Long-distance travels complicate conservation of migratory birds

Migratory birds have fascinated humans for centuries. Every year, millions of individuals travel between their summer breeding grounds and their wintering ranges, often over several thousand kilometres. Migrants thus experience environmental conditions in different parts of the world.

For example, breeding success and population trends of Central European migrants do not depend on local environmental conditions alone. Also, unfavourable conditions in the wintering grounds or during the migration can have detrimental effects on the breeding populations. These issues have been widely acknowledged. Still, impact assessments primarily focus on breeding ranges.

Now, a HU researcher together with colleagues from Switzerland, France and South Africa, have assessed potential large-scale impacts from climate and land cover change on migratory birds.

They analysed over 700 long-distance migratory bird species breeding in the Holarctic and estimated potential global change risks resulting from summer range loss, winter range loss, and from increased migratory distance between seasonal ranges.

The results indicated that these different risks are largely independent from each other and their magnitudes also vary between continents. This means that only assessing potential summer range loss will provide a rather incomplete picture of the global change risks that migratory birds may face.

The researchers further calculated that impact assessments focussing on summer ranges alone could underestimate the number of potentially threatened species by 18-49% and underestimate the potential impact from multiple risks for 17-50% species. Also, many species that could suffer multiple global change risks are not currently listed by the IUCN as threatened or near threatened.

These results provide a first indication how neglecting seasonal ranges in impact assessments could misguide conservation targets, both spatially and at the species level. Hopefully, this global assessment will inspire more detailed work taking into account the full annual cycle and complex behaviour of migratory species.

Dr. Damaris Zurell
Geography Department
Humboldt-Universität zu Berlin
damaris.zurell@hu-berlin.de

Zurell, D., Graham, C.H., Gallien, L., Thuiller, W., Zimmermann, N.E.. Long-distance migratory birds threatened by multiple independent risks from global change. Nature Climate Change. DOI: 10.1038/s41558-018-0312-9

https://www.nature.com/articles/s41558-018-0312-9