|Breeding range Resident range Non-breeding range|
The killdeer (Charadrius vociferus) is a relatively large plover found in the Americas. It was described and given its current scientific name by Carl Linnaeus in the 10th edition of his Systema Naturae. There are three subspecies, including the nominate subspecies. This plover's common name comes from its often heard call. Its are mostly brown with rufous fringes. It also has patches of white and black on its head, in addition to two black breast bands. The belly and the rest of the breast is white. The breeding range of the killdeer extends from southeastern Alaska and southern Canada to Mexico. It is resident in the southern half of its breeding range, in addition the subspecies C. v. ternominatus likely being resident in the West Indies and C. v. peruvianus being resident to Peru and areas of the surrounding countries. This species winters from its resident range south to Central America, the West Indies, and the northernmost portions of South America.
The non-breeding habitat of the killdeer are coastal wetlands, beach habitats, and coastal fields. Its breeding grounds are generally open fields with short vegetation (but locations such as rooftops may also be used), and, although it is a shorebird, it does not necessarily nest close to water. The nest itself is a scrape lined with vegetation and white material, such as pebbles or seashell fragments. It lays a clutch of four to six buff to beige eggs with dark markings. They are generally laid from mid March to early June in the southern portion of the range, and from mid April to mid July in the northern part, with the breeding season extending to August in both areas. Incubation is performed by both sexes, and last for 22 to 28 days on average. The young stay in the nest until the day after being hatched, when they are led by their parents to a feeding territory (generally with dense vegetation where hiding spots are abundant) where the chicks feed themselves. They are almost always watched over by one parent. The young then fledge about 31 days after hatching, and may be watched over by their parents until about 10 days after this event. Breeding first occurs after one year of age.
The killdeer primarily feeds on insects, although other invertebrates and seeds are also taken. It forages almost exclusively in fields, especially those with short vegetation and those with cattle and standing water. In addition to foraging during the day, in the non-breeding season, it forages during the night when the moon is full or close to full in the lunar cycle. This is beneficial because insects are more abundant and there is reduced predation. The predators of the killdeer include various birds and mammals; predation is not just limited to the eggs and young, with mustelids being able to kill incubating adults, for example. There are multiple responses to predation, ranging from calling at a stand to the "ungulate display", which, in some cases, is fatal for the performing individual. This bird is considered to be least concern by the International Union for Conservation of Nature (IUCN), because of its large range and population. Although this is true, its population is declining, but this trend is not severe enough for the killdeer to be classified as a vulnerable species.
Etymology and taxonomy
The killdeer was first described as Charadrius vociferus by Carl Linnaeus in the 10th edition of his Systema Naturae. This was based on an account of it by Mark Catesby in his The Natural History of Carolina, Florida and the Bahama Islands, where he gave it the name of the "chattering plover".
The killdeer's binomial name is Charadrius vociferus. The genus name Charadrius is a Late Latin word for a yellowish bird mentioned in the fourth-century Vulgate. It derives from Ancient Greek kharadrios a bird found in ravines and river valleys (kharadra, "ravine"). The specific vociferus is Latin and comes from vox, "cry" and ferre, "to bear".
There are three subspecies of the killdeer, including the nominate:
- C. v. vociferus Linnaeus, 1758 – The nominate subspecies, found in the US (including southeastern Alaska), southern Canada, Mexico, and very locally south to Panama. It winters to northwestern South America.
- C. v. ternominatus Bangs & Kennard, 1920 – This subspecies is found on the Bahamas, the Greater Antilles, and Virgin Islands.
- C. v. peruvianus (Chapman, 1920) – This South American subspecies is found in west Ecuador, Peru, and extreme northwest Chile.
The killdeer's name comes from its frequently heard call.
The killdeer is a relatively large plover, with adults ranging in length from 20 to 28 centimetres (7.9 to 11.0 in) and having a wingspan between about 59 and 63 centimetres (23 and 25 in). It is usually between 72 and 121 grams (2.5 and 4.3 oz) in terms of weight. It has a short, thick, and dark bill, flesh-coloured legs, and a red eye ring. Its are mostly brown and fringed rufous, with its cap, back, and wings being the former colour. 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 that is black on its upper border. The female generally has a browner mask. The rest of the face is brown. The breast and belly are white, with the exception of two black breast bands (although the female's bands are usually more brown). The rump is red, and the tail is mostly brown. The latter also has a black subterminal band, a white terminal band, and barred white feathers on the outer portion of the tail. In flight, a white wing stripe at the base of the flight feathers is visible. The juvenile is similar to the adult. The upperparts of the chicks are dusky and buff in colour. Their underparts, forehead, neck, and chin are white. They additionally have a single band across their breast. The adult of the subspecies Charadrius vociferus ternominatus is smaller and more pale and grey than the nominate, and the subspecies C. v. peruvianus differs on the basis of its smaller size and more extensive rufous feather fringes.
