The Horned Grebe is most likely to be confused with the similar-sized and similar-plumaged Eared Grebe throughout the year, with molting and non-breeding birds offering particular identification challenges. Once familiar, subtle, but diagnostic, differences in size and structure should allow for identification of most or all individuals. Specifically, the Horned Grebe is a slightly larger and bulkier species than the Eared Grebe, with a slightly thicker, shorter neck. More importantly, the head of the Eared Grebe is noticeably peaked over the eye, whereas the peak on the head of the Horned Grebe occurs behind the eye (at the back of the crown). This feature is of primary identification importance outside of the breeding season. Finally, Eared Grebe has a much more slender, pointed bill that is slightly upturned and lacks the tiny white tip that is present on the bill of the Horned Grebe.
The plumage of these two species is also an important consideration for identification. During the breeding season, the colour of the neck (rufous in Horned Grebe, black in Eared Grebe) is an obvious field mark, although this can be somewhat difficult to determine on very distant birds. In addition, the upperparts of Horned Grebe show narrow paler grey scaling throughout, whereas those if the Eared Grebe are solid blackish. The size and shape of the yellowish plumes on the sides of the head also differ between these species, and provide an important field mark at long range. In the Horned Grebe, a broad yellow post-ocular stripe extends from the eye back towards the nape, where it flares into a pair of broad, solid yellow “horns”. Eared Grebe, in contrast, shows a wispy, diffuse patch of yellow plumes behind (but not reaching) the eye. These differences in head pattern become considerably more difficult to use during molt in the spring and fall, when both species can show intermediate head patterns that are much more similar than during the height of the breeding season.
In the winter (and when in juvenal plumage), Horned and Eared Grebes become particularly difficult to distinguish. The pattern of the head and neck, as well as the aforementioned differences in size and structure, are the most important field marks in these plumages. Most importantly, Eared Grebe has a more extensive black cap on the head that often extends down onto the sides of the face (becoming paler and greyer) where it isolates a crescent-shaped white area along the rear of the ear coverts. Horned Grebe, in contrast, has the black cap extending down only as far as the eye with a bold, broad white area across the throat, cheeks, and sides of the face. Finally, the foreneck of the Eared Grebe averages considerably darker and greyer than the foreneck of Horned Grebe (which is white to pale grey), although darker Horned Grebes can approach pale Eared Grebes in this characteristic.
| Calls frequently only on the breeding grounds, with migrant and wintering birds vocalizing only rarely. The most commonly-heard call is a whining, nasal, descending, often repeated way-urr or ja-orrrrh that ends with a throaty rattle. Pairs on the breeding grounds often engage in “duetting”, which consists of both individuals producing a loud, high-pitched, accelerating, often pulsating trill: dji-ji-ji-ji-ji-ji-ji-ji-ji-ji-ji-jrrh. Duets can also be more staccato and stuttering, with less continuous cadence and shorter phrases of 2-3 notes ( kru-vu, kru-vu, kru-vu or dji-ji, dji-ji, dji-ji), or more intense and squeakier ( dji-ji……JOARRH, dji-ji……JOARRH). Multiple pairs often call simultaneously, producing a sustanined chorus. When alarmed, gives a drier, shriller chatter. Wintering and migrant birds occasionally produce a variety of high, thin notes (especially when in flocks), and fall migrants may give a complaining, nasal keeawuk-keeawuk-keeawuk. Source: Sibley (2000); Stedman (2000) |
Courtship
Pair formation occurs in mid- to late winter or during spring migration and pairs remain monogamous throughout the breeding season (sometimes for multiple years). Four different courtship displays have been described, including a ‘Discovery Ceremony’, ‘Weed Ceremony’, ‘Head-shaking Ceremony’, and ‘Triumph Ceremony’. During the ‘Discovery Ceremony’, which initiates the courtship process and may be given by unpaired males in mid-winter as they seek mates, the male adopts an upright posture with the base of the neck and rear portion of the body puffed-out, the remaining feathers partly erected, and the crests erected (but not flared); the male often gives the aaaanrrh or jaorrrh advertising call during this display. When a prospective mate approaches a displaying male, he further puffs out the body feathers, partly spreads the wings, and adopts a more hunched posture while the approaching female dives and pops up briefly (often several times in a row). The two birds then swim parallel, rise up on their feet, and ‘run’ across the surface of the water for several seconds using rapid movement of their feet. Following this, the birds return to the surface of the water and engage in mutual preening. The pair often engages in multple bouts of such displays before finally swimming away from each other. Some pairs, apparently in the place of the early stages of the ‘Discovery Ceremony’, engage in a ‘Head-shaking Ceremony’ that involves the two birds facing each other with head feathers and horns flared and then performing a series of rapid, lateral head waggles of variable duration.
