Some thick-knees, such as the stone-curlew, are generally found alone. Other thick-knees are often found in small groups. All thick-knees spend the majority of their time on the ground, usually perching no higher than a few feet off the ground. However, thick-knees are strong fliers and will fly away if disturbed by intruders. Many species of thick-knees are nocturnal, quiet by day and active at night, when they call loudly.
Breeding in thick-knees occurs in the spring, except in the tropics, when it may occur year-round. The stone-curlew is a monogamous (muh-NAH-guh-mus) species, with a single male mating with a single female. Stone-curlews keep the same mate throughout life. Many other thick-knee species are also monogamous, but the breeding system for a few species remains uncertain. Thick-knee nests are simple and formed by scraping the ground. The male and female select the site together by bowing towards a particular spot. The male chooses the final spot, and the female scrapes at the ground with her feet to clear a nest. Twigs, small stones, and leaves may be scattered around the nest site. Often, several nests are built this way by the pair before one is finally chosen.
In most thick-knee species, the female lays two or three eggs at a time. In the beach thick-knee, only one egg is laid. The eggs are usually light brown in color and either spotted or streaked to make them less visible on the ground. Both male and female incubate, or sit on, the eggs. Eggs hatch after twenty-four to twenty-seven days. The parents immediately move the eggshells away so that potential predators will have a harder time locating the chicks. Thick-knee chicks are able to leave the nest before they are a day old. However, parents continue to protect and to help feed the young. Adults scare off potential predators by fanning their wings and tail. Thick-knee young become mature and capable of breeding after two or three years.
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