Two robins (Turdus migratorius) hopped through the yard this week – spring is on its way. The sound of lawn mowers now drift through the air, confirming the avian prediction. Shockingly, these two very distinct signs of warming weather are actually related, according to a backyard research study conducted in 1979.
L.A. Eiserer conducted a series of scientific (well, somewhat) studies examining the impacts of lawn mowing on robin-hunting behaviors. Robins spend more time foraging when grass is short, especially just after it has been mowed.
So is it the mowing or the height of the grass that impacts robin behavior? Eiserer mowed his lawn to two different heights, 2.5 and 4.5 inches. (I wonder if his neighbors complained.) The robins spent 10x as much time in the shorter patch. Apparently, the birds eat different foods when exposed to different heights of grasses. In short grass, robins go for worms; in longer grass, they pluck small insects off the blades. The short-grassed hunting grounds may just be more efficient for finding a heartier meal.
But that doesn’t discount the act of mowing. Observations over the same time of day show the birds prefer hunting in a freshly mowed yard rather than the day after. No difference in grass height, but perhaps the act of mowing disturbs invertebrates, allowing for a more successful hunt.
Overall, I miss the days when a researcher could sit on a suburban porch and time how long a couple of robins spend looking for food. As I struggle to teach my students how to think like scientists, reading a study like this makes me long for the good old days.
Eiserer, L.A. 1980. Effects of Grass Length and Mowing on Foraging Behavior of the American Robin. The Auk. 97(3) 576-580.
As Yogi said, “You can observe a lot just by watching.”
Too much time today with eyes on screens…(K)
While I don’t get much time to be bored, I’m a big fan. Such interesting ideas come from watching the world. I’m with you 100%, K!
The colours on the robin are beautiful. I love a good yellow mix. This was brilliant.
Thanks, Sabiscuit! I’ll try to add extra yellow to my next post!
That’s really nice of you. I appreciate that. ❤
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The robins don’t waste any time in my yard. As soon as I start mowing, they start feasting. Usually two of them at first. They will eat with me just feet away pushing the mower around. Then when I’m done, their friends and relatives swoop in to join them. And they hang around for days. There are six in my backyard right now.