Wind Speeds Predict How Successful Birds are in Massive Spring Migrations

Each year, flocks of birds travel hundreds or even thousands of miles during migration. Now, scientists have found that there may be a way to predict how successful these birds will be in the spring. It turns out wind conditions during migration can actually tell the timing of breeding and survival in yellow warblers.

Migratory birds are important for ecosystems across the world. They pollinate plants, disperse seeds and munch on insects and small mammals. In the case of the yellow warbler, the birds breed in western Canada before traveling to Mexico-a long trek for the small bird each year.

In order to better examine this migration and what might impact its pattern, the researchers used data collected from 380 birds over seven breeding seasons. They then compared these routes and their timing with climatic models. In the end, they found out that wind speeds on migration were the best predictors of annual adult survival, mal arrival date, female egg laying and annual productivity.

More specifically, the researchers found that higher westerly wind speeds during migrations are associated with lower annual survival. This could be because they reflect storm events tat can increase in-flight mortality. In addition, high wind speeds flowing against bird migration can cause the birds to expend more energy, making them take more stops and thus delaying their arrival

"We know that winter conditions have large impacts on migratory birds in eastern North America, but to our surprise we found that conditions on migration had a far greater impact on survival and reproduction of yellow warblers in the west," said Anna Drake, one of the researchers, in a news release. "This is an intriguing result and suggests that differences in the geography of the flyways across eastern and western North America alter when climatic conditions influence the populations dynamics of migratory songbirds."

The findings are published in the journal PLOS One.