April 30, 2009
By Susan Benson,
CNHM Director of Education
Robins hopping over lawns in search of food, singing from tree branches and utility wires, or bathing in rain puddles, are all familiar sights to most people. On the evening of April 16, I observed probably forty robins migrating through my yard. Museum staff often asked about robin behavior. “What do robins do for food when snow is on the ground,” is a common question. This week a call came into the Museum from a member asking, “What is happening with the robin in my back yard? It keeps pecking and flying against the windows of my house.” Robins exhibit many interesting behaviors throughout the year that are worth studying when outdoors.
Late winter seems to always bring a snowfall after the robins arrived. Most of us believe that robins must be struggling, but in truth, robins are not earthworm specific birds. In the late winter and early spring, when insects are not available, robins feed on ripe fruits and berries in trees and shrubs. During the breeding season robins will eat earthworms, beetles, snails, spiders, caterpillars, ants, grasshoppers and other ground-dwelling insects.
When breeding, male robins actively defend their territory, which is one-third of an acre up to several acres. If another male intrudes in his territory, he will fly at the trespasser to scare him away. If this doesn’t work, he will dive-bomb the bird, hitting the invader chest to chest. It is this behavior that occurs when a male mistakes his own image in a window for an opponent. Male robins will beat themselves against windows, thinking they are attacking another robin. They might also attack vehicle mirrors for the same reason. Other times, robins may see the reflective nature of a window, and simply fly into it thinking it is safe to do so. Robins are also known to attack red objects, such as socks or other items on a clotheslines, or ornaments or toys in the lawn, again mistaking them for an imposter. This behavior can go on for days or weeks, but usually the birds do not injure themselves seriously. Usually after the romance of the season ends, so do their territorial antics.
If we watch robins long enough in the spring, we might see several other different displays associated with courtship and territorial behavior. Robins will lift their tails when they believe there is danger. The male or female will lower their head and raise their tail to a forty-five degree angle and flick their tail repeatedly while calling out. They drop their wingtips so they are drooping after a dangerous encounter, and sometimes puff their breast feathers out. They also are known to sound their alarm call at a human approach when nesting. Robins will mob nest predators such as crows in areas where there are large numbers of robin nests. When you see a robin perched or flying in midair with a wad of mud or grass in its beak, or a line of mud across the female’s breast, she is nest building. The females work this mud into place with their feet and bill, molding it into that perfectly circular shape with their bodies. When we observe a robin flying off with food in its beak, which is a sign that there are young in a nearby nest. After breeding season is over, we can watch as robins gather for the night in communal roosts, located in trees, under bridges or barns, containing a few to several hundred birds. These are all behaviors worth watching for.
Sometimes we may observe robins “listening,” apparently for their food. It is believed that robins use sight rather than sound for finding food. When tilting their head they are most likely checking the ground with one eye, looking for worms or their castings. Another common thing to look for is when robins thump on the ground with their feet, trying to stimulate movements from the worms before catching them. If we took our shoes and socks off, stamped our feet on the soil a few times, would we be able to feel the movement of worms? What an amazing feat.
Robins have less reproductive success, with up to 80 percent of the young dying each year. Blue jays, ravens, crows, squirrels, chipmunks and raccoons eat robin eggs and nestlings. During the winter they are a favorite food for great horned and barred owls, and hawks and falcons will prey upon the adults in flight. Since they feed on the ground, young and old are exposed to domestic cats. Historically, robins suffered from the insecticide DDT (in the 1950s and 1960s) as they ate earthworms with higher levels of DDT in their bodies.
What can we do to aid robins’ success? Avoid using insecticides. Leave some “forest floor” in open soil by leaving leaf litter to provide for ground foraging. Plant native fruit and berry-producing trees and shrubs. If robins are attacking our car mirrors, place small paper sacks over the mirrors when parked. Where birds are striking windows, break up the window’s reflection by hanging strips of tape, string, or other material six inches apart on the outside of windows. Avoid using commercial silhouettes used to frighten birds, as robins quickly lose their fear of the shapes. Rubbing a bar of soap on the exterior surface of the window with a design that leaves no area six inches or larger uncovered, or cover windows with black netting.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 13470 County Highway M or on the web at www.cablemuseum.org to learn more about exhibits and programs.