Speaking of Nature

Speaking of Nature: palm warblers

Things may seem normal to you, but they are far from normal for me this week. On a “regular” day, I’ll make myself a cup of coffee, grab any last-minute reference materials I might need for my column and then head up to my office to compose what I hope will be the next great masterpiece of natural history writing.

This week, I have done my best to recreate all of these steps. I got myself a cup of coffee, grabbed a couple books that I wanted to look at and headed for my computer. The difference is that instead of heading up to my office I am now in hotel in Manhattan. My beautiful wife, Susan, has been nominated for an Emmy and we are here in New York to attend the awards ceremony. Needless to say, things are more than a little different this week.

In February, I traveled to Florida and I managed to find a palm warbler flitting about the lush vegetation at the edge of a marsh. This bird was clearly in the process of molting into its breeding plumage, but the coloration was complete. It was by far the closest I have ever managed to get to a palm warbler. It is also quite appropriate that palm trees were a major component of the habitat I was visiting.

Since this is the first time I have ever featured the palm warbler in a column, I will give it the old-fashioned treatment. I always enjoy this sort of writing because it closely resembles the natural history work that was done by the first naturalists lucky enough to discover the species. In a way, I feel like I am helping you to discover yet another beautiful animal that lives in your backyard.

When it comes to describing warblers, it can all start to sound pretty familiar. There are 52 species of wood warblers that can be found in the U.S. and those 52 species have been classified into five different genera. Two of the species (the prothonotary and black-and-white warblers) are the sole members of their own genera, while another two species (the northern and tropical parulas) are members of a third genus.

This leaves only two genera, “Virmivora” and “Dendroica,” with Dendroica being the larger of the two. The palm warbler is a member of Dendrioca and it has one of the simplest and most appropriate of the scientific names. Dendroica is a combination of the Greek words “dendros,” which means tree, and “oikos,” which means “living.”

The species name “palmarum” is a Latin word that means “of the palms.” When you put it all together, you get “the tree dweller of the palms.” We don’t often think of warblers as tropical birds. Instead, we tend to think of them as temperate birds that simply head south for the winter and then return to their homes during the summer. I find it refreshing that the name of this particular species reinforces the “other” life of one of “our” birds.

Palm warblers spend the winter months in Florida and the Caribbean. They retreat, regroup and refresh themselves where the threat of ice and snow cannot follow and then prepare themselves for the long trip back to the breeding grounds. They do not fly as far south as some, but they do hold the distinction of flying further north than most other warblers.

Their destination is the Boreal Forest and if you look at a map of their breeding range, you see that only the northern portions of Maine, Michigan, Minnesota and Wisconsin are graced with their presence during the breeding season. The rest of us can only catch a glimpse of them as they pass through on their way to Canada, which they spread out into almost from coast to coast. Only the Yukon Territory and British Columbia are deprived of their presence.

Once it arrives on the breeding grounds, this bird seems to enjoy a fairly broad range of habitat circumstances for nesting. Weedy fields, forest edges, marsh edges, sphagnum bogs and dry pine forests are all acceptable choices. From there, the sexes definitely segregate their breeding efforts.

Males acquire and defend territories while females set about the process of building a nest. The nest is cup shaped and made of grasses and then lined with finer plant materials and feathers. If not placed on the ground (which seems to be the preferred location), the nest may be in a low tree or shrub no more than 4 feet up.

Into this nest the female will lay four to five white eggs marked with a fairly liberal smattering of brown blotches and speckles. The eggs are incubated by the female (perhaps with some help from the male) for only 12 days. Warblers are very small and their breeding season is quite short, so they don’t have time to dillydally when it comes to breeding.

Upon hatching, the parents will finally unite with a single task in mind — find enough food for the kids! The chicks are fed a diet of insects and, due to the extreme northern location of some of these birds, their feeding time may extend almost all the way around the clock. In only 12 days, the chicks are ready to fly and then the life history of this species gets a little fuzzy. There may be a second nesting and there may not be. The regularity of second-nesting is somewhat in question.

One thing that is not unclear is the fact that palm warblers are not often victims of brown-headed cowbird parasitism. Their wide breeding range may have resulted in fairly long-term contact with cowbirds and, as a result, the birds with us today may be the descendants of birds that could recognize cowbird eggs in their own nests. It seems as though a female palm warbler will be willing to abandon an entire clutch of eggs, bury them and lay a fresh clutch on top of them to avoid raising cowbird chicks.

This may also explain (at least partially) why there is some confusion regarding the number of nestings a palm warbler will regularly attempt in one breeding season. Are females with late nests trying to recover from cowbird attacks, or will a female that has successfully raised one set of chicks try for a second batch? Who knows?

We are now beginning a very short period of time when palm warblers are in our midst. They spend just two or three weeks stocking up on food as they migrate from the Caribbean to Canada and you have to actively get out and look for them as they pass by. Palm warblers are some of the earliest warblers to arrive in our area and their yellow feathers help them to stand out in the leafless brown of our forests at this time of year.

If you miss the palm warblers now, you will have a similarly brief opportunity to catch sight of them on their way south in the fall, but their presence is far more difficult to detect because of the ample vegetation that still covers the landscape. I managed to capture a photo of just such a southward-migrating bird last fall. Now that I have photographed a Florida bird, however, I am doubly interested in getting photos of palm warblers this spring. There is always a chance, small though it may be, that I can photograph the same exact bird.

And yes, for those that were wondering, Susan won her Emmy. We return home with treasure in hand and, if I am lucky, I will find more feathered treasures in the fields and forests around my home when I get back.

Bill Danielson has worked as a naturalist for 16 years. In that time, he has been a national park ranger, a wildlife biologist and a field researcher. He currently works as a high school chemistry and biology teacher. To contact Bill, or to learn more about his writing, visit www.speakingofnature.com

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