Grand Cayman Bullfinch

Cf. Cuban Bullfinch.  Cuban and Grand Cayman Bullfinches are very similar and were traditionally considered a single species until Garrido et al. (2014) published a detailed analysis of the differences between them.  They do not occur together naturally, so field identification based on geographical probability is usually sufficient.  However, probability alone was inconclusive for a bullfinch that appeared on Little Cayman in 2018.  Following are the principal differences between Cuban and Grand Cayman Bullfinches that Garrido et al. documented:

Size:  Overall, the Grand Cayman Bullfinch averages larger than Cuban in six out of seven measurements studied.  Its bill, in particular, is larger than the Cuban’s in every dimension, especially in its depth (i.e., height) at the base, where it averages about 20-25% larger.

Vocalizations:  The songs of Cuban and Grand Cayman Bullfinches show consistent differences in pattern and complexity.  Both begin with a trill and end with warbled phrases, but Cuban’s trill is longer and more rapid, and the ending phrases are more complex than Grand Cayman’s.

Coloration:  There are also differences in the plumages of both sexes.  Male Cubans have glossy-black plumage with a bluish or violet sheen, whereas male Grand Cayman Bullfinches are dull-black.  Females differ more distinctively: Cubans are dull-black (like male Grand Cayman), whereas female Grand Caymans are charcoal-gray with olive-brown tones.  On both sexes, Grand Caymans have white on two primaries, whereas Cubans typically have white on just one primary.