This video from the USA says about itself:
The destruction of tricolored blackbird breeding colonies through harvest of the grain crop that serves as the nesting substrate is an annual occurrence in the San Joaquin Valley of California. Typically, the harvest of these grain fields results in complete elimination of the potential productivity of tens of thousands of breeding birds. As a majority of tricolors breeds in the San Joaquin Valley, the losses due to these harvests greatly reduce the number of young born and fledged each year.
Tricoloured mega-colony saved
Audubon California has announced that it has reached an agreement with a farmer to safeguard a single colony of about 80,000 Tricoloured Blackbirds Agelaius tricolor – nearly a third of the world’s population of this Endangered species.
The estimated global population of Tricoloured Blackbirds is 250,000 to 300,000 birds, with at least 95% of these occurring in California. Tricoloured Blackbirds have declined dramatically in the past century as native wetland habitat has been lost and the species has consequently been classified as Endangered. Tricoloured Blackbirds form just a few large nesting colonies each year, and in most cases these occur in crop fields. This puts the colonies in grave danger when farmers cultivate the field before young birds are able to fly.