Islands Life: Timing, Size & Location All Matter To Birds

Image credit Noel Donaldson

Islands host an amazing number of resident and migratory birds all across the world. Islands in the Northern Hemisphere see bird numbers increase by a staggering amount as the migratory species arrive during the summer season.

Not surprisingly the bigger the island, the more bird species. The further away an island is from mainland, for example, more than 90 miles , there are fewer species.

The geographic characteristics of the world’s islands and the seasonal variation in the number of bird species they host has been studied by researchers from the Cornell Lab of Ornithology’s eBird program.

Tristan Thrush on access-restricted Nightingale Island. Image credit: James Holmes, Macaulay Library, Cornell Lab of Ornithology.

Frank La Sorte, Cornell Lab, explained:

“These findings emphasize the importance of evolutionary processes on the largest islands and the unique ecology of the world’s most remote islands.

“Overall, species richness was lowest across all four seasons on the smallest, most remote islands and species richness was highest across all four seasons on the largest islands located at intermediate distances from the mainland

“Our findings show that islands play a pivotal role as stopover sites and as wintering grounds for the world’s migratory birds.

“A better understanding of the geographical relationships between migratory birds and islands across seasons will improve our ability to practice effective bird conservation in these unique places.”

Saint Helena’s Plover. Image credit: Rafael Armada, Macaulay Library, Cornell Lab of Ornithology.

Link to Study: La Sorte FA, Somveille M, Dokter AM, Miller ET. 2022 Seasonal species richness of birds on the world’s islands and its geographical correlates. Proc. R. Soc. B 289: 20221105.   

Image credit Bell

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