Desert Nesting Bald Eagles: On the Wrong Side of Progress

The jeep grumbled in low gear as Janie Agyagos and Cecelia Overby both U.S. Forest Service biologists, and I inched up an impossibly steep hill outside Cornville, in central Arizona. Small green buds tipped the skeletal creosote bushes beside the road and gaudy Indian paintbrush flowers dotted the hills in every direction. At the hill’s crest the road abruptly ended, barely giving Agyagos enough time to stop the jeep before plunging 800-feet into Oak Creek. Perched on the cliff’s edge, I looked down into the valley and followed the creek’s serpentine path with my eyes. Giant cottonwood trees crowded its banks, their canopies dusted phosphorescent green with the first leaves of spring. The moist scent of new growth wafted up the hill to meet us as we peered down, squinting through binoculars. Scanning the cliffs, then the trees, Overby turned to Agyagos and me and whispered, “eagle!”

Desert bald eagles, sometimes called Desert nesting bald eagles or Sonoran bald eagles, represent a unique and particularly hardy population found only in the American Southwest. While a member of the same species as the rest of North America’s bald eagles (Haliaeetus leucocephalus), the desert variety have a unique genetic fingerprint. Exactly how unique is a point of contention amongst geneticists. Desert bald eagles are smaller than other bald eagles, weighing about 4 kilograms (kg) as opposed to 5kg or more for their Alaskan brethren. One of their more unique adaptations for desert life is their ability to nest, not just in trees, but also on cliffs and even saguaro cacti. Their specialized diet of native fish and water fowl generally tie them to bodies of water, but Desert bald eagles are occasionally seen in dry forests as high as 9,000 feet. Most notably though, Desert bald eagles live and breed in the southwest and do not migrate like other bald eagles. In all but one case, they have mated with other Desert bald eagles and not with the more than 300 bald eagles that migrate to the state each winter. This inability, or unwillingness to breed with non-Desert bald eagles makes them particularly susceptible to extinction, but also very unique. Arizona is home to approximately 166 individuals and 59 nesting pairs – a small population by anyone’s account. A handful more are scattered across New Mexico, Texas and northern Mexico. Two other unique populations are found in Florida and in southern Baja, Mexico.

I had been invited on a routine check-up of the Oak Creek Breeding Area where a pair of Desert bald eagles had been observed nesting in previous years. The cottonwood in which the nest had previously been seen, had fallen over four years ago, and the nest was promptly rebuilt on a nearby cliff. Apparently less than ideal, the cliff was abandoned last year and a new nest was built in a sturdy cottonwood just downstream. The nest’s new location was news to the two biologists, who were thrilled by their discovery. Although the day was fair and the eagles seemed content, the idyllic scene was far from complete. A number of houses had been built among the cottonwoods, just up and downstream from the nest tree. Outside one house, and no more than 100 yards from the nest tree, was a pile of trash, the tin cans gleaming in the sun. Another homeowner had reduced a large patch of forest to barren ground for his five somber horses that milled about in the heat looking for shade. Less than a quarter mile beyond the nest, a riverside RV park shimmered white and metallic under the mid-day sun. Dually trucks came and went on an inky black road between patches of meticulously manicured grass. While Agyagos plucked the tripod and scope from a rock outcropping and walked off to look for a better view, Overby took a moment to explain that the Desert bald eagle was fast becoming an “urban bird.”

One of the most significant threats facing the Desert bald eagle is what boils down to a turf war. Unfortunately water frontage is just as popular with Arizona’s human population as it is with the state’s bald eagles, and wildlife rarely wins when prime real estate is at stake. The Arizona Game and Fish Department (AGFD) and the Tucson based conservation group, Center for Biological Diversity (CBD), agree that as much as 90 percent of the state’s riparian areas – habitat bordering water – have been lost due to development, cattle grazing, human activity, and dams. While they agree on this single fact, they seem to disagree on everything else. ADGF and the Fish and Wildlife Service (FWS) insist Arizona’s eagles will survive, even thrive, under current management plans, with or without Endangered Species Act (ESA) protection. CBD argues that they are doomed without the habitat protection that only ESA “threatened” or “endangered” status provides.

