Migrating Shorebirds Base Their Layovers On Distance, Researchers Say

Birds set for long migrations share one thing in common: they all need to fuel up and put on large amounts of fat that will be burn over their their travels. Where they differ, say researchers, is in their migratory strategies. A recent study revealed that some birds take week long stops to rest during their long trips, while others make shorter, more frequent stops.

To better understand why migration patterns differ among bird species, researchers from Tulane University captured three migratory bird species along the northern Gulf of Mexico: semipalmated sandpipers, western sandpipers, and dunlins. All three of these sandpiper (Calidrid) species partake in seasonal migrations, although each of their routines differs, according to the university's news release.

After recording the birds' different stopover times and refueling rates, researchers discovered that birds making long migrations tend to remain at their rest stops for longer periods and gain weight faster than those making shorter trips.  

"The authors demonstrate rather convincingly that migration strategies reflect a complex interplay between time and condition - key metrics that determine the success of a migration event," Dr. Frank Moore, an expert in bird migration and stopover biology from the University of Southern Mississippi, said in the release.

Sandpipers are a large family of shorebirds that can be recognizable by their long bodies, legs and beaks and narrow wings. Their diets consist mainly of small invertebrates they can slurp up from the mud or soil. Researchers found Dunlins (Calidris alpina) stored more food before their migration and were able to make longer trips than Semipalmated Sandpipers (Calidris pusilla) and Western Sandpipers (Calidris mauri) who would descend to rest stops more frequently. Dunlins, however, don't have to travel as far as the other two sandpipers tested. They only travel from the uppermost parts of North America to southern coasts and rarely make it past the Equator. Semipalmated Sandpipers are long haulers, traveling each year from breeding grounds in the Artic to the coasts of South America. Western sandpipers travel from breeding grounds in Alaska and eastern Siberia to areas along either the North or South America coast.  

"Studies like this one are a great example of the type of cutting-edge work that is being done in this field. Shorebird stopover sites throughout the migratory flyway are slowly dwindling due to habitat losses, and this information can help to predict the impact of such losses to different bird species and develop conservation plans to mitigate these impacts," Andy Davis, Editor-in-Chief of Animal Migration, added in the release.

Their findings could help conservationists develop better strategies to protect migrating bird populations, the researchers noted. Their study was recently published in the journal Animal Migration.

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