Robins in the Back Yard

Two weeks ago I saw three fledgling robins wandering about in the back yard. They crisscrossed the grassy areas in looping search routes similar to the patterns that I have seen adult robins use as they hunt for insects and worms. The fledges had these overall movements correct, but they had not yet mastered any of the other techniques of hunting. They were not looking down at their feet where the food might be found. Their heads randomly swiveled from side to side, and frequently they looked up at passing birds (maybe they thought that it was “Mom” giving in and finally bringing them a worm?). They also spent a lot of time simply looking at each other. I did not see any of them catch any food.

A few days later, though, the fledges were hunting like pros. They stared intently at the grass that they disturbed in their passing and cocked their heads quickly from side to side to angle in on any possible food item. They ripped their feet through loose thatch and dry leaves and quickly searched through the rearranged piles. I saw several successful “grabs” and was very impressed by the steepness of their learning curve!

Cardinal fledges also joined in on the hunts around the back yard along with song sparrows, blue jays, an eastern phoebe, and two Carolina wrens. A pair of adult crows even brought two of their fledges into the yard, but the four of them departed fairly quickly (much to the relief of the other birds!). The yard was a schooling ground for gleaning birds, and the graduation rate was enviable!

Today the fledges were back. The robins are starting to molt some of their fluffier feathers. Their colorations are getting more and more distinct and, or so I imagine, their breast spots are starting to fade. Soon they will look like all of the adult robins, and I will have to wait on the next fledgling cohort for my afternoon entertainment.

robin_fledge.jpgToday, though, the fledges were doing something unusual, and several adult robins, cardinals, and the phoebe were joining in. One of the birds would land on the concrete squares of my old basketball court, or on the nearby grass, and flatten themselves out on the hot, sun-drenched surface. They would then spread their wings (sometimes both wings, sometimes first one wing and then the other) and rub them slowly on the hot surface. They would stay in these positions for several minutes and then jump back on their feet and fly away. At one point I had six birds (four robins and two cardinals) splayed out in the back yard. It looked like a bird massacre had occurred! But everyone popped up a few minutes later and were fine.

This behavior is called “sun bathing” and there are abundant references to it especially in the older, ornithological literature. Speculation about its purpose was also abundant. Was it a way to rid the feathers of lice and other parasites? Was it a way to dry recently water bathed feathers? The answers to both questions seem to be “no.” Parasites simply run (or hop or slither) to the cooler, shadier parts of the bird if they get too warm, and birds that had not recently water bathed still were observed to avidly sun bathe. One researcher suggested that the birds sun bathed because it felt good (an explanation that I find especially satisfying). The birds I observed did seem to be in various states and stages of molting, so possibly this sun bathing assists the drying out of old feathers or the oiling and finishing of the new ones. I cannot reject, however, the hypothesis that it just “feels good.”

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