|SOUTHEASTERN CARIBBEAN BIRDS
|Trinidad and Tobago Field Naturalists' Club Southeastern Caribbean Bird Alert Trinidad and Tobago Rare Bird Committee
|American Coot (Fulica americana) and Caribbean Coot (F. caribaea)|
The American Coot breeds from North America south to
northwestern South America and, in recent years, has been documented
breeding in the Greater Antilles and northern Lesser Antilles south to
Guadeloupe, where it appears to be expanding its range. The Caribbean
Coot breeds in the Greater Antilles, Lesser Antilles, Curacao and
western Venezuela. The two forms are currently regarded as specifically
distinct but reports of mixed pairs and intermediate individuals in the
northern Caribbean suggest that they may be conspecific. The degree of
clinal variation and assortative mating has not been thoroughly
investigated. The variability of these taxa, which has been discussed
by Clark (1985) and more thoroughly by Roberson and Baptista (1988), is
discussed in this photo essay.
Coots possess a 'shield' that represents an extension of the maxilla onto the forehead. The size and shape of the shield vary seasonally and is often swollen in both sexes during the breeding season. In some species a fleshy 'callus' represents an accessory atop the shield. American Coots typically possess a small white shield extending to the eyes or halfway between the eyes and crown, with a large reddish or brownish callus. Caribbean Coots typically possess a large white shield extending to the crown; the shield is sometimes tinged yellow and the callus is absent. Thus, any coot with a red callus can be assumed to represent an American Coot. However, up to 1.5% of American Coot males with high testosterone levels possess a large frontal shield with a reduced callus that may even be absent. Such individuals were intitially thought to represent Caribbean Coots but are now regarded as variants of American Coot (there are no satisfactory North American records of Caribbean Coot) essentially indistinguishable from Caribbean Coot. Thus, identification of white-shielded male coots in the potential range of overlap is problematic. Males of both species average larger than females. American Coots are proportionately longer winged and shorter legged than Caribbean Coots, but much overlap occurs.
Intermediate appearing individuals possessing a large white shield with a vestigial callus occur throughout North America, where hybridization obviously does not occur. Whether or not such intermediate birds in the northern Caribbean represent hybrids or variants within either taxon remains uncertain. Such individuals should be documented even though their specific identity may be uncertain.
Roberson and Baptista (1988) used the following categories for scoring shield type variation in coots:
A = normal American Coots with typical red callus
B = 'intermediates,' with red callus but washed with yellow on shield below callus, some having a very
C = bulbous shields strongly washed yellow, sometimes with reddish splotches
D = bulbous white shields, with obvious reddish spots, streaks, or splotches, but not a callus
E = bulbous white shields with little or no reddish staining, limited (if present) to extreme upper edge of shield
(i.e., normal Caribbean Coot)
These categories should be adopted by observers of coots in the Caribbean. Seemingly mixed pairs should be studied to determine the sex of each individual, if possible. Males should be larger and mount females. Both sexes participate in nest construction, incubation and parental care.
Clark, C. T. 1985. Caribbean Coot? Birding 17:84-88.
Roberson, D., and L. F. Baptista. 1988. White-shielded coots in North America: a critical evaluation. American
|Fig. 1. A possible mixed pair of American Coot (left) and Caribbean Coot (right) at Buccaneer Inn, St. Croix, US Virgin Islands, 25 October 2002. Note the large callus in the individual at left. The seemingly larger size of the American Coot suggests it may be the male, in which case the bird at right could be a female Caribbean Coot, but the sex of these birds is uncertain. Photo © by Floyd Hayes.|
|Fig. 2. This American Coot with shield type A is the same individual in Fig. 1. However, the frontal shield appears larger than normal for an American Coot, suggesting that it may be a hybrid American > Caribbean Coot. Photo © by Floyd Hayes.|
|Fig. 3. This possible Caribbean Coot with shield type E is the same individual in Fig. 1. Although not discernible in the photo, this individual had two tiny red dots atop the frontal shield, suggesting that it may be a male American Coot with high testosterone levels or a hybrid American < Caribbean Coot. Photo © by Floyd Hayes.|
|Fig. 4. This seemingly intermediate individual with shield type B was alone in a pond adjacent to that in which the mixed pair in Fig. 1 was photographed at Buccaneer Inn, St. Croix, US Virgin Islands, 25 October 2002. Note the high frontal shield and reduced callus, suggesting a male American Coot with high testosterone levels or hybrid American × Caribbean Coot. Photo © by Floyd Hayes.|
|Fig. 5. A presumed Caribbean Coot with shield type E accompanied by a chick at Fresh Pond, St. Martin, 6 June 2002. Note the slight yellow wash on the frontal shield and absence of a callus. Photo © by Hans van Buel.|
|Fig. 6. A possible pair of hybrid American × Caribbean Coots with three chicks (only two in this photo) at Fresh Pond, St. Martin, 27 March 2002. The individual at left with shield type E had a tiny red callus at the top of the shield (see Fig. 7 below), whereas the individual at right with shield type E had yellowish stains at the top of the shield (see closeup at right). Photo © by Anthony Levesque.|
|Fig. 8. This seemingly intermediate coot with shield type B was alone in the same salt pond as the pair in Fig. 6. It clearly has a small red callus at the top of the shield (see closeup at right), suggesting that it is a male American Coot with a high level of testosterone or a hybrid American × Caribbean Coot. Photo © by Anthony Levesque.|
|Fig. 7. This coot is the same individual at left in Fig. 6. Note the white, bulbous shield with a tiny red callus at the top (see closeup at right). Photo © by Anthony Levesque.|
|Fig. 9. Yet another possible hybrid pair of Caribbean Coot with shield type E (left) and American Coot with shield type A (right) at Fredensborg Pond, St. Croix, 13 January 2003. Photo © by Floyd Hayes|