Golden Eagle Food Habits

In the open habitats where it hunts, the golden eagle eats mainly rabbits, squirrels, and birds. To locate prey, a golden eagle uses high perches or glides in the air and then drops over unsuspecting animals on the ground. It then uses its sharp claws to subdue its catch.

• The golden eagle feeds mainly on small mammals.
• Their diet also includes birds and reptiles.
• The size of its prey varies between 1.1 – 9 lb. 
• It uses its vision to locate its prey.
• It is a solitary hunter in open habitats.
• It locates its prey from high perches or the air.
• They can go up to a week without eating.
• Occasionally golden eagles feed on carrion.
  Photo: Ron Porter-Pixabay.

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What does the golden eagle eat?

The golden eagle feeds mainly on prey of intermediate size (1.1 – 8.1 lb). However, it can opt for smaller prey (such as mice, voles) or larger ones (canids or cervids). 

With such wide geographic distribution in the northern hemisphere, the golden eagle catches a wide variety of prey. However, it normally hunts locally abundant species.

Ornithologists Preston B. and colleagues (2017) reviewed 35 studies of the golden eagle diet during the nesting season. The study included 45 separate locations in western North America. 

The study found that the golden eagle feeds primarily on mammals (84%) and medium-sized birds (15%).

Reptiles, fish, and large insects are occasionally captured and makeup only about 2% of their total prey.

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Hunting habits of the golden eagle

Golden eagles are mostly solitary hunters who consume their prey alone. 

Occasionally, it will use a cooperative hunting method, usually with the other member of its pair.

The typical cooperative hunting strategy is for one member of the pair to follow the prey while the other goes directly to intercept it.

Usually, the individual that captures the prey kills it and shares it with the other member of the pair or transports it to the nest to feed the chicks.

An even rarer mode of hunting is group hunting which includes more than two individuals who are usually unrelated. 

Communal hunting is generally used to capture large animals such as foxes, wild turkeys, and newborn deer among others.

Golden eagles catch most of their prey on the ground. 

Other ways of procuring food 

These methods of procuring food are less used and often opportunistic. 

Kleptoparasitism: Klepto means to steal and parasitism to live off of another(s). The golden eagle attacks other birds of prey, generally smaller ones, or also lower-ranking adults and juveniles of the same species to take away their prey.

Some golden eagles become pirates by visiting areas or places where other birds of prey forage to take their prey.

Fishing for live fish: Although the golden eagle is known to hunt mostly relatively small mammals, given the opportunity they will also catch fish. 

The fish they catch are large and are at shallow depths or stranded which makes it easy for the golden eagle to catch them.

In regions where fish is abundant, golden eagles include fish in their diets in more significant proportions.

An example is golden eagles in Alaska that consume and feed their chicks salmon. In this region, salmon is easy to catch during periods of migration.

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Golden eagle hunting strategies 

The hunting strategy of the golden eagle is to visually detect prey from a high place and launch an attack to capture it.

The elevated place can be a high perch or from the air.

Once the eagle locates a potential prey, depending on its location and type, it dives in a perpendicular or vertical trajectory to catch it.

Prey that is likely to run and may involve an additional chase on or near the ground, such as rabbits, are more likely to be attacked diagonally.

In order to take prey without giving it a chance to run away, such as birds, they are more likely to be attacked vertically.

Prey that is not likely to give the hunting eagle a second chance (such as birds) are more likely to be attacked vertically.

For prey that quickly flees to a nearby burrow, the golden eagle has to surprise its prey before the prey detects the eagle and flees to the burrow.

For these types of prey, after finding a target prey from the air or high perch, the golden eagle flies low to the ground to surprise and capture the prey from an angle that the prey does not expect.

The hunting and attack strategy of the golden eagle varies depending on the climatic conditions, the topography, the type of prey, and its escape strategy. 

If the eagle fails to catch its prey on the first try, it chases it on the ground. If the attempt fails, it proceeds to return to the perch or rise into the air and begin hunting again.

