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.

Development

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 Seton, E. T. (1884). Nest and habits of the Connecticut Warbler. Auk 1:192. Close ); fru-chapple fru-chapel fru-chapel whoit (201 Thompson, E. E. (1891). The birds of Manitoba. Proceedings of the United States National Museum 13:457–643. Close ); whip-pity whip-pity whip (7 Bent, A. C. (1953). Life Histories of North American Wood Warblers. Bulletin of the United States National Museum 203. Close ); chap-el-free chap-el-free chapel-free-chap, chuckety chuckety chuckety chuck, chipety chipety chip (202 Allin, A. E. (1957). Connecticut Warbler. In The Warblers of North America (L. Griscom and A. Sprunt Jr., Editors), Devin-Adair Company, New York, NY, USA. pp. 203–206. Close ); and tu-chibee-too chibee-too chibee-too (203 Harrison, H. H. (1984). The Wood Warblers' World. Simon and Schuster, New York, NY, USA. Close ). Song is described as building in emphasis "from weaker first notes to more emphatic ones at middle and end" (202 Allin, A. E. (1957). Connecticut Warbler. In The Warblers of North America (L. Griscom and A. Sprunt Jr., Editors), Devin-Adair Company, New York, NY, USA. pp. 203–206. Close ). Bent (7 Bent, A. C. (1953). Life Histories of North American Wood Warblers. Bulletin of the United States National Museum 203. Close ) 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 Bergeron, S. (2020). Variabilité du chant de la paruline à gorge grise (Oporornis agilis). M.S. thesis, Université du Québec à Chicoutimi, Chicoutimi, QC, Canada. Close ) and Hannah et al. (205 Hannah, K. C., E. M. Bayne, and N. V. Sanchez (2020). First description of the structure and geographic patterns in the songs of the Connecticut Warbler (Oporornis agilis). Wilson Journal of Ornithology 132:598–607. Close ). Bergeron (204 Bergeron, S. (2020). Variabilité du chant de la paruline à gorge grise (Oporornis agilis). M.S. thesis, Université du Québec à Chicoutimi, Chicoutimi, QC, Canada. Close ) 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 Plastino, K. K. C. Hannah, R. Russell, and J. R. Foote (2022). Hitting all the notes: Connecticut warblers sing an extended song type. Journal of Ornithology. Close ) 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 Spector, D. A. (1992). Wood-warbler song systems: A review of Paruline singing behaviors. Current Ornithology 9:199–238. Close ). 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 Plastino, K. K. C. Hannah, R. Russell, and J. R. Foote (2022). Hitting all the notes: Connecticut warblers sing an extended song type. Journal of Ornithology. Close ). 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 Hannah, K. C., E. M. Bayne, and N. V. Sanchez (2020). First description of the structure and geographic patterns in the songs of the Connecticut Warbler (Oporornis agilis). Wilson Journal of Ornithology 132:598–607. Close ). 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 Plastino, K. K. C. Hannah, R. Russell, and J. R. Foote (2022). Hitting all the notes: Connecticut warblers sing an extended song type. Journal of Ornithology. Close ) 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 Bent, A. C. (1953). Life Histories of North American Wood Warblers. Bulletin of the United States National Museum 203. Close ), and a softer poit call (208 Shanahan, D. (1992). Notes on calls of breeding Connecticut Warblers. Ontario Birds 10:115–116. Close ). 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 Shanahan, D. (1992). Notes on calls of breeding Connecticut Warblers. Ontario Birds 10:115–116. Close ). The plink call sometimes grades into zeep call, perhaps especially when highly agitated after playback (209 Pieplow, N. (2017). Peterson Field Guide to Bird Sounds of Eastern North America. Houghton Mifflin Harcourt Publishing Company, NY, USA. Close ).

