American Kestrel Diet: What Does This Tiny Bird of Prey Eat?

The American kestrel’s diet is indeed diverse, encompassing four primary categories: insects, mammals, birds, and a minor fraction of amphibians (frogs and lizards). The relative prevalence of each prey group fluctuates throughout the year in response to shifting prey availability. This article delves into the kestrel’s prey types, its hunting and handling techniques, its role in regulating insect populations, and the challenges faced by the American kestrel in securing food within its habitat.

The American Kestrel’s Diverse Diet

What does the American Kestrel eat?

Multiple studies on the food habits of the American Kestrel determined that this small raptor’s diet consists of:

• 74% invertebrates, primarily grasshoppers, crickets, beetles, dragonflies, and butterflies
• 16% small mammals, including mice, voles, shrews, and bats
• 9% small passerine birds, such as sparrows, finches, and warblers
• 1% amphibians and reptiles, including frogs and lizards

The American Kestrel’s diet varies depending on the time of year and the availability of prey in the region. In the summer, when insects are abundant, insects make up the majority of the kestrel’s diet. In the winter, when insects are less abundant, small mammals make up a larger part of the kestrel’s diet. 

How do kestrels hunt their prey?

The American Kestrel is entirely diurnal, foraging for food most actively in the morning hours, though it is also active throughout the day. Its foraging activities depend on the activity of its prey; more active prey are easier to detect.

Kestrels visit their favorite hunting perches within their territory. If hunting is productive at one perch they spend more time at such perch. Less productive perches are visited for brief periods of time.

Its basic hunting activity is scanning the ground from an elevated perch or vantage point to detect prey. Once the prey is detected the kestrel swoops down and uses its sharp claws to catch it. Subsequently takes the prey to a prey to consume it.

Once prey is captured a kestrel may spend little time on the ground prior to taking it to a perch for consumption. Larger and heavier prey such as mice require more time on the ground to handle and immobilize prior to taking it to a perch for consumption. 

Hunting Techniques

The American Kestrel is a skilled hunter and has developed several techniques to catch its prey. 

Sit and scan from an elevated perch

American kestrels use perches of all heights to sit and scan the surrounding ground for prey. They use fence poles, fence wire, branches of trees, utility poles and wire, communication towers and any vintage point that allows them to scan  the surrounding ground.

The hovering technique

One of its most impressive abilities is its hovering technique, which allows it to remain stationary in mid-air while scanning the ground for prey. Once it spots a potential meal, the kestrel will swoop down and capture its prey.

The hovering technique is used in open areas that have prey but lack perches to scan the ground from. Kestrels would use a perch rather than hovering since hovering demands much more energy than sitting on a perch.

Other hunting techniques

Kestrels are opportunistic and flexible hunters and may combine or adapt their hunting techniques to the prey and situation. They can swoop down to chase-pursuit small birds or  lizards as the opportunity presents itself. They may ambush unsuspecting small birds or catch dragonflies in mid air.

The American kestrel is able to see urine of mice

American kestrels can detect the urine of mice. They have a special ability to see ultraviolet light, which allows them to see the scent marks that mice leave behind. These scent marks are invisible to humans, but they are very visible to kestrels.

Kestrels use these scent marks to find mice. They will fly over open fields and grasslands, looking for the bright blue-green glow of mouse urine. When they spot a urine mark mice are likely to be around. They hover over, often for a long time and are likely to catch the mouse.

This ability to see ultraviolet light is a unique adaptation that gives kestrels a competitive advantage over other predators. It allows them to find food in areas where it would be difficult to see otherwise, such as in tall grass or undergrowth.

Success rate of a kestrel hunt

Ornithologist Brian Toland (1983) assessed kestrel hunting success by tallying the number of attempts an individual made to catch prey and the corresponding outcomes. In the study area, kestrels demonstrated an 82% success rate in capturing invertebrates, a 66% success rate in capturing rodents, and a 33% success rate in capturing birds. The following chart shows a graphic representation of the hunting success of the American Kestrel.

The American Kestrel’s Role as an Insecticide

The American Kestrel plays a significant role in controlling insect populations. According to a study conducted by the USDA, the kestrel’s diet consists mainly of insects and small mammals.

