Dear Rob and Devon,
An interesting paper on drop-catch behavior in Herring Gulls trying to discern if gulls dropping and catching clams was play or something else. The authors generated some predictions and decided that it was play ---

http://people.wm.edu/~dacris/pdfs/Gamble_and_Cristol.pdf

I've seen swallows do a similar behavior with feathers after breeding season is over.

Peter Wimberger
Tacoma, WA
Slater Museum of Natural History

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