- 5.1–6.7 in
- 8.3–9.4 in
- 0.4–0.5 oz
- Trail's Flycatcher (together with Willow Flycatcher)
- Moucherolle des aulnes (French)
- Mosquero ailero, Mosquerito de charral (Spanish)
- The Alder Flycatcher is so similar to the Willow Flycatcher that they were thought to be the same species. Song is the only definitive way to tell them apart. However, measurements of crown color with a colorimeter, together with other measures of wing shape, bill and tail, may be able to distinguish birds in the hand that are not calling.
- The Alder Flycatcher's nest is a coarse, loose cup that nearly always has material hanging off it. The nest of the Willow Flycatcher tends to be neater, with no hanging material.
- Willow and Alder flycatchers do not respond to playback of recordings of each other's songs, even where their ranges overlap.
- In an experiment on song learning, Alder Flycatchers were "tutored" with Willow Flycatcher song in the first two months of life. The next spring, the Alder Flycatchers sang normal Alder Flycatcher song.
- The longest-lived Alder Flycatcher was over 9 years old, when it was recaptured and rereleased during a banding operation in British Columbia.
Breeds in wet thickets, especially of alder, maple, and birch. Winters in early successional scrubby growth.
Mostly insects, some fruit in winter.
- Clutch Size
- 3–4 eggs
- Egg Description
- Creamy white or buff, unmarked or dotted with dark irregular markings around large end.
- Condition at Hatching
- Helpless and with only small patches of olive-brown down.
A coarse, loose cup with material hanging off it, usually placed low in bushes.
Insects caught in the air or gleaned from foliage of trees and shrubs.
Alder Flycatcher numbers are stable in the U.S. but declined by about 44% in Canada between 1966 and 2014, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 130 million with 24% breeding in the U.S., 76% breeding in Canada, and all of them migrating through Mexico to their wintering grounds in South America. They rate a 7 out of 20 on the Continental Concern Score and are not on the 2014 State of the Birds Watch List, although they are a U.S.-Canada Stewardship species.
- Lowther, P. E. 1999. Alder Flycatcher (Empidonax alnorum). In The Birds of North America, No. 446 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
- North American Bird Conservation Initiative, U.S. Committee. 2014. State of the Birds 2014 Report. U.S. Department of Interior, Washington, DC.
- Partners in Flight. 2012. Species assessment database.
- U.S. Department of the Interior, USGS Patuxent Wildlife Research Center. 2015. Longevity records of North American Birds.
- USGS Patuxent Wildlife Research Center. 2014. North American Breeding Bird Survey 1966–2014 Analysis.