Red-necked grebes breed every year and are seasonally monogamous. They are able to breed in their first year of life, yet they usually begin when they are two or more years of age. During mate selection, this species exhibit complex courtship rituals that include a large variety of displays. These rituals are similar to other species of grebes except they tend to be more vocal and contain extensive whinny-braying, which has been described as an eerie sound that resembles a screaming squeal of a scared young pig. One of these rituals involves the mates swimming around each other, then facing each other to make contact with their breasts while rising upright and making loud ticking sounds. Mating pairs have been observed diving to the bottom of the lake and pulling out vegetation with their bills and presenting it to each other.
The breeding patterns of red-necked grebes have some variation. In some areas it has been observed that a single breeding pair will isolate themselves from other birds and act aggressively to protect their claimed territory for breeding and feeding. In contrast, in other areas it has been observed that red-necked grebes breed in colonial groups. These birds engage in open interaction with other birds. Red-necked grebes nesting in a dispersed fashion is more common than in colonies.
Red-necked grebes also have a copulation ritual that includes a variety of actions that are accompanied by the whinny-braying call that is specific to this species. During copulation the female is present on the nest with her head low and the feathers on the back of her neck are erect. The male swims around behind the female and then hops up with his wings closed and his crest up and proceeds to make a number of steps on the female’s backside before making cloacal contact. After copulation has occurred the male then slides off the side of her and reenters the water. A common postcopulatory display involves the male diving down to the bottom of the lake, pulling out some vegetation, and presenting it to his mate.
Mating System: monogamous
Most breeding pairs form on wintering grounds prior to the spring migration. Because of this, most of the birds arrive at the nesting sites for breeding season already paired. If this is not the case, the birds are paired soon after.
Red-necked grebes have a breeding season that spans from May to September. Nest building typically occurs in May and most pairs lay their first clutch within the first two weeks. They often build their nests on vegetation that is floating on or anchored near the edge of bodies of water. Vegetation that forms thick mats or provides substantial cover and anchorage is preferred. Males initiate the nest-site selection process, but both sexes participate in nest building. The nest base is built out of partially decayed vegetation that is gathered from above and below the surface of the water. The rim of the nest is built out of primarily sticks and bulrushes.
Generally, a breeding pair of red-necked grebes only produces one brood per season. If the first clutch of eggs and or the nest becomes destroyed, the pair will often attempt a subsequent set. This may occur up to 5 times in one breeding season. Although rare, a pair may lay a second set even when the first set was a success. Each clutch usually consists of 4 to 5 eggs, but anywhere from 1 to 9 has been observed. The eggs are usually laid at 1 to 2 day intervals. Eggs are light blue when they are laid, but they often fade to white within one day of being laid. Over time, the wet nest material may stain them to a dark tan color. Hatching occurs 22 to 35 days after the eggs are laid. Chicks will fledge and reach independence between 9 and 10 weeks after hatching.
The behavior of red-necked grebe mating pairs differs depending on whether or not they are a part of a solitary pair or a colonial pair during the nesting season. Solitary pairs tend to leave their nest vacant and unguarded more often then colonial pairs. In the period prior to nesting, both female and male colonial birds are more aggressive towards other birds than are solitary birds. However, after the eggs have been laid and the nest has been fully established, the females of both colonial and solitary pairs lose much of their aggressive behavior. In both groups, the females spend more time near the nest during the egg-laying period than males. However, throughout the duration of the incubation period the colonial males spend much more time near the nest and their female than the solitary males do. It is believed that colonial nests are more likely to be exposed to predators because they stand out. Therefore, the nesting behavior of red-necked grebes depends on their social situation considerably. Regardless of this, they have been observed to successfully breed in both solitary and colonial aggregations.
Breeding interval: Red-necked grebes breed once yearly.
Breeding season: Breeding season for red-necked grebes is from May to September.
Range eggs per season: 1 to 9.
Average eggs per season: 4-5.
Range time to hatching: 22 to 35 days.
Range fledging age: 9 to 10 weeks.
Range time to independence: 9 to 10 weeks.
Average age at sexual or reproductive maturity (female): 1-2 years.
Average age at sexual or reproductive maturity (male): 1-2 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization
Both parents participate in incubating the eggs. The young red-necked grebes leave the nest via the parents' backs soon after the last egg hatches, although in some cases the parents will leave the nest before every egg has hatched. The chicks continue to ride on the parents back until they are ten to seventeen days old, the age at which they begin swimming themselves.
The parents feed the young for six to seven weeks. The primary food source of the hatchlings is insect larvae and other small prey items. The parents also feed feathers to the young birds. The young eat directly from the parents' bill. The young are typically completely independent from their parents at the age of nine to ten weeks and usually begin flying at about this time.
Parental Investment: precocial ; male parental care ; female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)