HI:
I got this response from John Marzluff:
ian, i am not sure why they wash some items, but often the "wash" dry food
to increase the moisture content. especially this time of year when it is
hot and dry it is a good way to get water to their nestlings. by soaking
food the parents are able to get food and water to nestlings all in one
trip. it would be interesting to see how great a variety of foods are
washed, how long various items are soaked, etc--that might tell us if
water
absorption or other factors are behind this neat behavior. john

John Marzluff
Denman Professor of Sustainable Resource Sciences
Professor, Wildlife Science
College of Forest Resources

--
Ian Paulsen
Bainbridge Island, WA, USA
A.K.A.: "Birdbooker"
"Rallidae all the way!"