Quick Answer
The willow flycatcher and the Acadian flycatcher are two similar-looking bird species found in North America. The main differences between them are:
- Range – Willow flycatchers breed in the western half of North America, while Acadian flycatchers are found in the eastern half.
- Habitat – Willow flycatchers prefer wet, shrubby areas like meadows and marshes, while Acadian flycatchers prefer dry, forested areas.
- Song – The willow flycatcher’s song is a sneezy “fitz-bew” or “fitz-bew-rew.” The Acadian flycatcher sings a rolling “pit-see-pit-see-pit-see.”
- Appearance – Acadian flycatchers have brighter yellow underparts and wingbars compared to the pale yellow on willow flycatchers.
- Eggs – Willow flycatcher eggs are creamy white with brown speckles. Acadian flycatcher eggs are white with reddish-brown blotches.
Differences in Range and Habitat
The ranges of the willow flycatcher and Acadian flycatcher only overlap in a narrow region along the Mississippi River and Great Lakes. Willow flycatchers breed west of this region across most of the western half of North America. Their breeding range extends from Alaska down to southern California, across to the Great Plains states and Southwest.
Acadian flycatchers are found far to the east. Their breeding range covers areas east of the Mississippi River up to the Atlantic Coast. This includes the southeastern United States, portions of the Midwest, and along the Atlantic Coast up to southern New England.
This divergence in range is largely due to differences in preferred breeding habitat between the two species. Willow flycatchers live up to their name and primarily nest in wet, shrubby areas with willow thickets. This includes wet meadows, riparian areas along streams and rivers, pond edges, damp thickets at beaver ponds, and boggy areas.
In contrast, Acadian flycatchers prefer much drier forested areas. Their typical breeding habitat is open, mature deciduous or mixed forests with an open understory and nearby clearings or forest edge habitat. You may find them in oak-hickory forests, bottomland hardwood forests, and even wooded suburban areas.
Table 1. Comparison of Habitats
| Willow Flycatcher | Acadian Flycatcher |
|---|---|
| Wet meadows | Mature deciduous forests |
| Riparian vegetation along streams | Open understory |
| Beaver ponds | Clearings/forest edges |
| Boggy areas | Oak-hickory forests |
| Willow thickets | Bottomland hardwood forests |
| Marshy areas | Wooded suburban areas |
The preference for damp, shrubby habitat allows willow flycatchers to take advantage of plentiful insects near water. Acadian flycatchers evolved in the relatively drier forests of the eastern United States. Their broader beaks are adapted to capturing larger insects on the wing.
Differences in Song and Call
Given their overlapping ranges, one of the best ways to distinguish a calling willow flycatcher from Acadian flycatcher is by listening to their vocalizations.
The willow flycatcher’s most common song is a sneezy-sounding “fitz-bew” or “fitz-bew-rew.” They repeat this whistled song incessantly from low perches when defending territories. It sounds rather weak and thin compared to many bird songs.
Acadian flycatchers produce a much more rolling, melodious song. Their common song is a repeating “pit-see-pit-see-pit-see.” It has an almost electrifying or rising and falling quality to human ears. This song carries well through their forest habitat compared to the willow flycatcher’s song.
In addition to different songs, their call notes differ as well. Willow flycatcher call notes are a harsh sounding “whit” or “brit.” Acadian flycatchers may make a soft, whistled “weeh” contact call. Getting to know these vocalization differences aids identification when only one species is heard calling.
Table 2. Comparison of Songs and Calls
| Willow Flycatcher | Acadian Flycatcher |
|---|---|
| Song is a sneezy “fitz-bew” | Song is a melodious “pit-see-pit-see-pit-see” |
| Call note is a harsh “whit” or “brit” | Call note is a soft, whistled “weeh” |
| Song is weak and thin | Song carries well through forest habitat |
| Sings from low, exposed perches | Sings high in forest canopy |
Appearance and Physical Differences
Visually differentiating willow and Acadian flycatchers is more difficult. They are both medium-small songbirds, about 5.5-6.5 inches in length. Their plumage patterns are very similar with olive to gray-green upperparts and pale yellow underparts.
However, there are some subtle physical differences in plumage that can aid identification:
- The yellow on an Acadian flycatcher’s underparts and wingbars is brighter and more saturated compared to the pale, washed-out yellow on a willow flycatcher.
- Willow flycatchers have faint olive-gray wingbars, while Acadian flycatchers have bright yellow-whitish wingbars.
- Acadian flycatchers have whiter throats compared to the pale yellow throat of willow flycatchers.
- Willow flycatchers tend to have longer primary wing feathers giving them a more slender, attenuated look in flight.
There are also some slight structural differences between the two species:
- Acadian flycatchers have a relatively longer tail and broader bill adapted to aerial insect hunting.
- Willow flycatchers have a smaller bill and shorter tail suited to catching insects near vegetation.
When seen side-by-side, the brighter colors of the Acadian flycatcher compared to the duller willow flycatcher become even more apparent. But subtle plumage differences like these can still be difficult for amateur birders to distinguish in the field.