Insects make up 50-74% of their diet, and they can consume up to 10-20% of their body weight in insects per day. This means that a single kestrel can consume up to 1,000 grasshoppers or crickets in a week.

How many insects can an American Kestrel eat?

The impact of the American Kestrel on insect numbers is impressive. A pair of kestrels and their offspring can eat up to 6,000 grasshoppers in a single breeding season. This translates to a significant reduction in the number of insects that can cause damage to crops, gardens, and other vegetation.

The ecological benefits of the kestrel’s insectivorous diet are significant. By controlling insect populations, the kestrel helps to maintain a healthy ecosystem. In addition to pest control, the kestrel’s diet also includes pollinators such as bees and butterflies. 

The American Kestrel’s role as an insecticide is crucial to maintaining a healthy ecosystem. By consuming large numbers of insects, the kestrel helps to control pest populations, which in turn helps to protect crops and vegetation. 

Regional Variations in American Kestrel Diet

American Kestrels are highly adaptable birds of prey that are known to select their prey based on regional availability. Their diet is influenced by habitat, climate, and seasonality. 

In the eastern United States, American Kestrels have been observed hunting mostly insects, with grasshoppers and dragonflies being their primary prey. 

In the western United States, they tend to hunt more small mammals, such as voles and mice. In the winter, when small mammals are scarce, kestrels are known to switch to a diet of mostly birds, such as sparrows and finches.

In the desert regions of the southwestern United States, American Kestrels have been observed hunting lizards and large insects, such as grasshoppers and beetles. 

Overall, the American Kestrel’s diet is highly flexible and adaptable. They are capable of adjusting their diet based on the availability of prey in their region. This flexibility is a key factor in their success as hunters and their ability to survive in a variety of habitats.

Surprising Prey Choices of American Kestrels

American Kestrels are known for their diet of small mammals and birds, but they occasionally consume unexpected prey items. These unconventional prey choices can include reptiles, amphibians and small snakes.

One example of an unconventional prey choice for American Kestrels is lizards. While not a primary food source, kestrels have been known to prey on lizards such as skinks and geckos. This opportunistic feeding behavior may occur when other prey is scarce or when the kestrel is in need of additional food.

Another surprising prey choice for American Kestrels is frogs and toads. While not a common prey item, kestrels have been known to hunt these amphibians when they are available. This may be due to the high protein content found in amphibians, which can be beneficial to the kestrel’s diet.

Do American kestrels eat fish?

There are two published records of American Kestrels eating fish. 

Brian G. Self (2001) Observed a female kestrel make three attempts to catch fish in shallow water. Each time the kestrel plunged into the water and tried to grab very small fish with her talons. The bird was not successful in catching any fish.

J. Parkurst and R. Brooks Observed an American Kestrel that pirated and ate a trout fingerling from a common grackle. The grackle caught the fingerling as it accidentally cast up on a bank. Subsequently, the kestrel took it from the grackle and consumed it. 

In this case, the kestrel ate the fingerling but there was no attempt to capture a fish from the water. While regarded as an unusual prey for an American kestrel, this cannot be regarded as a kestrel feeding on a fish. 

Accordingly, I believe that kestrels do not feed on fish but given the opportunity, they can consume small fish as they would any other prey item they normally consume.

Overall, while American Kestrels primarily feed on small mammals and birds, their occasional consumption of unconventional prey items highlights their adaptability and opportunistic feeding behavior.

Threats to the American Kestrel’s Food Sources

The American Kestrel is a bird of prey that feeds primarily on insects, small mammals, and birds. However, the kestrel’s food sources are under threat due to habitat loss, pesticide use, and climate change. These factors have led to a decline in insect populations, which in turn has impacted the kestrel’s ability to find food.

Habitat loss

Habitat loss is a major concern for the American Kestrel’s food sources. As human development continues to encroach on natural habitats, the kestrel’s prey base is shrinking. In addition, the loss of hedgerows, trees, and brush due to “clean” farming practices has removed important nesting sites and foraging areas for the kestrel’s prey.

