The Least Flycatcher (Empidonax minimus) is a small songbird found throughout much of North America. It is best known for its distinctive call, which sounds like “che-bek” or “che-bunk.” This call is often described as sounding like a squeaky gate or the words “cheap suit.” The Least Flycatcher uses its call to establish breeding territories and attract mates in the spring and summer. Understanding the details of this species’ iconic vocalization can provide clues into its ecology and behavior.
Description of the Call
The Least Flycatcher’s call is a two-note “che-bek” or “che-bunk” vocalization made by males during the breeding season. The first note “che” is high-pitched and loud, while the second note “bek/bunk” is lower-pitched and sometimes described as sounding like a hiccup. The entire call lasts about a quarter of a second. It is repeated steadily every 1-2 seconds, sometimes up to 20 times a minute. The call carries up to 300 yards in ideal conditions. It is mostly heard from dawn to mid-morning and again from late afternoon until dusk on breeding territories.
Regional Variations
There are some subtle regional dialects in the Least Flycatcher’s call. Western populations have a more clipped and sharp “che-bek,” often sounding more like “chep-bek.” Eastern populations tend to have a more drawn-out slurred call that sounds more like “cheee-bunk.” Some ornithologists can even identify if an individual is from the far eastern or western parts of the range by slight variations in the call. However, the general pattern remains consistent throughout their breeding range.
Individual Variation
While the Least Flycatcher has a stereotypical call, each individual male has a unique version that varies slightly in pitch, tone, volume, and rhythm. These minor variations make it possible for birds to distinguish specific individuals by call alone. Females can likely identify their mates by call. The ability to recognize other individuals is important for both territorial defense and mate recognition in the dense habitats this species breeds in.
Nestling Begging Calls
Nestling Least Flycatchers give a different call while begging for food from parents. This is a constant, loud, rhythmic peeping or cheeping, given at a rate of about 3-6 calls per second. The call increases in speed and urgency as a parent approaches the nest with food. It provides crucial auditory cues to guide the parents to the nestlings.
When and Why the Call is Given
Territory Establishment
Male Least Flycatchers sing their “che-bek” call most actively between early May and mid-June during territory establishment and pair formation. The persistent calling advertises that a territory is occupied to other males and helps attract females. Both members of a pair may use the call to communicate and maintain contact in dense habitat where they can’t always see each other.
Mate Attraction
Persistent “che-bek” calling also helps males attract and court females. Unpaired males call almost constantly on arrival at breeding sites hoping to lure females to inspect potential nesting habitat. The rate and repetition of calling indicates male fitness. Females prefer males with robust and consistent calling rates.
Territorial Defense
Males vigorously call when defending territories from incursion by other males. Calling escalates during boundary disputes and encounters between neighboring birds. The resident bird will call persistently until the intruder retreats. Both males and females participate in defensive calling.
Communicating With Mate
Paired birds use the call to maintain contact with their mate during the breeding season. This is important in dense habitats where they can easily lose sight of each other. Frequent contact calling allows them to coordinate activities like nest building, incubating, and feeding young.
Distraction Displays
When disturbed near the nest, Least Flycatcher adults will sometimes feign injury to lure potential predators away by fluttering on the ground while calling loudly. These distraction displays are accompanied by incessant “che-bek” calling and help divert threats from the nest.
Acoustics and Structure of the Call
Frequency
The Least Flycatcher’s call covers a wide frequency band. The first “che” note ranges from about 5 to 8 kilohertz. The second “bek” note covers 2 to 4 kilohertz. This makes the call very high-pitched to human ears. The wide frequency range and complex harmonics help the call carry through dense foliage.
Amplitude and Volume
The “che” note is louder than the “bek”, reaching up to 90 decibels at close range. By comparison, normal human conversation is about 60 decibels. The second note is softer, around 78 decibels. This combination of one loud and one soft note gives the call its distinctive rhythm.
Speed and Cadence
The Least Flycatcher’s call is a short, clipped vocalization. Each 2-note call lasts about a quarter of a second. Males can repeat the call at an impressive rate of up to 20 calls per minute during the height of territory defense and mating activities. The cadence is generally slower during less intense daily communication.
