Grebe

Many molecular and morphological studies support a relationship between grebes and flamingos.

Recent molecular studies have suggested a relation with flamingos[9][10][11] while morphological evidence also strongly supports a relationship between flamingos and grebes. They hold at least eleven morphological traits in common, which are not found in other birds. Many of these characteristics have been previously identified in flamingos, but not in grebes.[12] The fossil Palaelodids can be considered evolutionarily, and ecologically, intermediate between flamingos and grebes.[13]

For the grebe-flamingo clade, the taxon Mirandornithes ("miraculous birds" due to their extreme divergence and apomorphies) has been proposed. Alternatively, they could be placed in one order, with Phoenocopteriformes taking priority.[13]

Juncitarsus merkeli fossil

The fossil record of grebes is incomplete; there are no transitional forms between more conventional birds and the highly derived grebes known from fossils, or at least none that can be placed in the relationships of the group with any certainty. The enigmatic waterbird genus Juncitarsus, however, may be close to a common ancestor of flamingos and grebes.

The Early Cretaceous (Berriasian, around 143 mya) genus Eurolimnornis from NW Romania was initially believed to be a grebe. If it is indeed related to this lineage, it must represent a most basal form, as it almost certainly predates any grebe-flamingo split. On the other hand, the single bone fragment assigned to this taxon is not very diagnostic and may not be of a bird at all.[14]

Telmatornis from the Navesink Formation – also Late Cretaceous – is traditionally allied with the Charadriiformes and/or Gruiformes.[15][16][17][18][19] However, a cladistic analysis of the forelimb skeleton found it highly similar to the great crested grebe and unlike the painted buttonquail (now known to be a basal charadriiform lineage), the black-necked stilt (a more advanced charadriiform), or the limpkin (a member of the Grui suborder of Gruiformes), namely in that its dorsal condyle of the humerus was not angled at 20°–30° away from long axis of the humerus. The analysis did not result in a phylogenetic pattern but rather grouped some birds with similar wing shapes together while others stood separate. It is thus unknown whether this apparent similarity to grebes represents an evolutionary relationship, or whether Telmatornis simply had a wing similar to that of grebes and moved it like they do.[20]

True grebes suddenly appear in the fossil record in the Late Oligocene or Early Miocene, around 23–25 mya. While there are a few prehistoric genera that are now completely extinct; Thiornis (Late Miocene –? Early Pliocene of Libros, Spain)[21][22] and Pliolymbus (Late Pliocene of WC USA – Early? Pleistocene of Chapala, Mexico)[23][24] date from a time when most if not all extant genera were already present.[21] Because grebes are evolutionarily isolated and they only started to appear in the Northern Hemisphere fossil record in the Early Miocene, they are likely to have originated in the Southern Hemisphere.[25]

A few more recent grebe fossils could not be assigned to modern or prehistoric genera:

• Podicipedidae gen. et sp. indet. (San Diego Late Pliocene of California) – formerly included in Podiceps parvus[23]
• Podicipedidae gen. et sp. indet. UMMP 49592, 52261, 51848, 52276, KUVP 4484 (Late Pliocene of WC USA)[26]
• Podicipedidae gen. et sp. indet. (Glenns Ferry Late Pliocene/Early Pleistocene of Idaho, USA)[26][27]

Living Podicipediformes based on the work by John Boyd.[28]

Compiled from the following websites: Extinct species assignment follows the Mikko's Phylogeny Archive[29] and Paleofile.com websites.[30] and subspecies names from English Names of Birds.[31]

• Genus †Miobaptus Švec 1982
  • †M. huzhiricus Zelenkov 2015
  • †M. walteri Švec 1982 [Podiceps walteri (Švec 1984) Mlíkovský 2000]
• Genus †Miodytes Dimitreijevich, Gál & Kessler 2002
  • †Miodytes serbicus Dimitreijevich, Gál & Kessler 2002
• Genus †Pliolymbus Murray 1967 [Piliolymbus (sic)]
  • †Pliolymbus baryosteus Murray 1967
• Genus †Thiornis Navás 1922
  • †Thiornis sociata Navás 1922 [Podiceps sociatus (Navás 1922) Olson 1995]

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.

The North American and Eurasian species are all, of necessity, migratory over much or all of their ranges, and those species that winter at sea are also seen regularly in flight. Even the small freshwater pied-billed grebe of North America has occurred as a transatlantic vagrant to Europe on more than 30 occasions.

Grebes make floating nests of plant material concealed among reeds on the surface of the water. The young are precocial, and able to swim from birth.[2]