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Do golden eagles capture prey in each attempt?

Golden eagles usually hunt alone, although sometimes they hunt with a partner or with other golden eagles.

Hunting alone or with other golden eagles has a different level of success.

When the eagle hunts alone, out of 73 observed attempts, hunting success was 29%. In other words, 29 out of every 100 attempts at hunting result in a catch.

When the eagle hunts in groups, out of 42 observed attempts, only 4.6% resulted in the capture of prey.

The average hunting success of the golden eagle is 20% in 115 observed attempts, which is relatively low.  

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Where does the golden eagle hunt?

Golden eagles hunt in open habitats with little presence of dense forests.

To detect and kill prey, golden eagles rely entirely on their vision and strong claws.

They are rarely seen hunting near or over bodies of water. Although in regions where ducks and coots are an important part of their diet, they forage more frequently over water.

The golden eagle needs to have a panoramic view first to locate its prey. Therefore the ideal hunting habitat has high perches to monitor the landscape for possible prey.

High perches include trees, power poles, communication towers, hills, or precipices that overlook open spaces. 

Also, the golden eagle patrols its hunting grounds from the air and needs a habitat with few elements that obstruct the view to the ground where its prey is.

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What time of day does the golden eagle hunt?

The golden eagle hunts throughout the day using different strategies at different times of the day.

Their prey is generally more active in the morning, therefore easier to spot. Hence the golden eagle hunts actively in the morning but continues to hunt throughout the day, particularly when they are unsuccessful or raising young.

The time of the day and weather conditions influence the golden eagle’s hunting activity.

Early in the morning or during rainy or cloudy weather, golden eagles use high perches to detect their prey. Flying in these conditions requires more energy, and prey doesn’t move much on rainy days.

Golden eagles tend to fly to spot their prey from the air during clear skies and warm weather.

On sunny days, warm air masses form about 4 hours after sunrise. During the early morning hours, golden eagles tend to hunt from perches, and later, during the warm hours, they hunt from the air.

Masses of warm air greatly facilitate gliding flight, allowing the eagles to forage over large areas without expending much energy.

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What is the size of the golden eagle’s prey?

Depending on the region and abundance of prey, the size of the golden eagle’s prey varies.

In North America, they usually choose prey ranging from 500 to 4,000 gr. However, they also opt for small prey that weigh between 200 and 300 grams. 

In some regions, the golden eagle has been reported to take prey weighing up to 5,800 g. 

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How many prey items a day does a golden eagle eat?

The number of prey items of an adult golden eagle depends on the size of the prey item and varies between males and females. 

An adult golden eagle can eat one hare every three days or one gopher every day.

A study of the daily energy requirements of the golden eagle determined that an individual adult needs to eat 5.7 to 6.6% of its body weight daily, therefore:

• An average adult male weighing 8.1 pounds needs to eat approximately 0.5 pounds of meat per day.
• An adult female weighing 11.4 pounds on average needs to eat about 0.7 pounds of meat a day.

As mentioned above, in North America, jackrabbits (6.7 lbs.) and ground squirrels (1.3 lbs.), followed by pheasants (2.6 lbs.), partridges (1.3 lbs.), and other birds of similar size make up the majority of the types of prey consumed by golden eagles.

Using daily meat consumption needs of 0.5 and 0.7% of their body weight, an adult eagle needs to eat a jackrabbit about every 5 days, or a gopher or ptarmigan every 2 days.

These calculations take into consideration that not the entire weight of a prey item is edible and that golden eagles sometimes eat only part of a prey item and then discard it.

These are only rough estimates, however, field studies have found that depending on prey availability, golden eagles can eat every day or go without eating for up to a week.

Golden eagles can eat up to 2 pounds at a time and store food in their crops so they don’t have to eat every day.

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The golden eagle also consumes carrion

Given the availability, the golden eagle does not pass up the opportunity to eat carrion (mainly from ungulates such as deer). 

