Bicknell's Thrush
A species of American Brown Thrushes and Nightingale-thrushes Scientific name : Catharus bicknelli Genus : American Brown Thrushes and Nightingale-thrushes
Bicknell's Thrush, A species of American Brown Thrushes and Nightingale-thrushes
Botanical name: Catharus bicknelli
Genus: American Brown Thrushes and Nightingale-thrushes
Content
Description General Info
Description
Bicknell's thrush is just slightly smaller than the other northern migratory Catharus thrushes, with an average length of approximately 17 cm (6.7 in) and a weight ranging generally from 26 to 30g. Both sexes are identical in the field and are roughly the same size, although males average slightly larger in wing length. Adults are olive-brown to brownish on the upperparts (head, nape, back) contrasting with chestnut-tinged tail. The contrast is, however, less evident in worn plumage. The underparts are off-white with gray on the flanks; the breast is off-white with buffy wash, showing dusky spots that becomes more diffuse toward the sides and the lower breast. They have pink legs, a faint grey eye ring, and gray cheeks. Two-thirds of the lower mandible is yellow colored, while the tip of the lower mandible and upper mandible is blackish. They average slightly smaller than the very similar gray-cheeked thrush but are all but indistinguishable in outward appearance. Together, gray-cheeked and Bicknell's thrush form a cryptic species pair, and were indeed formerly considered conspecific. The song is a jumbled series of flute-like tones ending on a higher note. 
Size
13 - 23 cm
Life Expectancy
11 years (male), 8 years (female)
Nest Placement
Shrub
Clutch Size
3 - 4 eggs
Incubation Period
1 - 2 broods
Number of Broods
9 - 14 days
Nestling Period
9 - 13 days
Feeding Habits
Bicknell's Thrush's diet primarily consists of insects and other arthropods, with a preference for ants and beetles, supplemented by small fruits when accessible. Their ground foraging is characterized by scratching and vigilant watching, akin to robins. During offspring rearing, they expand their search to the entire forest, capturing a variety of insects and larvae using various techniques, such as gleaning and flycatching. Their diet largely consists of arthropods and is critical for feeding young.
Habitat
Bicknell's Thrush is typically found in montane forests, favoring high-elevation habitats marked by dense balsam fir and various stages of forest regeneration, often resulting from natural disturbances or human activity. These birds show a preference for altitudes ranging widely from 1,500 to 3,600 feet, depending on the region. They thrive in cool, wet climates within thickly vegetated areas rich in undergrowth, along with fallen snags and dead trees. The presence of mossy grounds and stunted tree growth provides the ideal breeding environment for bicknell's Thrush. During migration, bicknell's Thrush looks for similar habitats with abundant food sources like overgrown woodlots rich in invertebrates and fruits. Winter grounds in the Greater Antilles consist of similar wet montane forests.
Nest Behavior
Female bicknell's Thrush selects the nest site and constructs the nest. Nesting activities, such as building and egg-laying, occur in sequence with the breeding season, adhering to species-specific timelines. Both parents engage in caring for the eggs and young, which includes incubation, feeding, and protection.
Nest Characteristics
The nest of bicknell's Thrush is situated typically near a tree trunk within dense balsam fir stands, about 5 feet above ground. It's a cup nest crafted from fir or spruce twigs and moss, with possible inclusions of grass, sedge, fern, leaves, bark, hair, or lichen. It's lined with grasses or horsehair fungus, measuring 4.8 inches wide and 3.4 inches tall, with a 2.7 x 1.8 inches cup.
Dite type
Insectivorous
General Info
Feeding Habits
Bird Feeder Type
Ground
Platform
Behavior
Bicknell's Thrush exhibit a unique sociobiological lifestyle, particularly in their mating practices. While males broadcast their songs over extensive home ranges with incidental overlap, they only occasionally engage in pursuits of other males, differing from conventional avian territorial confrontations. Females are the more territorial gender, aggressively safeguarding their nesting vicinity during sensitive periods of nesting and egg deposition. Moreover, bicknell's Thrush engage in multifaceted mating behaviors unseen in most North American birds, save perhaps for Smith’s Longspur. They maintain polygamous relationships, with nests frequently housing offspring from various males. Astoundingly, males simultaneously provide nourishment for nestlings in multiple nests, with little regard for paternity, discarding the typical pair bond paradigm. During winter, both sexes claim distinct territories, with a notable altitudinal segregation between genders, staunchly defended to preclude intrusion by conspecifics.
Scientific Classification
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