McGILL BIRD OBSERVATORY |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Seasonal status at MBO:
Ageing and sexing details: AHY (Jun-Dec) / ASY (Jan - Jun) Black-billed Cuckoos can be easily recognized by their red orbital ring. It may be possible to differentiate ATY individuals based on molt patterns, but this requires further study. There is no reliable way to differentiate sexes, as plumages are identical, and both males and females develop brood patches, while males rarely develop prominent cloacal protuberances.
SY Black-billed Cuckoos usually have a greenish to gray orbital ring, and the pale tips on the rectrices typical of ASY birds are either indistinct or absent. There is no reliable way to differentiate sexes as plumages are identical, and both males and females develop brood patches, while males rarely develop prominent cloacal protuberances.
AHY Black-billed Cuckoos can be identified by their red orbital ring, but there is no way to differentiate sexes in fall.
HY Black-billed Cuckoos can be easily recognized by their greenish to gray orbital ring. Additionally, the pale tips of their rectrices are either indistinct or absent. Sexes cannot be differentiated in fall.
|
© 2002- The Migration Research Foundation Inc. |