PRELIMINARY FINDINGS: THE DIET OF ARIZONA’S GOLDEN EAGLE

Thought I would post some of my own work! This is a poster presentation for the Arizona Field Ornithologists Meeting October 5, 2013 in Sierra Vista, AZ. 

PRELIMINARY FINDINGS: THE DIET OF ARIZONA’S GOLDEN EAGLE

*Losee, M. J., 

Antioch University New England

Jacobson, T. Licence, K. and K. McCarty, K.

Arizona Department of Game and Fish

In Arizona, the Golden Eagle (Aquila chrysaetos) has been largely unstudied. In 2011, Arizona Game and Fish Department (AZGFD) began a two-year nest survey for cliff nesting Golden Eagles throughout the state. Golden Eagle occupancy and diet assessments began in 2013. During the 2013-nesting season, we collected prey remains from six active Golden Eagle nest in the northern region of the state. The number of prey items ranged from 3 to 29 with the number of different species ranging from 2 to 6. The Black-tailed Jack Rabbit (Lepus californicus) was the only prey species found in all six nests and the highest percentage (33-81%) of total species found in each nest as well as contributing to the highest biomass (2.7-5.9kg) for each nest. The two heaviest, single prey species were a Pronghorn Antelope (Antilocapra americana) fawn (3kg) and a juvenile Gray Fox (Urocyon cinereoargenteus) (3.2kg). The more unique prey species were snake, an adult Raven (Corvus corax), domestic feline and a juvenile Pinyon Jay (Gymnorhinus cyanocephalus). The nest with most diversity of prey species (6) was the only nest with two nestlings.

These preliminary findings revealed important information pertaining to the dietary habits of Golden Eagles nesting in Northern Arizona. The results showed that jack rabbits (Lepus spp.) were the dominant prey species for nesting pairs. This was consistent with both (Eakle and Grubb 1986, Stahlecker et al. 2009), in which both studies documented at least 50% of the prey species were jack rabbits. In this study, as well as (Eakle and Grubb 1986, Stahlecker et al. 2009), the Rock Squirrel (Otospermophilus variegatus) was the second most abundant prey species. There was a lower than expected amount (1%) of Prairie Dog (Cynomys spp.) remains. This could have been just a factor of what was present in the nest at the time of collection or could show a decrease in availability for this species. Stahlecker et al. (2009) documented 8% of prey species were prairie dogs, while (Eakle and Grubb 1986) documented none. This information as well as data collected from next year’s nesting season will help describe the dietary and foraging requirements for Golden Eagle pairs nesting in Arizona. These requirements coupled with occupancy data will assist AZGFD to generate better conservation action and policy recommendations.

*Presenting author  

Prey Species	Number of Individuals	Weight (kg)	Biomass (kg)	Proportion of Individual Species (%)	Proportion of Biomass (%)
Jack Rabbit (Lepus californicus)	46	9.1	124.2	68	83
Rock Squirrel (Spermophilus variegatus)	10	0.66	6.6	15	4
Desert Cottontail Rabbit (Sylvilagus audubonii)	3	1.2	3.6	4	2
Raven (Corvus corax) - Adult	1	1.3	1.3	1.5	1
Pronghorn Antelope - Fawn (Antilocapra americana)	1	3.3	3.3	1.5	2
Feline domestic - sub adult	1	1	1	1.5	1
Prairie Dog (Cynomys spp.)	1	1.5	1.5	1.5	1
Duck (Spp?)	1	1.2	1.2	1.5	1
Raven/Crow (Corvus spp.)	1	0.9	0.9	1.5	1
Pinon Jay - Juvenile (Gymnorhinus cyanocephalus)	1	0.1	0.1	1.5	1
Rabbit (Lagomorpha)	1	1.95	1.95	1.5	1
Gray Fox - Juvenile (Urocyon cinereoargenteus.)	1	3.2	3.2	1.5	2
Total	68	25.41	148.9	These results are from all six nests for the 2013 nesting season.

                          

 

Literature Cited

Eakle, W. L. and T. G. Grubb. 1986. Prey remains from Golden Eagle nests in central Arizona. Western Birds 17:87-89.

Stahlecker, D. W., D. G. Mikesic, J. N. White, S. Shaffer, J. P. DeLong, M. R. Blakemore, and C. E. Blakemore. 2009. Prey remains in nests of Four Corners Golden Eagles, 1998-2008. Western Birds 40:301-306.