This is especially troublesome for birds flying long distances, such as Neotropical migrants that winter in the Caribbean, Central and South America and travel to North America to breed in the summer.
“This means that if changes in spring arrival are not uniform along migration routes and between wintering and breeding habitats, birds have trouble keeping up with the shifts.” “Migrating birds depend on the right conditions in habitats that are spread out over really large distances” said co-author Jake Weltzin, an ecologist with USGS and the Director of USA-NPN. Spring advance was significantly earlier in the north compared to the south in all flyways except for the Pacific. Spring leaf out and bloom not only advanced between a third of a day and more than half a day per decade on average, within flyways, but also demonstrated different rates of change across latitude. Along the migratory flyways, the researchers calculated rates of change in spring onset from south to north across the continent. Combined, this shows that many of our national jewels – parks and wildlife refuges alike – are experiencing seasonal changes over time.Įxtending beyond the scope of wildlife refuges, this study shows how local changes are embedded in continental-scale change.
This study confirms recent findings of similar changes in spring onset in the national parks. Shifts in spring leaf out were as high as three days earlier per decade. To calculate the changing timing of spring leaf out and bloom in wildlife refuges, the researchers compared the onset of spring in recent decades to the onset of spring over the last century. The authors found that the rate of spring advance was higher at northern latitudes than lower latitudes in the Central, Mississippi, and Atlantic flyways (USGS). In the Central, Mississippi, and Atlantic flyways, the rate of spring advance was greater at northern latitudes than southern latitudes. Also, the shift to earlier spring is not uniform across migratory flyways. They found that in recent decades, spring leaf out and bloom arrived extremely early at 49 percent of refuges. In a newly released study, a team of USGS, University of Arizona and USA National Phenology Network (USA-NPN) scientists puts the annual onset of spring over the last century in the context of National Wildlife Refuges and the four major migratory flyways of North America. The indices estimate when the emergence of new leaves, known as leaf out, and bloom of early season plants occur each year, with data going back to the early 1900s. A depiction of North America’s major waterfowl flyways (left to right: Pacific, Central, Mississippi, and Atlantic Credit NWF) (Public domain.)įood resources and nesting conditions are closely linked to the start of spring activity in plants, which the USGS-led USA National Phenology Network predicts with indices of Spring Leaf and Bloom.
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