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willow flycatcher

Empidonax traillii

What do they look like?

Adult willow flycatchers have brownish olive backs, dull off-white breasts and white throats, although their color can vary based on their range. There are no obvious differences between male and female plumage. Their head is somewhat flat, with a fairly long bill and a weak white ring around their eyes. Their wings are black, with two white bars across the top and their tail is fairly long and thick. Due to the slight feather crest on their crown, willow flycatchers look similar to eastern wood-pewees, although willow flycatchers are smaller. Likewise, willow flycatchers look very similar to alder flycatchers, although willow flycatchers generally have browner plumage and a less noticeable eyering. In both cases, these species can be told apart by their songs. (Alderfer, 2006; Crossley, 2011; Kaufman, 2000; Phillips, 1948; Sedgwick, 2000; Sibley, 2003)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    11.3 to 16.4 g
    0.40 to 0.58 oz
  • Average length
    8.85 (female); 9.5 (male) mm
    in

Where do they live?

Willow flycatchers (Empidonax traillii) migrate each year, so they may be found in North, South or Central America at different times of the year. In North American, they can be found in southern Canada and throughout the United States. Willow flycatchers are sometimes misidentified as alder flycatchers, and although these species may be found in overlapping ranges, willow flycatchers are usually found further south and mostly nest south of Canada. During their migration, they are found in the southern United States. Willow flycatchers winter in Mexico, Central America and as far south as northern Columbia. (Crossley, 2011; Kaufman, 1996; Phillips, 1948; Sedgwick, 2000; Sibley, 2003)

What kind of habitat do they need?

Willow flycatchers are found in moist areas where there are many flying insects. They may also be found in semi-dry areas, the borders of forests, mountain meadows and riparian forests. Willow flycatchers live in a variety of areas, but prefer habitats within low growing willow thickets and shrubby areas, usually near a water source, and they usually breed near brushy thickets. During their wintering period, willow flycatchers are often found in clearings near tropical forests. (Alderfer, 2006; Kaufman, 1996; Kaufman, 2000; Sedgwick, 2000; Yong and Finch, 1997)

How do they reproduce?

Willow flycatchers are usually monogamous, which means that males and females only mate within a breeding pair. However, polygyny, where one male mates with several females, has also been seen in this species. Singing is probably an important part of maintaining a monogamous pair bond. Willow flycatchers often return to previous breeding sites after successful breeding years, although, they may also look for new sites. (Sedgwick, 2000; Sedgwick, 2004)

Willow flycatchers have about a month and a half window, during which egg laying, hatching and fledging happens. They build cup nests from grass, bark and other plant materials in trees about 1.2 to 4.5 meters from the ground. They lay eggs from June to August and usually have clutches of 3 to 4 whitish eggs with brown spots. Willow flycatchers incubate their eggs for about 12 to 14 days. Their breeding season varies based on their range, but mostly takes place during the summer and early fall. (Kaufman, 1996; Sedgwick, 2000; Sedgwick, 2004)

  • Breeding season
    Willow flycatchers typically breed from June to August, but it may vary based on their range.
  • Average eggs per season
    4
  • Average time to hatching
    12 to 14 days
  • Average fledging age
    2 to 3 weeks

Eggs are mostly incubated by the female. At first, they mostly sit on the eggs during the day, but eventually they sit on the eggs overnight as well. While females watch the nest, they turn the eggs using their beaks and feet. Once the eggs hatch, females remove the eggs shells from the nest. The female shades her nestlings during the first few days after they hatch. Both parents feed the young, although females do more. The nestling stage may last anywhere from 13 to 16 days, followed by the fledgling stage. By about two weeks of age, fledglings are able to fly short distances, but remain near the nest for three to four more days. Juveniles leave about 14 to 25 days after hatching. (Sedgwick, 2000)

  • Parental Investment
  • altricial
  • male parental care
  • female parental care
  • pre-hatching/birth
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

How long do they live?

There is currently very little information available about the lifespan of willow flycatchers. Their estimated lifespan is around 1.02 to 1.63 years. The oldest known willow flycatcher was caught 11 years after being tagged, although its age at the time of tagging is unknown. Similarly, several willow flycatchers have been caught 5 years after being tagged. (Finch and Stoleson, 2000)

  • Range lifespan
    Status: wild
    11 (high) years
  • Typical lifespan
    Status: wild
    1.02 to 1.63 years

How do they behave?

