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The “first robin” is an eagerly awaited sign of spring. Robins however, are always here, just keeping out of sight during winter in large flocks in the woods.
Early European settlers named the New World bird for its resemblance to their familiar robin, with its red breast and similar habit of living near people. The common name endured, but the resemblance ends there. Unlike the European robin, whose Latin name translates to “solitary little red one,” our robin is gregarious. Turdus is the Latin for thrush, and migratorius means wandering or migratory.
The American robin is the largest and most widespread American thrush, ranging over all of North America except for far north Alaska, Canada and Greenland. It continues to expand its territory wherever cultivation of crops and mowed lawns replace wild areas.
Robins are about 10 inches long. The male is a little larger than the female and has richer coloration, especially on his blacker head. Both have grey backs, but the female is duskier all over. Both have incomplete white eye-rings, yellow bills, a white chin with dark stripes, orange or brick-red breasts, and a white lower belly. Juveniles have spotted breasts tinged with orange. Robins are among the earliest singers in the morning and the latest singers in the evening. Their whistling song is extremely complex and cheery. Individual robins sing their own variations.
Robins are food generalists. Their diet is diverse and changes from bugs to berries seasonally and even during a day. Robins eat vertebrates and invertebrates from more than 100 families and over 50 different types of fruits and berries. One researcher suggested that robins make food do double duty by selecting fruits with bugs in them. Robins have an extendable esophagus and can store food in order to weather cold snaps.
The summer robin prefers freshly mowed grass, the shorter the better, and will often follow a gardener who is mowing, planting, weeding or otherwise churning up the ground and exposing soil animals.
The robin has a distinctive upright posture as it runs and stops, staring at the ground while foraging. Early observers assumed the robin was listening for worms. A 1965 study indicated that robins were instead using eyesight.
Quoting “Cornell Birds of America Online”: “In Head-Cocking, one eye points toward a spot on the ground, 3-5 cm directly in front of the bird, along the longitudinal axis of the body. After holding this position for a few seconds, the robin rotates and flexes its head to bring the other eye into a similar relationship with the ground. Bill-Pouncing then occurs, whereby the bill is thrust quickly into the ground, presumably at visually detected prey, at the spot where the eyes had been directed.” A subsequent 1995 study suggested that robins use a combination of visual, auditory, olfactory senses, and vibration to find prey, but vision is probably predominant. The jury is still out.
Earthworms are a major robin food during the breeding season. After the introduction of DDT, earthworms, which accumulate the pesticide in their tissues, transferred the toxin to robins. In the 1950s, the robin population in Rachel Carson’s study area at Michigan State University crashed, and she demonstrated the connection. Although the robin was not the only bird that led to the book “Silent Spring,” it became a powerful symbol for banning the pesticide’s use.
The robin is one of the earliest nesting songbirds in spring. Male robins arrive a week earlier than females. Because robins typically return to their previous breeding grounds, if both male and female of a previous pair survive the winter, they may accidentally find each other and be monogamous for another season. There is no elaborate courtship obvious to humans. The consensus seems to be that fertile territory and coincidence, not male display or song, creates the bond.
The female selects the nest site and builds the nest, while the male brings some materials. Nests consist of grasses on the outside, with a middle layer of mud lined with fine grass. Miscellaneous materials are frequently incorporated: twigs, rags, plastic, feathers and paper wrappers. The first nests of the season are usually on lower branches of evergreens, because other trees may not have leafed out to provide the needed protection. Nests are placed on horizontal branches of trees or on just about any surface humans have inadvertently provided.
An average clutch is four “sky blue” eggs. Typical birds lay eggs first thing in the morning, but robins lay eggs even around noon. The female incubates the eggs for about 13 days, leaving for about 10 minutes an hour to feed. During the 13-day nestling period, both male and female feed the young. When feeding nestlings, parents choose one particular spot on the edge of the nest on which to stand, forcing the siblings to jockey for position to get a morsel.
Fledglings remain within 500 feet of the nest until they are about four weeks old, and are fed by both parents. The young remain in the vicinity of the nest until they are about four months old. When they are independent enough to fly and feed themselves, the male takes them to an evening communal roost while the female starts another brood.
Robins begin flocking in late August, joining hundreds of other birds of various species. The flock begins “migrating” around October, moving during the day in search of shelter and berry-producing trees and shrubs. It follows no predictable route. Our robins probably fly south, to be replaced by robins from the north. The Evanston North Shore Christmas Bird Count has recorded an average of 1,200 robins over the past 15 years. Individual robins, no matter their birthplace, do not return year after year to the same wintering ground. Conversely, in spring, approximately 70 percent will return to the vicinity of their birthplace to breed.
Considering the robin’s familiar and engaging presence, the big surprise is that there is still mystery about its song, courtship and how it locates worms.