Empidonax virescensAcadian flycatcher

Geographic Range

Acadian flycatchers arrive in the Nearctic region between April and May for breeding. Their range is limited to the United States from the southeastern region of Minnesota to the eastern half of Texas and east to the Atlantic Coast from those two areas. Very small populations of Acadian flycatchers are found in southern Ontario, Canada. During the winter months, Acadian flycatchers migrate south across Mexico and the Caribbean, where they take up residence in the Neotropical region (the most Northwestern regions of Colombia, Ecuador, and Venezuela). Acadian flycatchers are considered native to these areas and have not yet been found as an introduced species in any region. ("Acadian Flycatcher", 2011; "Empidonax virescens", 2012)


Acadian flycatchers have very specific habitat requirements. Breeding habitats include mature, deciduous forests with thick, shaded canopies and open understory, typically situated near wetland habitats such as streams, ravines or swamps. They occupy the lowest tree canopy and understory layers of the forest and are considered to be interior forest dwellers. Acadian flycatchers usually build hammock or cup-like nests 3 to 9 m above the ground in forks of horizontal branches of trees and shrubs. Nests are built with plant stems and fibrils and held togeter with dried grass stems and spider silk. They will also adorn their nests with "nest tails" (hanging plant debris) for concealment. It is not uncommon for nests to be built over water in ravine settings or in areas where the understory is open (for better nest defense). During non-breeding season, Acadian flycatchers winter in lowland tropical forests of South America. ("Wisconsin All Bird Conservation Plan", 2012; Bull and Farrand, Jr., 1998; Wilson and Cooper, 1998)

Physical Description

Acadian flycatchers can be difficult to distinguish from other members of the genus Empidonax (commonly confused with alder flycatchers (Empidonax alnorum), yellow-belied flycatchers (Empidonax flavivenris), willow flycatchers (Empidonax traillii), and least flycatchers (Empidonax minimus)). Adult Acadian flycatchers are small in size (13 to 15 cm) with a triangular head. They are olive in color with white and sometimes yellowish flank and belly areas, white bars (typically two) on their wings, a black upper mandible, and a yellow to pink lower mandible. Acadian flycatchers also have a distinct, thin, white ring around each eye and this, along with their distinctively different voices, habitats and breeding habits, helps to distinguish them from similar species. Juvenile Arcadian flycatchers tend to be more brownish in color than adults, with buff-edged feathers. Their wing bars are also a darker buff than those of adults. ("Birds in Forested Landscapes", 2011; "Patuxent Bird Identification InfoCenter", 2000; Bull and Farrand, Jr., 1998)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    11 to 14 g
    0.39 to 0.49 oz
  • Range length
    13 to 15 cm
    5.12 to 5.91 in
  • Average wingspan
    23 cm
    9.06 in


Acadian flycatchers have been known to make pair bonds that last multiple years, with the pairs usually returning to the same nest as the previous year and younger birds typically dispersing to other sites. Polygny has occasionally been documented in Acadian flycathchers but they are primarily socially monogamous. Acadian flycatcher courtship behavior occurs between April and August and involves swift, frantic chasing of the female by the male. The male will also hover over the female while she is perched on an exposed branch. Territorial males will frequently sing throughout the breeding season, while females tend to only sing occasionally, and both sexes frequently call to each other. When defending nests, vocalization rate and aggression increase. These tactics are usually successful against nest predators but not against brood parasites. (COSEWIC, 2010)

Acadian flycatchers reach sexual maturity at 1 year (similar to other Empidonax species). Breeding occurs in the United States between May and August. Females can have 1-2 broods each season, with each brood yielding 2 to 4 eggs. Incubation lasts only 13 to 14 days. Once hatched, the helpless young are cared for by both parents for 13 to 15 days until they fledge. After leaving the nest, young are cared for by both the female and male for another 12 days; if the female begins to incubate another clutch, the young will be taken care of solely by the male. ("Acadian Flycatcher", 2011; DeGraaf and Yamasaki, 2001)

