Why do birds form large winter roosts and flocks?
September 17, 2008 Five hundred starlings dove out of the line of trees next to the road, swooping low in front of my truck. Pounding rain, too much for wipers set on high, only partially revealed the tight-knit flock of birds. I could not put on my brakes out of fear of hydroplaning. Thud! Thud! Thud! Thud! I pulled off of the road to clean a blood mixed with feces off of the windshield. I grabbed a wet rag out of the back of the truck and as I scrubbed, back hunched over against the windblown rain, I glanced back to the row of trees. The birds had flown because the farmer had started up a big tractor and were already returning as the big machine lumbered towards a barn. Starlings are one of a number of species that form big night-time roosts when nesting season is over. Great-tailed grackles do the same, much to the dismay of homeowners who have to clean thick crusts of droppings off of vehicles and driveways. Red-winged blackbirds, cowbirds, and Brewer s blackbirds will crowd into d