Table 3. Comparison of Physical Features
| Willow Flycatcher | Acadian Flycatcher |
|---|---|
| Pale, dull yellow underparts | Bright yellow underparts |
| Faint olive-gray wingbars | Bright yellow-white wingbars |
| Pale yellow throat | White throat |
| Smaller bill | Broader bill |
| Shorter tail | Longer tail |
| More slender, attenuated profile | Stockier through head and chest |
Nesting Behavior
When it comes to their nesting habits, willow and Acadian flycatchers have adapted their breeding strategies to match their preferred habitats.
Willow flycatchers often nest very low in dense shrubbery, small trees, or vines over water or wet soil. They construct a loose open cup of plant fibers, grasses, and other materials. The nests are typically less than 10 feet off the ground concealed in thick vegetation at the edge of marshes, streams, or beaver ponds.
In contrast, Acadian flycatchers nest high up in mature forest trees. They build more sturdy, compact nests 10-60 feet up in a tree fork against the trunk. Their nests are constructed from plant fibers, strips of bark, moss, lichens, and spider webs. Nests are often located high in an oak, beech, or sugar maple tree.
Since Acadian flycatchers nest high in the forest canopy, their nests are more exposed to predators. They may rely more heavily on concealing tree foliage for protection. Willow flycatchers tuck their nests away in the concealment of low, dense shrubs right at wetland level.
Clutch sizes are comparable with 3-4 eggs being typical of both species. But Acadian flycatchers may lay just 2-3 broods per season compared to 3-4 broods for willow flycatchers. The longer-lived Acadian flycatchers appear to put more effort into fewer broods.
Table 4. Comparison of Nesting Habits
| Willow Flycatcher | Acadian Flycatcher |
|---|---|
| Nest low in shrubs and small trees | Nest high in mature forest trees |
| Nest close to wet soil or water | Nest in tree fork against trunk |
| Loose, open cup nest | Sturdy, compact cup nest |
| Concealed in thick low vegetation | More exposed in tree canopy |
| 3-4 broods per season | 2-3 broods per season |
Eggs and Young
The eggs and young of willow and Acadian flycatchers also show some subtle differences that reflect their divergent breeding habitats.
Willow flycatcher eggs are creamy white with dense fine brown speckling across their surface. The speckled pattern helps camouflage the eggs against vegetation in their concealed nests sites.
Acadian flycatcher eggs are white but feature reddish-brown blotching instead of fine speckles. This bolder blotched pattern stands out more against the nest material instead of vegetation.
Both species incubate their eggs for around two weeks. Willow flycatcher chicks leave the nest at 14-15 days old. Acadian flycatchers fledge slightly faster at 13-14 days after hatching.
The nestlings of both species have fluffy down, pink skin, and an obvious gape at the corner of the mouth for feeding. But Acadian flycatcher chicks tend to be more robust and chunky compared to the thinner willow flycatcher young.
Since Acadian flycatchers produce fewer broods per year, the survival of each chick to fledging is more critical. Their stout build may promote resistance to weather and predators in their more exposed high nest sites.
Table 5. Comparison of Eggs and Young
| Willow Flycatcher | Acadian Flycatcher |
|---|---|
| Creamy white eggs with brown speckles | White eggs with reddish-brown blotches |
| Speckled pattern camouflages eggs | Blotched pattern stands out against nest |
| Chicks fledge at 14-15 days | Chicks fledge at 13-14 days |
| Thinner nestlings | Chunkier, more robust nestlings |
Conservation Status
Despite some similarities, willow and Acadian flycatchers have experienced very different population trends in modern times.
Acadian flycatchers remain common and widespread across their historic range in eastern North American forests. Their population increased between 1966 and 2015, according to the North American Breeding Bird Survey. They are evaluated as a species of Least Concern by the IUCN.
Willow flycatchers have declined more severely, particularily in the Southwest. Loss of riparian habitat to dams, water diversion, and development reduced their nesting sites. Livestock overgrazing has also degraded wet meadow breeding areas. They have lost an estimated 15% of their population between 1966-2015. Willow flycatchers are considered a Sensitive Species by the U.S. Forest Service.
Ongoing conservation programs aim to protect and restore critical wetland and riparian habitats across the willow flycatcher’s range. Careful water management and responsible livestock grazing practices can maintain their preferred nesting areas. With cooperation from public and private landowners, stable willow flycatcher populations can still thrive.
Table 6. Comparison of Conservation Status
| Willow Flycatcher | Acadian Flycatcher |
|---|---|
| 15% population decrease since 1966 | Population increased since 1966 |
| Sensitive Species status | Species of Least Concern |
| Habitat loss to development | Common in eastern forests |
| Vulnerable to cattle grazing | Adapted to suburbs and parks |
Conclusion
While willow flycatchers and Acadian flycatchers appear very similar at first glance, a closer look reveals interesting differences in their breeding biology and habitat preferences. Paying attention to their voice, plumage, nest placement, egg patterning, and even chick appearance can help distinguish these birds. Conservation efforts for the declining willow flycatcher focus on protecting wetland habitats in the West, while Acadian flycatchers remain secure across eastern forests. Careful management and appreciation of both species will allow birders to enjoy these vocalizing flycatchers across North America.