In the nation’s second fastest growing state – as much as 40 percent more people annually – Arizona’s habitat vs. growth conundrum will likely get worse before it gets better. Compounding the issue is Phoenix, the country’s fifth largest city, with almost 1.6 million people, positioned just south of the Verde and Salt Rivers. These two rivers are where 51 percent of Arizona’s bald eagles nest. Some estimates suggest the population of Phoenix could swell to more than 12 million by 2030, putting even more development and recreation pressure on land already pushed to the limit. A new nesting site on the Salt River in metropolitan Phoenix shows that Desert bald eagle’s are either adaptable or desperate, probably both.

One of the most significant causes of riparian degradation is cattle grazing on USFS and BLM lands throughout the state. Even the relatively lush hillsides around the Oak Creek nest will be grazed this spring, according to Agyagos. Mature cottonwood trees near water are the preferred nesting sites for all Desert bald eagles, particularly along the Salt and Verde Rivers. Aging trees are not being replaced because saplings are eaten by cows and trampled by both cows and off-road vehicles. “The philosophy of AGFD is no different than the Arizona Cattle Growers Association,” said Dr. Robin Silver, a founding member of CBD. “In less than 50 years, most of the mature trees we now see along central Arizona’s rivers will have fallen.” Because so few young trees are able to grow higher than a cow’s lips, Desert bald eagles may be forced to nest in less favorable locations in the future. “Despite many outstanding scientists in the federal agencies, there is a disconnect between the feds and science,” lamented Silver.

In addition to habitat destruction, Desert bald eagles are vulnerable to other dangers and annoyances. In riparian areas, monofilament fishing line discarded by anglers continues to be a problem for Desert bald eagles and their young. According to a 1994 AGFD memo, “…We have continued to observe monofilament and fishing hooks attached to adult and nestling eagles. Fishing tackle has been found at half of all the breeding sites in Arizona and has killed two nestlings…” A 2000 AGFD note elaborated:

Anglers, hikers and boaters further disturb Desert bald eagles by approaching nests and by making excessive noise. Far more wary of people than bald eagles in northern climes, Desert bald eagles will flee or even permanently abandon their nests with sufficient disturbance.

When riparian and river ecosystems are harmed, a host of other species are affected, including the Desert bald eagle’s prey. Even after the chore of establishing a nest is taken care of, Desert bald eagles must feed themselves and one or more ravenous chicks. One of their primary foods is soft (non-boney) warm water native fish, primarily of the genus Catostomus, also known as sucker fish. Spawning in shallow water in the early spring, sucker fish are easily caught by Desert bald eagles. Desert bald eagles rely so heavily on these fish that they have altered their own breeding season to take advantage of the increased prey. But due to greatly fluctuating water levels and the introduction of non-native boney fish such as bass and carp, native fish are imperiled in virtually every part of their range. Non-native fish compete for precious resources and can carry diseases native fish are not immune to. In a 2004 statement by the Desert Fish Team, “The distribution and abundance of all fish species in the [Gila] basin have declined in modern times. This trend continues and is accelerating.” The Gila Basin encompasses the Salt and Verde Rivers, as well as Phoenix and other fast-growing urban centers. While some non-native fish are edible to Desert bald eagles, most are not.

Native fish, even when available, often carry heavy metals, specifically mercury. The majority of mercury pollution comes from power and chemical plants, as well as from mining and heavy industry. Fish absorb the metal through their gills as they breathe and store it in their bodies. When eagles dine on these fish, they also absorb and store the metal. In high concentrations, the metal can be passed on to their eggs and offspring where its effects are more toxic than in adults. According to AGFD, of ten eggs collected from 1994 to 1997, five were at or over the toxic limit of 2.2 parts per million. Mercury can lead to fatal brain lesions and hemorrhaging, as well as developmental problems in young birds, and has been linked to egg shell thinning.

