Kirtland's Warbler has long been among Canada's rarest breeding birds, with sporadic sightings of the species in Ontario dating back to 1916 (Harrington, 1939). Until recently, breeding had only been confirmed in two locations in Canada, both in Ontario. The first record was in 1945 near Barrie and the second was in 2007 at Garrison Canadian Forces Base Petawawa, where a pair successfully fledged two young (Richard, 2008). The Atlas of the Breeding Birds of Ontario reported one territorial bird in 1985, but no breeding evidence in 2001-2005 (Aird, 2007). With the significant increase in the United States' population, largely in Michigan (up from 167 pairs in 1974 to 2,365 in 2015), more frequent sightings of Kirtland's Warblers on territory have been documented in Ontario (Holmes et al., 2015). Small populations are now found in three locations in Ontario, along the northeastern shore of the Georgian Bay, Simcoe County and Petawawa. The species has only one confirmed report in Quebec, a pair reported in 2017 (Tuininga, K., CWS, pers. comm). Extensive surveying since 2012 using both acoustic recording units and call playback surveys have documented only one bird in northern Ontario (Holmes et al., 2015). Overall, the Canadian population of Kirtland's Warbler has almost certainly increased since the early 1970s, although the magnitude of change is difficult to estimate.

No population goal is set for Kirtland's Warbler because there are not enough data to estimate population trends. More monitoring is needed to enable development of a population goal for this species. The existing Recovery Strategy for Kirtland's Warbler has not set a population goal for the species under the Species at Risk Act (ECCC, 2006). A goal is expected in the next update of the strategy, and this account will be updated at that time.