Crab Plover: Dromadidae - Behavior And Reproduction
BEHAVIOR AND REPRODUCTION
Crab plovers are found in large groups throughout the year. They gather in large flocks of as many as hundreds of individuals to forage, or hunt for food. Crab plovers also breed in large colonies, digging their nest burrows close together in sand dunes. Roost sites, where birds rest, can include as many as a thousand crab plovers. The calls from these sites, described as a barking "crow-ow-ow" are sometimes heard as far as a mile (1.6 kilometers) away.
Some populations of crab plovers migrate during the year, traveling from one living area to another and back. Other populations remain in the same place throughout the year. All crab plovers are most active at dawn and dusk as well as at night, because their habitats tend to be extremely hot during the day.
Unlike many other birds, crab plovers nest during the hottest, driest times of year, generally between the months of April and June. Crab plovers time their reproduction so that there will be plenty of crabs available as prey when the chicks hatch. Because of the extreme heat, however, crab plovers build their nests underground, using their bills and feet to dig large burrows in sand dunes. Burrows measure approximately 47.2 to 74 inches (120 to 188 centimeters) long. Crab plovers are the only species in the order Charadriiformes (which includes gulls, terns, plovers, and other shorebirds) to nest in burrows. Burrows not only provide a cool environment for adults, eggs, and chicks, but help provide protection from potential predators.
Crab plovers are believed to be monogamous, with a single male breeding with a single female during the breeding season. However, as many as ten adult birds are sometimes seen at a single nest burrow, suggesting that some individuals may nest together, or that adult siblings may help their parents raise younger siblings. Females lay only one egg at a time. The crab plover egg is extremely large compared to the bird's body size. It is not known how long eggs take to hatch. It is also not known for certain whether both parents help raise chicks, but it is likely that only females are responsible for this task. Although crab plover young are precocial (pree-KOH-shul), hatching at an advanced stage of development, feathered and able to move, they remain in the burrow for a considerable length of time, being fed by adults.