The horned grebe or Slavonian grebe (Podiceps auritus) is a relatively small waterbird in the family Podicipedidae. There are two known subspecies: P. a. auritus, which breeds in the Palearctic, and P. a. cornutus, which breeds in North America. The Eurasian subspecies is distributed over most of northern Europe and the Palearctic, breeding from Greenland to western China. The North American subspecies spans most of Canada and some of the United States. The species got its name from large patches of yellowish feathers located behind the eyes, called "horns", that the birds can raise and lower at will.
Horned grebes can be easily recognised by its red-and-black alternate (breeding) plumage, its black-and-white basic (non-breeding) plumage, and its characteristic "horns". It is 31–38 cm long, has a wingspan 55–74 cm wide and weighs 300–570 g. It has a moderately long neck, flat forehead and a rear crown of black feathers. Its beak is straight and pointy with a white tip. Both subspecies are physically similar, with P. a. auritus (Palearctic) appearing darker than P. a. cornutus (North America), which has light grey feathers on its back, which are inconspicuous or absent in P. a. auritus. The horned grebe is often confused with the black-necked grebe, which is similar in size and colouring but differentiates by a steeper forehead, a more slender bill and a fluffier rump.
The alternate (breeding) plumage of the horned grebe has bright erectable "horns", black fan-shaped cheek feathers and an overall red-and-black colour. The neck, flanks, lores and upper-chest are chestnut brown, while the crown and back are black. The belly is a dull white. Males are slightly larger and brighter than females but are generally indistinguishable.
The basic (non-breeding) plumage is overall black and white. The neck, chest and cheeks are white, while the back and crown are a dull black-grey. The border between the crown and the cheeks extend in a straight line behind the eyes. The basic plumage does not have the "horns".