SPECIES

Cocos Cuckoo Coccyzus ferrugineus

Javier Tenorio Brenes
Version: 2.0 — Published October 22, 2020

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Identification

Coccyzus are small to medium sized cuckoos. The body is very slender; the bill usually is slightly decurved; and the tail is long and graduated, with white tips to the rectrices. In many species there is a narrow ring of bare skin around the eye. The upperparts of most species are brown or gray, whereas the underparts may be white, gray buffy, or rufous. Cocos Cuckoo is a typical member of the genus. It is brown above and buffy below; the wings have a rufous wash, most apparent when breeding (1). It also has a dark gray crown, a black 'mask' through the eye, a narrow yellow eyering, rufous primaries, a long, black tail with white feathers tips, and a black and yellow bill.

Similar Species

Similar to Mangrove Cuckoo (Coccyzus minor) of the mainland, but there is no range overlap between the two species. Furthermore, Cocos Cuckoo has rufuous remiges, wing coverts, and nape, which contrasts more strongly with the gray cap. It further differs from island populations of Mangrove Cuckoos by lacking the grayish wash on the sides of the neck (2). The white spots on the distal ends of r2-r5 are much larger, sometimes overlapping when the tail is folded so that little black shows on the ventral surface (JMH). The vocalizations of the two species also are different.

Plumages

Juvenile

Differs from adult by having a paler eye ring; the color contrast between the back and the head is less than that shown by adults, and the mask also is less contrasting than in the adult. The throat, chest and belly are whitish, and the wing coverts are pale grayish. The mandible is pale yellow. The pattern on the underside of the tail is less distinct than in the adult (1).

Adult

Adult grayish brown above. Forecrown and crown slate, with a narrow blackish facial mask. Remiges rufous. Underside of rectrices black, the feathers broadly white-tipped. Throat and breast buffy white, becoming rich buff on belly and undertail coverts.

Molts

Molt undescribed, but presumably it follows the Complex Basic Strategy, as seems to be the general pattern for New World cuckoos (3, 4).

Bare Parts

Bill

Maxilla black; mandible yellow with a black tip (5, 6, 7), but the mandible is orange-yellow during the breeding season (1).

Iris and Facial Skin

Iris is dark brown; narrow eyering yellow (6, 7), becoming more orange-yellow during the breeding season (1).

Tarsi and Toes

Variously described as slaty gray (6) to dark gray (7).

Measurements

Linear Measurements

Total length: 32 cm (5, 7), 33 cm (6, 8)

Wing length (flat):

  • male, mean 131.5 ± 3.6 mm (range 126-137 mm; n = 13) (7)
  • female, mean 134.2 ± 1.7m (range 131-137 mm; n = 7) (7)

Tail length:

  • male, mean 163.1 ± 5.8 mm (range 152-177 mm; n = 13) (7)
  • female, mean 161.2 ± 3.0 mm (range 158-164 mm; n = 7) (7)

Bill length (culmen from base):

  • male, mean 31.0 ± 0.7 mm (range 30-32.3 mm; n = 13) (7)
  • female, mean 28.5 ± 2.0 mm (range 26.4-31 mm; n = 7) (7)

Tarsus length:

  • male, mean 26.6 ± 2.3 mm (range 22.1-28.4 mm; n = 13) (7)
  • female, mean 28.1 mm (range 27.5-28.6 mm; n = 7) (7)

Mass

70 g (n = ?) (6)

Recommended Citation

Tenorio Brenes, J. (2020). Cocos Cuckoo (Coccyzus ferrugineus), version 2.0. In Birds of the World (T. S. Schulenberg, S. M. Billerman, and B. K. Keeney, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.coccuc1.02