Every year when I see my FOS (first of season) Lucy’s Warbler I’m reminded that this tiny, nondescript bird is half the answer to one of birding’s most often heard trivia questions.  Can you name our only two warbler species that nest in cavities?  As usual, last month I saw my first Lucy’s in a mesquite bosque along the Salt River, this time a female carrying nesting material, and I was able to track her to a hole in a Mesquite snag.

Lucy’s are one of our smallest warblers, but they breed in the densest concentration of any species in that family because they are nearly obligate Mesquite nesters and mesquite forest habitat has declined over much of the low Sonoran Desert.  So, despite their inconspicuous gray appearance, they are the easiest of our four desert breeders to find and record.  This is why I believe when the powers-that-be change common names to reflect habitat preference or physical features, Lucy’s will become the Mesquite Warbler.

And speaking of the desert warblers, those other three are Yellow, Common Yellowthroat, and Yellow-breasted Chat.  We all subconsciously associate warblers with color, and birds with color are anything but inconspicuous, so it is ironic but not surprising that the only other North American warbler that nests in cavities is the Prothonotary, a bird at the furthest end of the warbler spectrum from our Mesquite Warbler in so many ways.

The Golden Swamp Warbler (more on that in a minute) is one of our largest warblers, bright yellow, eagerly sought and easy to see, an eastern bird that is widely distributed, and one associated with forested wetlands for nesting.  Yes, so different from our western mesquite dweller, but they curiously share two things in common.  They are both cavity nesters and both will readily nest in bird boxes.  They have both undergone population declines, Lucy’s in the dry southwest as mesquite is cut for heating and cooking and Prothonotary on its wintering ground in South America as mangrove swamps are cleared for development.

If you think Lucy’s, named for the thirteen year old daughter of early ornithologist Spencer Baird, is a particularly obscure honorific, try explaining to me the derivation of the name “Prothonotary.”  This leads to another fun birding trivia question.  Give me two species which are very indirectly named for their colorful plumage.  Sure, Northern Cardinals are bright red like the robes of Catholic Church hierarchy, but Prothonotary?

It seems this totally abstruse name also comes to us from the early Catholic Church when the Papal clerics, called prothonotaries because they documented proclamations and validated documents), wore bright yellow vestures.  This reference seems so obscure, and “Golden Swamp Warbler” so perfect because it spotlights both habitat and plumage, that I can’t imagine the powers-that-be wouldn’t consider it as they dive into changing common English bird names.

With the coming of spring I’ve now seen both these unique warblers in Arizona within the last year, Lucy’s in its preferred mesquite habitat of course, and a vagrant migrant Prothonotary, also in its preferred habitat, in one of the reedy, overgrown canals at the Gilbert Water Ranch.  No avian species, it seems, abandons its preferred habitat unless under some duress, and habitat as much as plumage itself should tell birders where to find birds.