Golden eagles tend to consume carrion even when other prey is available. This may be because carrion is easier to obtain than live prey.

The consumption of carrion is more frequent during the non-reproductive period, that is, the carrion is for its own consumption and not to be used as food for the chicks. 

How do you find carrion?

The golden eagle consumes carrion opportunistically. That is, it does not necessarily go out looking for carrion but rather finds it during its hunting routine.

While flying high looking for possible prey, the golden eagle observes the activity of other typical scavenger birds such as crows and vultures. 

Once the carcass is located, it generally stops on the ground at a certain distance (> 40 m) from the carcass and then approaches it on foot. The reason for such caution is poorly understood.

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Golden eagle diet varies by ecoregion and over time

Golden eagle prey varies according to what is available and most abundant in each region.

For example, in the Boreal Range, Alaskan Tundra, and South Arctic ecoregions of North America, arctic hare (Lepus arcticus) and ptarmigan (Lagopus muta) are the primary prey for golden eagles, while Arctic ground squirrels (Urocitellus sp.) is hibernating.

Once the Arctic ground squirrel comes out of hibernation, it becomes the golden eagle’s primary prey. 

In the Western Cordillera and Mediterranean region of California, rock squirrels and California ground squirrels are the golden eagle’s favorite prey.

In the Mojave Desert, snakes comprise much of the golden eagle’s diet.  

The diet of the golden eagle has also changed over time

The golden eagle hunts the most abundant and easy-to-obtain prey. Ecological changes at the regional level have resulted in changes in the abundance of the eagle’s prey base.

Studies of the golden eagle diet during the 1960s reported that white-tailed jackrabbits and other rabbit species were the most common prey items in south-central Montana.

Fifty years later, hares and rabbits only account for <4% of the golden eagle’s diet. 

In southwestern Idaho between 1971 and 1981, black-tailed jackrabbits and cottontail jackrabbits accounted for 54% of their diet. These came to represent only 13% of the golden eagle’s diet in studies conducted 30 years later. 

Also, in Idaho, coots and mallards increased from <2% of prey to 27% (Heath & Kochert, 2016). 

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What methods do ornithologists use to determine the diet of the golden eagle?

Ornithologists use direct and indirect methods to determine the type and amount of prey consumed by the golden eagle.

Indirect methods: they are based on analyzing food remains (regurgitation pellets, prey remains, granules, etc.) collected mainly from the breeding season. These remains are collected around the nests.

Other indirect methods include analysis of stomach contents and collection of pellets and food debris near resting sites. These methods are used to determine the diet of golden eagles in non-breeding seasons.

Direct methods: They are based on observing the eagles hunting directly in the field.

Another similar method is to monitor the nests using cameras to determine the type of prey that the parents bring to feed their chicks.

References:

• Boag, D. A. (1977). Summer food habits of Golden Eagles in southwestern Alberta. Canadian Field-Naturalist 91: 296–298.
• Heath, J. A., and M. N. Kochert (2016). Golden Eagle dietary shifts in response to habitat alteration and consequences for eagle productivity in the Morley Nelson Snake River Birds of Prey National Conservation Area. Cooperator Final Report to the U. S. Fish and Wildlife Service. Boise State University, Raptor Research Center, Boise, ID, USA.
• Moss, E. H. R., T. Hipkiss, I. Oskarsson, A. Häger, T. Eriksson, L.-E. Nilsson, S. Halling, P.-O. Nilsson, and B. Hörnfeldt (2012). Long-term study of reproductive performance in Golden Eagles in relation to food supply in boreal Sweden. Journal of Raptor Research 46: 248–257.
• Preston, B. Woodbridge, G. E. Williams, K. R. Keller, and R. H. Crandall (2017). Spatial and temporal patterns in Golden Eagle diets in the western United States, with implications for conservation planning. Journal of Raptor Research 51(3): 347–367.