Western grebe
The western grebe is a species in the grebe family of water birds. Folk names include "dabchick", "swan grebe" and "swan-necked grebe".
Western grebe fossils from the Late Pleistocene of southwest North America were described as a distinct species, but later ranked as a paleosubspecies Aechmophorus occidentalis lucasi. Later studies found them to fall within the variation now known to exist in today's birds.
Description
The western grebe is the largest North American grebe. It is long, weighs and measures across the wings. It is black-and-white, with a long, slender, swan-like neck and red eyes. It is easily confused with Clark's grebe, which shares similar features, body size, behavior and habitat, and hybrids are known. Clark's grebes generally populate more of the southern part of North America Other differences are whiter flanks and paler gray backs when comparing Clark's grebe to the western grebe.The western grebe has black around the eyes and a straight greenish-yellow bill whereas Clark's grebe has white around the eyes and an up-turned bright yellow bill. The downy young of western are grey; Clark's downy young are white.
Distribution
This species of waterbirds is widespread in western North America and there is no specific place of abundance. Western grebes nest in colonies on lakes that are mixed with marsh vegetation and open water. Western grebe nests are made of plant debris and sodden materials, and the nest-building begins roughly around late April through June. The construction is done by both sexes and is continued on throughout laying and incubation.Subspecies
In 1858 George Newbold Lawrence recognised Podiceps occidentalis based on darker coloured specimens, and P. clarkii based on three paler coloured specimens -two from California and one from Chihuahua. These two colour morphs were found to occur, roost and even interbreed together, and were long regarded to be synonyms. Deignan designated the Mexican specimen as the holotype of the taxon P. clarkii in 1961. In 1963 Dickerman reinstated the taxon as Aechmophorus clarkii, which he defined as the smaller birds, both dark and pale coloured, from Mexico. In 1979 a comprehensive study by Ratti demonstrated the apparent existence of reproductive barriers between different phases of the grebes. In 1986 Dickerman recognised the taxonomic significance of the distinctions between the dark and pale phase, and classified these phases as different subspecies:- A. occidentalis ssp. occidentalis,, large, dark morph, from western Canada & United States
- A. occidentalis ssp. ephemeralis, Dickerman, 1986 - Smaller than the western grebe, dark morph, from north & central Mexico.
By 1992 Storer & Nuechterlein were promoting another concept to the taxon A. clarkii, now regarding the pale morphs from the US and Canada to be this taxon.
Breeding
Western grebes nest in colonies of hundreds on large inland lakes, sometimes using coastal marshes, in western North America. It has a spectacular courtship display; two birds will rear up and patter across the water's surface. Northern birds migrate west to coastal ocean in winter; birds in the southwest and Mexico may be permanent residents. During the breeding season, the birds advertise themselves through ceremonies. Rushing Ceremony, which can be also called as water dance, race or run, is a ceremony that is the most frequent display to form a pair-bond. This is performed in pairs of either both male Western grebes or one male and one female. One of two individuals initiates Rushing, and the paired individual follows immediately and performs in synchrony. The birds lift their wings stiffly to the side and run in an upright position with its head held forward and neck curved. The males seem to perform the rushing together to attract the attention of females, and when one of two males attracts a female from his rushing behavior, a competition arises between males to get the female. One out of two withdraw and the "winning" male mates with the female by performing Rushing together and continue to perform Weed Ceremony.Weed Ceremony usually precedes the acts of mating and nest building. It is done after the pair is formed, and the ceremony begins as the mates bob their heads in water. Then they dive in place and come back up to surface while holding weed on their beaks. This ceremony is continued until one of the pair flips away its weeds and drops to a normal position in water. They continue their mating with Greeting Ceremony. Greeting ceremony is similar to the form of rushing ceremony and involves dip-shaking, bob-shaking, bob-preening and arch-clucking. Dip-shaking consists of dipping the head in the water and raising it up while rapidly waggling the bill side to side. This involves a low neck posture and conspicuous water splash while bob-shaking does not. These breeding dances are known to be the most elaborated dances in the waterbird species.
After the breeding, the male Western Grebes feed their mate, thus performing mate feeding behavior. The feeding resembles the feeding of the young by parents, and through the feeding they obtain, females are able to have enough energy to form their eggs. During the incubation period, male and female Western Grebes trade places to incubate their eggs for weeks, and those that are not incubating feed their mate.