Where did the robins go?

     Where I live robins are the harbinger of spring and a common sight in the summer. Yesterday I put some stale bread out for the birds, but, of course, this time of the year there were no robins. By the way I have never seen them eating bread. 

     Where do robins go for the winter? Do robins migrate? The answer is yes and no. While they are associated with spring and summer here, not all robins escape the winter. Unlike many long-distance migrating birds which head south en masse during the fall, robins react to winter's onset in two ways. 

     Many retreat southward. They skedaddle out of Northern Canada and the cold, snowy parts of the country and head to areas far to the south like Texas and Florida. But they are not motivated by the cold because robins can withstand extremely cold temperatures, adding warm, downy feathers to their plumage. No, their motivation for heading south is food. 

     As their warm-weather diet of worms and insects becomes scarce, robins begin searching for fresh supplies. For unknown reasons though some stay up north and tough it out just like we humans do. Robins have been observed in every US state except Hawaii and all southern Canadian provinces in January. 

     They survive by changing their diet, transitioning from insects and worms to winter fruits and berries, including junipers, hollies, crabapples and hawthorns. In the spring and summer, robins aggressively defend their territories and raise young. In the winter, they change. They become nomadic, searching far and wide for food. If a heavy snowfall persists for more than a few days they will leave in search of greener pastures, so to speak. 

     Although I have never seen one (probably because there isn't a lot of food for them in the winter around here) robins also form flocks in the winter which can number in the hundreds or thousands which is totally unlike their summer behavior where they pair up and raise young. 

     Flocking means the larger groups have more eyes pealed to spot and avoid predators. It also increases the chances of discovering food. Here's another odd fact about robins that winter over in flocks...they make little noise during winter months. Although some males begin singing toward winter's end as spring approaches and mating hormones kick in, they typically maintain a subdued silence. Taken together, these changes lower robins' profile in the northern part of their range, making sightings much less common, and leading some people to assume they have all gone elsewhere.

     The burning question is, how do robins decide whether to stay or go during the winter? Nobody knows, but it is thought that it's mostly males that remain because it allows early access to the best breeding grounds. When spring arrives the winter robins disperse and change their diet back to worms and insects. Then a few days to two weeks later the females show up. 

     Robin populations are increasing, but they are vulnerable to pesticide poisoning because they forage on lawns and other open spaces that are often sprayed with weed killers. Additionally, pesticides can also kill earthworms, a major food source for robins. Because they forage on the ground, robins often end up as food for outdoor cats. Collisions with windows, communications towers and car strikes are other common hazards.