Willow flycatchers are solitary birds that usually form monogamous bonds during the breeding season. They can also be somewhat aggressive, especially when another bird is close to their nest. They often attack larger birds that come near their nest when nestlings are present. Male willow flycatchers defend larger territories than they need to survive, this helps avoid food shortages. Males use a “sit and wait” strategy for foraging, where they rest, search for prey and watch for intruders all at the same time. These birds travel over gulf coast areas to migrate in the spring, from mid- to late May and again in the early fall, from August to September. (Alderfer, 2006; Kaufman, 1996; Prescott and Middleton, 1988; Sedgwick, 2000)

  • Range territory size
    1,000 to 5,000 m^2
  • Average territory size
    3,000 m^2

Home Range

The territory sizes maintained by willow flycatchers vary from 3,000 meters squared up to 18,000 m2. In their wintering territories, they maintain a smaller area, generally around 1,100 m2. (Prescott and Middleton, 1988; Sedgwick, 2000)

How do they communicate with each other?

There are three vocalizations typically used by willow flycatchers including sounds like 'fitz-bew', 'creet,' and 'fizz-bew'. Most vocalizations are performed by males, although females respond to mates and vocalize when they sense a threat. Willow flycatchers make a specific call when they first arrive in the spring, through the pre-nesting season. When mating season begins, a new call is used. The season begins with long calls, or songs, and as the season progresses, the songs get shorter. Their breeding call is related to mate attraction and they rarely sing while migrating. (King, 1955; Sedgwick, 2000)

What do they eat?

Willow flycatchers mostly eat flying insects, although raspberries, blackberries and dogwood berries also make up a small part of their diet. Their prey includes bees, wasps, ants, flies, butterflies and moths. To hunt, they either swoop down from a perch to capture their prey or hover over their prey. Willow flycatchers are often seen hunting near brushy habitats. (Bakian, et al., 2012; Sedgwick, 2000; Sibley, 2003)

  • Animal Foods
  • insects
  • Plant Foods
  • fruit

What eats them and how do they avoid being eaten?

Willow flycatchers are preyed on by several mammal, bird and reptile species. Milk snakes and common king snakes are known to eat their eggs, in addition, cooper's hawks, great horned owls, long tailed weasels, voles, and common ravens are also known predators. Brown-headed cowbirds sometimes lay their eggs in willow flycatchers' nests. When a brown-headed cowbird is nearby, willow flycatchers chase them and vocalize less. (Cain, et al., 2003; Sedgwick, 2000)

What roles do they have in the ecosystem?

Brown-headed cowbirds are brood parasites, which means they lay their eggs in the nests of other birds, such as willow flycatchers. When cowbirds successfully parasitize their nests, flycatchers build a new nest directly over the cowbird eggs, abandon the nest and build a new one, or sometimes raise the cowbird and flycatcher chicks together. Likewise, flycatchers from their genus (Empidonax) may be parasitized by mites and ticks. By eating berries, willow flycatchers may also disperse seeds. (Hamer, et al., 2012; Sedgwick, 2000; Skoracki, et al., 2008; Uyehara and Narins, 1995; Willson and Whelen, 1993)

Commensal or parasitic species (or larger taxonomic groups) that use this species as a host
  • brown-headed cowbirds (Molothrus ater)
  • mites (Syringophilopsis)
  • ticks (Acarina)

Do they cause problems?

There is little information available on the negative economic impacts of willow flycatchers.

How do they interact with us?

There is little information available on the positive economic importance of willow flycatchers, although they may help control pest populations due to their insectivorous diet. (Prescott and Middleton, 1988)

Are they endangered?

Currently, willow flycatchers are considered a species of least concern according to the IUCN Red List of Threatened Species, although their overall population size is decreasing. The biggest concerns for the species are brood parasitism and habitat destruction. While the overall population is stable, the southwestern subspecies (Empidonax traillii extimus) is currently endangered. (Alderfer, 2006; BirdLife International, 2013; Sedgwick, 2000; Sibley, 2003)

Some more information...

Willow flycatchers are often mistaken for alder flycatchers. Although these species have different songs, are found in different habitats and do not interbreed, they were considered a single species until the 1970s. (Fergus, 2003)

Contributors

Emily Brazil (author), Northern Michigan University, Leila Siciliano Martina (author, editor), Animal Diversity Web Staff, Alec Lindsay (editor), Northern Michigan University.

