In 1992, Fort Polk banded its first juvenile kestrels, which were from a nest located in an enlarged RCW cavity. The kestrel nest tree was within 100 feet of an RCW nest tree, which indicates that RCWs and SAKs prefer the same type of nesting habitat. Both the RCW and kestrel had successful nests and fledged chicks.
The SAK often hunts over large openings in the forest. Fort Polk has a large number of openings in the forest, called firing ranges that are utilized by the SAK for hunting. Our most successful nest boxes are located on the edge or near firing ranges. Another favorite habitat on Fort Polk is Longleaf pine seedtree stands that have approximately 20 mature pine trees per acre. On Fort Polk, we thin our pine stands down to a basal area of 60, sometimes lower, and we have a three-year rotational prescribed fire program. Not only does this habitat management benefit the SAK and RCW, it also benefits other species of concern including Bachman’s and Henslow’s Sparrows, and the rare Louisiana Pine Snake.
Since 1993, we have placed 20-25 SAK nest boxes on Fort Polk. The boxes are placed 20 feet above the ground on pine trees. It is very important that a snag or telephone lines are located near the nest boxes; the SAK uses them for perching and hunting. Our nest boxes usually have 5-6 successful nests a year, producing 3-4 young each. In addition to our nest boxes, we usually find 3-6 nests located in natural cavities each year. Nearly all the nests are found in enlarged RCW cavities located in living or dead cavity trees. All chicks are banded with a U.S. Fish and Wildlife aluminum band and a combination of color bands. There is a lot of competition for the nest boxes from other bird species and squirrels. We usually have more Eastern Screech Owl nests than SAK nests. We have also found Great-crested Flycatchers, Tufted Titmice, and Eastern Bluebirds nesting in our boxes. If we find other bird species using the boxes, we leave them alone, but Fox Squirrels and Southern Flying Squirrels are removed. Flying squirrels are a big problem. It is not uncommon to find 4-8 flying squirrels occupying a nest box. The number one nest predator on nesting SAKs is the Texas Rat Snake, a great tree climber. We have found adults, young, and eggs consumed by the rat snake. To limit predation, we place aluminum sheeting (4 ft. wide) at the base of each nest box tree. The slick aluminum prevents the snake from climbing the trees and reaching the nest boxes.
With proper management, SAK populations should remain stable and possibly increase in the future on federal lands, including Fort Polk and National Forest Service lands. It is critical that regular prescribed fires and timber thinning continue into the future. Not only is this necessary for maintaining healthy populations of SAK, but for other rare species that share its habitat.
Contributed by: Kenneth Moore
Also by Kenneth Moore: Southeastern American Kestrel in Louisiana
The American Kestrel (Falco sparverius) is the smallest member of the family Falconidae in North America. The American Kestrel can be identified by two distinct black streaks on each side of the head that contrast with the white throat and cheeks, and by a blue-gray patch encircling a rufous-colored spot on the top of the head. The males have a prominent rufous coloration on the back and tail. The Southeastern American Kestrel (F.s. paulus), which is one of two subspecies that occurs in the United States, is a local resident of Louisiana. It is approximately the size of a robin, and the female is larger than the male. The Southeastern American Kestrel (SAK) is often seen during the winter months in Louisiana perched on telephone lines located along fields and pastures.
The resident SAK is often confused during the winter with the migratory subspecies F.s. sparverius, although the resident species is smaller. The mean body mass of the SAK is approximately 22 percent lower in males and 26 percent lower in females, as compared to the migratory subspecies. It is very difficult to distinguish the two subspecies in the field. F.s. sparverius may look chunkier, but it takes someone who has spent long hours in the field watching kestrels to determine the difference between the two subspecies.
SAKs form strong pair bonds that tend to remain permanent. Displaying high site fidelity, pairs often remain on or near their nesting territories. SAK territories can range in size from 300 to 700 acres. In Louisiana, the SAK prefers open, park-like pine forest and open areas with scattered mature trees, which are needed for perch and nest sites. It is important that forest stands do not have a dense understory. The SAK prefers the same type of habitat preferred by the endangered Red-cockaded Woodpecker (RCW).
The SAK begins breeding courtship in late winter. The courtship includes aerial displays in which the male performs dives and a flutter-glide to advertise to the female. The SAK nests in cavities located in snags or living trees, usually excavated by woodpeckers. The Pileated Woodpecker often plays on important role in creating cavities suitable for nesting SAKs by enlarging the cavities of smaller woodpecker species. The SAK will also use nest boxes, when they are placed in suitable habitat. On Fort Polk, we usually find our first eggs in early April, and a full clutch usually consists of four to five eggs. The incubation period lasts 29 to 30 days. The young will fledge around the age of 30 days. The adults and young will forage together until dispersal, which occurs in the fall.
The SAK hunts from a perch, on the wing, and hovering. It is a generalized predator, feedings on rodents, insects, reptiles, amphibians, and small birds. The favorite food items on Fort Polk are lizards, including anoles, fence lizards, and skinks.
The U.S. Fish and Wildlife Service formerly considered the SAK a candidate subspecies for listing as threatened or endangered. It is no longer being considered a candidate for listing, but is considered a species of concern. The SAK is listed as threatened in Florida by the state’s game and fish commission. The SAK is a nonmigratory resident of the gulf coast states, now very rare over much of its former range. Current range includes east Texas, Florida, Louisiana, and the southern portions of the states of Mississippi, Alabama, South Carolina, and Georgia. The ranges of the two subspecies overlap during the winter.
Habitat loss is the main factor in the population decline of SAK in parts of its range. Industrial forest lands provide open areas important for the SAK, but they do not provide mature trees for nests sites. When the timber matures, the timber stand is usually too dense to be suitable for the SAK. Lack of prescribed fire is also detrimental to the SAK, because it prefers open, park-like forest stands kept open by regular prescribed burning. Prescribed burning and placing nest boxes in suitable habitat are the quick and feasible ways to improve SAK habitat.
Contributed by: Kenneth Moore
Also by Kenneth Moore: Southeastern Kestrel Management on Fort Polk