Pacific-slope flycatchers are mostly monogamous. A single study done on mating Pacific-slope flycatchers in British Columbia reported that 1 in 7 males partnered with 2 females.
Mating System: monogamous ; polygynous
Pacific-slope flycatchers usually hatch several broods in a given breeding season from mid April to mid July. In Monterey County, California they have been found to build nests from April 15 to May 1 for first broods and June 1 to July 15 for second broods and re-nesting. Mean clutch size is four eggs per brood. Incubation time lasts between 13 and 16 days and fledging time is around 14 to 17 days after hatching. Age is presumed to be one year at first breeding and they breed annually afterwards.
Breeding interval: Pacific-slope flycatchers breed once annually.
Breeding season: Pacific-slope flycatchers breed from mid-April through mid-July.
Average eggs per season: 4.
Range time to hatching: 13 to 16 days.
Range fledging age: 14 to 17 days.
Range time to independence: 14 to 17 days.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)
The female alone incubates the eggs but both sexes bring food to the fledgling young and remove fecal sacs.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
- Ainsley, D. 1992. Vocalizations and nesting behaviour of the Pacific-slope Flycatcher, Empidonax difficilis. M.Sc. thesis, Univ. of Victoria, Victoria, BC.
- Lowther, P. 2005. "Pacific-slope Flycatcher" (On-line). The Birds of North America Online. Accessed May 11, 2007 at http://bna.birds.cornell.edu/BNA/account/Pacific-slope_Flycatcher/.