01/06/2017 The Warblers of Winter

Orange-crowned Warblers are rather drab for a warbler. Olive gray on the back and pale yellow below, these warblers don’t stand out. Even the small, but bright orange, feathers on the top of its head are usually covered over by surrounding gray plumage. Notice the “broken” eye-ring (two half circles) with a dark line going through the eye. Orange-crowned Warblers readily visit our suet feeders in winter. Robert Benson photo.

01/06/2017 – The Warblers of Winter

If you are like me, you probably seldom put the words “warbler” and “winter” in the same sentence.  This is because winter is not the best time to see warblers in south Texas.  Our best warbler-watching comes during the spring and fall migrations.

Still, even in the dead of winter, we usually find a couple of hardy species in our area.  These are the Orange-crowned Warbler and the Yellow-rumped Warbler.

The Orange-crowned Warbler (Vermivora celata) has perhaps the dullest plumage of all the warbler species.  It has no bright yellows or striking blacks and whites.  It is just olive-gray with slightly yellow underparts.  You could be forgiven for not recognizing it as a warbler.  Even the orange feathers on its crown (hence the name) are few in number and almost always covered over by surrounding drab plumage. This warbler only exposes its orange crown during courtship (which does not occur in Texas) or sometimes when it is scolding an owl.  Personally, I have never seen an Orange-crowned Warbler agitated enough to display its “orange crown.”

However, this calm and hardy little winter resident is common in our brushlands, parks and gardens.  It forages along the branches and frequently investigates clumps of lichens and old nests looking for insects.  Orange-crowns readily come to suet feeders.  A suet feeder is perhaps the best way to attract one of these warblers.  Or you can “pish.”  Orange-crowned Warblers are curious creatures and they will pop up to check you out if you utter pishing noises.

My most unusual encounter with an Orange-crowned Warbler was in a grocery store.  As I walked from the produce section into the bakery, I caught a glimpse of a small, grayish thing scurrying across the floor.  My first thought was of a mouse (but in HEB? no way!) so followed it.  It flew across the bread tables and landed under the sushi counter.  I realized it was a bird.  Other shoppers were amused (or more likely appalled) to see me scrambling after “Lord-knows-what” in the aisles.  I finally caught the bird, which was indeed an Orange-crowned Warbler.  I showed it around, of course, but no one seemed particularly delighted to see it.  I begged a cake box from the bakery manager and took the warbler home.  I rationalized that if I released it right outside the store, it might find its way in again.

It was dark when I got home.  I placed the bird, in its box, on a high shelf planning to release it at daybreak.  However, the box was empty in the morning!  Uh-oh.  Did the cats get it?  I worried.  Then out of the corner of my eye, I saw a dust ball run across the hallway.  The dust ball was the warbler, covered with cobwebs, cat hair, and lint.  It must have been running along the baseboards for hours to get that dirty!  (Really, I DO vacuum from time to time!)

After peeling the debris off the bird, I released it in the brush near our pond.  It gave its distinctive chip note, a “stick”sound, as it flew off.  It was as if it were saying:  “Thank you.”  Or maybe something less gracious.

Yellow-rumped Warblers are named for the postage-stamp-sized patch of bright yellow on their lower backs. They also sport patches of yellow on the sides of their breasts. Those with yellow throats are a form known as Audubon’s Warblers. The white-throated form is the Myrtle Warbler. These two forms will probably be designated as separate species later this year. Wikimedia Commons photo.

The Yellow-rumped Warbler (Setophaga cornata) is the other common wintering warbler.  It is named for its bright patch of yellow on the lower part of its back.  Unlike the Orange-crowned Warbler’s orange crown, the yellow rump is always visible.  A denizen of open woods, brushy edges and backyards, the Yellow-rumped Warbler frequently “perches upright on prominent twigs with its yellow rump exposed, flitting up to catch flying insects.”  Its call note is a hard “check” given regularly as it forages.

Although primarily insectivorous in summer, Yellow-rumps feed extensively on small fruits and berries during the winter.  They are fond of bayberries and poison ivy berries.  Their ability to digest a varied diet is one reason for their abundance in the US in winter.  Many species of warblers, less adaptable in their food habits, must migrate to the tropics for a sufficient insect supply.

You should look closely at any Yellow-rumped Warbler you see.  These warblers have quite varied plumages.  Some have white throats; these are the Myrtle form of Yellow-rumped Warbler.  Those with bright yellow throats are the Audubon’s form.  Forty-five years ago, these two forms were considered separate species.  Field research in 1969 found that the two species interbred in areas where their ranges overlapped.  According to the then accepted definition of a species, this breakdown in the isolating mechanisms between the Myrtle and Audubon’s Warblers, suggested that they were one species.  So, in 1973, the American Ornithologists’ Union lumped the two species under the name Yellow-rumped Warbler.

Recent genetic and DNA studies are showing something surprising.  The Yellow-rumped complex may actually be three separate species, possibly even four!  In spite of the interbreeding between Myrtle and Audubon’s forms where they meet, the two are genetically quite distinct.  And two species south of the US/Mexico border are also being re-evaluated.  Goldman’s Warbler, in the mountains of Guatamala, has long been considered part of the Audubon’s group but it is a strikingly darker bird and its DNA is distinct.  A fourth group, the Black-fronted Warbler of northwestern Mexico is problematic.  It may be an isolated population of Audubon’s or it may be yet another species.

Kenn Kaufmann (September 2016, Audubon magazine) suggests that we get ready for a splitting of the Yellow-rumped Warbler complex.  Since the winter ranges of both Myrtle and Audubon’s reach south Texas, we could be looking at two different species of Yellow-rumps in our own backyards:  Two species for the effort of finding one!  Although “the split won’t be official until it’s accepted and published by the AOU Checklist Committee” which could happen as early as July of 2017, “savvy birders would be wise to spend a little more time looking at any Yellow-rumps they encounter.”

Let’s go warblering this winter!

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