Grassland birds are the most threatened populations of birds in Canada, with a 67 per cent decline since 1970, a report published Tuesday found — but a surprising alliance with beef producers is emerging to protect their habitat. Much of the decline is attributed to the disappearance of grassland habitats across Canada, located largely in the Prairies. Birds that live only in grasslands have declined even more steeply, suffering a 90 per cent collapse since 1970, the report found.