  • Breeding interval
    Acadian flycatchers typically have 2 broods during the breeding season.
  • Breeding season
    Acadian flycatchers typically breed from late May to mid-August, peaking in early June-early July)
  • Range eggs per season
    4 to 8
  • Range time to hatching
    13 to 14 days
  • Range fledging age
    13 to 15 days
  • Average time to independence
    12 days
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Females choose nesting sites and build nests, usually leaving long streamers of plant debris dangling for concealment. They also incubate the eggs, during which time males will not typically feed them. Once hatched, both parents tend the young over 13-15 days (until fledging), and then for 12 days after fledglings leave the nest. Both parents heavily invest in caring for the young until they reach independence (approximately 27 days after hatching), including defense of the nest and providing juveniles with a diet consisting almost entirely of insects. If the female begins to incubate a second clutch, the fledglings will only be fed and cared for by the male. ("Birds in Forested Landscapes", 2011; COSEWIC, 2010)

  • Parental Investment
  • altricial
  • male parental care
  • female parental care
  • 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


The greatest lifespan of an Acadian flycatcher recorded in the wild is 10 years and 11 months, and the expected lifespan is approximately 10 years and 9 months (remarkably long for a small bird). Lifespan in captivity is undocumented. ("AnAge", 2009)

  • Range lifespan
    Status: wild
    10.92 (high) years
  • Average lifespan
    Status: wild
    10.75 years


Acadian flycatchers are very manueverable flyers and have been known to fly backwards. This agility is useful when catching insects in the air ("aerial hawking") or gleaning insects or berries from branches. This species has no known ability to walk or hop. To bathe, Acadian flycatchers dive into water, striking only their chests and returning to a branch to clean themselves. These birds are sometimes difficult to locate because they prefer dense, shady forests and are very inconspicuous, and also because females typically evacuate a nest when a potential threat is within 23 m. They are semi-social creatures during the breeding season, creating pair bonds near other Acadian flycatchers. ("Acadian Flycatcher", 2011; "Birds in Forested Landscapes", 2011)

  • Range territory size
    5000 to 17000 m^2

Home Range

1 to 43 pairs of mating Acadian flycatchers (averaging 22 males) have been found per 40 ha. Nesting territory size is generally 0.5 to 1.7 ha/breeding pair. (DeGraaf and Yamasaki, 2001)

Communication and Perception

Acadian flycatchers are songbirds. Their distinctive "peet-sah" or "tee-chup" songs can be a great identification tool when trying to distinguish them from other Empidonax species, but these songs can vary depending on the time of day. Communication between Acadian flycatchers can also vary depending on territory. Males will typically become more vocal when in the presence of territorial neighbors, while females tend to remain quiet, especially while on nests. Acadian flycatchers are similar to most animals in perceiving their environment primarily through auditory and visual cues. ("Empidonax virescens", 2012; Wiley, 2005)

Food Habits

Acadian flycatchers are mainly insectivores, with diets consisting of mosquitoes, flies, insect larvae, small moths, flying ants, small beetles and some spiders. As their common name implies, Acadian flycatchers are adept at catching insects with their beaks from the undersides of leaves and even in flight, using gleaning and hawking tactics. They have been known to occasionally eat fruits such as blackberries and raspberries. Juveniles are fed diets consisting almost entirely of insects. ("Acadian Flycatcher", 2011; "Birds in Forested Landscapes", 2011)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • fruit


Although their nests are built in a messy fashion with streamers of plant debris hanging off the nest (a tatic used for concealment), nest predation has been known to occur in this species from animals such as accipters, red-shouldered hawks, red-tailed hawks, broad-winged hawks, American crows, blue jays, black ratsnakes, cats, southern flying squirrels, mice, squirrels, barred owls, and chipmunks. This, along with brood parasitism by yellow-billed cuckoos and brown-headed cowbirds, is the main cause of nest failure. (COSEWIC, 2010; Cox, et al., 2012)

Ecosystem Roles

Little information is available on the ecosystem roles of Acadian flycatchers. However, since they are susceptible to negative impacts caused by deforestation, they could be a good indicator species, based on population sizes, of declining forest habitats. Acadian flycatchers are parasitized by brown-headed cowbirds, mites, and deer ticks. ("Species Profile: Empidonax virescens", 2012; COSEWIC, 2010; Knee and Proctor, 2010; Peters, 2009)

Species Used as Host
  • None known
Mutualist Species
  • None known
Commensal/Parasitic Species

Economic Importance for Humans: Positive

There is no known positive economic impact of Acadian flycatchers on humans.

Economic Importance for Humans: Negative

There is no known negative economic impact of Acadian flycatchers on humans.

