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By Root 1319 0

in the snow. Days later when I went back to Vermont, I stuck them into our freezer and, unfortunately, due to other diversions that soon intervened, I forgot about them until July, six months later. When I thawed them, to my great surprise I found five of them still very much alive. Not knowing what to feed them, I put them into a plastic lettuce crisper with sprigs of potential food plants; those found where I had collected them, including spruce, balsam, fir, maple, and beech. On the very next day I was pleasantly surprised when I found five caterpillars, all hungrily feeding. But even though I had collected them on maple twigs, they were feeding on balsam fir needles! So I added more fir twigs, expecting to finally rear moths. No such luck. A few days later all the caterpillars were wrinkled and dead. The cause was a small but by then plump spider that I had inadvertently introduced on a fir twig. Spiders inject digestive juices through their fangs, then suck out the insects’ contents, leaving only dry husks. This spider had, apparently, been a very hungry spider.

The kinglet I followed in the maple grove—it was feeding on caterpillars!

The “outbreak” of caterpillars on sugar maples that year was apparently unusual, and it did not go unnoticed by kinglets who otherwise forage exclusively on conifers. On the fourth, fifth, and seventh of January, after cold (-24° to -34°C) and windy nights, I followed two separate pairs of kinglets (for 93 and 75 minutes, respectively), and all four individuals spent the entire time foraging in my young sugar maple grove. I saw them pick off and eat several caterpillars of the same kind that I had also collected. The birds foraged tirelessly, without pause. I timed them at an average of 45 hop-flights per minute, without any apparent change of pace. They bypassed conifers repeatedly (the grove was bordered by balsam, fir, red spruce, and white pines on three sides). Given the windy and cold nights that must have produced a chill factor of near -50°C, I marveled not only that they were alive, but that they switched from spruce/fir to maple, apparently having learned to associate food with specific trees.

Each bird species, like every organism on earth, feels most at home in the specific environment to which it has been tailored by natural selection and instinctively seeks that environment and avoids others. For kinglets, that environment is dense coniferous forest, as for us it is probably the open savannah where we can have long open vistas, scattered trees, and water. However, we are much more flexible than kinglets and can readjust; although I find the clearing around the cabin with the view toward the mountains and the lake aesthetically appealing, I also love the forest. The wonder is that although most birds are strictly programmed to remain in specific environments, the kinglet can escape that programming when it has to. It pursues caterpillars even when they occur outside its normal bounds.

In still a third winter, 1999–2000, I joined a third pair of students, Joshua Rosenberg and Jonathon Taylor, and took up tree banging to again sample winter insects on trees to find out where most of them are, and what they might be. We sampled six tree species (thirty trees of each). As before, we clubbed trees with some force to see what would fall off onto the snow. (Not all caterpillars are knocked off by this method. Some caterpillars are attached by a thin silk anchor to the twigs. Sometimes they were left hanging from this safety line, and when they thawed out they used that lifeline to crawl back onto the branch.) Most of the sample (87 percent) was geometrid caterpillars, for a total of 80 larvae from the total of 180 trees. This year the number of larvae from sugar maples (13), was not significantly different from red spruce (11), beech (19), although the number was significantly higher on pine (30) and lower on balsam fir (2) and red maple (5). In this winter and all subsequent winters, we did not again find the kinglets foraging in the sugar maples, making their behavior