Killdeer

Name and taxonomy

Carl Linnaeus described the killdeer in 1758 and gave it the name it still holds. He worked from an account written by the English naturalist Mark Catesby in 1731. Catesby called the bird the chattering plover. In Late Latin, charadrius named a yellowish bird that appears in the Vulgate Bible. That word goes back to a Greek term for a bird of ravines and river valleys. The species name vociferus joins the Latin words for cry and carry.

The common name copies the call, which sounds like the two words kill deer. Older American names for the bird include soldier bird and pond bird. Three subspecies are described. The nominate form breeds from southeastern Alaska and southern Canada down to Panama. C. v. ternominatus lives in the Bahamas, the Greater Antilles and the Virgin Islands. C. v. peruvianus stays all year in western Ecuador, Peru and the far north of Chile.

Evolution and relatives

The killdeer sits in Charadrius, the genus of the ringed and banded plovers. That genus belongs to the plover family, Charadriidae, in the wader order Charadriiformes. Like other plovers, it hunts by sight rather than by probing mud with a long bill. The short thick bill and the long legs are typical of the group. Most relatives wear one breast band, so the killdeer's second band stands out.

The three subspecies differ in size and in the rufous edging on the back and wings. Birds of the West Indian form are smaller, paler and greyer. The South American form is also smaller but carries broader rufous fringes. The Caribbean and Peruvian birds do not migrate, unlike many northern ones. Their separation probably follows from the long distance between the breeding areas.

Appearance

The killdeer is a tall, slender plover with a fairly long tail. Adults measure 20 to 28 centimetres long and span 59 to 63 cm across the wings. Weight runs from 72 to 121 grams. The bill is short, thick and dark, and the legs are the colour of flesh. A red ring circles each eye.

The crown, back and wings are brown with rufous edges to the feathers. The forehead is white, and a white stripe runs back behind the eye. Black marks the area between the eye and the bill, and the top of the white forehead. A white collar with a black upper edge circles the neck. The breast and belly are white, cut by the two black bands. The rump is red-orange, and a white wing stripe flashes in flight.

A breeding female often shows browner face and breast markings than a male. Young birds look much like adults, with buff edges to the feathers. A chick is dusky and buff above and white below, with a single breast band. The extra band probably appears with the first full plumage.

Habitat and range

The nominate subspecies breeds through the United States, southern Canada and Mexico. Scattered breeding ground reaches south to Panama. Birds in the southern half of that range stay put all year. Northern breeders leave after the middle of July, and passage peaks in August and September. They winter as far south as Colombia, Ecuador and the islands off Venezuela. The return north begins in February and finishes in the middle of May.

In winter the killdeer uses beaches, coastal marsh and open fields. It breeds on flat ground where the plants stand under a centimetre tall. Ploughed fields, meadows, gravel roads, lawns and airfields all serve. A breeding home range covers about 6 hectares, and more when the nest sits far from water. In autumn some birds turn up in mountain meadows right at the snow line. GBIF holds records from 61 countries, and iNaturalist carries 153,370 observations.

Diet and feeding

Insects make up most of the diet, and beetles and flies lead the list. The bird also eats millipedes, worms, snails and spiders. It takes some seeds and berries, and it will pick up a dead minnow or a tree frog. Killdeer eat mosquitoes, ticks and locusts, so farmers gain from having them about. Almost all foraging happens in fields rather than on the tide line. Short grass, cattle and standing water together make the best feeding field.

The killdeer hunts by sight, and it runs a few steps and then stops to look. In foot-trembling it stands on one leg and shakes the other in shallow water. It pecks at whatever the shaking stirs up, after about five seconds of it. In a ploughed field it follows the plough and takes the worms turned up. Outside the breeding season it feeds at night when the moon is full. Night feeding brings more insects and fewer hunters.

Behaviour and social life

Killdeer live alone or in pairs, and loose flocks form outside the breeding season. They are active in the day and also at night. Most birds stay in one area, and cold weather pushes them south. A drop below about 10 degrees Celsius seems to start the movement. The species has settled into parks, farms and other ground that people have changed.

A male claims his territory as soon as he reaches the breeding ground. He calls from a high spot and scrapes out a dummy nest to advertise. In a killdeer flight he crosses the territory with slow, deliberate wingbeats. A bird that is approached too often on the ground will chase the intruder off. Flight chases follow when the challenge comes from the air. Breeding home ranges in two studies ran from 0.23 to 0.68 hectares.

Communication and senses

The killdeer is one of the noisiest birds of open country and calls even after dark. Its notes are nasal, and the best known is the ringing kil-deee. A display flight brings a repeated kil-deer or kee-deeyu. A disturbed bird fires off a fast run of notes such as kee-di-di-di. The alarm call is a long, quick trill.

