Broad-billed Hummingbird nest, Tucson, 23 February 2009

In the 2007 edition of "Finding Birds in Southeast Arizona," Broad-billed Hummingbirds (Cynanthus latirostris) are listed as "rare" in winter - which, in fact they are overall. However, in the foothills of the Santa Catalina Mountains on the northern end of Tucson, it is not uncommon to see them in many washes throughout the winter. My discovery of a nest in a small wash in northeast Tucson on 2/23/2009 led me to wonder: is this early?


(Click on the pictures for a much larger image!)

Most migrants do not show up for another few weeks, and many of those birds begin breeding in mid-April. I wonder if the individuals that winter in Tucson stick around so that they can get a jump start on nesting? By nesting earlier than the migrants, they could take advantage of the first flowers of the season. Warmer days seem to be upon us earlier than usual this year, so that would make sense: these winter residents are well aware of that fact, and got to nesting in a hurry!



I waited about 15 minutes at a good distance so as not to disturb this nesting bird. When she decided she was ready to leave the nest for a bit of foraging, I dashed in and grabbed this quick picture. You can just barely see a tiny bit of egg sticking out from the lower rim of the nest in the foreground!


I'll check for early nesting facts in the Arizona Breeding Bird Atlas when I get back to my home library, but in the meantime here is a nice summary of the breeding biology of these hummers:

"In Mexico most Broad-billed Hummingbirds are resident, but in late spring and summer many individuals migrate to extreme northern Mexico, portions of southeastern Arizona, southwestern New Mexico, and the Big Bend region of southwestern Texas to breed. In these areas breeders inhabit riparian zones of arid canyons, usually below 2,000 m, which contain sufficient resources to support nesting for up to 5 months. Breeding behavior of females is typical of other hummingbirds except that nests are constructed low to the ground and rarely decorated with lichen."

Powers, Donald R. and Susan M. Wethington. 1999. Broad-billed Hummingbird (Cynanthus latirostris), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/430

Gnatcatchers in Arizona: a very brief tail study

"The Sibley Guide to Birds" mentions that under exceptional field conditions, one might be able to see the more graduated shape of the tail feathers in Black-capped Gnatcatchers (BCGN) as viewed from below. By comparison, Blue-gray Gnatcatchers (BGGN) show much less difference between the lengths of each individual tail feather. Specifically, he illustrates this with closed-position undertails. But what about uppertails? This is far too much detail to expect from a standard field guide, so I dug out more detailed references when I got curious about a recent photo I took.

What's even better than studying tail shape under brief but exceptional field conditions? A photo! While not the sharpest image in the world, I was lucky enough to catch a Black-capped Gnatcatcher in mid tail-swing as it was moving low through some mesquite (see the entry for Patagonia from 1/25/2009). I borrowed an image from Peter Pyle's "Identification Guide to North American Birds, Part I" (Slate Creek Press, 1997) to demonstrate, since illustrator Steve N.G. Howell drew such an excellent detailed comparison of gnatcatcher tail morphology and patterns. It's a bit pricey, but every advanced birder and serious ornithologist should own a copy! It's worth every penny if you want to scrutinize obscure traits that are probably not visible in the field...

Graduated tail shape tends to be most easily observed from below, since the outermost tail feathers fold underneath of the innermost tail feathers. An evaluation of the tail shape from above, it stands to reason, would be just as valid so long as the tail is spread so you can see the length of each feather compared to the next. No, you probably can't use this in the field at a quick glance, but catch a photo at exactly the right split second and suddenly it becomes useful.

Please excuse the following images from the Pyle guide being flipped; I wanted to compare the patterns of coloration on the tail as well, and my picture is most in-focus on the right hand side (if you ignore those branches).



BGGN tail morphology and pattern, page 378 in above-referenced book (Pyle 1997).



BCGN near Patagonia, 1/25/2009 (Yerger) compared with BCGN tail morphology and pattern, page 384 in above-referenced book (Pyle 1997).


The outermost tail feather (r6) in the photographed bird is clearly much shorter than the second feather from the outside (r5). I feel that you can also draw some very clear conclusions about the bird's ID by comparing the pattern of white in the outermost tail feathers, which is why I have the images flipped. But Pyle's Guide doesn't specifically mention this and I can't find all of the references I need, so I won't speculate about how useful it is!

Hope some folks find that interesting,
John Yerger