Bicknell's Thrush
Encyclopedia
The Bicknell's Thrush, Catharus bicknelli, is a medium-sized thrush
, at 17.5 cm (6.9 in) and 28 g (1 oz). It was named after Eugene Bicknell, an American
amateur ornithologist, who discovered the species on Slide Mountain
in the Catskills
in the late 19th century.
Adults are olive-brown on the upperparts, slightly redder on the tail. The underparts are white with gray on the flanks; the breast is greyish brown with dark spots. They have pink legs, a faint grey eye ring, and gray cheeks. 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 http://elibrary.unm.edu/sora/Wilson/v105n04/p0545-p0572.pdf. The song is a jumbled series of flute-like tones ending on a higher note.
Their breeding habitat is the coniferous forests in southeastern Quebec
to Nova Scotia
and the sky island
s of northern New England
and New York
state. It is the rarest and most secretive of the breeding thrushes in North America and it is the only bird whose breeding is restricted to the Northeastern part of the continent. They usually breed at higher elevations, normally nesting above 915 m (3,000 ft).
Bicknell's Thrushes have an unusual mating system in which females mate with more than one male. Such a practice is not known to occur in other thrushes. As many as four males perform duties connected with one nest, including bringing food for the nestlings. The nest itself is typically a bulky cup, close to the trunk of a conifer. Nestlings grow rapidly, developing in 12 days from peanut-sized hatchlings to completely feathered adult-sized birds. Tick
s, blowflies, and lice are some of the parasites with which Bicknell's Thrush must contend. The red squirrel
is the main predator of eggs and nestlings, according to breeding ecology studies.
Other predators include the Sharp-shinned Hawk
, the long-tailed weasel
, and the Northern Saw-whet Owl
.
The thrush's diet consist mainly of insects, but wild fruits are added in late summer, during migration, and on the wintering grounds. They usually forage on the forest floor, but also catch flies, and glean
insects from the foliage of trees.
These birds migrate
to the West Indies, (the Greater Antilles
), with an estimated 90% of the individuals wintering on Hispaniola
http://www.soh.org.do/Palmchatter1_2%20English.pdf. Bicknell's and Gray-cheeked Thrush, along with the Veery
, make up a close-knit group of migrant
species (Winker & Pruett, 2006).
Its numbers are declining in some parts of its already limited range as a result of habitat degradation. Scientists believe that industrial pollution
is one of the main reasons for the decline of the red spruce, an important element in Bicknell’s Thrush habitat in the United States. Airborne heavy metals may also damage high-elevation forests in the northeastern United States. Furthermore, based on expected substantial carbon dioxide increases
by the end of the century, scientists predict a radical reduction of balsam fir
forest in the eastern United States. If average global temperatures increase and forests change as much as predicted, Bicknell’s Thrush habitat is very likely to be altered in ways that may seriously affect the species’ survival.
Other potential threats to Bicknell’s Thrush habitat are the development
of recreational skiing
and summer sports areas, increasing numbers of telecommunication towers
on mountaintops, cyclical spruce budworm
outbreaks, and commercial forestry operations. Industrial forestry
practices, although possibly harmful, may be modified to aid in conservation efforts to protect Bicknell’s Thrush. While more study is needed, the bird’s apparent acceptance of certain commercial second-growth forest gives promise to possibilities of “growing” Bicknell’s Thrush habitats in the future.
There is also considerable concern about the degradation of Bicknell’s Thrush’s wintering habitats. The Dominican Republic
’s native forests are under considerable pressure from naturally occurring events such as hurricanes, as well as changes from agricultural activities, particularly at low altitudes. The forested lands of Haiti
have been almost completely eliminated, and in Cuba
, most of the known suitable habitat exists only in protected parklands.
Thrush (bird)
The thrushes, family Turdidae, are a group of passerine birds that occur worldwide.-Characteristics:Thrushes are plump, soft-plumaged, small to medium-sized birds, inhabiting wooded areas, and often feed on the ground or eat small fruit. The smallest thrush may be the Forest Rock-thrush, at and...
, at 17.5 cm (6.9 in) and 28 g (1 oz). It was named after Eugene Bicknell, an American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
amateur ornithologist, who discovered the species on Slide Mountain
Slide Mountain (New York)
Slide Mountain is the highest peak in the Catskills. It is located in the Town of Shandaken in Ulster County, in southern New York. While the contour line on topographic maps is generally accepted as its height, the exact elevation of the summit has never been officially determined by the U.S...
in the Catskills
Catskill Mountains
The Catskill Mountains, an area in New York State northwest of New York City and southwest of Albany, are a mature dissected plateau, an uplifted region that was subsequently eroded into sharp relief. They are an eastward continuation, and the highest representation, of the Allegheny Plateau...
in the late 19th century.
