The Prothonotary Warbler is restricted in Canada to extreme southern Ontario where the already small population appears to be decreasing. The species is actively monitored by a combination of amateur and professional birders (COSEWIC 2016d). Annual surveys of the Prothonotary Warbler run since 1997 in Canada estimated a drop of 80% in abundance from the mid-1990s to 2011 (COSEWIC 2007, J. McCracken, pers. comm.), despite an unchanged distribution. Numbers have remained stable or declined slightly since then, from 28-34 individuals in the previous report (COSEWIC 2007), to 28 individuals in 2015 in fewer than 10 locations in Canada in any given year (COSEWIC 2016d). These results indicate that the population has exhibited a large, long-term decrease in Canada. Breeding Bird Survey results from throughout North America indicate a moderate, long-term decrease in the continental population. The population objective for Prothonatory Warbler is to recover the Canadian population to what is believed to be its historical population size and distribution of at least 40 breeding pairs spread among at least six geographically distinct nesting areas (Environment Canada 2011g). The current population is below that goal.
Additional information on: Atlas of the Breeding Birds of Ontario
Additional information on: Breeding Bird Survey (BBS) - Canadian analysis