In addition to the pressures placed on Desert bald eagles by people, they face a host of natural obstacles including a population naturally limited in its range and size, extreme summer heat and limited and hard to find prey. While Desert bald eagles have evolved to cope with heat, the increased drought cycles and heat resulting from climate change have already negatively affected Arizona’s bald eagles and could become worse in the future. AGFD reported 11 eaglet mortalities from 1987 to 1998 as a direct result of heat stress. Though the Desert bald eagle is superbly adapted to desert conditions, the environment they have evolved into was never likely to support large numbers of eagles.

Despite a reasonably successful management program, the question remains: will Desert bald eagles be able to survive Arizona’s growing pains without protection from the Endangered Species Act (ESA)? For the time being, conservation groups and the federal agencies charged with managing the eagles agree that the Desert bald eagle is doing well. The question on everyone’s mind, though, is how will they be doing in 50 years?

Because there are so few Desert bald eagles, and their population appears to be unique and separate from other bald eagles, the Center for Biological Diversity (CBD) and the Maricopa Audubon Society, both of Arizona, petitioned the Fish and Wildlife Service (FWS) to list the Desert bald eagle as a Distinct Population Segment (DPS) on October 6, 2004. Under this classification, the Desert bald eagle would remain protected even after the anticipated ESA delisting of the thriving North American bald eagle. When FWS did not respond to the petition in the required 90-days, the conservation groups sued for unreasonable delay. Almost two years later, FWS issued a negative 90-day finding – the Desert bald eagle would not be granted ESA protection. Despite a challenge by the plaintiffs, all bald eagles in the contiguous U.S., including the Desert bald eagle, were removed from ESA protection on July 9, 2007. Seeking a ruling on their original case, the conservation groups with several Arizona tribal groups, successfully argued in district court that the FWS’s negative 90-day finding in 2004 was “arbitrary and capricious.” FWS agreed that Desert bald eagles are a “discrete population,” but argued they did not occupy a unique ecological setting, which alone would grant them DPS status and entitle them to ESA protection. The ruling held and FWS was forced to reconsider their 90-day finding, taking into account the testimony of Arizona Native tribes, the public and the scientific data originally collected by the plaintiffs. Furthermore, the court concluded that a teleconference between Southwest FWS officials and their superiors in Washington D.C. on July 18, 2006 was not consistent with scientific method. In this conversation, the Southwest FWS office was given “marching orders” not to grant Desert bald eagles DPS status. The court directed FWS to determine if the Desert bald eagle was a DPS before December 2008, which was extended to October 2009 after Arizona Native tribal interests requested more time to determine the Desert bald eagle’s historic significance. Until the review concludes in October 2009, the Desert bald eagle is listed as “threatened” and protected under the ESA.

When I asked Robin Silver of CBD what the center will do if ESA protection is denied in October, Silver said, “We will go back into court and put their biologists on the stand. We’ll see what they say when we ask them the hard questions about their own demography studies. The bottom line,” Silver continued, “is that Desert bald eagles will not survive in Arizona without their habitat, and ESA protection is the only way to protect habitat.”

In 1782, at the behest of Benjamin Franklin, America very nearly adopted the turkey as the nation’s symbol. Instead the Confederation Congress adopted the bald eagle. At the time, North America had an estimated 250,000 bald eagles. The symbol was stamped on coins, emblazoned on flags, printed on money and promoted throughout the country, becoming one of the most recognized national symbols on earth. Despite the nation’s zeal for the bald eagle, their numbers declined through the 19th century from habitat destruction and hunting. As early as 1921, the journal Ecology reported that bald eagles were threatened with extinction. Some reports suggested the bald eagle had disappeared entirely from New England by the 1930’s. But the bald eagle faced its most significant challenge after WWII when the pesticide dichlorodiphenyltrichloroethane (DDT) came into widespread use in the U.S. and Mexico. DDT thinned the eggshells of bald eagles and a host of other bird species, making them extremely susceptible to breakage during incubation. By 1963, the continental U.S. was home to just 417 nesting pairs of bald eagles. America’s highest profile species was suddenly on the brink of extinction.

