Connecticut Warbler Oporornis agilis Scientific name definitions

Jay Pitocchelli, Julie L. Jones, and David C. Jones
Version: 2.0 — Published June 2, 2023

Sounds and Vocal Behavior


The male Connecticut Warbler has a loud, clear primary song with a jerking rhythm that is presumably used to attract females on breeding grounds and advertise territory ownership. There is also a more complex extended song whose function remains unknown. Several different calls make up the rest of the vocal repertoire, including the zeep call used during migration.



Information needed.

Vocal Array

Song. Figure 2A . A loud, ringing song in which a two-part or (more typically) three-part phrase is repeated several times in a row. Songs of this species vary considerably among males. Some songs are choppy with rapid acceleration, and reminiscent of Northern Waterthrush (Parkesia noveboracensis), whereas others are similar in rhythm and pitch to that of Kentucky Warbler (Geothlypis formosa) or Ovenbird (Seiurus aurocapilla). Various descriptions of the song have been published: beecher-beecher-beecher-beecher-beecher-beecher (200); fru-chapple fru-chapel fru-chapel whoit (201); whip-pity whip-pity whip (7); chap-el-free chap-el-free chapel-free-chap, chuckety chuckety chuckety chuck, chipety chipety chip (202); and tu-chibee-too chibee-too chibee-too (203). Song is described as building in emphasis "from weaker first notes to more emphatic ones at middle and end" (202). Bent (7) described a variation of the song that includes four-part phases.

The first detailed spectrographic analysis of songs has been recently conducted by Bergeron (204) and Hannah et al. (205). Bergeron (204) analyzed songs of the Connecticut Warbler in Abitibi and Lac-Saint-Jean, Quebec. She found extensive inter-individual variation and that this variation could be reliably used to identify individuals. The characteristics of song that best distinguish individuals were song duration, average frequency, maximum frequency, minimum frequency, and number of note types per song. Based on these results, she suggested using voice identification as an alternative tool to intrusive techniques such as color marking for studying the ecology, demography, and management of this species.

Extended Song. The first example of an extended song was recorded by Plastino et al. (206) using autonomous recording units in northwestern Ontario. Extended songs of New World warblers are typically a combination of syllables from the species’ primary song mixed with additional notes and syllables. It is usually sung in flight or under low-light conditions (207). Extended songs of the Connecticut Warbler were recorded most often around sunset and much less often near sunrise. An extended song contained an introductory phrase of atypical song syllables, a middle phrase with the species typical primary song, followed by a concluding phrase of more atypical syllables (206). An extended song lasted an average of 7.10 s (n = 10, range of 2.5–24.5 s) compared to primary songs of 1.37 s (205). These longer songs had more syllables with an average of 14.8 syllables per song and range of 3–33 syllables per song. The function of these songs remains unknown. Plastino et al. (206) speculated that singing these songs at night might avoid masking or vocal interference from other species that sang primarily in the morning.

Plink. Several call notes described in the literature include: a sharp peek or witch, a metallic plink (from 7), and a softer poit call (208). Gives peek, plink, and witch calls while scolding intruders near fledglings or nest (Figure 2B). Also gives poit call near nest; it may be an alarm call to warn young birds about presence of predators (208). The plink call sometimes grades into zeep call, perhaps especially when highly agitated after playback (209).

Zeep. The zeep call is a buzzy nocturnal flight call the behavioral function of which is unknown. The physical characteristics of the Connecticut Warbler zeep call were (on average): 43 ms duration, minimum frequency 6.8 kHz, maximum frequency 8.3 kHz, and 7.7 peak kHz frequency in the middle portion of call (210). The zeep call of the Connecticut Warbler is very similar to the zeep of several other species including the Bay-breasted Warbler (Setophaga castanea), Yellow Warbler (Setophaga petechia), Blackburnian Warbler (Setophaga fusca), Blackpoll Warbler (Setophaga striata), Magnolia Warbler (Setophaga magnolia), Cerulean Warbler (Setophaga cerulea), Louisiana Waterthrush (Parkesia motacilla) , and Worm-eating Warbler (Helmitheros vermivorum) (210, 211). These species are often lumped together as the zeep group because their calls are so similar that they cannot be reliably separated from each other using statistical analyses or spectrographic cross correlation analyses of the calls (210). Although this zeep call is different from many other species of nocturnal migrants, it should not be used to identify birds down to the species level. Zach et al (211) suggested that the similarity of zeep calls between distantly related species may be due to overlapping migration patterns of species within the zeep complex. They pointed out the similarity in transoceanic migrations between the Connecticut Warbler and the Blackpoll Warbler as possible evidence of convergence of flight calls between these species, but urged caution in interpreting these results because of small sample sizes.