Voicebox Anatomy
The Least Flycatcher has specialized syrinx anatomy in its voicebox to produce its call. The syrinx is where airflow from the lungs is converted into sound through vibrations. Muscles surrounding the syrinx allow birds to control sound frequency and volume. This level of control enables the unique notes of the Least Flycatcher’s call.
Habitats Where the Call is Heard
Deciduous Forests
The classic ringing “che-bek” is most associated with deciduous forest fragments across eastern North America. Territories are carved out among maple, beech, oak, aspen, and birch trees. The call echoes through these leafy woods each spring.
Coniferous Forests
In the western mountains, the Least Flycatcher breeds in open coniferous forests dominated by firs, spruces, and pines. The calls ring through high elevation montane habitats. The notes may sound sharper as they reflect off conifers.
Forest Edges and Openings
Least Flycatchers often place their territories along forest clearings, meadows, and shorelines. Nesting in cluster of trees bordering openings provides ample food sources. Their calls ring out from small groves and lines of trees in open areas.
Orchards and Farmland
This species has adapted to nest in orchards, hedgerows, and scattered trees in agricultural areas. The “che-bek” call can be heard from lone deciduous trees in the middle of crop fields or pastures.
Urban and Suburban Parks
The Least Flycatcher nests in neighborhood parks and other urban green spaces with adequate broadleaf tree cover. Its persistent call is a regular soundtrack of small urban nature preserves during spring.
Abandoned Fields
Early successional overgrown fields with scattered saplings are another preferred nesting habitat. Expect to hear the Least Flycatcher’s call from fence posts and young trees reclaiming abandoned agricultural areas.
Identification Tips
Similar Species
Several other flycatchers with two-note calls could potentially be confused with the Least Flycatcher, including:
– Alder Flycatcher: Call is a “pip-bek” instead of “che-bek” with a much shorter first note.
– Willow Flycatcher: Call is a “fitz-bew” and lower-pitched.
– Western Wood-Peewee: Call is a rising “pee-yer” two syllables of nearly equal length.
– Eastern Wood-Peewee: Call is a melancholy descending “pee-ah-weeee” three syllables instead of two.
Behavioral Cues
In addition to call differences, watching behavior can aid identification:
– Least Flycatchers sit very upright and elevate their crest during calling.
– They prefer isolated perches like fence posts and will flycatch from low exposed spots near openings.
– Their flying style is abrupt and darting with sudden changes in direction.
Visual Differences
When seen well, Least Flycatchers can be identified by:
– Small size and large head giving a very rounded head profile.
– Gray overall plumage with olive-gray back, gray head, and pale gray underparts.
– Two pale wingbars formed by whitish edges to the wing feathers.
– Long tail that often bobs up and down.
Nesting and Reproduction
Nest Sites
Least Flycatchers build small cup nests in upright forks of branches 6-50 feet high in trees or shrubs. Nests are made of grasses, bark strips, twigs, lichens, and lined with finer grass and sometimes hair. Favorite nest trees include maples, alders, aspens, and beech.
Eggs
Clutches contain 3-5 white eggs with brown and lavender spotting. The eggs measure about 0.7 x 0.5 inches. Only the female develops a brood patch and incubates the eggs for around 14 days.
Nestlings
Both parents feed the nestlings with insects like flies, beetles, moths, caterpillars, and spiders. Nestlings fledge at 14-17 days old but remain dependent on parents for 2-3 more weeks. The demanding begging calls stimulate adults to find adequate food.
Double Brooding
Least Flycatchers are prone to raising two broods per season. After fledging the first clutch in early summer, they will often build a new nest and lay more eggs while the first brood is still dependent on them. The male continues caring for the first brood while the female incubates again.
Diet and Foraging
Major Prey
Least Flycatchers are insectivores that favor small flying insects with a focus on:
– Flies
– Midges
– Mosquitoes
– Flying ants and termites
– Beetles
– True bugs
– Moths and butterflies
– Spiders
Aerial Foraging
They hunt flying insects by sallying out from an exposed perch to capture prey in mid-air. Perches less than 5 feet up allow them to quickly launch at passing insects. They also sometimes hover-glean insects from foliage.