Conservation Status

Populations of Acadian flycatchers have declined in states such as Minnesota and Wisconsin, as well as in southeastern Canada. This migratory species is protected under the Migratory Bird Act, although there is no national concern for their population since they are still abundant in most of their breeding ranges within North America. Since Acadian flycatchers are interior forest dwellers needing large, intact forests with dense canopies, they are sensitive to habitat fragmentation and deforestation, especially in agricultural areas. ("Species Profile: Empidonax virescens", 2012; COSEWIC, 2010)


Amanda McDonald (author), Minnesota State University, Mankato, Robert Sorensen (editor), Minnesota State University, Mankato, Jeremy Wright (editor), University of Michigan-Ann Arbor, Catherine Kent (editor), Special Projects.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in the southern part of the New World. In other words, Central and South America.

World Map


uses sound to communicate


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.


Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


uses smells or other chemicals to communicate

  1. active during the day, 2. lasting for one day.

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


An animal that eats mainly insects or spiders.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males


marshes are wetland areas often dominated by grasses and reeds.


makes seasonal movements between breeding and wintering grounds


Having one mate at a time.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


having more than one female as a mate at one time


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.


Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


uses sight to communicate


2011. "Acadian Flycatcher" (On-line). The Cornell Lab of Ornithology - All About Birds. Accessed February 08, 2012 at http://www.allaboutbirds.org/guide/Acadian_Flycatcher/lifehistory/ac.

2009. "AnAge" (On-line). The Animal Ageing & Longevity Database. Accessed April 25, 2012 at http://genomics.senescence.info/species/.

2011. "Birds in Forested Landscapes" (On-line). Cornell Lab of Ornithology. Accessed March 28, 2012 at http://www.birds.cornell.edu/bfl/speciesaccts/acafly.html.

2012. "Empidonax virescens" (On-line). IUCN Redlist of Threatened Species. Accessed March 28, 2012 at http://www.iucnredlist.org/apps/redlist/details/106004277/0.

2000. "Patuxent Bird Identification InfoCenter" (On-line). USGS - Patuxent Wildlife Research Center. Accessed March 28, 2012 at http://www.mbr-pwrc.usgs.gov/id/framlst/infocenter.html#Tyrannidae.

2012. "Species Profile: Empidonax virescens" (On-line). Minnesota Department of Natural Resources. Accessed February 08, 2012 at http://www.dnr.state.mn.us/rsg/profile.html?action=elementDetail&selectedElement=ABPAE33020.

2012. "Wisconsin All Bird Conservation Plan" (On-line). Accessed March 29, 2012 at http://www.wisconsinbirds.org/plan/species/acfl.htm.

Bull, J., J. Farrand, Jr.. 1998. National Audubon Society Field Guild to North American Birds. New York: Alfred A. Knopf, Inc..

COSEWIC, 2010. Assessment and Status Report on the Acadian Flycater Empidonax virescens in Canada. Committee on the Status of Endangered Wildlife in Canada, 1: 4-29. Accessed April 25, 2012 at http://publications.gc.ca/collections/collection_2011/ec/CW69-14-5-2010-eng.pdf.

Cox, W., F. Thompson, J. Faaborg. 2012. SPECIES AND TEMPORAL FACTORS AFFECT PREDATOR-SPECIFIC RATES OF NEST PREDATION FOR FOREST SONGBIRDS IN THE MIDWEST. The Auk, 129/1: 147-155. Accessed August 09, 2012 at http://www.biosci.missouri.edu/avianecology/cox/Cox%20et%20al%20Auk%202012.pdf.

DeGraaf, R., M. Yamasaki. 2001. New England Wildlife: Habitat, Natural History and Distribution. New Hampshire: University Press of New England.

Knee, W., H. Proctor. 2010. "Interactive HTML-based Dichotomous Key to Female Rhinonyssidae (Mesostigmata) from Birds in Canada" (On-line). Accessed August 13, 2012 at http://www.biology.ualberta.ca/bsc/ejournal/kp_09/Sternostoma/Sternostoma%20key.htm.

Peters, R. 2009. "Avian Tick Burdens Across an Urban to Forest Land-Use Gradien" (On-line pdf). Accessed August 13, 2012 at http://digilib.gmu.edu:8080/dspace/bitstream/1920/5608/1/Peters_Ryan.pdf.

Wiley, R. 2005. Individuality in songs of Acadian flycatchers and recognition of neighbours. Animal Behaviour, 70: 237-247.

Wilson, R., R. Cooper. 1998. Acadian Flycatcher Nest Placement: Does Placement Influence Reproductive Success?. The Condor (Los Angeles, Calif.), 100: 673-679.