If the birds involved in the ‘Discovery Ceremony’ or ‘Head-shaking Ceremony’ appear to be compatible, the separating birds repeatedly dive and return to the surface with weeds or algae in the bill (‘Weed Ceremony’), subsequently approaching each other with their weeds. The two birds then rise up breast-to-breast, immediately turn side to side, and ‘run’ across the surface of the water together for 5-10 m. This sequence often occurs multiple times in succession. Finally, if the pair formation has been successful, the individuals of the pair will swim side-by-side in a hunched posture while eliciting trilling duet calls (‘Triumph Ceremony’).
Nest
Nests are often solitary or in small, loose aggregations, in contrast to the colonial nesting behaviours of several other species of grebe (Eared, Red-necked, Western). Both members of the pair contribute to the construction of the nest, but construction is often initiated by the male. The construction of the nest takes as little as only a few hours to as much as several days. It is a low, mounded mass of aquatic vegetation, mud, and debris (usually collected from within 25 m of the nest) that is usually either affixed to emergent vegetation and floating or is built in shallow water from the bottom up; however, occasional nests are built on dry land at or very near the edge of the water. The nest is ~20-40 cm in diameter, with a central depression that is ~10-20 cm in diameter. Nest construction, especially around the rim of the nest, continues after the eggs are laid.
Eggs
An initial clutch of (3) 4-5 (8) eggs is laid between mid-May and mid-June and is incubated by both parents for 22-25 days before hatching; a second clutch may also be laid as late as mid-July. Eggs are laid at daily intervals, with incubation beginning on the third or fourth egg. The eggs are smooth and pure white. Eggs are present in B.C. between mid-May and mid-August, with most clutches active between mid-June and early July.
Young
The young are active and fully precocial upon hatching leaving the nest almost immediately to follow the adults. The downy chicks are pale greyish on the body and pale buffy on the head and neck and are extensively striped with long, longitudinal black stripes throughout. There is a small, pinkish patch of bare skin on the crown and the short, pointed bill is pinkish with two vertical dark bands on the upper mandible. The eyes are dark and the legs and feet are dark grey. The chicks are fed and closely tended by both parents (sometimes only one parent for older chicks) for 10-14 days after hatching, often riding on the back of the parent. The young remain as a family group even after parental feeding ceases, and are able to fly at 41-50 days of age. Dependent young are present in British Columbia between early June and early September, with most broods occurring throughout July.
Source: Campbell et al. (1990a); Baicich and Harrison (1997); Stedman (2000)
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The selection of food items varies throughout the year, reflecting a change from freshwater habitats during the breeding season to largely marine habitats in the winter (at least along the coast). During the summer, it feeds mainly on aquatic arthropods (aquatic insects, freshwater crustaceans, etc.), although it occasionally snatches flying insects directly from the air and may even take larger prey such as tadpoles, small frogs, small fish, leeches, etc. In marine habitats during the winter and migration, its diet switches to include primarily small fish, crustaceans, and marine worms, most of which are captured in benthic (bottom) rather than midwater habitats. The Horned Grebe tends to forage in shallow to moderately deep (up to 6 m in depth) waters, selecting particularly shallow foraging habitats during the breeding season. Prey is captured during relatively brief dives. Smaller prey is consumed underwater, but larger prey (fish, etc.) is brought to the surface to be manipulated prior to consumption. Most foraging birds occur singly or in small groups (<5 individuals) throughout the year, although during the winter and migrantion may form aggregations or even loose flocks of up to 200 individuals.
Source: Stedman (2000)
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