Guardian of the Fields: Understanding and Protecting the American Kestrel

Whether you are out servicing antenna towers in rural fields or scanning tree lines on a quiet morning, you’ve likely caught sight of North America’s smallest falcon: the American Kestrel (Falco sparverius). Roughly the size of a blue jay or mourning dove, this brightly colored predator packs the fiercest hunting instincts of the raptor family into a miniature frame.

Unfortunately, despite their wide distribution, American Kestrel populations have declined by over 50% across North America since 1966. Understanding their biology, hunting strategies, and environmental needs is the first step toward reversing this trend in our local communities.

1. Native Range and Habitat

The American Kestrel boasts one of the largest geographical ranges of any bird of prey in the Western Hemisphere:

• Breeding & Year-Round Range: Found throughout the contiguous United States, Central America, and parts of South America.
• Northern Range: Breeding grounds extend deep into Canada and Alaska during spring and summer. Northern populations migrate south to the southern U.S. and Mexico during the harsh winter months.
• Preferred Habitat: Open country, farmlands, open fields, clearings, deserts, and powerline corridors. They rely on high, open perches such as telephone wires, fence posts, and ham radio towers to spot prey.

2. Eating Habits and Hunting Tactics

Unlike larger raptors that pursue medium-sized mammals or waterfowl, the kestrel focuses on smaller creatures that thrive in grass and low cover.

Primary Diet:

• Insects: Grasshoppers, crickets, beetles, dragonflies, and caterpillars make up a huge portion of their spring and summer food supply.
• Small Mammals: Voles, field mice, shrews, and small rats.
• Reptiles & Amphibians: Small lizards, skinks, and snakes.
• Small Birds: Occasionally small songbirds (sparrows, finches) when insect or rodent populations are low.

The “Hover-Hunt” (Kiting)

One of the kestrel’s signature behaviors is kiting or hover-hunting. A kestrel can face directly into the wind, flap its wings rapidly, and lock its head completely still in mid-air acting like a stationary camera platform while scanning the ground for movement.

3. Incredible Kestrel Facts (You Might Not Know)

• Ultraviolet Vision: Kestrels can see in the ultraviolet light spectrum. Because field mice and voles mark their trails with urine, which reflects UV light, kestrels can literally see “bright glowing highways” leading straight to rodent burrows.
• Cavity Nesters: Kestrels cannot build their own nests out of sticks. Instead, they rely on existing tree hollows (often carved out by flickers or woodpeckers), rock crevices, or human-made nest boxes.
• False “Eyes” on the Back of the Head: Kestrels have two dark spots on the back of their necks called ocelli. These act as false eyes to fool potential predators (like larger hawks or owls) into thinking the kestrel is looking right at them.
• Distinct Sexual Dimorphism: Unlike many birds of prey where males and females look identical, kestrels are easily sexed by sight:
  • Males: Slate-blue wings with a rust-orange back and tail (with a single black terminal band).
  • Females: Rusty-brown on both wings and back, covered in dark brown horizontal barring across the entire tail.

4. Native Plants and Trees That Support Kestrels

Kestrels don’t eat plants or seeds directly, but they depend on native plants that host the insect and rodent populations they eat, as well as native trees for nesting.

Essential Trees for Nesting & Perching

1. Dead Snags / Standing Cedar & Oak: Dead trees provide natural nesting cavities and high, unobstructed perches.
2. Shortleaf Pine & Loblolly Pine (Pinus spp.): Excellent roosting shelter during cold nights and storm events.
3. Oak (Quercus spp.) & Hickory (Carya spp.): Large native trees attract high densities of insects and small mammals.

Native Forbs & Grasses for Foraging Habitats

To support the insects and rodents kestrels feed on, plant or preserve native meadows rather than manicured turf lawns:

• Little Bluestem (Schizachyrium scoparium) & Switchgrass (Panicum virgatum): Native bunchgrasses that provide ideal cover for field mice without becoming a dense, impenetrable mat.
• Coneflowers (Echinacea), Black-Eyed Susans (Rudbeckia), & Milkweed (Asclepias): Support dense populations of grasshoppers, beetles, and pollinators are a main food source for kestrels during breeding season.

5. How You Can Help American Kestrels

A. Avoid Rodenticides and Pesticides

Secondhand poisoning from rodent baits (anticoagulants) is a primary driver of raptor deaths. When a kestrel eats a poisoned mouse, the toxin accumulates in the bird. Avoiding chemical pesticides also preserves the grasshopper and beetle populations kestrels rely on to feed their chicks.

B. Put Up a Proper Nest Box

Because dead trees are often removed from residential and agricultural property, kestrels face a severe housing shortage. Installing a nest box on a pole or the side of an outbuilding can give a pair a safe place to raise young.

Key Nest Box Guidelines:

• Interior Height/Depth: 16 to 18 inches tall (boxes shorter than 15 inches are dangerous because chicks can fall out or overheat).
• Floor Dimensions: 8" x 8" or 9" x 9".
• Entrance Hole: Exactly 3 inches in diameter, located near the top (10 to 12 inches above the floor).
• Bedding: Add 2 inches of coarse pine shavings to the bottom (kestrels do not bring nest materials inside).
• Mounting Height: 10 to 20 feet above ground in open, grassy areas facing south or east (away from prevailing cold winds).

Conclusion

The American Kestrel is a vital ally for farmers, gardeners, and property owners, acting as natural pest control for insects and rodents. By preserving snag trees, minimizing chemical use, planting native grasses, and setting up correctly sized cavity boxes, we can ensure these dynamic little falcons continue to grace our skies for generations to come.