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New Utah study shows how dry years disrupt bird populations

Black-chinned hummingbird
Posted at 1:15 PM, Oct 28, 2021
and last updated 2021-10-28 15:53:43-04

SALT LAKE CITY — As droughts in the West cause natural habitats to become dry and cracked for birds, they flock to riparian areas—those green areas near rivers that remain relatively lush. But this means increased competition for the birds who naturally call the river home.

New research from the University of Utah (U) and the Utah Division of Wildlife Resources (DWR) found that increased diversity is accompanied by overcrowding and an overall decrease in populations of birds who rely on rivers to live.

“In a changing climate, it is critical to understand how birds and other organisms are responding,” says Monte Neate-Clegg, a recent University of Utah graduate and postdoctoral scholar at the University of California, Los Angeles. “From a conservation standpoint, the results are troublesome.”

Their study, published in Animal Conservation, looked at how important rivers and riparain areas were to bird migrations.

“Riparian birds are reporting in on Utah’s most important habitat, the health of our riparian systems,” says Russell Norvell, Avian Conservation Program Coordinator for the UDWR. “We all know how crucially important water is in the West for human populations and everything else.”

This study grew from studies thirty years ago when the DWR and federal partners began monitoring these birds to assess the size and health of the population, but funding cuts in 2010 meant the data went unused for twenty years.

But in 2016, Neate-Clegg began his doctoral studies at the U, and spent time banding migrating birds at the U’s Rio Mesa research station in southern Utah, which includes a stretch of the Dolores River—and the previous study took on new life.

“It became apparent how important these rivers and riparian habitats were for migratory birds within the harsh desert landscape,” he says.

Neate-Clegg and his colleagues noticed that during particularly dry years they were finding more birds than usual near rivers, so turned to the data set gathered twenty years earlier to explore changes in how droughts affected the bird populations.

This data showed that more than 31,000 birds over 15 years came from 148 species, with nearly twice as many being "non-riparian" birds, showing the importance of rivers as a "stop over."

It also showed that the hotter and drier the year, the more birds from all over the landscape found their way to rivers, as they could not survive in their typical environment.

Also troublesome was a finding that bird breeding was down, which the study's authors thought could be caused by more more competition for fewer resources.

“This study shows how native bird populations utilize these habitats,” Norvell says. “As droughts intensify, this becomes increasingly the refuge that everything’s relying on. And I don’t think humans are all that different in this case. We’re all increasingly relying on these very same areas.”

Currently, the DWR is working to restore riparian habitats through Utah’s Watershed Restoration Initiative, a partnership between state and federal agencies that has completed more than 2,400 restoration projects, with 258 ongoing.

DWR has also shifted its bird monitoring program to all habitats throughout the state, recognizing the importance and interconnectedness of bird populations.

“It’s an outgrowth of the value we saw from the riparian data,” Norvell says. “We’ve been able to convince partners like the Bureau of Land Management, the United States Forest Service, the Department of Defense and several NGOs to expand this idea into a collaborative all habitat, all bird approach.”

Read how the Bird Conservancy of the Rockies is coordinating bird monitoring here.

Find the full bird monitoring study here.