The Winter Warblers

Warblers are birds in the family Parulidae, with shared traits including smallness, a general habit of bug-eating, and frequent splashes of yellow or other bright colors. They are a New World family, maintaining their global headquarters in tropical Central America from where many members migrate northward to spend their summers in Canada and the United States. Species like the orange-crowned, Wilson’s, yellow, hermit, and black-throated gray warblers, for instance, nest here in California before heading south around September. We have two migratory warblers, however, who nest in large numbers to our north and then fly south to our latitudes for the winter: the yellow-rumped warbler and the Townsend’s warbler. These two birds will be the main subject of today’s discussion, along with a quick look at the common yellowthroat, an atypical warbler who we can see all year round.

Warbler Basics

Warblers evoke high passion from many birders – a passion often opaque to more casual nature lovers, even sympathetic ones. In the eastern part of the country, spring warbler migration is one of the more thrilling parts of the year for birdwatchers, with the treetops suddenly filled with an influx of newly-arrived and soon-to-depart species – colorful, active, challenging, gone. There is such a diversity and abundance of migratory warblers that this excitement does overflow into the Bay Area in a narrower way, with birders searching “migrant traps” at Point Reyes and elsewhere along common flight paths for both passing western species and vagrant eastern warblers.

When it comes to regularly-occurring species, however, the basic situation for local birders is that we have relatively few warblers here, and that group is further winnowed down in winter to two main species: the yellow-rumped warbler and the Townsend’s warbler (out of 50+ North American species). These two birds typically associate with trees, yellow-rumped favoring relatively more open areas and Townsend’s more continuous woodland. (The warblers are sometimes referred to as the wood warblers, and our two winter species both formerly belonged to the biggest and famousest warbler genus, Dendroica, literally the tree-dwellers. Since then, genetic studies and rules of taxonomic precedent have shuffled them all into Setophaga, the moth-eaters, which sounds rather less evocative to me.)

Let me clear up a few other preliminary possible confusions:

Warblers are not goldfinches and are mostly not feeder birds: Warblers are small birds, many of them with some yellow in their plumage. But warblers are very different from our other small yellow birds, the goldfinches. If you’ve got a flock of them sitting on your seed feeder, they’re finches. If you see one constantly in motion, darting under leaves and between branches in pursuit of insects, that may be a warbler. Although primarily insect-eaters, our two winter warblers will sometimes come to feeders offering shelled sunflower, suet, or mealworms, especially during cold periods when prey is scarce.

Don’t count on striking singing: Warblers are songbirds, and learning their songs is a powerful help when trying to find and identify warblers in spring. But as a whole, warblers are not necessarily particularly melodious despite their name. And since our two main species today are essentially winter birds in our area, you probably won’t hear them sing much.

Yellow-rumped Warbler

Yellow-rumps (or butter-butts as they are sometimes affectionately called), are most easily recognized by that very feature: a yellow rump patch, which may be partially obscured by their wings when perched. They also have yellow under their wings and on their throats, though with the range of females, young birds, and non-breeding plumages your main impression of some birds from some angles will be of an overall light gray-brown. Watch closely and the yellow rumps will be revealed.

There is another area of potential confusion in the land of yellow-rump identification in that there are two different races of yellow-rumps, which are sometimes argued to be two separate species. Our more common race, known as the Audubon’s warbler, has a yellow throat. The other race, the Myrtle warbler, is the common species in the east, but can also be found here in winter in lower numbers. They have a white throat. As Alexander Skutch summarized and elaborated, the (male) Audubon’s warbler “wears five patches of yellow – on the crown, throat, both sides and rump – while the myrtle warbler shows only four, lacking that on the throat.” (For more on the perennial back-and-forth on splitting vs. lumping these birds, as well as a handy comparative map of breeding ranges, see this article on All About Birds.)

As a whole, yellow-rumps are the most hardy and widespread warbler in North America, capable of handling cold (they are the only winter warbler in much of the East) and insect-deprivation (they are the rare warbler that will eat berries, including the wax-myrtle berries that give the eastern version their name). Locally, they can be found more or less all over the place in winter (September through April), as well in selected area of Douglas-fir forest on Mt. Tam and Bolinas Ridge during the spring-summer breeding season.

