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Aechmophorus clarkii -Monterey Bay, California, USA -swimming-8

Superregnum: Eukaryota
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Cladus: Craniata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclassis: Tetrapoda
Cladus: Reptiliomorpha
Cladus: Amniota
Classis: Reptilia
Cladus: Eureptilia
Cladus: Romeriida
Subclassis: Diapsida
Cladus: Sauria
Infraclassis: Archosauromorpha
Cladus: Crurotarsi
Divisio: Archosauria
Subsectio: Ornithodira
Subtaxon: Dinosauromorpha
Cladus: Dinosauria
Ordo: Saurischia
Cladus: Eusaurischia
Cladus: Theropoda
Cladus: Neotheropoda
Infraclassis: Aves
Cladus: Euavialae
Cladus: Avebrevicauda
Cladus: Pygostylia
Cladus: Ornithothoraces
Cladus: Euornithes
Cladus: Ornithuromorpha
Cladus: Ornithurae
Cladus: Carinatae
Parvclassis: Neornithes
Cohors: Neognathae
Cladus: Neoaves
Cladus: Mirandornithes
Ordo: Podicipediformes

Familia: Podicipedidae
Genus: Aechmophorus
Species: Aechmophorus clarkii
Subspecies: A. c. clarkii – A. c. transitionalis

Aechmophorus clarkii (Lawrence, 1858)

Aechmophorus clarkii Coues, 1862: 229
Podiceps clarkii Lawrence, 1858: 895 (protonym)

Primary references

Baird, S.F. 1858. Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean. Vol. 9: i–lvi, 1–1005. Washington. DOI: 10.5962/bhl.title.11139 BHL. Part II, with the cooperation of Cassin, J. & Lawrence, G.N. Birds. BHL Reference page.
Coues, E. 1862. Synopsis of the North American Forms of the Colymbidae and Podicipidae. Proceedings of the Academy of Natural Sciences of Philadelphia 14: 226–233. BHL Reference page.

Vernacular names
العربية: غطاس كلارك
català: Cabussó nord-americà carablanc
Cymraeg: Gwyach Clark
Deutsch: Clarktaucher
English: Clark's Grebe
Esperanto: Klarka grebo
español: Achichilique de Clark
فارسی: کشیم کلارک
suomi: Meksikonuikku
français: Grèbe à face blanche
עברית: טבלן קלארק
magyar: Fehérarcú vöcsök
italiano: Svasso cigno di Clark
日本語: クラークカイツブリ
Nederlands: Clarks fuut
norsk: Gulnebbdykker
Diné bizaad: Naalʼeełii keelóóltsoh bitsiitʼáád halzhinígíí
polski: Perkoz żółtodzioby
پنجابی: کلارک ڈبکنی
русский: Поганка Кларка
svenska: Ljus svandopping

Clark's grebe (Aechmophorus clarkii) is a North American waterbird species in the grebe family.[2] 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.

This species nests on large inland lakes in western North America and migrates to the Pacific coast over the winter. It maintains local populations year-round in California, Nevada, and Arizona (the Lower Colorado River Valley), as well as in central Mexico. It feeds by diving for insects, polychaete worms, crustaceans, and salamanders.[3]

It performs the same elaborate courtship display as the western grebe.[4]

1 Etymology and common names
2 Description
3 Taxonomy
3.1 History
3.2 Subspecies
4 Habitat and distribution
4.1 Habitat
4.2 Distribution
5 Behaviour
5.1 Vocalizations
5.2 Diet
5.3 Reproduction
6 Gallery
7 References
7.1 Sources
8 External links

Etymology and common names

The "Clark" of its common name—and its specific epithet clarkii—honors John Henry Clark, a 19th-century American surveyor who was also a naturalist and collector.[5] The genus name Aechmophorus comes from the Ancient Greek words αἰχμά (transliterated "aichme"), meaning 'point of a spear',[6] and φόρος ("phoros"), meaning 'bearing'; together translating as 'spear point bearer' and referring to the bird's long, dagger-like beak.

