Thanks to a wet year, vigilant human nannies and lots of wriggling fish, Arizona's population of Desert Bald Eagles produced a record 53 chicks this spring, according to the state Department of Game and Fish.
The desert eagles who build nests in cliffs and cottonwoods mostly along the Salt and Verde Rivers logged a 26 percent increase in the number of new chicks that lived long enough to leave the nest. The number of chicks produced also increased by about 4, indicating that the supply of food in swollen, longer-running creeks bolstered by a strong winter snowpack increased chick survival. Normally, only about half of chicks produced live long enough to leave the nest and fly on their own.
The number of Bald Eagles born in Arizona has increased steadily in the past 30 years, despite hard times for the desert riparian areas on which the eagles depend. The number of nesting pairs has risen from a low of about 11 to this year's high of 56. Only three of the nesting pairs this year failed to produce a fledgling, a dramatic increase in survival rates over the long-term average.
The streams and rivers flowing out of the Rim Country provide prime habitat for the desert eagles, including the East Verde and Tonto Creek. Several others nest near Lake Roosevelt. The eagles usually occupy and defend nesting territories along streams, resulting in the regular spacing of nesting pairs along riparian corridors. Biologists had assumed the Bald Eagles had all but saturated the good nesting territories, but then the eagles setup new territories in wet years like this one.
The U.S. Fish and Wildlife Service is currently trying to decide whether to continue to list the Desert Bald Eagles as an endangered population, even though it has taken the birds off the endangered species list nationally. Environmental groups sued and forced the federal wildlife agency to reconsider an earlier decision to downlist the Desert Bald Eagles. The Tonto Apache Tribe joined in that lawsuit, arguing that the Bald Eagles have unique cultural and spiritual importance that justify the continued listing.
The Desert Bald Eagles are a bit smaller than their relatives nationally and apparently almost all of the birds that fledge in Arizona return here to build nests, often after meandering migrations that take them to Canada and Alaska or down into Mexico and out across the American Midwest. Although more than 300 Bald Eagles born elsewhere migrate through Arizona in the winter, only the native-born eagles apparently nest here, according to various studies.
Wildlife officials attributed the record crop of baby eagles this year to intensive management, partially funded by the federal government through the endangered species act. The Arizona Game and Fish Department deploys about 16 teams of nestwatchers, which keep an eye on eagle nests near heavily used lakes and streams.
The nestwatchers warn people away from the nests and sometimes call in biologists for rescue missions. In some years, the nest watchers save 5 or 10 percent of the chicks -- significantly increasing reproduction. They have stopped bulldozers in their tracks, rappelled down cliff faces to remove potentially lethal tangles of fishing line from chicks and once even plucked fledgling eagles from the top of a cottonwood trees just as rising floodwaters reached the nest.
"Arizona's intensive management of the species is paying off," said Kenneth Jacobson, Arizona Game and Fish Department Bald Eagle management coordinator. "The period between the bird hatching and taking its first flight is a critical time. The Bald Eagle nestwatch program and regular monitoring played a significant role in helping these nestlings develop from eggs into independent fledglings."
The eagles typically remain pair-bonded for life. They generally mate in December and their chicks leave the nest by June. They generally return to the same nest site year after year, generally a cliff face or cottonwood within a mile of a stream. They live mostly on fish, chiefly desert suckers and catfish they pluck out of the shallow riffles of desert rivers. However, they'll also eat small animals and carrion. The eagles in the colder northern areas of the state hatch and fledge sooner than the eagles in the south.
Researchers have put satellite radio transmitters on many of the desert born eagles to track their wanderings. They have found that the young eagles scatter across the continent -- north to Alaska, west to Oregon, south deep into Mexico and east to Kansas or beyond. Biologists believe these far-ranging migrations developed in response to ancient food patterns, perhaps calibrated to the migrations of great herds of animals or massive fish spawns on ancient rivers.
The Arizona Game and Fish Department, a leading partner in recovery efforts for the species, attributes the success of the Bald Eagles in Arizona to cooperative on-the-ground management. Through the Southwest Bald Eagle Management Committee (SWBEMC), a broad coalition of 23 government agencies, private organizations and Native American tribes, a plan is in place to help ensure the continued success of the Bald Eagle population in Arizona.
For more information on Bald Eagles in Arizona, visit www.swbemc.org.
The Payson birders will hear a state expert talk about the effort to protect Bald Eagles in Arizona. Visitors welcome at 1:30 p.m. on Wednesday in the Payson Public Library.