F. H. King (1883) has considerable to say about the damage done to Delaware and Catawba grapes in Wisconsin; as soon as they are wounded, they are attacked by ants, bees, and flies and soon destroyed. But he thinks the service rendered more than compensates for the harm done. He refers to the feeding habits of the Tennessee warbler as follows:
It is very dexterous in its movements, and obtains the greater part of its food upon and among the terminal foliage of trees. Titmouse-like, it often swings pendant from a leaf while it secures an insect which it has discovered. Small insects of various kinds, not especially attractive to larger birds, are destroyed by this species in large numbers; and its slender, acute bill serves it much better in picking up these forms than a heavier, more clumsy one could. * * * Of thirty-three specimens examined, two had eaten two very small hymenoptera (probably parasitic); seven, thirteen caterpillars; three, fifteen diptera; six, thirteen beetles; three, forty-two plant-lice, among which were two specimens of the corn plant-louse Aphis maidis (?); three, thirty-five small heteroptera, .09 of an inch long; and one, eleven insect eggs.
Alexander F. Skutch has sent me the following interesting notes on the feeding habits of the Tennessee warbler in Central America: “I was surprised to find last month [March] that these warblers were visiting my feeding shelf on the guava tree in the yard. About the only food I ever serve to the birds on this table is bananas and occasionally plantains; and my chief guests are tanagers of about half a dozen brilliant kinds, a few finches, honeycreepers, and wintering Baltimore orioles. But the Tennessee warblers soon formed the habit of visiting the table and sharing the food with the bigger resident birds.
“Some seemed to linger in the vicinity much of the day, making frequent visits to the board and each time eating liberal portions of banana or the somewhat harder ripe plantain. They were intolerant of each other, and one individual would not let a second alight on the board until it had finished its own meal, although there was plenty of room and plenty of food for all. I have noticed also that the Tennessee warblers chase each other as they forage among the trees in wintering flocks. I cannot recall ever having seen any other wood warbler eat banana.
“Last November 14 a Tennessee warbler behaved most surprisingly. The grass in the yard had grown very long, and I had it cut with a machette. Late in the afternoon, after the usual rain, a lone Tennessee warbler flew down on the fallen grass and began to hop over it, catching small insects.
“It also entered the uncut grass, about a foot high, and disappeared momentarily amidst it. Twice driven up by passing people, each time it promptly returned to the grass. Its third visit to the cut grass was longest. While I stood quietly watching, it hopped deliberately about, much in the manner of a house wren, and gathered an abundant harvest from the fallen herbage. Once it found a caterpillar about an inch long, which it carefully bruised in its mandibles before swallowing it. The warbler was amazingly bold, and hopped over the grass within a yard of my feet, and allowed me to follow closely as it moved away. Early the following morning, and again at the close of the day, the warbler foraged over the lawn in the same fashion. In the evening, it continued to creep slowly over the mown grass and after all other birds had disappeared into their roosts, and the light was becoming too dim to see it clearly.”
Behavior.—Much of the behavior of the Tennessee warbler has been mentioned above, and there is little more to be said. It is a very close sitter on its nest, when incubating, and has been caught there by throwing a hat or a net over it; but, when flushed, it is rather shy about returning to it, usually making its demonstrations of protest by flitting about at a safe distance and nervously uttering a sharp chip.
The Prebles (1908) witnessed a rather remarkable flight behavior at Fort Resolution, Mackenzie:
During the forenoon of June 25, an extremely windy day, we observed a remarkable movement of these warblers. They came from the northward, flying over the point of land on which the fort is built In loose flocks of from 10 to 20 individuals. After passing the point, they either struck out directly across the bay or skirted the shore, in either case having to face a strong southeast wind. Some paused a few moments among the low bushes on the point, but the slightest alarm started them off. The flight lasted over two hours, and, during this time, upward of 300 birds were seen from our camp. Two specimens, a male and a female, were collected. The ovaries of the female contained eggs only slightly developed.
Voice.—Aretas A. Saunders contributes the following: “The song of the Tennessee warbler is a rapid series of short, loud, unmusical notes. It has been compared to the song of the chipping sparrow, but it varies more in pitch, time, and loudness, and is distinctly in two or three parts. To my ear it is much more like the chippering of a chimney swift.