Avian range expansion
Encyclopedia
Avian range expansion describes how bird
s expand their habitat
. Because of the activities of birdwatchers these range expansions are well documented.
Throughout the last century a number of birds have expanded their range. Birds that were once thought to be only located on the West Coast
of North America
have moved eastward all the way to the East Coast
, an example would be the Brewer's Blackbird
. Since the 1950’s the Brewer’s Blackbird, a relative of the Red-Winged Blackbird
, has been moving eastward first from the West Coast of Oregon
and California
to the Great Lakes
Region and then towards the East Coast, with the range expanding from Coast to Coast according to the Audubon’s 2005 Christmas Bird Count. The Inca Dove
first arrived as a native of Mexico
and has slowly expanded Northward into Kansas
and Arkansas
. Great Tailed Grackles have also moved in similar fashion northward. Range expansion may be explained by several different reasons.
; however expansions are presently occurring at an alarming rate. One of the reasons for increased expansion is due to human alteration. Human causes such as changing of habitat and global climate change are leading factors in avian range expansion. Species that were previously adapted to the old niche are often replaced by species that are more adapted for newly created niche. For example when forests are replaced by more urban areas, species such as the Inca Dove
are replaced by the Mourning Dove
, allowing the Mourning Dove to expand its range. Bird populations are not static and naturally change over time. However, due to human effects such as global climate change and loss of habitat, a number of species are expanding in a particular range as the native species they displace are declining.
In addition to environmental aspects that cause range expansion and subsequent decline of certain species, humans have introduced species
that are largely responsible for decline of native species. Exotic species, such as the European Starling
which were introduced by Eugene Schieffelin
in 1890 in New York City
and then expanded to California by 1955, often do very well in new habitats. The lack of predators and new niche offer perfect conditions for the introduced species to flourish. These “exotic” species often displace other native species. For example the European Starling pursues aggressive breeding strategies that help it colonize new breeding areas. The European Starling is an early breeder and out competes other native cavity nesters for nesting sites. Other cavity nesters include the kestrels, flycatchers, swallows, wrens, and bluebirds. The urbanization of much America also aids in the spread of the European Starling (Podluka et al. 2004, Askins 2000, Elrich et al. 1998).
began to decline. Beginning in 1912 the Barred Owl
began expanding its range westward and Northward. Once considered an East Coast Resident, the Barred Owl moved into the Rocky Mountains and Southern Canada, into the Spotted Owls territory. The Barred Owl is extremely adaptable, whereas the Northern Spotted Owl is much more stagnate. The Barred Owl can live in virtually any forest and eat almost anything. The Northern Owl is adapted to best survive in old growth forest and relies mainly on the flying squirrel as a food resource. Much like human counterparts, as the Barred Owl expanded westward these larger more adaptable birds forced native owls, such as the Northern Owl, off their territory. The Barred Owl is about 20% larger and will feast on flying squirrels out of convenience. Biologists have noted a severe decline in the breeding population of Northern Owls, whereas the Barred Owl populations thrive (Levy, 2004).
is a brood parasite
, which places its own eggs in nest of other birds, placing the burden of parenting on other birds. The Brown-headed Cowbird is thought to have a center of origin in the Great Plains of North America, but has expanded in both directions to spread across most of North America. The behavior of the Brown-headed Cowbird causes range expansion at the expense of other birds such as warblers, sparrows, and vireos. The efforts required for raising the cowbird chick often exhaust the parent and lead to either the death of the parent or the death of the other chicks within the nest, thus decreasing the chances of reproduction for that songbird. In a study conducted by the University of British Columbia, cowbird parasitism was shown to be a direct cause of population declines in Black-capped vireos, Bell’s vireo, and the Southwestern willow Flycatcher (Levy, 2004).
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s expand their habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
. Because of the activities of birdwatchers these range expansions are well documented.
Throughout the last century a number of birds have expanded their range. Birds that were once thought to be only located on the West Coast
West Coast of the United States
West Coast or Pacific Coast are terms for the westernmost coastal states of the United States. The term most often refers to the states of California, Oregon, and Washington. Although not part of the contiguous United States, Alaska and Hawaii do border the Pacific Ocean but can't be included in...
of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
have moved eastward all the way to the East Coast
East Coast of the United States
The East Coast of the United States, also known as the Eastern Seaboard, refers to the easternmost coastal states in the United States, which touch the Atlantic Ocean and stretch up to Canada. The term includes the U.S...
, an example would be the Brewer's Blackbird
Brewer's Blackbird
The Brewer's Blackbird is a medium-sized New World blackbird, named after the ornithologist Thomas Mayo Brewer....
. Since the 1950’s the Brewer’s Blackbird, a relative of the Red-Winged Blackbird
Red-winged Blackbird
The Red-winged Blackbird is a passerine bird of the family Icteridae found in most of North and much of Central America. It breeds from Alaska and Newfoundland south to Florida, the Gulf of Mexico, Mexico, and Guatemala, with isolated populations in western El Salvador, northwestern Honduras, and...
, has been moving eastward first from the West Coast of Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
and California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
to the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
Region and then towards the East Coast, with the range expanding from Coast to Coast according to the Audubon’s 2005 Christmas Bird Count. The Inca Dove
Inca Dove
The Inca Dove is a small New World dove; it might belong to the genus. It ranges from the southwestern United States and Mexico through Central America to Costa Rica; the Inca Dove only lives on the Pacific side of Central America. Despite being named after the Inca Empire, this species does not...
first arrived as a native of Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
and has slowly expanded Northward into Kansas
Kansas
Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...
and Arkansas
Arkansas
Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...
