The Capped Heron is the only "all white" heron with a black cap and blue facial skin and bill. Additionally, the feathers of the neck usually are yellowish white or a light cream. The body shape has been described as "rather chunky" (Ridgely and Gwynne 1989), but this is a striking heron that is in no danger of being confused with any other species.
The Capped Heron perhaps is most similar to the Whistling Heron (Syrigma sibilatrix) but has much paler upperparts, and a longer bill that is blue, not pink with a dark tip (Sick 1993). In flight, suggests a white Black-crowned Night-Heron (Nycticorax nycticorax) (Ridgely and Gwynne 1989).
The following description is based on Wetmore (1965), except where otherwise indicated:
Adult: Sexes similar. Crown black, except for a white forecrown. Several (four or five) white plumes extend from the rear of the crown, ca 200-230 in length. Back and wings light gray. Breast, hindneck, and under surface of the wing are light cream-buff. Belly white. Neck is thick for a heron (Kushlan and Hancock 2005).
The creamy or yellowish color of the neck, breast and underwing have been described as an alternate ("breeding") plumage (Wetmore 1965, Ridgley and Gwynne 1989, Blake 1977, Hancock and Elliott 1978). Most ardeids do not have an alternate plumage (Pyle and Howell 2004), however, so it is unlikely that the creamy color is acquired through a molt. The cream colored neck may simply represent the definitive plumage (Odgen and Thomas 1985), or perhaps is a result of preening from the patches of powder-down feathers, as it is in the Whistling Heron (Syrigma sibilatrix) (Hancock and Elliott 1978).
Juvenile: Similar to adult, but paler gray above, and with shorter nuchal plumes. Also the crown may be streaked with gray (Ridgely and Gwynne 1989).
No information known, but see Detailed Description (appearance) for details on the debate between breeding and adult plumage.
The following descriptions are based on Wetmore (1965), except where otherwise indicated:
Iris yellow or (Blake 1977) may be light brown.
Orbital skin and lores light blue.
Bill bluish neutral gray, somewhat darker at base, with a yellowish white tip. Bill may be red in the center and the blue of the soft parts may deepen during the breeding season (Kushlan and Hancock 2005).
Tarsi and toes bluish neutral gray.
Measurements are from Wetmore (1965) and based on specimens from Panama and northern Colombia. Mean in mm, followed by range in mm in parentheses.
Males (n=6): wing chord 271 (267-280); tail 99.1 (96-103.5); culmen from base 79.9 (75.8-81.7); tarsus 96 (92.6-98.7)
Females (n=5): wing chord 269 (263-274); tail 98.5 (95.5-101.4); culmen from base 82.1 (76-93); tarsus 93.5 (92.1-94.8)
Mass: 444-632 g (Willard 1985); January, male 518 g (Haverschmidt 1952)