Other animals use those alarms as a warning, so the killdeer guards more than itself. The species hunts by sight, so good eyes probably matter more than touch. Colour also carries a message, and the orange rump appears in threat displays. Posture does the rest, from a drooped wing to a raised tail. A pair calls to each other in flight during courtship.

Reproduction and life cycle

Killdeer are monogamous, and pairs form as soon as the birds reach the breeding ground. A resident pair may stay together all year and breed together for several seasons. Nesting starts as early as March in the southern states and as late as June in central Canada. In Puerto Rico and other Caribbean islands the birds may nest in any month. A killdeer often breeds close to the place it used the year before.

The nest is a shallow scrape in bare ground, edged with stones and grass blades. Pale material usually lines it, such as white pebbles or bits of seashell. Pale lining keeps the eggs cooler and hides them better against the ground. A study of piping plovers found such nests 2 to 6 degrees Celsius cooler than the soil. On a rooftop the birds pick flat gravel and add white stones or shell.

A clutch holds four to six buff eggs with brown marks and black speckles. Each egg is about 38 by 27 millimetres, and they arrive 24 to 48 hours apart. Both parents incubate for 22 to 28 days, and the male usually sits at night. In hot weather a parent shades the clutch instead of warming it. A pair can lay up to five replacement clutches after a failure.

Chicks hatch covered in down and walk within their first days. Both parents lead them from the nest to thick cover where they can hide. The young feed themselves, which is unusual among birds. They fledge about 31 days after hatching and move to damper ground. Parents may still tend them for 10 days after that, and rarely much longer. Killdeer breed at one year old, and the oldest known wild bird reached 10 years and 11 months.

Predators and threats

Eggs and chicks feed a long list of hunters. Herring gulls, crows, ravens, birds of prey, raccoons, striped skunks and opossums all take them. Snakes, foxes, coyotes and free-roaming cats and dogs add to the toll. Weasels and their relatives can kill a sitting adult on the nest. About 53% of eggs are lost, and 52 to 63% of nests raise nothing at all.

The bird answers a predator with display rather than flight. In the broken-wing display it runs from the nest, calls, then droops a wing and fans its tail. It turns the orange rump towards the hunter and shuffles away from the eggs. In the ungulate display it lifts its wings, lowers its head and charges the intruder. That charge sometimes kills the bird that makes it. Displays are strongest just after hatching, when a brood is worth most.

The killdeer carries thorny-headed worms, tapeworms, roundworms and flukes. One count found at least 13 species of parasite in the bird. Nests on roads, car parks and roofs may be crushed or disturbed by accident. The wider decline probably comes from changes in farming and open land.

Population and conservation

The IUCN once listed the killdeer as Least Concern. The range covers about 26.3 million square kilometres. The IUCN puts the population near one million birds. The Handbook of the Birds of the World Alive gives a figure closer to two million. In 2024 the bird moved to Near Threatened.

The trigger was a fall of more than 20% across three generations. The decline is not fast enough to make the species Vulnerable. The Migratory Bird Treaty Act of 1918 protects the killdeer in the United States. The Migratory Birds Convention Act does the same in Canada. Regional lists in Quebec, Nova Scotia, Newfoundland and Labrador and the Yukon rank the breeding birds as vulnerable. The bird still nests on ground that people use daily, which probably softens the loss of wild habitat.

Relationship with humans

Few wild birds probably live as close to people as the killdeer does. It nests on gravel roofs, road shoulders, car parks and playing fields. Grazed pasture suits it, because cattle keep the grass short. Farmers gain from the insects it removes, including mosquitoes and ticks. The species does no known harm to people or to crops.

The loud call makes the bird easy to find, so beginners probably learn it early. Its droppings carry seeds and small water organisms between wet places. Both American and Canadian law forbid killing the bird or taking its eggs. A nest on a building site may therefore halt work until the chicks leave. The broken-wing display is probably the best known piece of bird behaviour in North America.

In culture and myth

The genus name links the killdeer to an old legend. Medieval bestiaries describe the caladrius, a snow-white bird with the power to heal. The name comes from the same Greek word that gave the genus its name. A sick person recovered if the bird met their gaze, and died if it turned aside. The caladrius was said to carry the illness up towards the sun and burn it away. Christian writers used the story as a figure for Christ.

Art historians have suggested that a white plover lay behind the legend. Doves and herons have also been put forward as the model. The real link to the killdeer appears to be a name rather than a story. Mark Catesby gave the bird its first English description in 1731. He called it the chattering plover, a name that seems to fit as well as the modern one.

American country names appear to catch the same idea in different ways. Soldier bird probably points to the two dark bands across the chest. Pond bird may point to the wet fields where the birds gather. The modern name simply repeats what the bird shouts all summer. Few animals appear to have named themselves so plainly.