The status and distribution of Loggerhead Shrikes (Lanius ludovicianus) in southern Ontario and Quebec was studied during the 1991 and 1992 breeding seasons. Shrikes returned from wintering areas in April and egg laying began by the end of April and early May. The population of Loggerhead Shrikes in eastern Ontario was found to consist of 51 pairs distributed over three core areas, each associated with a limestone plain. Only one pair of birds was found breeding in the province of Quebec in 1991 and 2 in 1992. Shrikes nested in hawthorn (Crataegus spp.), red cedar (Juniperus virginiana) and other species, most often inactively grazed pastures. Suitable historic nesting sites were reoccupied and there was a high rate of reoccupancy of 1991 sites in 1992. Breeding territory selection was affected by the amount of habitat fragmentation around a site, but nest site selection appeared to be random within a suitable territory. Shrikes nesting in Ontario have a high rate of reproductive success (58 to 93%). The number of fledglings per nest is high, however, only half survive the 3 to 4 weeks needed to become independent of their parents (2.30 of 3.90 in 1991 and 2.50 of 4.17 in 1992). Shrikes were found to renest several times and double brooding was observed. More time was spent hunting and feeding mates and young as the demand for food increased through the reproductive cycle.

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