Podicipedidae – Grebes

The Podicipediformes order is a widely distributed order of freshwater diving birds, some of which visit the sea when migrating and in winter. This order contains only a single family, the Podicipedidae, with twenty-two species in six genera. They are most closely related to flamingos.

They are small to medium-large in size, have lobed toes, and are excellent swimmers and divers. They swim by simultaneously spreading out the feet and bringing them inward, with the webbing expanded to produce the forward thrust in much the same way as frogs. Although they can run for a short distance, they are prone to falling over, since they have their feet placed far back on the body.

Little Grebe Tachybaptus ruficollis – ©Dubi Shapiro

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. Extant species range in size from the Least Grebe, at 120 grams and 23.5cm to the Great Grebe, at 1.7kg and 71cm.

Great Crested Grebe Podiceps cristatus – ©JJ Harrison CC BY-SA 4.0 via Wikimedia Commons

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 many occasions.

Western Grebe Aechmophorus occidentalis – ©Dubi Shapiro

Bills vary from short and thick to long and pointed, depending on the diet, which ranges from fish to freshwater insects and crustaceans. 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.

Clark’s Grebe Aechmophorus clarkii – ©Dubi Shapiro

Grebes have unusual plumage. On average grebes have 20,000 feathers, the highest among birds. The feathers are very dense and strongly curved. In the larger species feathers are more dense but shorter, while the opposite is true in smaller species where the feathers are longer but less dense. The density and length of feathers is correlated exponentially with heat-loss in cold water. For this reason, grebes invest the most time and effort of all birds in plumage maintenance. The uropygial glands secrete a high concentration of paraffin. The secretion provides a dual purpose of protecting the feathers from external parasites and fungi, as well as waterproofing them.

Red-necked Grebe Podiceps grisegena – ©Dubi Shapiro

In the non-breeding season, grebes are generally plain-coloured in dark browns and whites. However, most have ornate and distinctive breeding plumages, often developing chestnut markings on the head area, and performing elaborate display rituals. These can include ‘dancing’ across the water with the intended mate, with bodies fully erect and above the water. Nesting material may be offered by the male to the female. The young, particularly those of the Podiceps genus, are often striped and retain some of their juvenile plumage even after reaching full size. In the breeding season, they mate at freshwater lakes and ponds, but some species spend their non-breeding season along seacoasts.

Great Grebe Podiceps major – ©Dubi Shapiro

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.

Hooded Grebe Podiceps gallardoi – ©Dubi Shapiro

They 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.