Clark's Grebe
Aechmophorus clarkii
Summary 5
Clark's Grebe (Aechmophorus clarkii) is a North American waterbird species in the grebe family. Until the 1980s, it was thought to be a pale morph of the western grebe, which it resembles in size, range, and behavior. Intermediates between the two species are known.
Presence at Rosewood 6
Months Present: December-July
Seen on Surveys: June
"Months Present" obtained from Lahontan Audubon Society at https://www.nevadaaudubon.org/birds-in-town.html
Description 7
Clark's grebe closely resembles the western grebe and occurs in the same colonies together with it. Storer and Nuechterlein in 1992, following earlier morphological studies by Storer and others, define the species as being distinguished from the western grebe by an overall paler plumage on its back, as well as a larger portion of its face covered in white, as it extends above the eyes, rather than just below them. A distinguishing feature is its bill, which is bright yellow in the US, whereas the Western Grebe's bill is greenish-yellow in the US, which had been noted by others. Storer and Nuechterlein in 1992 claim that the bill is slightly upturned in this species whereas the western grebe has a straight bill, this was not noted in earlier studies.
The grebe has a long, slender neck and the species ranges in size from 22–29 inches (56–74 cm), with a wingspan of 24 inches (61 cm). The Clarks' grebe has a weight range of 25.3–44.4 oz (720–1,260 g).
There are few changes between the sexes, the most notable feature that distinguishes males from females is the presence of a slight crest on the heads of males. In juveniles, the plumage is again similar to the Western Grebe, however it is also paler compared to the greyer Western species.
Its relative size compared to the western grebe is confused. Dickerman showed that grebes from the south of the range were smaller than northern examples, irrespective of which color morph, with both morphs being the same size depending on location, and Dickerman originally reinstated the name A. clarkii in 1963 for the smaller, southern populations (irrespective of which color morph). Studies by Storer, Ratti, Mayr and Short in the 1960-70s did not find any size differences between morphs. Nonetheless, some publications now state the paler-coloured grebes are slightly smaller, which might be due to confusion with the species concept advocated by Dickerman (in which Clark's grebe doesn't not occur in the USA or Canada, pale-coloured grebes in the US and Canada are western grebes, and dark-colored morphs in Mexico are Clark's grebe).
Although darker and lighter-colored morphs of grebes occur in the resident non-migratory populations occur in Mexico, it is unclear if these can be distinguished by the other morphological characteristics described above, as most studies have only looked at US populations. Lighter-colored morphs in Mexico are said to have orange-coloured bills, and the darker morphs have yellow bills. In the winter in California numerous examples of dark-colored western grebes displayed the mostly white face of Clark's grebe, although this was intermediate and thought to be possibly due to seasonal changes.
Vocalizations 7
The calls of the Clark's grebe are similar to its western counterpart, however, during courtship the birds make an 'advertising call' to attract mates -this sounds like a single, extended kreeeed as opposed to the two-note kreed-kreet of the western grebe. The calls of the grebe tend to vary very little between sexes.
Sources and Credits
- (c) Greg Lasley, some rights reserved (CC BY-NC), uploaded by Greg Lasley
- (c) Len Blumin, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/9062441@N02/2159811219
- (c) Ken Schneider, some rights reserved (CC BY-NC), uploaded by Ken Schneider, http://www.flickr.com/photos/zonotrichia/3474225276/
- (c) BJ Stacey, some rights reserved (CC BY-NC), http://www.flickr.com/photos/finaticphotography/8148659544/
- Adapted by Hayden Wright from a work by (c) Wikipedia, some rights reserved (CC BY-SA), https://en.wikipedia.org/wiki/Aechmophorus_clarkii
- (c) Hayden Wright, some rights reserved (CC BY-SA)
- Adapted by Hayden Wright from a work by (c) Wikipedia, some rights reserved (CC BY-SA), https://en.wikipedia.org/wiki/Clark's_grebe