Geographic Variation

Hannah et al. (205) studied geographic variation in song using recordings from multiple sources from the 1950s to the present. Most males sang a simple song composed of one phrase repeated 3–4 times. Each phrase contained 3–4 notes, rarely 2 notes. A summary of the average physical characteristics of songs included: average duration of 1.37 s, average minimum frequency of 1.85 kHz, and average maximum frequency of 5.78 kHz. They described a mosaic pattern of geographic variation in song types with extensive individual variation and no geographic structure. There were 20 different song types on the breeding range (labeled A–T), based on differences between unique notes and phrases. The Type H song was the most common song type and it was found throughout the breeding range. Some rare song types (e.g., C, I, J) were also widely distributed. Only five song types were unique to different regions of the breeding range. Song types D and K were only found in the western region, while G, L, and O were only found in the center of the breeding range. There was evidence that the songs changed over time. Some song types were present over several decades, but other song types from earlier recordings prior to 2000 were not found later in the study. Some new songs appeared that were not present prior to 2000.


Song is heard primarily on breeding grounds and during spring migration (7, 129). The species is nearly silent during fall migration, with call notes uttered infrequently. It rarely sings in the fall, but has been heard singing in late September during fall migration (114, 7). No published information is available on vocal behavior on overwintering grounds, but several recordings exist from Bolivia (xeno-canto, XC121778); these show some plasticity in call type and include examples of plink and zeep calls as well as intergrades between them.

Daily Pattern of Vocalizing

Song activity is greatest early in the morning on breeding grounds (JP). The male begins singing around sunrise or soon after in June and early July in Michigan (25).

The male also sings in the morning during spring migration. Widmann (212) noted that singing peaked during spring migration in Missouri in late morning after other species stopped singing. Trautman (105) heard most males singing from 07:00 to 08:30 during spring migration in Ohio.

Places of Vocalizing

It sings from elevated tree branches; up to 3 m high in mixed tamarack and spruce in Minnesota (13, 208); in Michigan, 6–8 m up in tall trees, with a preference for tamarack (213), approximately 145 m from nest site (25); and in the tops of spruce and aspen during breeding season in Ontario (81). It may sing from the same tree for several hours (213). Height, timing of leaf formation, and habitat affect detection of songs in Alberta. Schieck (214) found songs were most easily detected in white spruce habitat at 50 m and 100 m, regardless of the timing of leaf formation or singing height; song detection decreased in aspen habitat, especially at the 100 m distance in both shrub and canopy layers and after leaf formation. Inability to detect songs is related to higher minimum frequency of songs (> 2.5 kHz).

Sex Differences

The male and female share call notes; no reports of singing by the female.

Repertoire and Delivery of Songs

Single song repertoire; extensive variation among males (see Vocal Array, above). The song is repeated at a regular interval during song bouts (JP). Walkinshaw and Dyer (25) observed two males singing at rate of 6 songs/min; Huff (213) recorded 5-min and 10-min gaps between song bouts. Males sang an average of 27 songs per 15-min period in Quebec, with most of the singing occurring in the morning. Unpaired males sang more often and were heavier than paired males (27). Males were observed feeding between songs (213).

Social Context and Presumed Functions of Vocalizations

Playback of song recordings stimulates aggressive response by males (JP); the songs are presumed to advertise territorial ownership and to attract females on breeding grounds. Songs and calls are also heard during migration, but their function is unknown. See Vocal Array (above) for the behavioral context of call notes.

Nonvocal Sounds

None reported.

Recommended Citation

Pitocchelli, J., J. L. Jones, and D. Jones (2023). Connecticut Warbler (Oporornis agilis), version 2.0. In Birds of the World (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.conwar.02