My favorite 1920s ornithologist, William Leon Dawson (move over, A.C. Bent), summed up the yellow-rump’s toughness and adaptability like this in The Birds of California:

Without tools or furnishings, without connections or backing, without so much as a hand-bag in which to keep a few cherished belongings, this brave young Argonaut faces the world… “Ho ho! Who cares! The world is mine. Not a tree, but I shall explore it; not a canyon, but I shall quaff water from its depths; not a mountain, but I shall mock at its glaciers; not a tempest, but I shall know how to escape its fury. Ho ho!” And so this tiny warbler, penniless and homeless, threads mazes which no surveyor has ever chained, scales heights which no aneroid has ever measured, sleeps in a hundred and forty different beds, from the lowly weed to the fir tree’s loftiest pinnacle, lunches at ten thousand counters, and comes back to us winter by winter, artless, unspoiled, cheerful, and courageous.

Townsend’s Warbler

For more on the Townsend’s Warbler, see our full essay, The Jewel in the Trees.

Our second winter warbler, the Townsend’s warbler, does not have any local breeding presence, instead making their nesting sites in the Pacific Northwest from Alaska to Oregon. In fall, they head south to two separate wintering areas, one along the California coast and another in Mexico and Central America. Two of their close relatives in the informal “black-throated” group of warblers, the hermit warbler and the black-throated gray warbler, do nest in Marin and the Bay Area in modest numbers, usually in Douglas-fir forest.

Townsend’s warblers are easy to recognize and are one of our most striking and distinctive birds. In fact, they have won several titles as the Most Beautiful Bird in Novato, a contest which is held at roughly three week intervals before a distinguished panel of judges consisting of me. Males have a vividly contrasting black and yellow pattern on their face, with a black throat and cap. Females still echo this distinctive pattern quite clearly, but are duller overall and have yellow throats. You can find them in a wide variety of winter habitats, tending on average to somewhat more wooded areas than yellow-rumps, but frequently venturing into areas with only modest tree covering, including typical residential areas.

The species was named after John Kirk Townsend, an ornithologist who went on one big adventure to the west (and onward to Hawaii) back in the 1830s. He described the expedition in his quite engaging travel diary, published with the catchy title The Narrative of a Journey across the Rocky Mountains to the Columbia River and a Visit to the Sandwich Islands. It was tough work advancing science out here back then, requiring a long, cold, wet, hungry, dangerous trek with myriad threats to one’s painstakingly collected specimens. For example, Townsend writes:

On returning, I was surprised to find Mr. N[uttall] and Captain T. picking the last bones of a bird which they had cooked. Upon inquiry, I ascertained that the subject was an unfortunate owl which I had killed in the morning, and had intended to preserve, as a specimen. The temptation was too great to be resisted by the hungry Captain and naturalist, and the bird of wisdom lost the immortality which he might otherwise have acquired.

And:

Thornburg had been killed this morning by Hubbard, the gunsmith… This Thornburg was an unusually bold and determined man, fruitful in inventing mischief, as he was reckless and daring in its prosecution. His appetite for ardent spirits was of the most inordinate kind. During the journey across the country, I constantly carried a large two-gallon bottle of whiskey, in which I deposited various kinds of lizards and serpents and when we arrived at the Columbia the vessel was almost full of these crawling creatures. I left the bottle on board…and on my return found that Thornburg had decanted the liquor from the precious reptiles which I had destined for immortality, and he and one of his pot companions had been happy upon it for a whole day.

Sometimes, it can feel like naming birds after people is a rather empty gesture to some forgotten person’s vanity or financial patronage or quirk of history. But Townsend seems to be one of the more deserving recipients of ornithological recognition, a man notable for his deep love of birds, commitment to science, and an impressive general optimism in the face of hardships and a crew of gluttonous, drunken, murderous companions who ate his specimens and drank his preservatives.

Bonus Warbler: Common Yellowthroat

We actually have one more, atypical warbler species that is found here not only in the winter, but all year round, albeit in reduced numbers from their winter peak: the common yellowthroat. Unlike our other warblers, including both the two above and our summer species, yellowthroats do not forage for insects in woodland and forest trees, giving observers the classic birder’s ailment known as “warbler neck.” Instead, yellowthroats are residents of marshes, skulking amongst the freshwater cattails or dashing down under the saltmarsh pickleweed, frequently causing the other birder ailment generally known as “what is that bird I can’t see?” In spring, it can help you pick up on their presence if you learn to recognize their witchity, witchity, witchity song.

Females are a relatively muted yellow, but males like the one above have a striking black bandit mask. Look for them in marshes and wetlands around the county, including local sites like Pacheco Pond, Cemetery Marsh at Rush Creek, the Bahia Lagoon, and the Las Gallinas Ponds in San Rafael.

Header photo: Female Townsend’s warbler by Minette Layne