Running trail offers fresh look at bird Yellow-rumped warbler intriguing

It never ceases to amaze me: I almost always get the best birdwatching done when I’m least expecting it. This doesn’t necessarily involve sightings of a rare or unusual bird; sometimes, it’s just a fresh look at a bird I’ve seen many times before.

This happened a few weeks ago as I headed out to one of my favorite running trails after work. The bright afternoon sunshine was deceptive; temperatures were chilly, made more so by a steady wind. I knew a good run would warm me right up, so I left my binoculars in the car ? no stops to view birds today. Or so I thought.

As I hit the start of the trail, I heard call notes coming from a thick white pine. As I scanned the tree for the bird, I was surprised to see a small spot of bright yellow near the trunk of the tree. I knew it had to be a warbler. I ran back to my car, retrieved my binoculars, and found the bird again. It was, indeed, a yellow-rumped warbler. But its behavior intrigued me.

Usually, warblers are hard to see and often must be identified by voice alone. This is because they are often hidden among treetop foliage, when looking for them will only earn you a cramped neck. This yellow-rumped, however, was instead investigating the cracks and crevices near the base of a thick branch issuing from the main trunk. In fact, before I discerned the bright spot of color, I initially thought I was seeing a brown creeper, a type of bird that specializes in this type of foraging behavior, living up to it name by “creeping” up tree trunks.

Yellow-rumpeds are extremely hardy warblers. They are the last warbler to leave in the fall, and the first to return in the spring. They even winter farther north than any other warbler. A few things enable them to do this: their ability to digest fruits other warblers cannot (such as bayberries); their variation in diet; and their variation in foraging behaviors.

Yellow-rumped warblers (nicknamed “butterbuts”) often sally from treetops, catching insects in midair. But there were no insects taking to wing on that cool, windy day, so the butterbut changed tactics: it hunted the insects taking refuge in the tree bark.

I soon lost sight of the warbler, but another movement caught my eye. It was in the same place I had first spotted the butterbut ? a complex swirl of cracks in the trunk, which must have harbored a number of cold, sluggish insects. It mustbe a brown creeper this time, I thought. Wrong again! It was a ruby-crowned kinglet.

This small insectivorous songbird is not as cold-hardy as the yellow-rumped warbler; nonetheless, it seemed to be holding its own as it, too, changed its foraging technique in response to ambient conditions. Instead of hovering at the tips of tree branches to catch its meal, it gained the shelter of the tree’s trunk while it hunted.

I watched the birds until the cold wind reminded me it wasn’t comfortable to remain in one place for too long, yet. But I had gotten my promise of warmer days to come, so I continued on.

Join the Penobscot Valley Chapter of Maine Audubon in a series of bird walks around Bangor in the coming weeks: Mt. Hope Cemetery on May 16; Bangor Land Trust property surrounding the Penjajawoc Marsh on May 19; and Cascade Park on May 24. All are free. For more information, call the Fields Pond Nature Center at 989-2591.

NEWS bird columnist Chris Corio can be reached at bdnsports@bangordailynews.net