Connecticut Warbler Oporornis agilis Scientific name definitions

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



Walking, Running, Hopping, Climbing, etc.

Often walks on the ground or among branches in dense thickets, unlike Mourning Warbler (Geothlypis philadelphia) and MacGillivray's Warbler (Geothlypis tolmiei), which hop (215). Movements are very bouncy; the tail is raised and lowered rapidly, reminiscent of wrens and Spotted Sandpiper (Actitis macularius) (JP). Territorial males stride along horizontal limbs very much like an Ovenbird (Seiurus aurocapilla) (F. Gill and D. O'Brien, personal communication).


Flapping flight is similar to Mourning Warbler and MacGillivray's Warbler; it flies deftly among branches above ground (JP).

Swimming and Diving

Not known to occur.


Preening, Head-Scratching, Stretching, Sunbathing, Bathing, Anting, etc.

Information needed. Preening not described in detail, but see video below.

Sleeping, Roosting

Information needed.

Daily Time Budget

Information needed.

Agonistic Behavior

Physical and Communicative Interactions

Information needed.

Territorial Behavior

Information needed. Male is highly territorial during summer and establishes and defends breeding territory (216, JP). Territory size ranged from 0.24 ha in open-canopy spruce forest to 0.48 ha in closed-canopy spruce forest in Minnesota (based on data from Niemi and Hanowski [217]). The average home range size for males (3.05 ha) was significantly larger than that for females (1.29 ha) (75).

Sexual Behavior

Mating System and Operational Sex Ratio

Information needed.

Courtship, Copulation, and Pair Bond

Information needed.

Extra-Pair Mating Behavior/Paternity

Information needed.

Brood Parasitism of Conspecifics

Not known to occur.

Brood Parasitism of Other Species

Not known to occur.

Social and Interspecific Behavior

Degree of Sociality

The Connecticut Warbler is not considered a social species, but families may join together to form small flocks of up to 25 birds before fall migration (7). It is reportedly solitary on overwintering grounds (197, 10), but pairs have been noted in fall migration (e.g., see video in Self-Maintenance).

Nonpredatory Interspecific Interactions

Information needed. Kells (83) described a territorial fight with a Red-eyed Vireo (Vireo olivaceus) in Ontario in which the Connecticut Warbler sang and uttered call notes while being chased by the vireo in low thickets. It is known to participate in multi-species feeding flocks on the breeding grounds from mid to late summer in the southern boreal mixed-wood forest of Saskatchewan (218). During fall migration, it was infrequently observed within mixed-species flocks of fall migrant songbirds in central Pennsylvania (219), and was observed feeding with Blackpoll Warbler (Setophaga striata), 20 m above ground in large willows (Salix) (111). During migration in Puerto Rico, it was observed foraging for caterpillars (Noctuidae) with Shiny Cowbird (Molothrus bonariensis), Greater Antillean Grackle (Quiscalus niger), Yellow-shouldered Blackbird (Agelaius xanthomus), Yellow-billed Cuckoo (Coccyzus americanus), and Venezuelan Troupial (Icterus icterus). Tropical residents were reported to be dominant over Connecticut Warbler on overwintering grounds (198).


Kinds of Predators

Information needed. In Quebec, 2 of 7 nests were depredated by unidentified predators, but an Eastern Chipmunk (Tamaias striatus) was suspected to be responsible for at least one of the nests (27). A first-fall (Formative Plumage) male was predated by a domestic cat (Felis catus) in early November from southern Maine (144).

Manner of Predation

Information needed.

Response to Predators

The female is very secretive near its nest, skulking low in underbrush in the presence of predators or intruders (7). Both parents respond to intruders near the nest with harsh scolding witch notes; parents may react directly to the presence of a predator or may be summoned by the distress notes of fledglings and nestlings (83). The female scolds intruders from perches 6 m high in trees near the nest; scolding may last 30 min (213).

Adults feign injury to distract predators from the nest (10); a bird holds its wings up and stretched out from the body. Running is another distraction display near the nest. It is very wary of potential predators; it may retreat from exposed perches to several different perches in thick foliage to observe intruders (7).

A fall migrant was attracted to a recording of Black-capped Chickadee (Poecile atricapillus) individuals mobbing an owl at the Parker River National Wildlife Refuge in Newburyport, Massachusetts, leading Ralph et al. (220) to conclude that the Connecticut Warbler is able to detect predators by recognizing anti-predator vocalizations of chickadees.

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