Modeling detection probability to improve marsh bird surveys in southern Canada and the Great Lakes States / Douglas C. Tozer, Kiel L. Drake, and C. Myles Falconer.

Includes bibliographical references.

Marsh birds are notoriously elusive, with variation in detection probability across species, regions, seasons, and different
times of day and weather. Therefore, it is important to develop regional field survey protocols that maximize detections, but that also
produce data for estimating and analytically adjusting for remaining differences in detections. We aimed to improve regional field survey
protocols by estimating detection probability of eight elusive marsh bird species throughout two regions that have ongoing marsh bird
monitoring programs: the southern Canadian Prairies (Prairie region) and the southern portion of the Great Lakes basin and parts of
southern Québec (Great Lakes-St. Lawrence region). We accomplished our goal using generalized binomial N-mixture models and
data from ~22,300 marsh bird surveys conducted between 2008 and 2014 by Bird Studies Canada’s Prairie, Great Lakes, and Québec
Marsh Monitoring Programs. Across all species, on average, detection probability was highest in the Great Lakes-St. Lawrence region
from the beginning of May until mid-June, and then fell throughout the remainder of the season until the end of June; was lowest in
the Prairie region in mid-May and then increased throughout the remainder of the season until the end of June; was highest during
darkness compared with light; and did not vary significantly according to temperature (range: 0-30°C), cloud cover (0%-100%), or
wind (0-20 kph), or during morning versus evening. We used our results to formulate improved marsh bird survey protocols for each
region. Our analysis and recommendations are useful and contribute to conservation of wetland birds at various scales from local
single-species studies to the continental North American Marsh Bird Monitoring Program.