Appearance

Pearly-breasted Conebill is a small bluish gray tanager of Cecropia-dominated woodland on old river islands. It is largely medium gray above and slightly paler gray below, with pale brown eyes, a dark gray, sharply pointed bill, and pinkish tarsi and toes. The sexes are similar. Juveniles are olive above and dusky yellow bellow.

Pearly-breasted Conebill is very similar to Bicolored Conebill (Conirostrum bicolor) in plumages, song, and habitat, and it can be found with that species at many sites. Pearly-breasted differs from Bicolored primarily in having evenly gray underparts, lacking any cream or buff tones. Juveniles of the two species are nearly identical, however, and are best identified by the accompanying adult. The song of Pearly-breasted is generally faster, more jumbled, and higher pitched than the song of Bicolored. The call of Pearly-breasted is a short and simple high-pitched seeet note, differing from the bi-syllabic call of Bicolored. Bicolored also gives a short buzzy call, but it is not known whether Pearly-breasted gives an analagous vocalization.

Chestnut-vented Conebill (Conirostrum speciosum) is more common in varzea forest, but overlaps locally with Pearly-breasted in river edge scrub. Males are much darker overall and have chestnut vents, while females are green on the back and wings, with a bluish gray crown and buffy gray underparts (Schulenberg et al. 2007).

Pearly-breasted Conebill potentially could be confused with females of the larger Hooded Tanager (Nemosia pileata), which also occurs in river edge Cecropia woodland, but note the larger size, bicolored bill, paler legs, and white supraloral spot of the tanager (Schulenberg et al. 2007).

Description of the type specimen, an adult male, from Holt (1931): "Upper parts uniform blue-gray, approximately between clear green-blue gray, and deep green-blue gray ... remiges blackish, margined externally with the color of the back, internally with whitish; under parts near light gull gray (though a trifle more bluish perhaps) becoming almost pure white on middle of belly and under tail coverts; upper surface of tail like back, under surface dusky grayish".

Specimens of adults at the Louisiana State University Museum of Natural Science match the above description well, but show variation in the color of the lower belly, with some individuals tending towards a creamy buff.

The juvenile is apparently identical to juvenile Bicolored Conebill (Conirostrum bicolor) (Schulenberg et al. 2007). The following description is from a specimen of a juvenile Bicolored Conebill: pale olive above, including the crown, nape, back, rump, and edges to the remiges; auriculars and underparts dusky lemon yellow, fading to pale yellow on the vent.

Limited information. Of the seven adult specimens at the Lousiana State University Museum of Natural Science (date range: 30 June - 11 August, all from Peru), none are in wing feather molt, three were undergoing assymetrical tail molt, and only one was undergoing body molt.

Given that there is no seasonal variation in the adult plumage, there is likely no alternate plumage. It is unknown whether there is a Formative plumage. Pearly-breasted Conebill follows either a Simple Basic Strategy or a Complex Basic Strategy. See Wolfe et al. (2010) for more information on molt cycles.

Data from specimens at the Louisiana State University Museum of Natural Science.

Adult (n = 7):

Iris: pale brown to tan

Tarsi and toes: pale horn to pinkish flesh

Bill: maxilla dark gray to black; mandible pale gray to gray

Juvenile: bare part colors undescribed

Data from specimens at the Louisiana State University Museum of Natural Science, unless otherwise noted. Average (mean) measurement is listed in parantheses. The sample size is 7 adults (5 males, 2 females). Measurements of male and females are given together ("adults"), followed by each separately. Measurements of juveniles are unknown.

Total length: 11.5 cm (Schulenberg et al. 2007), 12 cm (van Perlo 2009)

Mass:

adult: 12 - 14 g (12.9 g); adult male: 12 - 13.5 g (12.8 g); adult female: 12.5 - 14 g (13.3 g)

Linear measurements:

wing length (chord):

adult: 61.6 - 66.9 mm (64.1 mm); adult male: 61.6 - 66.9 mm (64.3 mm); adult female: 62.2 - 65.0 mm (63.6 mm)

tail length:

adult: 46 - 49 mm (47.4 mm); adult male: 46 - 49 mm (47.8 mm); adult female: 46 - 47 mm (46.5 mm)

tarsus length:

adult: 16.2 - 20.8 mm (18.1 mm); adult male: 16.2 - 20.8 mm (18.0 mm); adult female: 17.1 - 19.5 mm (18.3 mm)

bill length (nares to tip):

adult: 7.7 - 8.5 mm (8.1 mm); adult male: 7.7 - 8.5 mm (8.2 mm); adult female: 7.9 mm