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The killdeer is considered to be a vocal species, calling even at night. Its calls include nasal notes, like "deee", "tyeeee", and "kil-deee" (the basis of its common name). During its display flights, it repeats a call of "kil-deer" or "kee-deeyu". When this plover is disturbed, it emits notes in a rapid sequence, such as "kee-di-di-di". Its is a long, fast trill, like "trrrrrrrrr".
Habitat and distribution
The nominate subspecies of the killdeer is found in the US (including southeastern Alaska), southern Canada, and Mexico in addition to breeding very locally to south Panama. It is resident in the southern half of its breeding range. Migratory populations winter from the breeding range south from most of the contiguous United States to Central America, the West Indies, Colombia, Ecuador, and islands off Venezuela, leaving its breeding grounds after mid July, with a peak in migration from August to September. The subspecies Charadrius vociferus ternominatus is found in the Bahamas, Greater Antilles, and Virgin Islands, where it is thought to be resident. C. v. peruvianus is resident to west Ecuador, Peru, and extreme northwestern Chile.
During the non-breeding season the killdeer uses coastal wetland and beach habitat, as well as coastal fields. It prefers fields that have less recent precipitation. It almost exclusively forages in fields, especially those with short vegetation and cattle combined with short vegetation or standing water. When breeding, it has a of about 6 hectares (15 acres). Those with nests more than 50 metres (160 ft) away from water generally have larger home ranges.
The killdeer likely forms pairs on breeding grounds. Both males and females (although the former more often than the latter) advertise in flight with loud "killdeer" calls, and the former can advertise by standing in a high spot and making the same call. Ground chases occur when a killdeer has been approached multiple times by another killdeer. Males also advertise to females by scraping out a fake nest.
To nest, the killdeer uses open fields or other flat areas with short vegetation (usually below 1 centimetre (0.39 in) tall), including agricultural fields, and meadows. Nesting habitat is characterized as having enough nest materials to form a scrape but otherwise having little or no vegetation. Nests are also sometimes located on rooftops. The killdeer frequently nests near the site it nested the previous year. It is likely that the male usually returns to nest in the same area regardless of whether or not it retains the same mate. This does not seem to be true of the female, who does not nest in the same territory if it does not have the same mate. The nest itself is merely a shallow depression or bowl in the ground, fringed by some stones and blades of grass. It generally chooses to build with white nesting material over darker colours; the function of this is suspected to either help keep the nest cool or to help conceal the nest. In a study of piping plovers, the former function was supported, as nests were 2 to 6 °C (36 to 43 °F) cooler than the surrounding ground. The latter function also had some support, as the plovers generally chose pebbles closer in colour to the eggs, but, nests with higher contrast with the ground suffered more predation. When nesting on rooftops, the eggs may be placed on a flat roof, or in a nest of raised gravel, sometimes lined with white pebbles or pieces of seashells.
The eggs of the killdeer are typically laid from mid March to early June in the southern portion of the range, and from mid April to mid July in the northern part. In both cases, the breeding season itself extends to about August. In Puerto Rico, and possibility in other Caribbean islands, breeding occurs year round.
The killdeer has a clutch of four to six eggs, buff to beige in colour, with brown markings and black speckles. They are around 38 by 27 millimetres (1.5 by 1.1 in) in size. These eggs are laid at intervals of 24 to 48 hours. When these eggs are being laid, the energy expenditure of both sexes is at its highest; the female needs to produce eggs, whereas the male needs to defend its territory. Both the female and male are closer to the nest site during egg laying and incubation, with the male generally being closer to the nest during all stages of breeding. This latter fact is likely due to the male's increased investment in nest-site defense. Up to five replacement clutches can be laid, and there are occasionally two broods. The eggs are incubated for 22 to 28 days by both the male and the female, with the former typically incubating during the night. The time dedicated to incubation is related to temperature, with one study recording that killdeer incubated eggs 99% of the time when the temperature was about 13 °C (55 °F), 76% of the time when it was around 26 °C (79 °F), and 87% of the time during temperatures of about 35 °C (95 °F). When it is hot (above at least 25 °C (77 °F)), incubation does not take the form of warming the eggs, but instead occurs through the cooling of eggs, generally through shading.