Hawking Style
Their flying style appears erratic and frantic, with rapid turns and zig-zagging flight paths as they chase down insects. They can often catch several insects from one perch before returning.
Ground Foraging
Least Flycatchers sometimes drop to the ground after flying insects or to pick up winged ants and termites during mating flights. About 15% of their foraging occurs on the ground.
Migration
Winter Range
Least Flycatchers winter primarily in Mexico, Central America, and northern South America. They occupy humid tropical forests, woodlands, and shrublands.
Migration Timing
They migrate at night and travel alone outside of the breeding season. Spring migration occurs from mid-April to late May. Fall migration is from late August through September. The route covers 4,000 miles between breeding and wintering grounds.
Migration Strategy
It is estimated the tiny Least Flycatcher makes the entire southerly migration in relatively few long-distance overnight flights. They can fly 200-300 miles per night by riding air currents and avoiding barriers like deserts and oceans.
Conservation Status
Population Trends
Least Flycatcher populations are declining across their range. Breeding Bird Survey data shows a survey-wide decrease of 1.4% per year from 1966-2015 resulting in a cumulative loss of 51% over 50 years.
Threats
Habitat loss on both the breeding and wintering grounds is the major threat. Forest fragmentation, urbanization, and increasing agriculture reduce nesting sites. Deforestation of wintering grounds in the Neotropics removes essential habitat.
Current Status
The Least Flycatcher has an extensive range and is still fairly common, though declining. Its global population is estimated at 68 million individuals. Due to the large range and population size, its conservation status is Least Concern. Local declines are a concern and require ongoing monitoring.
Significance of the Call
Defines Breeding Season
The resounding “che-bek” call is a quintessential sound of spring in northern forests. It advertises the start of breeding activities each year after migrating to nesting sites.
Stakes Territory
The persistent call declares that a breeding territory is occupied. It forms the acoustic centerpiece of defended nesting areas for mating and raising young.
Attracts a Mate
A vigorous dawn chorus of “che-bek” calls is one of the most important ways male Least Flycatchers attract females for pairing. Calling persistence indicates male fitness.
Facilitates Courtship
The call allows males and females to locate potential partners. Copulating pairs will call back-and-forth to each other. The call is part of courtship rituals before breeding.
Strengthens Pair Bonds
Mated birds continue calling to maintain contact and coordinate breeding activities like building nests, incubating eggs, and feeding young. Vocal responses keep pairs connected.
Defends Nest Sites
Both members of a pair use the call to defend the territory containing nests and young. Calling accelerates during boundary disputes or when predators approach active nests.
Appreciating the Call
Learn the Call
Make an effort to learn the Least Flycatcher’s distinct call by listening to recordings and verifying it in the field. Keying in on this vocalization opens up a new layer of spring’s dawn chorus.
Add to Life Lists
Keep a running life list of all bird species you detect by sight and sound. Include the Least Flycatcher once you recognize its call to document your ability to identify it by ear alone.
Volunteer to Survey
Participate in volunteer bird survey projects that monitor Least Flycatcher populations and distribution. Surveys based on the call provide valuable data to guide conservation.
Visit Flycatcher Habitats
Immerse yourself in the sights and sounds of Least Flycatcher breeding habitat during spring mornings when the call is most frequent. State parks, nature preserves, and rural towns offer access.
Join Birding Groups
Connecting with local birding and ornithology groups provides community, shared knowledge, and access to choice birding locations. Take advantage of group field trips and talks.
Contribute to Science
Report interesting Least Flycatcher observations through online citizen science portals. Scientific data repositories welcome bird call recordings, nesting records, population surveys, and documentation of range shifts.
Support Conservation
Help preserve essential breeding habitat by donating to land trusts and environmental nonprofits working to establish protected reserves and manage mature forests.
Conclusion
The Least Flycatcher’s iconic “che-bek” call is a central component of the spring soundscape across much of North America. Learning to identify this vocal hallmark opens up awareness and appreciation of the ecology and behavior of the species. Recognizing the call can also aid larger conservation efforts to track populations and protect critical forests for the future. Whether birding in local parks or remote wilderness, listening for the Least Flycatcher is a rewarding way to connect with nature and monitor environmental change.