In Mexico it is called achichilique pico naranja (the western grebe is called the achichilique pico amarillo).[7] A common name advocated in Spain for this bird is the calque achichilique de Clark.[8]
A family in California, USA. Two chicks are riding on one of the parent's back

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.[2]

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).[2] The Clarks' grebe has a weight range of 25.3–44.4 oz (720–1,260 g).[9]

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.[2]

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).[2][10][11]

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.[2][10][11]

Clark's grebe (Aechmophorus clarkii) is a waterbird of the family Podicipedidae in the order Podicipediformes, which are related to flamingos.[12]

This taxon is extremely similar to the western grebe: it has the same behaviour, including the elaborate courtship displays, occurs sympatrically in the same range and has the same migrations, and is morphologically almost alike, with this bird most noticeably being somewhat paler in colouration. The two taxa can even successfully cross-breed, with intermediates as a result. As such it was commonly thought to be a paler-colored morph (a version with paler colours and more white), as occurs in many bird species.[13]

In 1858 the lighter-coloured morph had first been described as a separate Mexican and Californian species, Podiceps clarkii by George N. Lawrence. Lawrence cited three specimens as representative of his new species, but did not cite a specific holotype. Of the three specimens Lawrence used, two were larger, migratory birds from California, whereas a single specimen was a smaller bird from Laguna Santa Maria in Chihuahua. Deignan designated this last specimen as the holotype in 1961.[10][11]

After the presence of this taxon throughout the range of the western grebe was discovered, along with the identical behaviour, the two taxa were synonymised, and this was situation was accepted by ornithologists throughout the first half of the 20th century.[10][11]

According to Robert W. Storer in 1965 besides the paler coloration there were other more subtle morphological differences between the two taxa: the bill of the western grebe is greenish-yellow, whereas this grebe has a bright yellow bill, and furthermore the black color of the crown extends less far down for this grebe, with the black extending below the eye, the lores and the thin line of bare skin extending from the eye to the corner of the bill in the case of the western grebe, whereas in this grebe the black reaches somewhat less far, leaving a thin line of paler color above the eye. Subsequent studies also showed the frequency of lighter morphs appeared more common in the south of the range than in the north, being relatively common in Mexico according to studies by Dickerman in 1973, but rare in Canada according to Nero (1962) and Storer (1965).[10]

Dickerman in 1963 was the first to cast doubt on the taxonomic status of the taxon, believing that the synonymy was incorrect, and thus he moved Lawrence's Podiceps clarkii to Aechmophorus clarkii, and restricted the distribution of this taxon to Mexico, rejecting Lawrence's identification of the larger-sized, pale-colored birds from California and elsewhere in the US and Canada as this taxon. His studies showed that there was little overlap in size measurements between Mexican and northern populations -irrespective of coloration; as such Dickerman's 1963 view was that A. clarkii are smaller grebes restricted to Mexico, which might be found in either light or dark morphs, and A. occidentalis are larger-sized, migratory grebes from the US and Canada also found in two colour morphs.[11]

A study in 1979 based on late 1970s observations of pairs the birds courting or nesting, however, noted that the frequency with which two different colour morphs were seen together or were found nesting together was much lower than one would expect if the pairings were random, some reproductive isolating mechanism was keeping the taxa separate. It also found that although the birds inhabited the same wetlands and the same habitats, the populations were not randomly distributed, with the taxa preferentially nesting with their own morph, and colonies being in large part of one type or the other, despite that one morph was much rarer in frequency than the other. There was also a marked difference in reproductive success in the study area, with Clark's grebe being initially quite low in frequency at around 12%, but increasing to a third of the population of both taxa in a three-year period. The study used the black coloration of the crown to distinguish the two taxa, but it was noted that some grebes in California in the winter appeared to be the dark morph, but that the black of the crown reached less far -the lores being whitish, confusing this distinguishing feature.[10]

