Bird Ecology and Conservation Ontario
Newsletter No. 8, August 2017
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Searching for Prairie Warblers

This year, we had the opportunity to continue our search for the elusive Prairie Warbler, to find out more about the distribution of this rare songbird. In May and June, while BECO's Bobolink research team was busy searching cattle pastures for nests and monitoring their outcome, the Prairie Warbler survey team was strategically surveying shrubby rock barrens along the southern edge of the Canadian Shield.

Prairie Warbler
A male Prairie Warbler sings his ascending and buzzy song "zee zee zee zee zee zee zee zee" from a red oak tree in his breeding territory.
Photo: Garth Casbourn
Despite its name, this species does not nest in prairies. In Canada, Prairie Warblers are found only in Ontario, in early successional vegetation. The core breeding population is located along the southeastern shore of Georgian Bay, where they nest in rock barrens with sparse and scrubby vegetation. The species is rare along the southern edge of the Shield, where scattered records exist and no systematic surveys have occurred previously. The entire Ontario population is estimated to be no more than 320 pairs.

To guide our surveys, we used a habitat model created by Andrew Campomizzi, BECO's Research Scientist. The model indicates the probability of occurrence of Prairie Warblers, based on habitat associations where the species has been detected previously. 
Prairie Warbler survey map
This map shows the Prairie Warbler habitat model predictions and locations of surveys in 2017. The model indicates areas where the probability of finding Prairie Warblers is low (cool colours) compared to areas where the probability of finding the species is higher (warm colours).
Many of the areas identified as potential habitat by the model are off the beaten track and not easily accessible, so we conducted most of our surveys by foot and by canoe. The Prairie Warbler habitat model led us to some wild and wonderfully beautiful areas of Ontario.
Survey snapshots
Surveying for Prairie Warblers_1
After an hour-long portage along a flooded ATV trail, we arrived at our launch point to begin surveying a seldom-frequented patch of crown land. [Pictured: Katherine Robbins]
Prairie Warbler habitat
The landscape looked ideal for Prairie Warblers and not long into the morning, we detected our first male, singing near the shoreline.
Photos: Zoé Lebrun-Southcott
Surveying for Prairie Warblers_2
Surveying at the top of Mount Moriah. [Pictured: Zoé Lebrun-Southcott]
Photo: Katherine Robbins
Mount Moriah
The view from the top of Mount Moriah.
Photo: Zoé Lebrun-Southcott
Surveying for Prairie Warblers_3
Surveying the backcountry for Prairie Warblers required tackling some obstacles. This was the first of many on one of our more challenging days. [Pictured: Garth Casbourn]
Surveying for Prairie Warblers_4
The effort was well worth it. We detected several Prairie Warblers and the scenery was spectacular. [Pictured: Garth Casbourn]
Photos: Zoé Lebrun-Southcott
Surveying for Prairie Warblers_5
Katherine Robbins at the bottom of Mazinaw Rock, Bon Echo Provincial Park ...
Surveying for Prairie Warblers_6
... and at the top.
Photos: Garth Casbourn
We surveyed more than 200 locations, from Gravenhurst to Kaladar, and detected Prairie Warblers at less than 10% of these locations. We also surveyed historical locations where Prairie Warblers have been detected previously across the southern edge of the Shield. We visited most historical locations twice, to increase our chances of detecting a bird if it was present. Prairie Warblers were detected at approximately 30% of the historical locations surveyed.

Although we didn't find many Prairie Warblers, the data we gathered, both detections and non-detections, will help to provide a better picture of the distribution of this rare warbler in Ontario and identify areas that are important for the species' conservation.
Funding for BECO's Prairie Warbler Project is provided by The McLean Foundation, the Helen McCrea Peacock Foundation at Toronto Foundation, a donation from Janet and Kenneth Dance, and additional individual donations.
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