About 53% of eggs do not hatch. The day after the (being able to move almost immediately after hatching) young hatch, they are led by both parents out of the nest. The family then generally moves to a feeding territory with dense vegetation which the chicks are able to hide under when a predator is near. The chicks are raised, at least in single-brood pairs, by both parents, likely because of the high failure rate of nests and the need for both parents to be present to successfully raise the young. In two parents broods, the young are usually attended by only one parent, generally the female, until about two weeks of age, after which the non-attentive parent occasionally tends the young. Otherwise, the non-attentive parent is generally at least 23 metres (75 ft) away from the chicks. Periods of attentiveness for each parent generally last about one to one hour thirty minutes. This time is mainly spent standing when the chicks are young, with the time dedicated to this decreasing as the chicks get older. When the young are below two weeks of age, the attending adult dedicates little time to foraging. The non-attentive adult defends the young most of the time when they chicks are less than a week old, but this task steadily shifts onto the attentive adult, until about three weeks of age, when the attending parent does almost all of the defense. One parent at a time generally broods the chicks, and does so frequently until they are two days old. They are also brooded, until about 15 days after hatching, during rain, and, until about 18 days after hatching, at night. The only time when the young are not in the presence of a parent is when the parents are responding to a predator or an aggressive conspecific, or when mating.
There are sometimes one parent broods when a pair has two broods. This brood is watched over by the male, who is able to hatch the chicks on its own, unlike the female. In this case, the adult does not spend most of the time standing, and the time it did spend did not decrease as a function of age. Like attentive adults in two parent broods, the sole parent of a brood increases the time spent foraging as the chicks get older.
The young fledge about 31 days after they hatch, and generally move to moister areas in valleys and on the banks of rivers. About 52% to 63% of nests fail to produce any fledged young. They may be cared for by their parents for up to 10 days after they fledge, and exceptionally 81 days after hatching. The young breed after reaching one year of age.
The killdeer feeds primarily on insects (especially beetles and flies), in addition to millipedes, worms, snails, spiders, and some seeds. It opportunistically takes tree frogs and dead minnows. It forages almost exclusively in fields (no matter the tide), especially those with short vegetation and those with cattle and standing water. Standing water alone does not usually have a significant effect on field choice, but when combined with cattle, it does. Viable disseminules can be recovered from killdeer feces, indicating that it is important in the transport of various aquatic organisms.
The killdeer uses visual cues to find food. An example of this is "foot-trembling", where, when feeding in water, it stands on one foot and shakes the other in the water for about five seconds, and then pecks at any prey stirred up by it. When feeding in fields, it may follow ploughs to take earthworms disturbed to the surface. The female forages significantly more than male when it is breeding. Foraging by females peaks during pre-laying and laying itself, decreasing when incubation starts (as there is little time for foraging), and returning to high levels after. During the non-breeding season, it forages during the night, depending on the lunar cycle. When the moon is full, it spends more time foraging during the night and more time roosting during the day. Foraging during the night has benefits that include increased insect abundance and reduced predation.
Predators to the killdeer include herring gulls, common crows, raccoons, and striped skunks. The mentioned birds and other avian predators make up the majority of predators in some areas, at least during the breeding season. Predation is not limited to eggs and chicks: mustelids, for example, can kill incubating adults.
Responses to predators
Various methods of distracting predators are employed during the breeding season by parents. During egg-laying, the most common response to predators is to quietly leave the nest. When incubation starts, and as it progresses, the intensity of predator responses increases, peaking just after hatching. This is likely because it is worth more to protect the young at that stage, as they are more likely to survive to fledge. After hatching, though, the intensity of responses decreases, until a normal response is calling at a stand. This is because as the young age, they become more independent.
One behaviour that is seen as a reaction to predators is the "broken-wing display", also known as "injury feigning". Before this display, the killdeer generally runs away from its nest and then makes alarm calls and other disturbances. When the bird has the attention of the predator, the former turns its tail towards the latter, displaying the threatening orange colour. Then, it crouches and droops its wings, with its tail depressed. With an increasing intensity, the wings are held higher, the tail is fanned out, and the tail becomes more depressed. Another behaviour that has received attention is the "ungulate display", where the adult raises its wings, exposes its rump, lowers its head, and charges at the intruder. In some cases, the displaying bird may be killed.
The killdeer is considered by the IUCN to be a least-concern species. This is due to its large range of about 26.3 million kilometres (16.3 mi) and its large population, estimated by the IUCN to be about one million birds, although another estimate, in the Handbook of the Birds of the World Alive, gives about two million birds. Even though it has a declining population, it is not declining fast enough to be considered a vulnerable species.
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|Wikimedia Commons has media related to Killdeer.|
|Wikispecies has information related to Charadrius vociferus|
- Killdeer at Enature.com - enature.com
- "Killdeer media". Internet Bird Collection.
- Killdeer - Charadrius vociferus - USGS Patuxent Bird Identification InfoCenter
- Killdeer Fact Sheet Hinterland Who's Who - produced by Environment Canada and Canadian Wildlife Federation
- Killdeer Bird Sound at Florida Museum of Natural History
- Killdeer photo gallery at VIREO (Drexel University)