In 1986 Dickerman, accepting a taxonomically significant difference between the two colour morphs, described the taxa A. occidentalis ssp. ephemeralis for the smaller Western grebes of southern Mexico, and A. clarkii ssp. transitionalis for the larger migratory North American Clark's grebe subspecies sympatric with the nominate Western grebe subspecies. In this view, the nominate form of A. clarkii constituted smallish, pale-colored grebes from Mexico.[11]

By 1992 Storer and Gary L. Nuechterlein, both having studied the grebes in the 1970s, recognised the paler-coloured morphs in the US and Canada in the book 'The Birds of North America' as A. clarkii, thus apparently rejecting Dickerman's species concept and subspecific classification, although they do not explicitly state this, and because this work does not include Mexico as part of North America, his work is not actually in their remit. Because of this, it is unclear if they consider the dark-coloured grebes of Mexico to be a morph of Clark's grebes, or to be smaller forms of western grebes.[2]

Two subtaxa of grebe classified as subspecies of Aechmophorus clarkii were recognised in 1986:[11]

A. c. ssp. clarkii, (Lawrence, 1858) - Smaller subspecies comparable to the sympatric subspecies of Western Grebe (A. occidentalis ephemeralis) from north & central Mexico. Nominate.
A. c. ssp. transitionalis, (Dickerman, 1986) - Larger than nominate clarkii, from Western North America between southeast Alaska south to north Mexico. [14]

Habitat and distribution

Being waterbirds, they require bodies of water that offer the necessary food and shelter that they need to thrive—usually lakes or suitable wetlands—that are also in proximity to suitable tree cover that they can use for nesting.[2]

Clark's grebes occur seasonally throughout the majority of Western America, with a distribution ranging as far south as Mexico, and reaching as far north as British Columbia and Saskatchewan. They avoid the cold and are only found in central USA and Canada during the summer breeding season. In the US and Canada breeding is done across a large portion of the west of these two countries, spanning from British Columbia to Texas, for which the grebes tend to favour larger bodies of water and congregate in large flocks.[2]

Storer and Nuechterlein in 1992 dubiously claim the birds winter in Central America, as well as in Mexico and some regions of California.[2] Out of almost 100,000 records of this taxon logged at the Global Biodiversity Information Facility there are zero records found south of northern Oaxaca, Mexico.[15]

The range of this bird in Mexico is distributed in two streaks southward; one from the California border along the Pacific coast throughout Baja California and across the gulf along the coast to southern Sonora, the other a higher altitude, inland distribution running down from the Big Bend region behind the Texas border down the mountains of central Mexico, with the highest concentration in population in the south from Jalisco to Puebla and northern Oaxaca, where the distribution abruptly ceases. These two distributional areas representing where grebes have ever been seen only meet each other in the very north of Mexico in a strip along the USA border, to the south they do not come together and are separated by a very large distance. It is completely absent from the Atlantic coast.[15]

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.[4] The calls of the grebe tend to vary very little between sexes.

Thought to be a fish specialist in the early 20th century as a result of the examination of their pellets and stomach contents, it was shown by 1962 that Clark's grebe is actually an opportunist when it comes to the food it eats, and is less picky with its selection than previously imagined. This means that the species will actually consume a wide variety of things such as salamanders, crustaceans, polychaete worms and insects while diving and foraging for their preferred small fish, so long as they fit the size constraints of the bill.[3]
Part of the complex courtship behavior of Clark's Grebes
Rushing Clark's Grebes

Clark's grebes appear to have semi-monogamous behavior, staying with a single mate, but possibly only for a single season as far as known. Unpaired males far outnumber the females. Males, while they stay with their mate until at least a few weeks after the hatching of their young, will have several sexual partners in their lifetime. It is less known if pairs will eventually mate again in the future. There are two courtship ceremonies that are performed before selection and mating take place: the "rushing ceremony" and the "weed ceremony". They entail a sequence of performances and advertisements/dances with the partner, or presenting the partner with a bundle of weeds and performing a different set of dances, respectively. As there are fewer females than males, the final decision of whether or not mating occurs depends on the females. Therefore, there is a level of sexual selection within the species.[16] These courtships take place during spring migration and shortly after arriving on the breeding grounds.

