Proposal (707) to South American Classification Committee

Treat Caribbean Coot Fulica caribaea as conspecific with American Coot F. americana

Note: This proposal was submitted to and passed unanimously by NACC.

Background: Fulica caribaea, the Caribbean Coot, was first included in the AOU Checklist in the 6th edition (1983), when geographical coverage expanded to include the West Indies. At this time, the AOU also recognized the first records of this species from the US, based on a specimen and six other birds observed near Ft. Lauderdale, Florida (Bolte 1974), and a record from Tennessee. The distinguishing feature of F. caribaea is its broader, higher, and bulbous frontal shield, whereas F. americana has a lower, narrower, and less bulbous frontal shield, typically with a red callus at the top of the shield; however, in some individuals of F. americana the callus is not present and the white shield can appear somewhat enlarged and yellowish. Photographs of the first and third birds found near Ft Lauderdale were sent to the NMNH and the AMNH for verification, and Alexander Wetmore and Bud Lanyon were among those who concurred in the identifications. The second bird found near Ft Lauderdale was eventually collected and deposited in the National Museum (USNM 567252). Bolte (1974) noted at the time that the intermediate frontal shields of some F. americana suggest that the two species may have been hybridizing.

The notes for this species in the 6th edition stated the following: “The relationships of F. americana and F. caribaea are not fully understood; the latter may eventually prove to be a morph of F. americana. Individuals with intermediate characteristics have been reported from southern Florida, Cuba, Hispaniola, and St. Croix.” This statement was repeated in the 7th edition (1998) with the additional statement that “Mixed pairs of F. americana and F. caribaea with young have been observed on St. John, Virgin Islands (1984, Amer. Birds 38: 252).

Most of the data bearing on the relationship of F. americana and F. caribaea concerns observations of Caribbean Coot-like individuals in North America and their interactions with American Coots. For example, Roberson and Baptista (1988) reviewed characters purported to separate the two species, reviewed records of F. caribaea from throughout the US, and conducted new surveys of coots in California. They found additional records scattered across North America, including Michigan, Texas, British Columbia, and Indiana, in addition to Florida and Tennessee. They concluded, based on the geographical spread of these records, reports of hybrids, and their survey findings that a small but noteworthy percentage (1.4%) of California birds had characters typical of F. caribaea, that records of this form in North America are indicative of variation within F. americana rather than the presence of F. caribaea and “that there is no evidence to show that coots of Caribbean origin have occurred anywhere in North America.”

New Information: McNair and Cramer-Burke (2006) studied nesting of F. americana and F. caribaea at Southgate Pond on the Caribbean island of St Croix. Using the criteria of Roberson and Baptista (1988) to distinguish the two forms, they determined that most pairings there were non-assortative. They identified both members of 17 nesting pairs (of 22 total nests): 6 of these were both F. caribaea, whereas the other 11 pairs were mixed pairs. Based on this pattern, McNair and Cramer-Burke suggested that F. americana and F. caribaea are morphs of a single species.

Although unpublished, information on voice (comment from Alvaro Jaramillo on the website of David Sibley, at http://www.sibleyguides.com/2011/03/the-caribbean-coot-in-north-america/) also suggests that F. americana and F. caribaea represent a single species. Jaramillo noted that vocally the two species are “extremely similar if not the same” and that both species respond to calls of F. americana on Guadeloupe. This contrasts with the differences in voice typically observed between other species of New World coots.

Recommendation: The single feature purportedly separating Caribbean Coot F. caribaea and American Coot F. americana is the morphology of the frontal shield, but this character is inconsistent: both forms occur in both the Caribbean and mainland North America and the forms appear to mate non-assortatively where they have been studied. Thus, morphology and behavior do not serve to separate these two forms. I don’t see any evidence to suggest that they are two species; rather, there may be something of a cline in frontal shield morphology. It would be ideal to have a bit of genetic data as the final nail in the coffin, but a finding of substantial genetic differences would be an extremely surprising result given the rest of the evidence. If we were building a checklist from scratch, I doubt that a two-species arrangement would be seriously considered. I recommend that we merge Fulica caribaea into F. americana. As for the English name, nothing occurs to me that would be better than simply calling the lumped species American Coot, although I’m open to alternatives.

References:

Bolte, W. J. 1974. Caribbean Coot, Fulica caribaea, in Florida. American Birds 28: 734-735.

Roberson, D., and L. F. Baptista. 1988. White-shielded coots in North America: a critical evaluation. American Birds 42: 1241-1246.

McNair, D. B., and C. Cramer-Burke. 2006. Breeding ecology of American and Caribbean coots at Southgate Pond, St. Croix: use of woody vegetation. Wilson J. of Ornith. 118: 208-217.

Terry Chesser, February 2015

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Comments from Stiles: “YES. Given that the only supposed distinction between caribaea and Americana (frontal shield pattern) has been effectively falsified, I see no reason not to consider the former a subspecies of americana.”

Comments from Pacheco: “YES. From what is in the proposal, I do not think that caribaea is not even a subspecies, but merely a morphotype of americana.”

Comments from Claramunt: “YES. I see no evidence of two separate species here.”

Comments from Jaramillo: “YES. As noted, lacking a recording of Caribbean Coot, I used American Coot voice in an area where only Caribbean phenotypes were present (in Guadeloupe), and they responded and called back giving the same call as an American Coot. I don’t think I recorded them as I was on tour and busy trying to show these birds to clients. But I went back over several years; each time the response was the same. I am certain that this is a morph rather than a species. Now the different types of Slate-colored Coots, that deems more attention!”

Comments from Areta: “YES. Natural history, morphological data, and examination of crucial museum specimens indicate that there are no reasons to retain caribaea as a different species. This has been long suspected (see for example Hellmayr & Conover 1942). Although this is clearly not the end of this story and more research is needed to understand the seasonal and geographic distribution of different shield-types, nothing indicates that two species are involved. Given how tenuous evidence for a two-species treatment is, the burden of proof should be on those giving credit to this alternative.”