Justification of Red List Category
The species has undergone a moderately rapid decline and therefore qualifies as as Near Threatened.
Rich et al. (2004).
This species has undergone a large and statistically significant decrease over the last 40 years in North America (76.3% decline over 40 years, equating to a 30.2% decline per decade; data from Breeding Bird Survey and/or Christmas Bird Count (Butcher and Niven 2007).
Contopus cooperi breeds across Canada (overlapping into eastern USA) and Alaska, and down the west coast of the USA as far as northern Mexico. There are also isolated populations in several states in the eastern USA (Altman and Sallabanks 2000). It winters primarily in Panama and the Andes Mountains, from north and west Venezuela south through Ecuador to south-east Peru and west Bolivia (Altman and Sallabanks 2000). Casual wintering also occurs in the Guianas, Trinidad, south Venezuela, Brazil and south Peru (Altman and Sallabanks 2000). Based on data from the Breeding Bird Survey the population has declined by 3.5% annually since 1980, equating to a 30% decline over a ten year period, but a 20.6% decline for the period 1993-2002. Given the apparent benefits to the species of some forest management practices in north America, populations may be being affected by loss or alteration of habitat in their wintering grounds.
It breeds along forest edges and openings, semi-open forest, water edges and harvested forest where some structure has been retained. Prominent trees serve as singing and foraging posts, and both sexes are aggressively territorial (Altman and Sallabanks 2000).
Habitat loss and alteration of forest management practices may limit breeding success (Altman 1997). However, numerous studies suggest that several types of harvested forest are beneficial to the species (possibly recreating preferred post-forest fire habitat mosaics) (Altman and Sallabanks 2000). Insect availability on the breeding grounds is affecting many flycatching species throughout North America, and especially in eastern Canada (G. Butcher in litt. 2016). This species has been reported to suffer mortality as a result of collisions with communications towers (Longcore et al. 2013). Unknown threats may be affecting the species on its wintering grounds.
Conservation Actions Underway
No species specific actions are known, but it is on the watch list as part of the State of North America's Birds (North American Bird Conservation Initiative 2016).
Text account compilers
Harding, M., Bird, J., Sharpe, C J, Westrip, J.
Rosenberg, K., Butcher, G., Wells, J.
BirdLife International (2023) Species factsheet: Contopus cooperi. Downloaded from http://datazone.birdlife.org/species/factsheet/olive-sided-flycatcher-contopus-cooperi on 06/06/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://datazone.birdlife.org on 06/06/2023.