. Great Tailed Grackles have also moved in similar fashion northward. Range expansion may be explained by several different reasons.
Reasons for range expansion
The largest reason for a bird to expand its range is to draw greater resources. Once resources for food, nesting, and potential mates become scarce in a particular area, birds and other animals move out of those areas to find new resources. Range expansion is a crucial component of evolutionEvolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
; however expansions are presently occurring at an alarming rate. One of the reasons for increased expansion is due to human alteration. Human causes such as changing of habitat and global climate change are leading factors in avian range expansion. Species that were previously adapted to the old niche are often replaced by species that are more adapted for newly created niche. For example when forests are replaced by more urban areas, species such as the Inca Dove
Inca Dove
The Inca Dove is a small New World dove; it might belong to the genus. It ranges from the southwestern United States and Mexico through Central America to Costa Rica; the Inca Dove only lives on the Pacific side of Central America. Despite being named after the Inca Empire, this species does not...
are replaced by the Mourning Dove
Mourning Dove
The Mourning Dove is a member of the dove family . The bird is also called the Turtle Dove or the American Mourning Dove or Rain Dove, and formerly was known as the Carolina Pigeon or Carolina Turtledove. It is one of the most abundant and widespread of all North American birds...
, allowing the Mourning Dove to expand its range. Bird populations are not static and naturally change over time. However, due to human effects such as global climate change and loss of habitat, a number of species are expanding in a particular range as the native species they displace are declining.
In addition to environmental aspects that cause range expansion and subsequent decline of certain species, humans have introduced species
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
that are largely responsible for decline of native species. Exotic species, such as the European Starling
European Starling
The Common Starling , also known as the European Starling or just Starling, is a passerine bird in the family Sturnidae.This species of starling is native to most of temperate Europe and western Asia...
which were introduced by Eugene Schieffelin
Eugene Schieffelin
Eugene Schieffelin belonged to the and the New York Zoological Society. He was responsible for introducing the starling to North America.-Starling release:...
in 1890 in New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
and then expanded to California by 1955, often do very well in new habitats. The lack of predators and new niche offer perfect conditions for the introduced species to flourish. These “exotic” species often displace other native species. For example the European Starling pursues aggressive breeding strategies that help it colonize new breeding areas. The European Starling is an early breeder and out competes other native cavity nesters for nesting sites. Other cavity nesters include the kestrels, flycatchers, swallows, wrens, and bluebirds. The urbanization of much America also aids in the spread of the European Starling (Podluka et al. 2004, Askins 2000, Elrich et al. 1998).
The Barred Owl and the Northern Spotted Owl
In the 1970’s the logging of Old Growth foresting accelerated, and the numbers of the Northern Spotted OwlNorthern Spotted Owl
The Northern Spotted Owl, Strix occidentalis caurina, is one of three Spotted Owl subspecies. A Western North American bird in the family Strigidae, genus Strix, it is a medium-sized dark brown owl sixteen to nineteen inches in length and one to one and one sixth pounds. Females are larger than males...
began to decline. Beginning in 1912 the Barred Owl
Barred Owl
The Barred Owl is a large typical owl. It goes by many other names, including eight hooter, rain owl, wood owl, and striped owl, but is probably best known as the hoot owl.-Description:...
began expanding its range westward and Northward. Once considered an East Coast Resident, the Barred Owl moved into the Rocky Mountains and Southern Canada, into the Spotted Owls territory. The Barred Owl is extremely adaptable, whereas the Northern Spotted Owl is much more stagnate. The Barred Owl can live in virtually any forest and eat almost anything. The Northern Owl is adapted to best survive in old growth forest and relies mainly on the flying squirrel as a food resource. Much like human counterparts, as the Barred Owl expanded westward these larger more adaptable birds forced native owls, such as the Northern Owl, off their territory. The Barred Owl is about 20% larger and will feast on flying squirrels out of convenience. Biologists have noted a severe decline in the breeding population of Northern Owls, whereas the Barred Owl populations thrive (Levy, 2004).
The Brown-headed Cowbird and other Songbirds
The Brown-headed CowbirdBrown-headed Cowbird
The Brown-headed Cowbird is a small brood parasitic icterid of temperate to subtropical North America. They are permanent residents in the southern parts of their range; northern birds migrate to the southern United States and Mexico in winter, returning to their summer habitat around March or...
is a brood parasite
Brood parasite
Brood parasites are organisms that use the strategy of brood parasitism, a kind of kleptoparasitism found among birds, fish or insects, involving the manipulation and use of host individuals either of the same or different species to raise the young of the brood-parasite...
, which places its own eggs in nest of other birds, placing the burden of parenting on other birds. The Brown-headed Cowbird is thought to have a center of origin in the Great Plains of North America, but has expanded in both directions to spread across most of North America. The behavior of the Brown-headed Cowbird causes range expansion at the expense of other birds such as warblers, sparrows, and vireos. The efforts required for raising the cowbird chick often exhaust the parent and lead to either the death of the parent or the death of the other chicks within the nest, thus decreasing the chances of reproduction for that songbird. In a study conducted by the University of British Columbia, cowbird parasitism was shown to be a direct cause of population declines in Black-capped vireos, Bell’s vireo, and the Southwestern willow Flycatcher (Levy, 2004).