Habitat use and characteristics of Connecticut Warbler during the nesting and post-fledging period

Abstract

Widespread declines in breeding bird populations have been documented across North America since the 1970s and concerns for loss of avian biodiversity are growing. Species with narrow habitat preferences are of particular conservation concern. Connecticut Warblers (Oporornis agilis) breed in forests in central Canada and around the western Great Lakes; throughout much of its breeding range, this species is associated with lowland black spruce (Picea mariana) and tamarack (Larix laricina) forests. Population trends of Connecticut Warblers indicate they are one of the most rapidly declining bird species in North America; but the species is understudied because they occur in relatively low densities across their breeding range. To better understand the breeding ecology of Connecticut Warblers, we studied their nesting and post-fledging habitat use and survival in northern Minnesota, USA at two study sites in 2019 and 2020. We mapped territories of 49 singing males, located and monitored 11 nests, and tracked the post-fledging movements of individuals from 5 broods. Nest sites were located in lowland-conifer stands with a semi-open canopy and dense understory. The average fledging age was 7.5 days post-hatch and the individuals (n= 14) tracked during 0-7 days post-fledging had a mean daily distance from nests of 35.5 m and a maximum distance from nest of 104 m during that time period. Connecticut Warblers were not observed making movements of greater than 100 m from the nest until 7 days post-fledge. . Our findings indicate that micro-site areas with high stem density were important features for post-fledgling birds and that the same habitats were used for breeding and the post-fledging time period. Results from this study can be used by managers to develop conservation strategies that will provide critical habitat to support this species.