Bicknell's Thrush

The Bicknell's thrush, Catharus bicknelli, is a medium-sized thrush, measuring approximately 17.5 cm in length and weighing around 28 grams. This bird is one of North America's rarest and most localized songbirds, with a breeding range confined to the northeastern part of the continent. It is distinguished by its olive-brown to brownish upperparts and chestnut-tinged tail, with less contrast in worn plumage. The underparts are off-white with a grayish flank and a breast showing dusky spots. Notable features include pink legs, a faint grey eye ring, and a two-toned bill with a yellow lower mandible and a blackish tip.

Identification Tips

In the field, both sexes appear identical and are roughly the same size, though males may have slightly longer wings. The Bicknell's thrush can be identified by its olive-brown upperparts, off-white underparts with a buffy wash, and dusky spots on the breast. The tail has a subtle chestnut tinge, and the bird sports a faint grey eye ring and grey cheeks. The bill is two-toned, with a yellow base and a blackish tip.

Habitat

Bicknell's thrush is a habitat specialist during the breeding season, favoring high-altitude coniferous forests affected by strong winds and heavy ice conditions, typically nesting above 915 meters. It also inhabits successional forests recently affected by the forest industry. In contrast, during migration, it becomes more of a habitat generalist.

Distribution

The breeding range of Bicknell's thrush extends from southeastern Quebec to Nova Scotia in Canada and includes the sky islands of northern New England and the Adirondacks and Catskills in New York. During winter, the species migrates to the Greater Antilles, with the majority wintering in Hispaniola.

Behaviour

Bicknell's thrushes exhibit polyandry, with females mating with multiple males. Multiple males may contribute to nestling care. They forage on the forest floor and in the foliage for insects and wild fruits, altering their foraging height based on their diet.

Song & Calls

The male Bicknell's thrush, and occasionally the female, vocalizes a flute-like song composed of four phrases, ending on a higher note. The primary call is a downward whistle known as the "Beer call." Other calls include a growl call in alarm situations and a flight call.

Breeding

Females build a bulky cup nest made of twigs and moss near the trunk of a conifer. They lay three to four eggs per clutch, with an incubation period of about two weeks. Nestlings are fed by both parents and develop rapidly, reaching adult size in 12 days.

Diet and Feeding

The diet of Bicknell's thrush primarily consists of insects, such as beetles and ants, and wild fruits from late summer onwards. They forage on the forest floor and in the foliage, employing various techniques including pausing and peering, hopping, short flights, and sometimes scratching the ground.

Conservation status

Bicknell's thrush is classified as Vulnerable by the IUCN and Apparently Secure by NatureServe. Population monitoring indicates declines in some areas, with habitat degradation and climate change posing significant threats. Conservation efforts include habitat management and reforestation to protect this species.