Adults are olive-brown on the upperparts, slightly redder on the tail. The underparts are white with gray on the flanks; the breast is greyish brown with dark spots. They have pink legs, a faint grey eye ring, and gray cheeks. They average slightly smaller than the very similar Gray-cheeked Thrush
Gray-cheeked Thrush
The Grey-cheeked Thrush, Catharus minimus, is a medium-sized thrush. This species is 15–17 cm in length, and has the white-dark-white underwing pattern characteristic of Catharus thrushes. It is a member of a close-knit group of migrant species together with the Veery and Bicknell's 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 http://elibrary.unm.edu/sora/Wilson/v105n04/p0545-p0572.pdf. The song is a jumbled series of flute-like tones ending on a higher note.
Their breeding habitat is the coniferous forests in southeastern Quebec
Quebec
Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
to Nova Scotia
Nova Scotia
Nova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...
and the sky island
Sky island
Sky islands are mountains that are isolated by surrounding lowlands of a dramatically different environment, a situation which, in combination with the altitudinal zonation of ecosystems, has significant implications for natural habitats. Endemism, vertical migration, and relict populations are...
s of northern New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
and New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
state. It is the rarest and most secretive of the breeding thrushes in North America and it is the only bird whose breeding is restricted to the Northeastern part of the continent. They usually breed at higher elevations, normally nesting above 915 m (3,000 ft).
Bicknell's Thrushes have an unusual mating system in which females mate with more than one male. Such a practice is not known to occur in other thrushes. As many as four males perform duties connected with one nest, including bringing food for the nestlings. The nest itself is typically a bulky cup, close to the trunk of a conifer. Nestlings grow rapidly, developing in 12 days from peanut-sized hatchlings to completely feathered adult-sized birds. Tick
Tick
Ticks are small arachnids in the order Ixodida, along with mites, constitute the subclass Acarina. Ticks are ectoparasites , living by hematophagy on the blood of mammals, birds, and sometimes reptiles and amphibians...
s, blowflies, and lice are some of the parasites with which Bicknell's Thrush must contend. The red squirrel
Red Squirrel
The red squirrel or Eurasian red squirrel is a species of tree squirrel in the genus Sciurus common throughout Eurasia...
is the main predator of eggs and nestlings, according to breeding ecology studies.
Other predators include the Sharp-shinned Hawk
Sharp-shinned Hawk
The Sharp-shinned Hawk is a small hawk. In fact, "sharp-shins" or "sharpies" are the smallest to reside in USA and Canada, though some Neotropical species are smaller...
, the long-tailed weasel
Long-tailed Weasel
The long-tailed weasel , also known as the bridled weasel or big stoat is a species of mustelid distributed from southern Canada throughout all the United States and Mexico, southward through all of Central America and into northern South America.-Evolution:The long-tailed weasel is the product of...
, and the Northern Saw-whet Owl
Northern Saw-whet Owl
The Northern Saw-whet Owl is a small owl native to North America.-Description:The scientific description of one of the sub-species of this owl is attributed to the Rev. John Henry Keen who was a missionary in Canada in 1896. Adults are long with a wingspan. They can weigh from with an average...
.
The thrush's diet consist mainly of insects, but wild fruits are added in late summer, during migration, and on the wintering grounds. They usually forage on the forest floor, but also catch flies, and glean
Gleaning (birds)
Gleaning is a term for a feeding strategy by birds in which they catch invertebrate prey, mainly arthropods, by plucking them from foliage or the ground, from crevices such as rock faces and under the eaves of houses, or even, as in the case of ticks and lice, from living animals. This behavior is...
insects from the foliage of trees.
These birds migrate
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
to the West Indies, (the Greater Antilles
Greater Antilles
The Greater Antilles are one of three island groups in the Caribbean. Comprising Cuba, Jamaica, Hispaniola , and Puerto Rico, the Greater Antilles constitute almost 90% of the land mass of the entire West Indies.-Greater Antilles in context :The islands of the Caribbean Sea, collectively known as...
