MacGillivray’s warbler (Geothlypis tolmiei) is a small songbird found in western North America. It is named after William MacGillivray, a Scottish ornithologist who first described the species in 1852. MacGillivray’s warbler is known for its distinct vocalizations, with a song that is often described as loud, clear, and musical. The species’ call is an important identifier and plays a key role in defending territory and attracting mates during the breeding season.
Physical Description
MacGillivray’s warbler is a relatively petite warbler, measuring 11-13 cm in length with a wingspan of 15-18 cm and weighing 8-12 grams. Males and females have similar plumage, with olive-gray upperparts, pale yellow underparts, and white crescents above and below the eye. The wings and tail are gray with two white wing bars. The bill is short and pointed. Juveniles resemble washed out versions of the adults.
Range and Habitat
The breeding range of MacGillivray’s warbler extends from British Columbia through the western United States to Baja California. It winters primarily in Mexico and Central America. This warbler inhabits riparian thickets near streams and wetlands, preferring areas with willows, cottonwoods, and alders. It is found in mountain forests up to about 9,000 feet in elevation.
Diet
MacGillivray’s warbler is primarily insectivorous, gleaning insects and spiders from foliage or making short flights to capture prey. Its diet consists mainly of caterpillars, moths, beetles, true bugs, ants, bees, wasps, and flies. This species will occasionally eat berries and seeds as well.
Nesting
The breeding season for MacGillivray’s warbler runs from May through July. Males establish breeding territories and sing to attract females. The nest is an open cup built by the female, made of grasses, bark strips, spiderwebs, and lined with fine materials. It is constructed low in a shrub or small tree, 1-6 feet above ground.
Clutch Size and Incubation
The clutch size is 3-5 eggs, which are creamy white with brown speckles. The female incubates the eggs for 12-14 days. Both parents feed the hatchlings, which leave the nest at 10-12 days old. MacGillivray’s warbler may raise two broods per season.
Song and Calls
The song of MacGillivray’s warbler is a rapid, buzzy trill described as “zu-zu zee zee zoo zee.” It is loud, high-pitched, and musical. Songs are delivered from an exposed perch to advertise the male’s territory and attract a mate. Both sexes sing, but the male’s song is longer and more complex.
Here are some key details about the calls:
Song Call
– Loud, clear, ringing
– High-pitched and musical
– Complex, hurried trill
– Sounds like “zu-zu zee zee zoo zee”
– Given frequently by males during breeding season
– Serves territorial advertisement and mate attraction
Call Notes
– Short, buzzy “beep”
– Sharp “pit” or “chit”
– Abrupt, rising “zreet”
– Softer, flat “dit”
– Used by both sexes year-round
– Serves communication between mates and flock members
Alarm Call
– Harsh, raspy “tzek”
– Drawn-out “zeeee”
– Signals disturbance or threat
– Stimulates flock to be alert and take cover
Call Type | Description | Purpose |
---|---|---|
Song | Loud, clear, hurried trill “zu-zu zee zee zoo zee” | Territory advertisement, mate attraction |
Call notes | Short “beep”, “pit”, “chit”, soft “dit” | Communication between flock members |
Alarm call | Harsh “tzek”, drawn-out “zeeee” | Signals disturbance or threat |
Identification Tips
Here are some tips for identifying MacGillivray’s warbler based on vocalizations:
– Listen for the loud, ringing, hurried trill song – this is diagnostic for the species.
– Note the variety of sharp, buzzy call notes used for communication.
– Pay attention to alarm calls like “tzek” or “zeeee” which indicate the birds are agitated.
– Learn the common birdsongs in the habitat and distinguish the MacGillivray’s warbler by its unique vocalizations.
– Use the song to detect MacGillivray’s warblers and then try to spot them moving through bushes.
– Notice singing males perched upright and conspicuous at the tops of shrubs and trees.
Sound Clips of Songs and Calls
Here are some video/audio clips that provide examples of MacGillivray’s warbler vocalizations:
[Song clip]
[Call notes clip]
[Alarm call clip]
Listen for these vocalizations when you are birdwatching in appropriate habitat during spring and summer to detect MacGillivray’s warblers. With practice, you’ll be able to distinguish this species by ear.
When are the Vocalizations Heard?
MacGillivray’s warblers vocalize most actively during the breeding season from May to July.
– Males sing constantly during this time to advertise territories and attract mates.
– Song activity peaks at dawn and dusk when more males are singing.
– Short call notes are exchanged between mates while nesting and feeding fledglings.
– Alarm calls may be heard when disturbed near the nest.
Outside of breeding season, MacGillivray’s warblers are less vocal but may still make call notes year-round, particularly during migration and on the wintering grounds. Overall, vocalizations are most prominent and reliable for identification during spring and summer.
Variation and Dialects
The songs of MacGillivray’s warblers are relatively consistent across their range, with minimal geographic variation or dialects noted. However, there can be some individual variation in songs:
– Number of introductory notes may vary from 2-6 notes.
– Trill speed and pitch can vary slightly.
– Some males sing shorter, simpler songs lacking trills.
– Songs can vary by amplitude and frequency modulation.
Despite these minor variations, the general structure and buzzy, hurried trill quality remains stable allowing the song to be recognized over the species’ entire breeding distribution.
Partnerships and Interactions
Male MacGillivray’s warblers may interact and sing together in a form of countersinging, where the song of one bird stimulates another nearby male to sing in response. This behavior helps establish territory boundaries and signal intruders.
Interactions with other species include:
– Mobbing owls or hawks with alarm calls when detected.
– Being parasitized by brown-headed cowbirds who lay eggs in warbler nests.
– Competing for nest sites and resources with other warblers.
– Benefiting from nest association with rufous hummingbirds that may help defend against predators.
Evolutionary History
MacGillivray’s warbler belongs to the wood-warbler family Parulidae, originating in the New World. This group arose approximately 22 million years ago and radiated rapidly to fill a variety of ecological niches. The genus Geothlypis evolved around 5 million years ago and consists of six species today including MacGillivray’s warbler.
Warbler songs likely originally evolved for territory defense. But over time, sexual selection shaped them into the complex, buzzy trills of MacGillivray’s warbler and relatives which play a key role in attracting mates in dense, obscured habitats. The song’s carrying power and high frequency penetrates vegetation and enables effective communication.
Threats and Conservation
MacGillivray’s warbler has a large range and population, estimated globally at 1.5 million birds. Its numbers are declining but the species is still considered of Least Concern by the IUCN. Potential threats include:
– Habitat loss and degradation, particularly of riparian areas
– Effects of climate change on stream flows and vegetation
– Competition with other warblers for nest sites
– Brood parasitism by brown-headed cowbirds
Conservation measures include protecting key breeding habitat, managing cowbird populations, and further monitoring of numbers. Maintaining healthy riparian areas will be important for the future of MacGillivray’s warbler and other species.
Conclusion
The song and calls of MacGillivray’s warbler are integral to its breeding biology and survival. This species uses its loud, buzzy vocalizations to attract mates and defend territories in dense riparian habitats across western North America. Distinguishing features of its song include the hurried, trilled structure, high pitch, and ringing carrying quality that enables effective communication through vegetation. Variation is minimal across the warbler’s range and songs are most prominent during the spring breeding season. By learning MacGillivray’s warbler’s diagnostic song patterns, birdwatchers can detect the presence of this species in appropriate habitat even without seeing the birds. Conserving riparian ecosystems will be crucial for maintaining viable populations of this vocal warbler into the future.