Back home I reviewed the morning's shots on my computer screen and as expected each shot from that brush pile showed nothing but black silhouettes, until the last one came up, and I was dumbfounded. It's below:
This wasn't the bird I was photographing, and what on Earth was it?
UPDATE: I couldn't identify it with certainty, eventually concluding that it might be the Gray-collared Becard, despite the markings not matching illustrations in any of the field guides. I published the picture on this page, inviting anyone who thought they might know to write to me. Finally in June, 2009, Sheri Williamson in Arizona wrote:
Based on overall proportions and coloration, this is actually one of the small members of the genus Myiarchus, probably a Yucatán Flycatcher rather than a Dusky-capped based on the relatively pale head and lack of visible rufous or cinnamon.
Yucatan Flycatchers, Myiarchus yucatanensis, are endemic to Mexico's eastern Tabasco state, north and central Yucatan Peninsula plus Cozumel Island, southern Quintana Roo, northern. Belize and northern Guatemala
If someone else has a different opinion, please write.