Habitat change as a factor in the decline of the western Canadian loggerhead shrike, Lanius ludovicianus, population

Abstract

Field studies of habitat use by loggerhead shrikes on breeding range in Alberta and Saskatchewan and on winter range in Texas, confirmed their preference for short grass pastures. Regions of Alberta and Saskatchewan showing large declines in populations of breeding loggerhead shrikes in recent decades lost 39% of their unimproved pasture area through converion to cropland between 1946-1986 and up to 79% of their pre-settlement pasture area. Regions where shrikes declined less lost only 12% of their unimproved pasture to cropland but had probably lost 65% of their pre-settlement pasture area. In probable shrike winter range in Texas, pasture area has also declined due to encroachment by cropland and brush invasion. -Author