51.   The convertible bond kills two birds with one stone.

52.   The deaths were first reported around Fort Totten, in Queens, in mid-August, although what killed the birds has remained a mystery.

53.   The experts ruled out St. Louis encephalitis, because generally that illness does not kill the birds that carry it.

54.   The Mexican authorities concluded last summer that industrial pollutants had killed the birds.

55.   The main damage was eggshell thinning, which killed baby birds before they hatched.

56.   The oil harms birds because it ruins their insulating feathers, and it can kill birds when ingested.

57.   The Pentagon contends that the Migratory Bird Treaty Act penalizes troops who kill migratory birds accidentally.

58.   The state occasionally gives farmers permits to kill nuisance birds, but farmers say it is hard to make an impact.

59.   The virus multiplies in and often kills birds, the so-called amplifying hosts, and multiplies further in mosquitoes that take blood from birds.

60.   The veterinary lab in Ames had already exhausted its capabilities, but could not specifically identify the strange virus that was killing the birds.