It is important to note that while there are very few cases of breeding between clark's and western grebes, there have been cases where phenotypic hybrids (birds with plumage that is similar to both species) have mated and produced fertile offspring. It is believed, however, that this becomes less likely when the individuals are from different migrations and are not hybrids, as they have a greater chance of failing during the courtships.

Breeding plumage

On nest


BirdLife International (2016). "Aechmophorus clarkii". IUCN Red List of Threatened Species. 2016: e.T22696634A93575258. doi:10.2305/IUCN.UK.2016-3.RLTS.T22696634A93575258.en. Retrieved 12 November 2021.
Storer, Robert W.; Nuechterlein, Gary L. (1992). "Clark's Grebe (Aechmophorus clarkii)". The Birds of North America, version 2.0 (P. G. Rodewald, editor). Cornell Lab of Ornothology, Ithaca, New York, USA. doi:10.2173/bna.26b. Retrieved 7 April 2017.
Palmer, R. S. (1962). Handbook of North American Birds, Vol. 1: Loons through Flamingos. New Haven: Yale University Press.
Nuechterlein, Gary L. (April 1981). "Courtship behavior and reproductive isolation between Western Grebe color morphs" (PDF). The Auk. 98: 335–349. Retrieved 25 November 2018.
Beolens, Bo; Michael Watkins (2003). Whose Bird?. Christopher Helm. p. 84. ISBN 0-7136-6647-1.
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Navarro, S.A.; Gordillo, A. (2006). "Catálogo de Autoridades Taxonómicas de las Aves de México". Base de datos del Sistema Nacional de Información sobre Biodiversidad (in Spanish). Facultad de Ciencias, UNAM for Comisión Nacional para el Conocimiento y Uso de la Biodiversidad. Retrieved 25 November 2018.
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"Clark's Grebe Identification, All About Birds, Cornell Lab of Ornithology". Retrieved 2020-09-26.
Ratti, John T. (July 1979). "Reproductive Separation and Isolating Mechanisms Between Sympatric Dark- and Light-phase Western Grebes" (PDF). The Auk. 96: 573–586. Retrieved 25 November 2018.
Dickerman, Robert W. (1986). "Two Hitherto Unnamed Populations Of Aechmophorus (Aves: Podicipitidae)". Proceedings of the Biological Society of Washington. 99: 435–436. Retrieved 25 November 2018.
Jarvis, E.D.; et al. (12 December 2014). "Whole-genome analyses resolve early branches in the tree of life of modern birds". Science. 346 (6215): 1320–1331. doi:10.1126/science.1253451. PMC 4405904. PMID 25504713.
"Understanding colour polymorphism in birds". FitzPatrick Institute of African Ornithology, University of Cape Town. 2017. Retrieved 25 November 2018.
"Aechmophorus clarkii (Clark's Grebe) - Avibase". Retrieved 2021-10-25.
"Aechmophorus clarkii (Lawrence, 1858)". GBIF Backbone Taxonomy. Checklist dataset. GBIF Secretariat. 2017. doi:10.15468/39omei. Retrieved 25 November 2018.

Nuechterlein, Gary L.; Storer, Robert W. (November 1982). "The pair formation displays of the Western Grebe". The Condor. 84 (4): 351–369. doi:10.2307/1367437. JSTOR 1367437. Retrieved 25 November 2018.

Ratti, John T. (1977). Reproductive Separation and Isolating Mechanisms Between Sympatric Dark- and Light-phase Western Grebes. Utah State University.

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