The killdeer is a large plover found in the Americas. It has a short, thick, and dark bill, flesh-colored legs, and a red eye ring. Its upperparts are mostly brown with rufous fringes; the head has patches of white and black, and there are two black breast bands. It has a white forehead and a white stripe behind the eye, and its lores and the upper borders to the white forehead are black. The killdeer also has a white collar with a black upper border. The rest of the face is brown. The breast and belly are white, with the exception of two black breast bands. The rump is red, and the tail is mostly brown. In flight, a white wing stripe at the base of the flight feathers is visible. The female's mask and breast bands tend to be browner than those of the male. The juvenile is similar to the adult. The upper parts of the chicks are colored dusky and buff. Their underparts, forehead, neck, and chin are white, and they have a single band across their breast.
Killdeer breed in the US (including southeastern Alaska), southern Canada, and Mexico, with less widespread grounds further south, to Panama. These birds are resident in the southern half of their breeding range, found throughout the year in most of the contiguous United States. Some northern populations are migratory and winter south to Central America, the West Indies, Colombia, Ecuador, and islands off Venezuela. Killdeer inhabit coastal wetlands, beach habitats, and coastal fields. Their breeding grounds are generally open fields with short vegetation. Although generally a low-land species, killdeer may be found up to the snowline in meadows and open lakeshores during their autumn migration.
Killdeer usually spend their time singly or in pairs and outside of the breeding season they may sometimes gather in loose flocks. They forage almost exclusively in fields, especially those with short vegetation and with cattle and standing water. They primarily feed during the day but, in the non-breeding season, when the moon is full or close to full, they forage at night. This is likely because of increased insect abundance and reduced predation during the night. Killdeer find their food using visual cues. An example of this is "foot-trembling", where the bird stands on one foot, shaking the other in shallow water for about five seconds, pecking at any prey stirred up. When feeding in fields, they sometimes follow plows to take earthworms disturbed to the surface. Killdeer are vocal birds and call even at night. Their calls include nasal notes, like "deee", "tyeeee", and "kil-deee'. During display flights, they repeat a call of "kil-deer" or "kee-deeyu". When killdeer are disturbed, they emit notes in a rapid sequence, such as "kee-di-di-di" and their alarm call is a long, fast trill.
Killdeer are monogamous and form pairs on their breeding grounds right after arriving. The breeding season (starting with egg-laying) occurs from mid-March to August, with later timing of egg-laying in the northern portion of the range. In Puerto Rico, and possibly in other Caribbean islands, breeding occurs year-round. Both the male and the female advertise in flight with loud "killdeer" calls. The male also advertises by calling from a high spot, scraping out a dummy nest, and with killdeer flights, where it flies with slow wingbeats across its territory. The birds also perform chases on the ground as well as in flight. Both are forms of territorial defense. Killdeer nest in open fields or other flat areas with short vegetation, such as agricultural fields and meadows. Nests are also sometimes located on rooftops. The nest itself is a shallow depression or scrape in the ground, fringed by some stones and blades of grass. When nesting on rooftops, killdeer may choose a flat roof, or build a nest of raised gravel, sometimes lined with white pebbles or pieces of seashells. The female lays a clutch of 4-7 eggs that are buff to beige in color, with brown markings and black speckles. Up to five replacement clutches can be laid, and there are occasionally two broods. Second broods are usually laid in the nesting territory of the first brood. The eggs are incubated for 22 to 28 days by both parents. The chicks hatch precocial, starting to walk within the first days of their life. After they hatch, both parents lead them out of the nest, generally to a feeding territory with dense vegetation under which the chicks can hide when a predator is near. The young fledge when they are 31 days old, and generally move to moister areas in valleys and on the banks of rivers. They may be cared for by their parents for up to 10 days after they fledge, and exceptionally for 81 days after hatching. Breeding starts after one year of age.
There are no major threats to the killdeer at present.
According to the IUCN Red List, the total population size of the killdeer is 1,000,000 individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List but its numbers today are decreasing.
Killdeer play an important role in the ecosystem they live in. These birds control the populations of insects they eat and also provide food for their predators.