By Alex Breitler Record Staff Writer The tricolored blackbird, once so numerous that its flocks were described as darkening the sky, never quite won protection on the federal endangered species list. But an agreement announced last week by conservationists, farmers and the government might help reverse the songbird's overall decline. Habitat conservation, research, monitoring and public education are all part of the 15-year plan for the blackbird, which nests primarily in dairy silage fields. During the harvest, eggs and hatchlings are killed. Some conservationists say the bird once numbered in the millions, declining to 154,000 by 2000. The U.S. Fish and Wildlife Service reported a population of 260,000 in 2005. "This is a real landmark agreement," said Garrison Frost, a spokesman with Audubon California, one of the participants in the plan.