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Science Frontiers ONLINE No. 110: Mar-Apr 1997 |
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Sparrows At Play
While looking through the ornithological literature for avian anomalies recently, we found an irresistible item that bears on that deeply profound bit on "Crow Woes" appearing in SF#109. Remember how the Yokohama crows placed stones on the train tracks and dropped others on houses? Well, this stone-dropping must have some adaptive value in the evolution of birds, because sparrows have also inherited the trait. E.C. Jaeger recounted this anecdote in a 1951 number of The Condor:
"During my high school days at West Point, Nebraska, my father was a merchant occupying a building of two stories with a long pebble-covered, tarred roof sloping to the rear. Forming a short walkway behind the rear entrance were two sloping doors, which, when opened up, admitted entry to the basement stairway. Over a period of several days in mid-May of 1903, I noticed many small pebbles scattered about on these doors. I also heard from time to time the sound of small objects falling on the doors. Efforts to find the pebble-droppers were of no avail until one day when I happened to approach the rear of the building from the alley. My position some fifty feet from the building now permitted me to see several House Sparrows (Passer domesticus) bringing small stones to the edge of the roof and dropping them. As each pebble was dropped the bird involved turned its head to one side, apparently the better to listen to it and watch it as it struck the door. It may have been a sort of bird pastime; it certainly was an activity of no evident value."
(Jaeger, Edmund; "Pebble-Dropping by House Sparrows," The Condor, 53:207, 1951.)