Florida's Resident American Kestrels
The Southeastern American Kestrel (Falco sparverius paulus) is a non-migratory falcon that inhabits open woodlands. Historically, the distribution of the subspecies was closely tied to the distribution of sandhill and open pine savannah habitat maintained by frequent fire. Today, the Florida landscape includes other open habitats that are used by Southeastern American Kestrels, including pastures and low-intensity agriculture, and open woodlots and fields within residential areas. High-quality kestrel habitat must provide both suitable nesting habitat and suitable foraging habitat where the birds can see and capture their prey.
Kestrels nest primarily in large dead trees in cavities previously excavated or hollowed out by woodpeckers. Kestrels also readily use nest boxes.
In Florida, grasshoppers and small lizards make up the majority of the Southeastern American Kestrel diet. Other invertebrates, including insects, worms, and spiders, and occasionally frogs and other small vertebrates are also eaten. Kestrels most often hunt by watching for prey from perches, but will hunt from the air when perches are not available. Prey is usually captured with the feet.
Territory sizes for kestrels range from 50-317 hectares (124-783 acres) depending on habitat quality. Breeding densities also vary with habitat and can range from 0.14 pairs per kilometer-squared (km2) (0.36 pairs/mile2) to 0.67 pairs/km2 (1.74 pairs/mile 2). Bonds between a breeding pair of kestrels will last for multiple years and pairs often maintain territories throughout successive years. Southeastern American Kestrels occur year-round in Florida, but little is known about their behavior or movements during the winter.
Southeastern American Kestrels breed from mid-March to early-June. Females lay 3-5 eggs per nest. Eggs are white to reddish-brown with a dark speckling. Eggs hatch after approximately one month of incubation. Nestlings gain adult weight by about 15 days after hatching and leave the nest approximately 30 days after hatching. Second nesting attempts occasionally occur, especially in Florida, when the first nest either fails or is completed early in the breeding season. The average life expectancy of a kestrel is about 15 months. Survival rates during the first year can be as low as 30 percent, and are about 50 percent in subsequent years. Sources of mortality include mammal and avian predators. Some kestrels also are killed by collisions with motor vehicles.
The Southeastern American Kestrel is listed as threatened in Florida due to an overall decline in nesting and foraging habitat, specifically the removal of isolated trees from agricultural fields, residential development, conversion of open pinelands to agriculture, and the modification of pine forest understory vegetation resulting from fire suppression. Understory is the structure of the vegetation underneath the forest canopy. Although long-term population trends are unclear, an overall decline of 82 percent over the past 70 years has been estimated. Conservation and proper management of open pineland habitat, specifically sandhills, as well as open fields with scattered trees clearly would benefit this species. Controlled burning should be used to maintain a grassy, open understory and dead tree snags should be preserved to provide nesting sites. Nest boxes also can be installed in areas where natural cavities are sparse.