countries were involved in the last census in 2020, the results of which are now available.

Such regular counts are important in order to identify changes in the populations at an early stage, said Meise. “The difficulty is that a migratory bird does not usually stay in one place – and sometimes it changes its flight route. So it may be that the number of birds of a certain species in the Wadden Sea decreases, but globally the population remains stable or even increases.” Therefore, in order to measure the global population, all locations where the birds can occur would have to be recorded simultaneously.

The last census showed that in 2020 half of the 83 observed migratory bird populations increased compared to observation data several decades ago. 16 percent of the populations were stable, the researchers recorded a decrease in 30 percent – for example in waders that breed in the Siberian Arctic.

A possible explanation for this is changing climatic conditions, said Meise. “The migratory birds have adapted to certain times over thousands of years.” Due to climate change, spring is beginning earlier, and with it snowmelt and the hatching of insects in the Arctic. Meise explained that this would result in poorer conditions for the breeding and rearing of young birds. This could explain a decline in breeding success.

In order to counteract threats and conserve migratory birds, the authors of the report name the protection of preferred bird habitats and the sustainable management of habitats as key measures.