In 1940, the Bald Eagle Protection Act was passed that prohibited killing, harming or disturbing bald eagles and their nests throughout the U.S. The act was amended in 1962 to include the golden eagle and became known as the “Eagle Act.” In 1962 FWS biologist, Rachel Carson published Silent Spring, which was the first many Americans had heard of the pesticide DDT. In 1972 the EPA banned the pesticide in the U.S. and a year later created the Endangered Species Act (ESA). The act designated species as either, “threatened” or “endangered.” “Threatened” was defined as a species that is likely to become endangered within the foreseeable future. “Endangered” was defined as a species that is threatened with extinction throughout all or a significant portion of its range. In 1978 the bald eagle was listed as “endangered” in the U.S. except in Michigan, Minnesota, Oregon, Washington, Wisconsin, and Alaska. Under the new protection, bald eagles and their habitat were protected and their numbers increased from 417 nesting pairs in the 1960’s to more than 10,000 pairs today.

Recognizing that the Desert bald eagle was unique and subject to additional pressures, USFS and the Arizona Audubon Society started the Nestwatch Program in 1978, which to this day, “is one of the best tools we have,” said James Driscoll, Raptor Management Coordinator for AGFD. The program hires biologists to watch active Desert bald eagle nests through their breeding season. Nestwatch biologists educate recreators who wander too near to nest sites, collect data on adults and young, and in some cases rescue young birds that have been abandoned or have fallen from their nest. Much of what biologists know about Desert bald eagles has been learned through direct observation by Nestwatch employees.

In 1982, the Southwestern Bald Eagle Management Committee (SWBEMC) began banding, tracking, and counting Desert bald eagles and took over management of the Nestwatch Program. SWBEMC is run and financed by 23 Arizona businesses, federal and state agencies (including AGFD, CBD, FWS, and USFS) and Native tribal groups. With ESA protection and under the watchful eye of SWBEMC, the number of Desert bald eagles in Arizona climbed from fewer than 5 pairs in 1970, to 59 in 2009. While the CBD and Audubon Society fight for ESA protection, many federal and state experts feel protection for Desert bald eagle will change very little if delisted. “We will manage Desert bald eagles as we always have, whether they’re listed or not,” said James Driscoll of AGFD. The reason ESA protection might not alter management is because of the incredible array of protections put into place to protect the Desert bald eagle specifically. These exist in addition to ESA protection and include the Migratory Bird Treaty Act, the Eagle Act, the Lacey Act and the Airborne Hunting Act. But these acts and protections only peripherally address habitat, instead focusing on saving individual birds. This is not enough according to Robin Silver of CBD. “If we released 50 healthy eagles into a degraded habitat, they would die,” he said. Expecting eagles to live without habitat is like asking people to survive without food, water or shelter.

While habitat protection is the number one priority for the Center for Biological Diversity (CBD), the Fish and Wildlife Service (FWS) and the Arizona Game and Fish Department (AGFD) walk a fine line between growth and conservation, and must consider interests beyond those of Desert bald eagles. Political forces from Washington and Phoenix demand protection for eagles, but also 800 million gallons of water for Arizona residents every day, irrigation for farms, grazing land for cattle, and recreational access for the ever-increasing number of people in central Arizona. While Silver is sure that Desert bald eagles will be extinct in less than 50 years without ESA protection, Driscoll believes the state will continue to see more eagles with or without it. Political obligations and environmental zealotry aside, the simple fact is, eagle habitat is being lost in Arizona every day. If the Desert bald eagle is denied ESA protection in October, the coming years will finally prove what the experts have not been able to agree on: can the Desert bald eagle thrive without habitat protection?

High on a cliff above Oak Creek, Janie Agyagos, Cecelia Overby, and I took turns squinting through the spotting scope as two uncoordinated eaglets negotiated their nest on oversized talons, balanced by stubby wings. Their parents perched on adjacent branches looking decidedly regal, but also haggard from meeting the demands of parenthood in a hot and inhospitable environment. Packing up the jeep for the long ride back to the office, I asked Agyagos what she will do if the Desert bald eagle is delisted in October. She looked at me and without a moment’s hesitation said, “We will never stop trying.”