Grebes are members of the Podicipediformes, a widely distributed order of freshwater diving birds, some of which visit the sea when migrating and in winter.

Grebes are small to medium-large in size, have lobed toes, and are excellent swimmers and divers. However, they have their feet placed far back on the body, making them quite ungainly on land. They leave the water only to nest, walking very short distances upright like penguins. They can run for a short distance, but often fall over.

Grebes have narrow wings, and some species are reluctant to fly; indeed, two South American species are completely flightless. They respond to danger by diving rather than flying, and are in any case much less wary than ducks.

However, 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.

Bills vary from short and thick to long and pointed; the feet are always large, with broad lobes on the toes and small webs connecting the front three toes. The hind toe also has a small lobe. Recent experimental work has shown that these lobes work like the hydrofoil blades of a propeller. Curiously, the same mechanism seems to have evolved independently in the extinct Cretaceous-age Hesperornithiformes.

Grebes have unusual plumage. It is dense and waterproof, and on the underside the feathers are at right-angles to the skin, sticking straight out to begin with and curling at the tip. By pressing their feathers against the body, grebes can adjust their buoyancy. Often, they swim low in the water with just the head and neck exposed.

In the non-breeding season, grebes are plain-coloured in dark browns and whites. However, most have ornate and distinctive breeding plumages, often developing chestnut markings on the head area, and perform elaborate display rituals. The young, particularly those of the Podiceps genus, are often striped and retain some of their juvenile plumage even after reaching full size.

When preening, grebes eat their own feathers, and feed them to their young. The function of this behaviour is uncertain but it is believed to assist with pellet formation and to reduce their vulnerability to gastric parasites.

The grebes were long considered to be relatives of the loons, which show many similarities. However, it is now clear that the two groups are unrelated, and that the ancestors of the grebes diverged from the mainstream of bird evoluton very early on. They have no close living relatives, but bear some relationship to the penguins, tube-nosed seabirds, Pelecaniformes, and Ciconiiformes.

There is just a single family in the order Podicipedidae. It contains 20 species in 6 genera.

• Order PODICIPEDIFORMES
• Family Podicipedidae
  • Genus Podiceps
    • Red-necked Grebe, Podiceps grisegena
    • Great Crested Grebe, Podiceps cristatus
    • Slavonian Grebe or Horned Grebe, Podiceps auritus
    • Black-necked Grebe or Eared Grebe, Podiceps nigricollis
    • Great Grebe, Podiceps major
    • Silvery Grebe, Podiceps occipitalis
    • Junin Flightless Grebe, Podiceps taczanowskii
    • Hooded Grebe, Podiceps gallardoi
  • Genus Tachybaptus
    

    Hoary-headed Grebe.
    • Little Grebe, Tachybaptus ruficollis
    • Australasian Grebe Tachybaptus novaehollandiae
    • Madagascar Grebe, Tachybaptus pelzelnii
    • Alaotra Grebe (Rusty Grebe), Tachybaptus rufolavatus
    • Least Grebe, Tachybaptus dominicus
  • Genus Aechmorphorus
    • Western Grebe, Aechmorphorus occidentalis
    • Clark's Grebe, Aechmorphorus clarkii
  • Genus Rollandia
    • White-tufted Grebe, Rollandia rolland
    • Titicaca Flightless Grebe, Rollandia microptera
  • Genus Poliocephalus
    • Hoary-headed Grebe, Poliocephalus poliocephalus
    • New Zealand Dabchick, Poliocephalus rufopectus
  • Genus Podilymbus
    • Pied-billed Grebe, Podilymbus podiceps