Friday, March 27, 2009
Forbush said of the American Robin: “What American bird is as adaptable as the Robin?” We have seen robins nearly everywhere, from the top of a spruce tree in a peat bog in down east Maine, to the wrack line at the Cape Cod National Seashore Park – and nearly everywhere in between. They have benefited from suburban development, where they find lawns with earthworms and insect larvae such as June beetles and Japanese beetles. They eat a wide variety of other invertebrates such as grasshoppers, crickets, weevils, lepidopteran (butterfly and moth) caterpillars and spiders. This winter, we saw robins “fishing” along small streams, and one grabbed what appeared to be a caddisfly larva case. Robins also eat many small fruits, including those of red cedar, wild cherry, choke cherry, blueberry, oriental bittersweet, pokeweed, dogwood and crabapple.
Robins breed throughout North America, as far north as Newfoundland and northern Alaska. In the first Massachusetts Breeding Bird Atlas, robins were confirmed breeding in 845 out of 969 atlas blocks (each block is about 10 square miles), making it the most widely distributed Massachusetts bird (in second place was the European Starling).
Robins return from their southern wintering grounds to Massachusetts between mid-March and early April. They usually return to the same general area where they hatched. The males, which have darker colored breasts, return earlier and establish territories by singing their familiar “cheerily, cheer up, cheer up, cheerily, cheer up” song. Females arrive later, and and if you have more than one robin territory on your property, you might see one male hopping along after another male, in an effort to drive him away.
The female builds the first nest in an evergreen if the deciduous trees have not leafed out; subsequent nests are built in deciduous trees and shrubs. The nests are usually lined with mud, and the pair might use the same nest for the second brood. The female lays three to five pale blue eggs (usually four) and does most of the incubating. The eggs hatch in 12-14 days after the last egg; the young leave after about 13 days in the nest. After the first brood has left the nest, the male feeds the fledglings while the female starts laying the second (and sometimes a third) brood of eggs. Unlike many other birds, robins do not suffer nest parasitism by the Brown-headed Cowbird, which lays its eggs in other birds’ nests. The female robin recognizes the foreign cowbird egg, punctures it, and ejects it from the nest.
During the breeding season, male robins gather in communal roosts at night while the females are still on nests. We have many fir and spruce in our yard, and small flocks of male robins (and other birds) roost there. Later in the season, the male robins are joined at the roosts by juveniles. After the last broods have fledged in mid-September, the roosts break up and the robins begin migrating south. Robins from New England winter in southern states as far as Florida. The robins we see here in winter breed much farther north, probably in Canada. The robin’s Latin name, Turdus migratorius, translates to “migrating thrush,” as they are often seen in large flocks during migration.
In the early 19th century, Audubon wrote of robins: “In all the Southern States, about that period [autumn] … their presence is productive of a sort of jubilee among the gunners, and the havoc made among them with bows and arrows, blow-pipes, guns, and traps of different sorts, is wonderful. Every gunner brings them home by the bags-full, and markets are supplied with them at a very cheap rate. Several persons may at this season stand round the foot of a tree loaded with berries, and shoot the greater part of the day, as fast as do the flocks of Robins succeed each other. They are then fat and juicy, and afford excellent eating.”
The robin figured prominently in the discovery of bird mortality caused by the insecticide DDT (dichloro-diphenyl-trichloroethane). Rachel Carson’s Silent Spring described the events at Michigan State University in the 1950s. In order to prevent the spread of Dutch Elm disease, the university sprayed the campus American Elms with DDT to kill a bark beetle which transmits a fatal fungal disease to the elm. The DDT was sprayed after the elms had leafed out, and residues were carried into the soil when the leaves fell and decayed. After a few years of spraying, earthworms living in the soil accumulated high levels of the insecticide, which led to the death of robins that ate the earthworms. DDT was also found to cause bird mortality from egg-shell thinning, and was banned in the United States for most uses in 1972.
Today, robin populations appear to be stable, and may even be increasing. I hope to see robins returning to their summer homes for many years to come.
1. Forbush, E. H. Birds of Massachusetts and Other New England States, Norwood Press, 1929.
2. Audubon, J. J. Ornithological Biography: or An Account of the Habits of the Birds of the United States of America, Vol. 2, Hilliard, Gray and Co., 1835.
3. Wauer, R. H. The American Robin, University of Texas Press, 1999.
4. Carson, R. Silent Spring, Houghton, Mifflin Co., 1962.
5. Sallabanks, R; James, F.C. American Robin (Turdus migratorius), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology, 1999. Retrieved from the Birds of North America Online:
© 2009 The Carlisle Mosquito