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 Landsborough, B. J., J. R. Foote, and D. J. Mennill (2019). Decoding the ‘zeep’ complex: quantitative analysis of interspecific variation in the nocturnal flight calls of nine wood warbler species (Parulidae spp.). Bioacoustics 28:555–574. Close ). 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 Landsborough, B. J., J. R. Foote, and D. J. Mennill (2019). Decoding the ‘zeep’ complex: quantitative analysis of interspecific variation in the nocturnal flight calls of nine wood warbler species (Parulidae spp.). Bioacoustics 28:555–574. Close , 211 Zach, G., R. Simpson, and D. Mennill (2021). The evolution of Wood Warbler flight calls: species with similar migrations produce acoustically similar calls. Evolution 75:719–730. Close ). 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 Landsborough, B. J., J. R. Foote, and D. J. Mennill (2019). Decoding the ‘zeep’ complex: quantitative analysis of interspecific variation in the nocturnal flight calls of nine wood warbler species (Parulidae spp.). Bioacoustics 28:555–574. Close ). 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 Zach, G., R. Simpson, and D. Mennill (2021). The evolution of Wood Warbler flight calls: species with similar migrations produce acoustically similar calls. Evolution 75:719–730. Close ) 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 Hannah, K. C., E. M. Bayne, and N. V. Sanchez (2020). First description of the structure and geographic patterns in the songs of the Connecticut Warbler (Oporornis agilis). Wilson Journal of Ornithology 132:598–607. Close ) 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.

Phenology

Song is heard primarily on breeding grounds and during spring migration (7 Bent, A. C. (1953). Life Histories of North American Wood Warblers. Bulletin of the United States National Museum 203. Close , 129 Granlund, J., G. A. McPeek, and R. J. Adams (1994). The Birds of Michigan. Indiana University Press, Bloomington, IN, USA. Close ). 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 Todd, W. E. C. (1940). The Birds of Western Pennsylvania. University of Pittsburgh Press, Pittsburgh, PA, USA. Close , 7 Bent, A. C. (1953). Life Histories of North American Wood Warblers. Bulletin of the United States National Museum 203. Close ). 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 Walkinshaw, L. H., and W. A. Dyer (1961). The Connecticut Warbler in Michigan. Auk 78(3):379–388. Close ).

The male also sings in the morning during spring migration. Widmann (212 Widmann, O. (1907). A preliminary catalog of the birds of Missouri. Transactions of the Academy of Science of St. Louis. Volume XVII, no. 1. Close ) noted that singing peaked during spring migration in Missouri in late morning after other species stopped singing. Trautman (105 Trautman, M. B. (1940). The birds of Buckeye Lake, Ohio. University of Michigan, Museum of Zoology Miscellaneous Publication 44. Close ) 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 Parmelee, D. F., and R. J. Oehlenschlager (1972). Connecticut Warbler nest in Hubbard County, Minnesota. Loon 44:5–6. Close , 208 Shanahan, D. (1992). Notes on calls of breeding Connecticut Warblers. Ontario Birds 10:115–116. Close ); in Michigan, 6–8 m up in tall trees, with a preference for tamarack (213 Huff, N. L. (1929). The nest and habits of the Connecticut Warbler in Minnesota. Auk 46:455–465. Close ), approximately 145 m from nest site (25 Walkinshaw, L. H., and W. A. Dyer (1961). The Connecticut Warbler in Michigan. Auk 78(3):379–388. Close ); and in the tops of spruce and aspen during breeding season in Ontario (81 Elder, D. H. (1991). Breeding habitat of the Connecticut Warbler in the Rainy River District. Ontario Birds 9:84–86. Close ). It may sing from the same tree for several hours (213 Huff, N. L. (1929). The nest and habits of the Connecticut Warbler in Minnesota. Auk 46:455–465. Close ). Height, timing of leaf formation, and habitat affect detection of songs in Alberta. Schieck (214 Schieck, J. (1997). Biased detection of bird vocalizations affects comparisons of bird abundance among forested habitats. Condor 99:179–190. Close ) 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 Walkinshaw, L. H., and W. A. Dyer (1961). The Connecticut Warbler in Michigan. Auk 78(3):379–388. Close ) observed two males singing at rate of 6 songs/min; Huff (213 Huff, N. L. (1929). The nest and habits of the Connecticut Warbler in Minnesota. Auk 46:455–465. Close ) 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 Saulnier, M-C. (2011). Biologie de la reproduction de la Paruline à gorge grise (Oporornis agilis) dans les pinèdes grises du Lac-Saint-Jean, Canada. M.S. thesis, Université du Québec à Chicoutimi, Chicoutimi, QC, Canada. Close ). Males were observed feeding between songs (213 Huff, N. L. (1929). The nest and habits of the Connecticut Warbler in Minnesota. Auk 46:455–465. Close ).

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.

None reported.