Pesticide use

Pesticide use is another threat to the American Kestrel’s food sources. Pesticides can kill insects directly or indirectly by reducing the availability of their food sources. 

Exposure to pesticides can also weaken the immune systems of insects, making them more susceptible to disease and predation. This can lead to a decline in the kestrel’s food sources over time.

Climate Change

Climate change is also affecting the American Kestrel’s food sources. Changes in temperature and precipitation patterns are altering the timing of insect emergence and migration, which can impact the kestrel’s ability to find food. 

In addition, extreme weather events such as droughts and floods can disrupt insect populations, making it difficult for the kestrel to find a reliable food source.

Conservation efforts are critical to protecting the American Kestrel’s food sources and ensuring its continued survival. This includes preserving natural habitats, reducing pesticide use, and mitigating the effects of climate change. 

FAQs

Do American kestrels eat ground squirrels?

An adult ground squirrel is too large of a prey for an American Kestrel. Not only does the size pose a problem, but ground squirrels can also inflict serious injuries to the thin legs of the kestrel, and there’s a risk that the squirrel could reach the body and harm the attacking kestrel.

Do American kestrels eat chickens?

American kestrels can potentially take a newly hatched baby chicken. A baby chicken is about the size of the finches and sparrows kestrels normally hunt. Young chickens of more than three weeks old are already too big for a kestrel to subdue and carry. 

Do American kestrels eat rats?

An adult rat would be too big and dangerous for a kestrel to trap and kill. Adult rats can seriously injure an adult kestrel. Kestrels could easily take baby rats, however baby rats do not get out of their den before they reach a certain size which may already pose a danger to a kestrel.

Do Kestrels eat snakes?

Kestrels are known to eat small snakes. Kestrels will eat whatever prey is available to them. If they come across a snake that is small enough to catch, they may attack it and eat it. However, snakes are not as easy to catch as insects or mice. Snakes are also more likely to fight back, which can injure the kestrel. Kestrels typically only eat snakes when other prey is scarce.

Are American Kestrels good hunters?

Yes, American kestrels are excellent hunters. They are small, agile and fast falcons that are well-adapted to catching a variety of prey, including insects on the ground and in mid air, elusive small mammals, and birds. They use multiple hunting techniques to catch their prey and are flexible and creative adapting their hunting techniques to prevailing conditions.

Can I attract kestrels to my yard with food?

Attracting one or two kestrels to your yard with food would not be difficult if your yard is adjacent to kestrel habitat. Kestrels take baby mice offered to them. Because kestrels are territorial and do not allow other kestrels in their territory, you would only be able to attract a single pair. A much better way to attract kestrels to your yard would be setting up a nesting box.

Do American kestrels hunt at night?

No, American Kestrels are diurnal birds, meaning they are most active during the day. They typically start hunting at dawn and continue hunting until dusk. At night, they roost in trees, cavities, or nest boxes.

There are a few reasons why American Kestrels are diurnal:

• Their eyesight is better in daylight. They have large, forward-facing eyes that are well-adapted to seeing in bright light.
• Their prey is also most active during the day. Insects, small mammals, and birds are all more likely to be seen and caught during the day.
• There is less competition for food during the day. Other diurnal predators, such as hawks and owls, are not as active at night.

Toland, Brian, 1987. The effect of vegetative cover on foraging strategies, hunting success and nesting distribution of American Kestrel in Central Missouri. J. Raptor Res. 21(1):14-20

References

• Ardia, D., K. Bildstein. 1997. Sex-related differences in habitat selection in wintering American kestrels, Falco sparverius. Animal Behavior, 53: 1305-1311.
• BirdLife International, 2012. “Falco sparverius” (On-line). IUCN Red List of Threatened Species. Accessed November 01, 2013 at http://www.iucnredlist.org/details/22696395/0.
• Johnsgard, P. 1990. Hawks, Eagles, and Falcons of North America. United States: Smithsonian Institution.
• Smallwood, J. A. and D. M. Bird. 2020. American Kestrel (Falco sparverius), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA.
• Toland, Brian 1983. The effect of vegetative cover on foraging strategies, hunting success and nesting distribution of American Kestrel in Central Missouri. J. Raptor Res. 21(1):14-20

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