American Kestrels are North America’s smallest falcons. Although they are birds of prey, American Kestrels measure just 9 inches from head to tail—about the size of an American Robin or Blue Jay.
The male is dramatically colored with a rufous back, blue-gray wings, and a speckled breast. The face is boldly patterned with a mustache stripe below the bill. The female is similar to the male but lacks its blue-gray wings, and the chest markings are more pronounced.
Behavior and Life Cycle
Kestrels are birds of open fields and meadows. One can be seen perching on a fencepost or snag, bobbing its tail as it surveys its surrounding. When a good perch is not available, it hunts from the air, hovering in place in a technique called “kiting.”
Kestrels are long-distance migrants, many overwintering in Central America, although some only make it to the southern United States. April is probably the best time to look for migrating kestrels in Massachusetts; in overcast weather, they may be grounded and it is possible to see dozens in a wide-open area such as an airfield.
Nest sites are in cavities, usually in a dead tree, but also in nest boxes and even in holes in buildings, especially in urban areas. The male prospects for nest sites then shows them to the female who makes the final choice. She lays four to six eggs directly on the bottom of the cavity without adding any nesting material.
The eggs are incubated by both parents for 28–31 days. The young are born naked and helpless and are brooded primarily by the female while the male brings food. The young fledge at about four weeks, but the parents continue to feed the young for up to two weeks after fledging.
Kestrels eat primarily insects and other invertebrates but will take rodents and small birds when possible. Grasshoppers are a favorite.
American Kestrels have undergone widespread population declines, particularly in the Northeast United States. As a result, American Kestrel is included as a Species of Greatest Conservation Concern in the wildlife action plans of all six New England states.
The specific causes of American Kestrel declines are not well understood, but almost certainly include habitat loss and pesticide use. Mass Audubon is expanding the grassland habitat at many sanctuaries to support kestrels and other grassland birds. Ipswich River Wildlife Sanctuary, for example, has added additional acreage of open fields and a nest box for kestrels over the last few years.
Beginning in 2021, Mass Audubon is working with the Massachusetts Division of Fisheries and Wildlife to track the movement of kestrels as they migrate to and from their wintering grounds by putting LifeTags on individuals and tracking them with the Motus Wildlife Tracking Network.
The data collected through this project will hopefully offer insight into the threats kestrels face across their life cycle and enable more effective management and protection of habitat.