When I approached Mirror Lake in Forest Lawn, I found more than a dozen people standing with binoculars and cameras pointed at a willow tree that had not yet leafed out.
I could see six or eight small birds hopping about among the branches. One of them was a ruby-crowned kinglet; the rest appeared to be yellow-rumped warblers. These were the warblers to be expected at that time in early May and I could hear other individuals singing in the trees behind me.
When these first yellow-rumped warblers flood into the region, they soon become what birders call “trash birds.” The reason: When you look for the other 29 warbler species that occur here at this time of year, you find every bird you see is this one instead. Further denigrating it, this bird’s unattractive name is often shortened by jaundiced observers to yellow-rump.
While I recognize the problem of overabundance, I still find myself attracted to these handsome little birds. After a winter spent watching drab finches and sparrows, warblers are a welcome sight.
I followed one as it hopped about, appearing to pick food from the willow twigs, and occasionally dashed out to snap up a flying insect. It was a bright male in what is now called alternate plumage. Its back was mostly a bluish-gray striped with black, its eyes were covered with a black mask and its white throat and belly were separated by another band of black. But the field marks that distinguish this species in all but juvenile plumages are its four bright yellow markings: the top of its head, its sides and, as the name implies, its rump.
That word rump certainly conveys the location of that fourth spot because we think of it in comparison with our own rear end, but this bird’s rump is more accurately described as its upper tail coverts. Of course, no one would like this bird to be designated the yellow-upper-tail-coverts warbler, but I wish we were still calling this delightful little bird the myrtle warbler, the name I knew it by when I first began birding.
In fact myrtle warbler is the name now assigned to the eastern subspecies of the yellow-rumped warbler, so I can certainly justify using it. (The reason most birders avoid that subspecies name is because only species count on their lists.) It derives from this species’ feeding on wax-myrtle berries (also called bayberries or sweet gale) especially along beaches in its southeastern United States winter range. As it migrates through this region, however, it feeds almost exclusively on insects.
The western subspecies is called Audubon’s warbler. It is easily distinguished from the myrtle warbler by its fifth yellow area: its throat is yellow whereas the myrtle’s is white.
Where do these names come from? The American Ornithologists Union has a Committee on Classification and Nomenclature that has, since 1886, published editions of the Check-List of North American Birds.
The most recent edition, the seventh, was published in 1998. Between editions the committee each year publishes a supplement to which birders refer. This series does much more than provide Latin and common names for bird species and subspecies that occur here. It also determines the order in which they are listed, which is supposed to reflect their evolutionary history. This changes as new information is discovered. When I began birding, the first listed bird was the common loon and the last was the bluebird. Today, those listed species occurring here are Canada goose and house sparrow.
That 1886 edition included 768 species; the 1998 edition, 2,099. That remarkable accumulation is due to a number of factors: new species identified, the area covered extended (to Hawaii, for example), species splits (cackling goose from Canada goose is one) and new arrivals.
Bird plumage names have also changed over time. According to the recent Humphrey-Parkes terminology birds’ fall and winter plumage is called basic plumage and what we have long referred to as breeding plumage is now alternate plumage.
Back at that willow tree I asked the man standing next to me why all the attention was being paid to these birds. “There’s a Cape May warbler among the yellow-rumps. There it is,” he said, pointing it out to me.