References

Alderfer, J. 2006. Complete Birds of North America. Washington, D.C: National Geographic.

Bakian, A., K. Sullivan, E. Paxton. 2012. Elucidating Spatially Explicit Behavioral Landscapes in the Willow Flycatcher. Ecological Modeling, 232: 119-132.

BirdLife International, 2013. "Empidonax traillii" (On-line). IUCN RedList of Threatened Species. Accessed December 10, 2013 at http://www.iucnredlist.org/details/22699848/0.

Cain, J., M. Morrison, H. Bombay. 2003. Predator Activity and Nest Success of Willow Flycatchers and Yellow Warblers. The Journal of Wildlife Management, 67.3: 600-610.

Crossley, R. 2011. The Crossley ID Guide of Eastern Birds. Princeton, NJ: Princeton University Press.

Fergus, C. 2003. Wildlife of Virginia and Maryland and Washington D.C. Mechanicsburg, PA: Stackpole Books.

Finch, D., S. Stoleson. 2000. Status, Ecology, and Conservation of the southwestern willow flycatcher. Ogden, Utah: United States Department of Agriculture.

Garcia-Hernandez, J., O. Hinojosa-Huerta, V. Gerhart, Y. Carrillo-Guerrero, E. Glenn. 2001. Willow flycatcher (Empidonax traillii) surveys in the Colorado River delta: implications for management. Journal of Arid Environments, 49.1: 161-169.

Hamer, S., T. Goldberg, U. Kitron, J. Brawn, T. Anderson, S. Loss, E. Walker, G. Hamer. 2012. Wild birds and urban ecology of ticks and tick-borne pathogens, Chicago, Illinois, USA 2005-2010. Emerging Infectious Diseases, 18:10: 1589-1595.

Kaufman, K. 2000. Field Guide to Birds of North America. New York: Hillstar Editions L.C.

Kaufman, K. 1996. Lives of North American Birds. New York: Houghton Mifflin Books.

King, J. 1955. Notes on the Life History of Traill's Flycatcher (Empidonax traillii) in Southeastern Washington. The Auk, 72.2: 148-173.

Koronkiewicz, T., M. Sogge, C. III van Riper, E. Paxton. 2006. Territoriality, Site Fidelity, and Survivorship of Willow Flycatchers Wintering in Costa Rica. The Condor, 108.3: 558-570.

Phillips, A. 1948. Geographic Variation in Empidonax traillii. The Auk, 65.4: 507-514.

Prescott, D., A. Middleton. 1988. Feeding-Time Minimization and the Territorial Behavior of the Willow Flycatcher (Empidonax traillii). The Auk, 105.1: 17-28.

Sedgwick, J. 2004. Site Fidelity, Territory Fidelity, and Natal Philopatry in Willow Flycatchers (Empidonax traillii). The Auk, 121.4: 1103-1121.

Sedgwick, J. 2000. "Willow Flycatcher (Empidonax traillii)" (On-line). The Birds of North America Online. Accessed February 01, 2013 at http://bna.birds.cornell.edu/bna/species/533/articles/introduction.

Sibley, D. 2003. The Sibley Field Guide to Birds of Eastern North America. New York: Andrew Stewart Publishing.

Skoracki, M., M. Flannery, G. Spicer. 2008. Quill mites of the genus Syringophilopsis Kethley, 1970 (Acari: Syringophilidae) from North American birds. Folia Parasitologica, 55: 291-300.

Uyehara, J., P. Narins. 1995. Nest Defense by Willow Flycatchers to Brood-Parasitic Intruders. The Condor, 97.2: 361-368.

Willson, M., C. Whelen. 1993. Variation of dispersal phenology in a bird-dispersed shrub, Cornus drummondii. Ecological Monographs, 63-2: 151-172.

Yong, W., D. Finch. 1997. Migration of the Willow Flycatcher along the Middle Rio Grande. The Wilson Bulletin, 109/2: 253-268. Accessed February 12, 2013 at http://www.jstor.org/stable/4163809?seq=14.

 
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Brazil, E. and L. Siciliano Martina 2014. "Empidonax traillii" (On-line), Animal Diversity Web. Accessed November 15, 2018 at http://www.biokids.umich.edu/accounts/Empidonax_traillii/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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