Expert: Roger Lederer - 8/27/2011

Question
I live in south eastern Wisconsin. I have also noticed that the robins have been vanishing from the area by early august in the last few years. By "area" I mean suburban yards and subdivisions, as well as city yards. I read your response to the same question from another person. You had thought that it could be do to global warming changing their habits, as well as changes in their food supply due to weather or drought. This is probably going to sound absurd, but I was wondering if it could have anything to do with the emergence of the Japanese beetle the last few years? They emerge about the same time the robins have been disappearing. They decimate the foliage everywhere, trees, shrubs, flowers, vegetable plants, and as far as i can tell, nothing eats them, not even the robins. I know robins eat mostly insects and larvae, but I'm wondering if these beetles affect the robins food supply, and they don't want to deal with them so they leave. I hope this isn't true, because every year these beetles are increasing in number by the thousands, maybe even millions. What do you think?

Answer
Well, sure , Japanese beetles could have an effect. Some birds eat Japanese beetles and their grubs; I can't tell you if they are eating them in your area. But they probably are. I doubt if the beetles are affecting the robins' food supply as the birds are so omnivorous. Is there spraying for these beetles? If not by the city or county, then I suspect individual homeowners are spraying and that would have a major effect. The poison lands on the ground and gets absorbed by worms and grubs and then robins. It's complicated - global warming, habitat destruction, pesticides, and other birds moving in or out with the climate changing. But I doubt if the beetles have a direct effect.