Pluvier kildir

Identification

The killdeer is a large plover, with adults ranging in length from 20 to 28 cm (7.9 to 11.0 in), having a wingspan between 59 and 63 cm (23 and 25 in), and usually being between 72 and 121 g (2.5 and 4.3 oz) in weight. It has a short, thick, and dark bill, flesh-colored legs, and a red eye ring.<p>Its upper parts are mostly brown with rufous fringes, its cap, back, and wings being the former color. 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, except for two black breast bands. It is the only plover in North America with two breast bands. 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. A white wing stripe at the base of the flight feathers is visible in flight.<p>The female's mask and breast bands tend to be browner than those of the male. The adult of the subspecies C. v. ternominatus is smaller, paler, and greyer than the nominate. The subspecies C. v. peruvianus is smaller than the nominate and has more extensive rufous feather fringes. 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.<p>The killdeer is 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 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 alarm call is a long, fast trill.

Taxonomie

Nom scientifique

Charadrius vociferus

Autorité

Linnaeus, 1758

Ordre

Charadriiformes

Famille

Charadriidés

Genre

Charadrius

Répartition et habitat

The nominate subspecies of the killdeer breeds in the US (including southeastern Alaska), southern Canada, and Mexico, with less widespread grounds further south, to Panama. Some northern populations are migratory. This bird is resident in the southern half of its breeding range, found throughout the year in most of the contiguous United States. It also winters south to Central America, the West Indies, Colombia, Ecuador, and islands off Venezuela, leaving its breeding grounds after mid-July, with migration peaking from August to September. Migration to the breeding grounds starts in February and ends in mid-May.<p>The subspecies C. v. ternominatus is thought to be resident in the Bahamas, Greater Antilles, and Virgin Islands. C. v. peruvianus is seen year-round in western Ecuador, Peru, and extreme northwestern Chile.<p>The killdeer uses beach habitats, coastal wetlands, and fields during the non-breeding season. It forages almost exclusively in these fields, especially those with short vegetation and with cattle (which likely shorten the vegetation) and standing water. When breeding, the killdeer has a home range of about 6 ha (15 acres), although this is generally larger when nesting more than 50 m (160 ft) away from water. Although generally a low-land species, it is found up to the snowline in meadows and open lakeshores during its autumn migration.

Migration

Complete migrants

Comportement

The killdeer forms pairs on its breeding grounds right after arriving. Both sexes (although the male more often than 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. Ground chases occur when a killdeer has been approached multiple times by another killdeer; similarly, flight chases occur when an individual has been approached from the air. Both are forms of territorial defense.<p>The killdeer nests in open fields or other flat areas with short vegetation (usually below 1 cm (0.39 in) tall), such as agricultural fields and meadows. Nests are also sometimes located on rooftops. This plover frequently breeds close to where it bred the previous year. The male seems to usually renest in the same area regardless of whether or not he retains the same mate. This does not appear to be true of the female, which has been observed to not use the same territory if she does not have the same mate. The nest itself is merely a shallow depression or scrape in the ground, fringed by some stones and blades of grass. It is generally built with white nesting material instead of darker colors; the function of this is suspected to either help keep the nest cool or conceal it. In a study of piping plovers, the former function was supported, as nests were 2 °C (3.6 °F) to 6 °C (11 °F) cooler than the surrounding ground. The latter function also had some support, as the plovers generally chose pebbles closer in color to the eggs; nests that contrasted more with the ground suffered more predation. When nesting on rooftops, the killdeer may choose a flat roof, or build a nest of raised gravel, sometimes lined with white pebbles or pieces of seashells.<p>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 possibly in other Caribbean islands, breeding occurs year-round.<p>The killdeer lays a clutch of four to six eggs that are buff to beige, with brown markings and black speckles. The eggs are about 38 by 27 mm (1.5 by 1.1 in) in size, and laid at intervals of 24 to 48 hours. The energy expenditure of both sexes is at its highest during egg-laying; the female needs to produce eggs, and the male needs to defend his territory. Both of the sexes are closer to the nest site than usual during egg-laying and incubation, although the male is generally closer than the female 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 occasionally two broods occur. Second broods are usually laid in the nesting territory of the first brood. The eggs are incubated for 22 to 28 days by both the male and the female, with the former typically incubating at 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 around 26 °C (79 °F), and 87% of the time at about 35 °C (95 °F). When it is hot (above at least 25 °C (77 °F)), incubation cools the eggs, generally through shading by one of the parents.<p>About 53% of eggs are lost, mainly to predators. The young are 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 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 these broods, the young are usually attended by one parent at a time (generally the female) until about two weeks of age, after which both parents are occasionally seen together with the chicks. Otherwise, the inattentive adult is at least about 23 m (75 ft) away from the chicks. Periods of attentiveness for each parent generally last from about one to one and a half hours. When the chicks are young, this is mainly spent standing; as the chicks get older, less time is dedicated to standing. When the young are below two weeks of age, the attending adult spends little time feeding; foraging time increases as the chicks grow. The inattentive adult defends the young most of the time when they 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 broods the chicks and does so frequently until they are two days old. The young are brooded during the day until about 15 days after hatching and during the night for about 18 days after hatching. The only time when they are not in the presence of a parent is when the parents are mating or responding to a predator or aggressive conspecific.<p>When a pair has two broods, the second is usually attended by just the male (which can hatch the eggs on his own, unlike the female). In this case, the male does not spend most of the time standing; the amount of time he does stand, though, stays constant as the chicks age. Like attentive adults in two-parent broods, the sole parent increases the time spent foraging as the young age.<p>The young fledge about 31 days after hatching, 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. About 52 to 63% of nests fail to produce any fledged young. Breeding starts after one year of age. The killdeer has a maximum lifespan of 10 years and 11 months.<p>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 with cattle (which likely shorten the vegetation) and standing water. Standing water alone does not have a significant effect on field choice unless combined with cattle. Viable disseminules can be recovered from killdeer feces, indicating that this bird is important in transporting aquatic organisms.<p>The killdeer uses visual cues to forage. An example of this is "foot-trembling", where it stands on one foot, shaking the other in shallow water for about five seconds, pecking at any prey stirred up. When feeding in fields, it sometimes follows plows to take earthworms disturbed to the surface. The female forages significantly more than the male during most stages of breeding. The former feeds the most before and during egg-laying, the least when incubation starts (as little time to feed remains), with a return to high levels after. During the nonbreeding season, the killdeer forages during the night, depending on the lunar cycle. When the moon is full, it feeds more at night and roosts more during the day. Foraging at night has benefits for this bird, including increased insect abundance and reduced predation.

Conservation

Tendance de la population

declining