Protecting Golden Eagle Habitats

A golden eagle takes flight. (Photo by DSRSD retiree Roger Lee)

The City of Dublin is uniquely located within an area surrounding the Diablo Range, where research has discovered a robust population of resident golden eagles. Each year DSRSD assists in preservation and protection of their nesting habitat with the help of a raptor biologist.

Colleen Lenihan, who works with the Center for Natural Lands Management (CNLM) to protect nesting eagles from human activity, provides updates to District staff during the golden eagle breeding season beginning in January when resident pairs build nests until July when newly fledged (flying) young are safely on the wing.

This information helps the District make informed choices about when to perform work or access reservoirs that are located close to the golden eagle breeding areas. Lenihan communicates with DSRSD as well as with the City of Dublin to ensure the area remains quiet. While the District continues normal maintenance throughout the year, large construction projects that could create a disturbance are scheduled for August through December, outside of breeding and fledging season.

In addition to golden eagles, CNLM manages this sensitive area for a variety of special status species including California tiger salamander and California red-legged frog. Lenihan has been monitoring golden eagles in the region since 1990. 

“Golden eagles have a long relationship with humans,” Lenihan says. “They are the most widely distributed eagle species in the Northern Hemisphere. Golden eagles are a symbol of wildness, strength, and grace. Many cultures regard them as sacred.”

An adult golden eagle is uniformly brown with a golden mane of feathers gracing the head and neck with legs feathered to the toes. Juvenile eagles are dark brown with a white band at the base of the tail and variable amounts of white creating distinct patches in the wings. The golden eagle’s wingspan spreads seven feet across and, like most raptors (birds of prey), females are larger than males.  

Golden eagles have three basic habitat requirements for survival and reproduction:  abundant prey resource, appropriate nest site, and minimal disturbance by human activity. In the Diablo Range, golden eagles primarily hunt and eat California ground squirrels and jackrabbits. Golden eagles nest predominantly in trees within a landscape mosaic of oak savanna (grasses and other herbaceous vegetation dominate the area with oaks as the principal trees scattered about), oak woodland (dominant trees are oaks, interspersed with other broadleaf and coniferous trees and grasses, herbs, geophytes, and California native plants), and grassland.

Why Protect Golden Eagles?

A golden eagle feeds its young. (Photo by Roger Lee)

Fortunately, golden eagle populations are relatively stable throughout their range, but current threats to survival and reproduction remain. An estimated 70% of eagle deaths are related to human impacts, usually unintentional. Energy generation and distribution account for many accidental deaths from collisions with wind turbines and electrocution from power poles. Landscape level conversion through urbanization and intensive agriculture eliminates hunting grounds and suitable nesting areas for golden eagles as well as other wildlife species. In addition, there are immediate threats to the health of eagles and other predators from secondary poisoning. Raptors feed on prey animals that may be exposed to powerful rodenticides used to subdue “pest” species. These poisons accumulate in top predators wreaking havoc with their health and reproduction.

During breeding season, golden eagles are particularly sensitive to human disturbance making this species susceptible to reproductive failure, especially during the first 10 weeks of the nesting season when eggs and young need constant care. For this reason, nest areas are closed to protect developing chicks. 

Finally, due to these aforementioned threats and sensitivity, eagles in the United States are protected under the Bald and Golden Eagle Protection Act, or “Eagle Act,” as well as other federal acts and state codes. The Eagle Act directly addresses protection for both species of eagle and prohibits unauthorized "take" of individual eagles, their nests or eggs.  

Nesting Season

During January, golden eagles are busy building or refurbishing nests. Some lay eggs as early as late January, but most pairs do so from February to mid-March.  Females lay from one to four eggs, and both parents share incubation duty for approximately six weeks. The adult eagles tend to the nestlings for another 10 weeks.

From mid-May to mid-June, young eagles fledge from the nest, taking their first short flight gliding to the ground. Flight practice continues through June, and Dublin’s young eagles are usually soaring safely by July 1. Golden eagle parents continue to protect and feed juveniles through summer, and gradually the young birds begin to explore farther afield, slowly becoming independent.

“Dublin eagles are amazing,” Lenihan says. “One of the most rewarding times is when the chicks fledge. It is stressful for the eagle family and for me as well. Sometimes a sibling pushes them out or they fall from the nest. But one day the wind just picks them up and off they go. After a couple weeks of practice they are flying well. It’s an absolutely gorgeous sight.” 

Drought, fire, and adult mortality throughout the Diablo Range golden eagle population may have decreased overall nesting success in 2021. Yet, golden eagle pairs within the city limits of Dublin successfully raised and fledged four chicks thanks to a cooperative community effort to protect them.

Posted: July 23, 2021