Grebes are aquatic diving birds in the order Podicipediformes. Grebes are widely distributed birds of freshwater, with some species also occurring in marine habitats during migration and winter. Some flightless species have occurred as well, most notable where they reside in stable lakes. The order contains a single family, the Podicipedidae, which includes 22 species in six extant genera. Although they resemble in passing to other diving birds such as loons and coots, they are most closely related to flamingos as supported by morphological, molecular and paleontological data. Many species are monogamous and are known for their courtship displays, with the pair performing synchronizing dances across the water's surface. The birds build floating vegetative nests where they lay several eggs. About a third of the world's grebes are listed at various levels of conservation concerns, the biggest threats including habitat loss, the introduction of invasive predatory fish and human poaching. As such three species have gone extinct.
Grebes are a nearly cosmopolitan clade of waterbirds, found on every continent except Antarctica. They are absent from the Arctic circle and arid environments. They have successfully colonized and radiated into islands such as Madagascar and New Zealand. Some species such as the eared grebe (Podiceps nigricollis) and great crested grebe (P. cristatus) are found in multiple continents with regional subspecies or populations. A few species like the Junin grebe (P. taczanowskii) and the recently extinct Atitlan grebe (Podilymbus gigas) are lake endemics. During the warmer or breeding seasons, many species of grebes in the northern hemisphere reside in a variety of freshwater habitats like lakes and marshes. Once winter arrives many will migrate to marine environments usually along the coastlines. The species is most prevalent in the New World with almost half of the world's species living in this part of the world.