), with an estimated 90% of the individuals wintering on Hispaniola
Hispaniola
Hispaniola is a major island in the Caribbean, containing the two sovereign states of the Dominican Republic and Haiti. The island is located between the islands of Cuba to the west and Puerto Rico to the east, within the hurricane belt...
http://www.soh.org.do/Palmchatter1_2%20English.pdf. Bicknell's and Gray-cheeked Thrush, along with the Veery
Veery
The Veery, Catharus fuscescens, is a small thrush species. It is occasionally called Willow Thrush or Wilson's Thrush. It is a member of a close-knit group of migrant Catharus species, which also includes the cryptotaxa Grey-cheeked Thrush and Bicknell's Thrush The Veery, Catharus fuscescens, is a...
, make up a close-knit group of migrant
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
species (Winker & Pruett, 2006).
Its numbers are declining in some parts of its already limited range as a result of habitat degradation. Scientists believe that industrial pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
is one of the main reasons for the decline of the red spruce, an important element in Bicknell’s Thrush habitat in the United States. Airborne heavy metals may also damage high-elevation forests in the northeastern United States. Furthermore, based on expected substantial carbon dioxide increases
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
by the end of the century, scientists predict a radical reduction of balsam fir
Balsam Fir
The balsam fir is a North American fir, native to most of eastern and central Canada and the northeastern United States .-Growth:It is a small to medium-size evergreen tree typically tall, rarely to tall, with a narrow conic crown...
forest in the eastern United States. If average global temperatures increase and forests change as much as predicted, Bicknell’s Thrush habitat is very likely to be altered in ways that may seriously affect the species’ survival.
Other potential threats to Bicknell’s Thrush habitat are the development
Land development
Land development refers to altering the landscape in any number of ways such as:* changing landforms from a natural or semi-natural state for a purpose such as agriculture or housing...
of recreational skiing
Skiing
Skiing is a recreational activity using skis as equipment for traveling over snow. Skis are used in conjunction with boots that connect to the ski with use of a binding....
and summer sports areas, increasing numbers of telecommunication towers
Radio masts and towers
Radio masts and towers are, typically, tall structures designed to support antennas for telecommunications and broadcasting, including television. They are among the tallest man-made structures...
on mountaintops, cyclical spruce budworm
Spruce Budworm
Spruce budworms and relatives are a group of closely related insects in the genus Choristoneura. Most are serious pests of conifers. There are nearly a dozen Choristoneura species, subspecies, or forms, with a complexity of variation among populations found throughout much of the United States and...
outbreaks, and commercial forestry operations. Industrial forestry
Forestry
Forestry is the interdisciplinary profession embracing the science, art, and craft of creating, managing, using, and conserving forests and associated resources in a sustainable manner to meet desired goals, needs, and values for human benefit. Forestry is practiced in plantations and natural stands...
practices, although possibly harmful, may be modified to aid in conservation efforts to protect Bicknell’s Thrush. While more study is needed, the bird’s apparent acceptance of certain commercial second-growth forest gives promise to possibilities of “growing” Bicknell’s Thrush habitats in the future.
There is also considerable concern about the degradation of Bicknell’s Thrush’s wintering habitats. The Dominican Republic
Dominican Republic
The Dominican Republic is a nation on the island of La Hispaniola, part of the Greater Antilles archipelago in the Caribbean region. The western third of the island is occupied by the nation of Haiti, making Hispaniola one of two Caribbean islands that are shared by two countries...
’s native forests are under considerable pressure from naturally occurring events such as hurricanes, as well as changes from agricultural activities, particularly at low altitudes. The forested lands of Haiti
Haiti
Haiti , officially the Republic of Haiti , is a Caribbean country. It occupies the western, smaller portion of the island of Hispaniola, in the Greater Antillean archipelago, which it shares with the Dominican Republic. Ayiti was the indigenous Taíno or Amerindian name for the island...
have been almost completely eliminated, and in Cuba
Cuba
The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...
, most of the known suitable habitat exists only in protected parklands.
External links
- Environment CanadaEnvironment CanadaEnvironment Canada , legally incorporated as the Department of the Environment under the Department of the Environment Act Environment Canada (EC) (French: Environnement Canada), legally incorporated as the Department of the Environment under the Department of the Environment Act Environment...
: Bicknell's Thrush - Hinterland Who's Who: Bicknell's Thrush
- Cornell Lab of Ornithology All About Birds Bird Guide: Bicknell's Thrush
- Bicknell's Thrush photo gallery VIREO
- IUCN Bicknell's Thrush rangemap