Assessing the relative use of clearcuts, burned stands, and wetlands as breeding habitat for two declining aerial insectivores in the boreal forest
Fires are an ecological process essential for species dependent on early successional habitat in forested landscapes. In a wildlife context, clearcut forestry practices can mimic forest fires through the creation of early successional forest clearings, however, evidence that clearcuts provide the same ecological value as fire is mixed. In temperate deciduous/hardwood forests, many species that depend on early successional habitat are known to use clearcuts, including Eastern Whip-poor-wills (Antrostomus vociferous) and Common Nighthawks (Chordeiles minor), two threatened aerial insectivorous birds. However, the relative importance of recent clearcuts as breeding habitat relative to other more naturally open habitat types in the boreal forest is unknown. In May-July 2015 we studied occupancy and detectability of these two species in the boreal forest of northwestern Ontario. We first determined whether occupancy differed among three open habitats: burned stands, recent clearcuts, and open wetlands, and whether it differed in relation to the size of clearcut patches. We also examined how detectability of each species varied with time of day, season and weather conditions. Site occupancy for the Eastern Whip-poor-will and Common Nighthawk averaged 0.413 and 0.437, respectively. We found no significant difference in occupancy of either species in relation to burned stands, recent clearcuts, or open wetlands, although Eastern Whip-poor-will occupancy tended to be higher in burned stands. Occupancy did not show a linear relationship with patch size but neither species was found in the smallest open patches (<3 ha), perhaps indicating a minimum size threshold, although further study is needed. The detection of each species was positively correlated with the occurrence of the other species, suggesting that they were both selecting similar site characteristics. Detectability for Eastern Whip-poor-will was highest after sunset and increased over the course of the breeding season, while for Common Nighthawk, detectability was similar during and after sunset and decreased over the season. Our results suggest that Eastern Whip-poor-will and Common Nighthawk show similar preference for natural and managed open sites and that recent clearcuts may provide early successional habitat in the absence of burned stands. Our results also extend the known breeding range of Eastern Whip-poor-will, which further emphasizes the need for future research on these poorly studied species in the boreal forest.
|Keywords||Aerial insectivore, Boreal ecology, Caprimulgidae, Clearcut silviculture, Forest management, Species-at-risk|
|Journal||Forest Ecology and Management|
Farrell, C.E. (Claire E.), Wilson, S. (Scott), & Mitchell, G. (Greg). (2017). Assessing the relative use of clearcuts, burned stands, and wetlands as breeding habitat for two declining aerial insectivores in the boreal forest. Forest Ecology and Management, 386, 62–70. doi:10.1016/j.foreco.2016.11.026