Birth control is to be used on pigeons in California in an effort to combat the "unmanageable" mess their increasing numbers are causing.
The pigeon population has risen to 5,000 in Hollywood
Animal rights groups support using the contraceptive in preference to other methods such as gates which give electric shocks and poisoning.
OvoControl P, which interferes with egg development, will be put in bird food in new rooftop feeders in Hollywood.
The pilot program is expected to show results within a year.
Laura Dodson, president of the Argyle Civic Association, the group leading the effort to try the new contraceptive, said: "We think we've got a good solution to a bad situation.
"Cleaning up after the pigeons has become unmanageable and this could be the answer."
Estimates suggest that about 5,000 pigeons live in the Hollywood area.
Their rising numbers have been partially blamed on people feeding the birds.
Hollywood area's pigeon population is expected to shrink by at least half by 2012, Ms Dodson said.