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Birds of the Hackensack: Tree Swallow By Ivan Kossak
Tree swallows are more versatile than other species of swallow in that they will also eat fruit such as berries. This allows the Tree swallow to winter farther north than other species of swallow. They can be locally abundant during migration, gathering in large flocks that have seemingly no fear of humans who walk along the birds’ feeding ground. I have often walked through “clouds” of these birds at De Korte Park, amazed that none of them fly right into the side of my head. Male Tree swallows are bright white below and a brilliant electric blue-green above in breeding plumage. Males seen outside the breeding season, as well as females and juveniles, are a more subdued brown on the upper parts with varying amounts of blue-green highlights, depending on the individual. Tree swallows are five and three-quarters inches long, with long, pointed wings that aid in their aerial acrobatics. They can often be seen perched on power lines or on their nest boxes when not in flight. Their call is a soft twitter with a (to my ear) faint electronic quality. Tree swallows are cavity nesters, historically using small holes in trees (hence their name), usually near water. They also will readily use man-made nest boxes that can be seen in a number of restored and managed wetlands in our watershed. They will fill their nest with 3-8 eggs that take approximately two weeks to hatch. The young are fed in and around the nest for two to three more weeks until they are ready to fledge. Tree swallows differ from other species of swallow in that they do not nest in colonies. Therefore, outside of migration they are seen in lower densities than other swallows. Tree swallows breed throughout most of North America and winter primarily from the southernmost United States to Central America. Smaller numbers of Tree swallows will attempt to winter along both U.S. coasts and can be found in southern New Jersey during mild winters. Although not the famous swallows that return to San Juan Capistrano, Tree swallows are often also seen as a sign of spring, usually arriving in New Jersey in early to mid-March. Most stay in our area until mid-September or early October, accumulating in spectacularly large flocks to journey to their wintering grounds. If you live near a body of water, you may want to install a Tree swallow nest box in your yard to help you organically control the local insect population. |
While lamenting the swarms of mosquitoes, gnats and other
flying insects that can, at times, seem a plague in our area in spring and
summer, one can also sing the praises of the Tree swallow (Tachycineta
bicolor). Tree Swallows are almost exclusively insect eaters, catching their
food while on the wing. In order to be able to feed in this manner, Tree
swallows are accomplished aerialists. They dart about in erratic flight
patterns that remind me of miniature fighter planes.