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| A golden eagle perched in Monte Field. Photo courtesy of Laura Pavliscak |
Those of you who have spent some time on Tejon Ranch know
that this property is replete with golden eagles (Aquila chrysaetos). Indeed, it is not uncommon to see 5, 10, or
even 15 eagles in a given day! Although golden eagles can be found throughout
the West, Tejon Ranch is a particularly reliable place to see them. Why is
that? What about the ranch is so conducive to their survival? While we do not
have the data necessary to reach a definitive answer for these questions, if we
look a little bit at golden eagle life history, it becomes clear that Tejon
Ranch meets many of their necessary requirements.
HABITAT
One of the biggest factors that has contributed – other than
the poisoning that led to their protection in 1962 – to the decline of golden
eagles over the last century is the destruction of their habitat. These raptors
prefer two broad categories of habitat for their daily activities- canyons and
rugged mountains for roosting and breeding, and flat, open country for feeding.
Contrary to Youtube accounts, golden eagles mainly prefer small mammals for
their prey. According the Cornell Lab Birds of North America Online, such food
consists of 80-90% of their diet (Kochert, Steenhof, Mcintyre, and Craig 2002).
A quick trip to the San Joaquin or Antelope Valley grasslands on Tejon Ranch
will confirm that California ground squirrels (Otospermophilus beecheyi) abound. While some may consider ground
squirrels to be a scourge on grasslands, we like to think of them as golden
eagle (and red-tail hawk, wintering ferruginous hawk, coyote, and bobcat) food.
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| A closer inspection reveals that it is mealtime. Photo courtesy of Laura Pavliscak |
NESTING
As mentioned above, golden eagles prefer to set up their
nests in trees atop rugged canyons. A look at the hillshade relief map of the ranch (below) reveals a plethora of such habitat. In fact, it appears that golden
eagles create pair bonds for life (or at least a very long time) and prefer to
use the same nest over and over again. Raptor researchers have told Conservancy
staff not to consider each nest individually, but as neighborhoods, where
established pairs have established nests and home ranges for as long as decades! Golden eagles also maintain alternate nest
sites in the vicinity of the active nest.
One can imagine how the history of land use changes and habitat
destruction in southern California have made the vast Tejon Ranch a “refuge”
for these birds. Conversely, the abundance of golden eagles on Tejon Ranch may
indicate what their numbers should be like throughout the region. These are the
kinds of questions we like to ponder around here.
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| This hillshade map of Tejon Ranch highlights the property's mix of rugged terrain and open grassland |
WINTERING
Although golden eagles tend not to travel the inter-continental
migration routes as raptors like the Swainson’s hawk (Buteo swainsoni), some do migrate over shorter distances (while
others are thought to maintain their territories through the year). Tejon’s
resident eagles are likely joined by wintering birds from northern latitudes, the
Conservancy’s Christmas Bird Counts have documented some of the highest golden
eagle numbers of any count in North America!
Tejon Ranch is an incredible place to see golden eagles. As
we continue to observe and learn about these amazing creatures, we are
particularly interested in finding out where they nest on the ranch and how
neighboring wind farms affect their populations.
To find out more about golden eagles, including
identification tips and life history, check out these great resources
http://www.allaboutbirds.org/guide/golden_eagle/id
http://animals.nationalgeographic.com/animals/birds/golden-eagle/
http://peregrinefund.org/explore-raptors-species/Golden_Eagle#sthash.RGfN4FQn.dpbs
REFERENCES
http://www.allaboutbirds.org/guide/golden_eagle/id
http://animals.nationalgeographic.com/animals/birds/golden-eagle/
http://peregrinefund.org/explore-raptors-species/Golden_Eagle#sthash.RGfN4FQn.dpbs
REFERENCES
Kochert, M. N., K. Steenhof, C. L. Mcintyre and E. H. Craig. 2002. Golden Eagle (Aquila chrysaetos),
The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab
of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/684
doi:10.2173/bna.684
doi:10.2173/bna.684
