Aquarium of the Pacific - Online Learning Center - Species Print Sheet
Killdeer are “true” shorebirds, although they range far from shores. They have some of the most common characteristics of these birds such as long legs and a long bill, but unlike many wading birds, Killdeer have short necks.
At the Aquarium
This bird is no longer on exhibit at the Aquarium. The information provided is for educational purposes.
Breeding: throughout North America from western Alaska through northern Chile. Year-round: southern US. Northern populations migrate north in summer and south in winter, and may also migrate to parts of Western Europe.
Killdeer make use of both saltwater and freshwater habitats, often living far from the coast but most always near water of some sort. They frequent mudflats and beaches, but also favor golf courses, meadows, pastures, dry uplands, agricultural areas, parks, lawns, and even graveled parking lots and roofs. Unlike most shorebirds, they often live close to humans.
Males and female Killdeer look alike. The upper back and most of the head is brownish. White patches mark the eyes, chin, and belly. Adults have two black bars across the breast while juveniles have only one stripe. The eyes are dark and surrounded by a black band. The tail feathers usually have a black border and are often orange-tan in color. Beaks are black and the long slender legs are pink or flesh-colored.
They are medium sized shorebirds. They have a body length of 20 to 28 cm (8 to 11 in) and a wingspan of 46 to 48 cm (18 to 19 in). They weigh between 75 g (2.7 oz) and 128 g (4.5 oz). Males and females are approximately the same size.
Diet and Feeding
These birds feed along water edges, on shorelines, mudflats, and in closely mowed pastures. They often follow plows to catch worms and insects exposed in the plowed soil. Their diet consists mainly of terrestrial invertebrates: earthworms, grasshoppers, and beetles. Occasionally they also use their pointed beaks to catch crayfish and mollusks, and to pick up seeds.
Killdeer probe the ground and muddy shallows with one foot using a quivering motion to expose their prey. In terrestrial environments, they search for prey by alternately running quickly, stopping, waiting as though to listen or look, then running again.
Breeding occurs during the summer except in the Caribbean where nesting is year-round. Males have a greater tendency to return annually to the same breeding sites than females do. Migratory Killdeer are generally seasonally monogamous, but resident birds commonly mate for life.
Males and females construct the nest in sand, grass, or gravel by scraping the ground with their feet to make a shallow depression. The nest is sometimes lined with pebbles or soft vegetation such as grasses and weed stalks. Clutches can consist of three to six eggs but the usual number is four. The eggs are gray-brown and spotted or scrawled with dark blotches, which allow them to blend in with the small stones often surrounding the nest.
Killdeer crouch over their eggs with wings extended to protect them from the sun. When the temperature gets high, the parent birds utilize ‘belly soaking’ as a cooling technique. The parent seeks out a water source to wet its breast feathers and then hovers over the eggs to cool them. Both parents incubate the eggs for 20- to 31 days.
Chicks hatch with downy feathers that are mottled brown, buff, and black on the back and white on the belly and chest. They have a single breast band (unlike adults that have two) and no obvious rump feather coloration. They are precocial, able to run after their parents and find food on their own within hours after hatching. When only a day old, the chicks make distress calls if they become isolated from their parents. The young fledge about 25 days after hatching.
Local Southern California areas include Seal Beach National Wildlife Refuge and Bolsa Chica Ecological Reserve. The birds that migrate do so both during the day and at night in flocks of 6 to 30 birds. When resting or foraging, individuals aggressively maintain distances from each other of 4-6 m (13.1 to 19.7 ft).
Killdeer react to human or other intruders by bobbing their bodies up and down while looking at the intruder. During the breeding season, they are famous for their “broken-wing act” or distraction display. If a predator, (or even a curious human), approaches the nest, the parent will twitter distress cries, fan its tail, and stumble away from its offspring. To enhance the effect, the parent will usually drag one or both wings against the ground. Often while one parent is displaying, the other takes over the nest. Once the threat is lead away from the nest, the defending bird will run or fly away, screaming to further distract the menace.
If ambient temperatures approach 40 o C (110o F) while a Killdeer is incubating eggs, the adult will open its mouth and begin to pant, much as a dog does to cool off. If the temperature continues to increase, the bird will stand over its eggs with mouth open, often dripping water from its bill.
Because Killdeer are migratory, they are protected under the Migratory Bird Treaty Act, a treaty of the US, Canadian, and Mexican governments.
Once the target of market hunters that resulted in serious declines in the population, Killdeer have recovered to become a very common shorebird. However, bird counts indicate that populations are declining in western states. Their wide range and willingness to nest near human activity allow them to survive in a variety of places where human activities expose them to pollutants such as pesticides and oil.
The common name, Killdeer, comes from the noise these birds make when alarmed—a distinct kill-deer cry. Their scientific species name, vociferous, is Latin for noisy. About two days before hatching, Killdeer chicks start making soft audible peeps. Some scientists believe that this may result in hatching of all the eggs at the same time.
Precocial chicks such as Killdeer are well developed when they hatch and require little to no parental care. In contrast, altricial chicks are blind, naked, helpless at hatching, and dependent on adult care for survival. A Killdeer chick stays in the egg two weeks longer than an altricial bird of the same size such as an American Robin so on hatching, it is two weeks older than a one day old Robin. In addition Killdeer eggs are twice as large as a Robin’s and contain more nourishment to sustain the embryo for the longer time it is in the shell.