(CBS/AP) LABARRE, La. - State biologists are trying to determine what killed an estimated 500 birds that littered a quarter-mile stretch of highway in Pointe Coupee Parish. The birds included red-winged blackbirds and starlings. The birds were found Monday along Louisiana Highway 1, about 300 miles south of Beebe, Ark., where more than 3,000 blackbirds fell from the sky three days earlier.