Summit Outside: Robins, are they still harbingers of spring?
Special to the Daily
Robins are considered harbingers of spring, the quintessential early bird. They are common sights on lawns across North America, and are often seen waging a tug of war with earthworms.
Though they’re familiar urban birds, they are also at home in wilderness areas and we certainly have there here in Summit County.
An article dated February 17, 2009, said: “the first robin of spring usually warms the heart after a long winter in Colorado,” but a study released by the National Audubon Society says they have stopped leaving the state in the winter and are a messenger of warming of a different kind: global warming. Over the past four decades, in late December American Robin counts in Colorado have increased more than 17-fold. The winter range of American Robins has moved more than 200 miles north during the last 40 years.
Robins are the largest of North American thrushes, and their profile is a model of the basic shape of most thrushes. They have a large, round body, long legs and a fairly long tail. Most people are familiar with these gray-brown birds with warm orange chests or breasts and dark heads. A white patch on the lower belly and under the tail can be distinctive when in flight.
Robins sing frequently and you can find them by listening for their clear, lilting, musical whistles, consisting of several discrete units that are repeated. They are among the first birds to sing at dawn. “The early bird gets the worm”. They are also the last to sing as evening sets in; singing from a high perch in a tree.
In addition to its song, the American Robin has a number of calls used for communicating specific information. When a ground predator approaches, but does not directly threaten, robins will make warning call. When a nest or robin is being directly threatened, another call is used, which sounds like a horse’s whinny.
American Robins are active birds that bound across lawns or stand erect with their beak tilted upward. When landing, they habitually flick their tails downward several times.
Robins are active mostly during the day and gather in large flocks to roost at night. Their diet consists of invertebrates such as beetle grubs, worms, and caterpillars and berries. Robins eat different types of food depending on the time of day: more earthworms in the morning, and more fruit later in the day. Because they forage on lawns, they are vulnerable to pesticide poisoning and can be an important indicator of chemical pollution.
The adult robin is preyed upon by hawks, cats and large snakes; but feeding in flocks allows them to be vigilant to predators.
Robin roosts can be huge, sometimes including a quarter-million birds during winter. In summer, females sleep at their nests and males gather at roosts. As young robins become independent, they join the males. Female adults go to the roosts only after they have finished nesting.
Females build the nest from the inside out, first they press dead grass and twigs into a cup shape using the wrist of one wing, then the nest may be decorated by paper, feathers, rootlets or moss. Once the cup is formed, she reinforces the nest using soft mud gathered from worm castings, and finally she lines the nest with fine dry grass.
When the nest is finished it is 6-8 inches across and 3-6 inches high. The nest is located typically on one or several horizontal branches hidden in or just below a layer of dense leaves, usually in the lower half of a tree, although they can be built in a treetop. They have also been known to nest in urban/suburban areas in human structures like in gutters, eaves and on outdoor light fixtures.
Robins do not mate for life. Pairs usually remain together during an entire breeding season, which can involve two or three clutches. However, in spring, sometimes a male and female who mated the previous year will both return to the same territory and end up together for another year. This happens most frequently when they were successful raising babies the previous year.
A clutch consists of three to five light blue (robin blue) eggs, and is incubated by the female alone. The eggs hatch after two weeks and the chicks are bald and have their eyes closed for the first few days after hatching. Baby robins poop in fecal sacks consisting of thick, strong mucus that a parent robin can pick up and dispose of easily, thus keeping the nest clean.
While the chicks are still young, the mother sits on the nest continuously. When they are older, the mother will sit on the nest only at night or during bad weather.
The chicks leave the nest after two weeks and even after leaving the nest, the juveniles will follow their parents around and beg for food.
The male and female both are active in protecting and feeding the fledged chicks until they learn to forage on their own. The adult Robin gives alarm calls and dive-bombs predators, including domestic cats, dogs and humans that come near the young birds.
The fledglings are able to fly short distances after leaving the nest. The wings of juvenile birds develop rapidly, and it only takes a couple of weeks for them to become proficient at flying.
Only 25 percent of young robins survive. The longest known lifespan in the wild of an American Robin is 14 years, while the average lifespan is about two years.
The American Robin It is the state bird of Connecticut, Michigan and Wisconsin. The Tlingit people of Northwestern North America held the Robin to be a culture-hero to please the people with its song. An American popular song featuring this bird has the phrase: “When the red, red robin (comes bob, bob, bobbin’ along).”
Breckenridge resident Dr. Joanne Stolen is retired from teaching microbiology Rutgers University, and has taught classes at CMC. She is now pursuing a career in art, specializing in nature and many of the animals she writes about. Her work can be seen locally.
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