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Species migrate to take advantage of more favorable conditions with respect to food availability, safety from predation, mating opportunity, or other environmental factors. [2] [3] Migration is most commonly seen in the form of animal migration, the physical movement by animals from one area to another. That includes bird, fish, and insect ...
The cause of migration may be local climate, local availability of food, the season of the year or for mating. To be counted as a true migration, and not just a local dispersal or irruption, the movement of the animals should be an annual or seasonal occurrence, or a major habitat change as part of their life.
Bird migration is a seasonal movement of birds between breeding and wintering grounds that occurs twice a year. It is typically from north to south or from south to north. Migration is inherently risky, due to predation and mortality. The Arctic tern holds the long-distance migration record for birds, travelling between Arctic breeding grounds ...
The bar-tailed godwit is a non-breeding migrant in Australia and New Zealand. Birds first depart for their northern hemisphere breeding sites at age 2–4. [23] Breeding take place each year in Scandinavia, northern Asia, and Alaska. The nest is a shallow cup in moss sometimes lined with vegetation. Clutch size is from 2 to 5, averaging four. [7]
Migrants tend to travel away from polar and temperate zones in the winter because of low temperatures and shortage of food in their breeding areas. [1] [2] During spring migration, birds return to their breeding sites to exploit the temporary superabundance of food, allowing them to raise more young. [3]
This concentration of birds during migration can put species at risk. Some spectacular migrants have already gone extinct, the most notable being the passenger pigeon . During migration the flocks were a mile (1.6 km) wide and 300 miles (500 km) long, taking several days to pass and containing up to a billion birds.
The white-ruffed manakin (Corapipo altera) is a well known altitudinal migrant.Third year male (left) and After Third Year male (right). In the tropics, altitudinal migrations are most commonly seen among frugivores or nectarivores, such as what is seen among tropical hummingbirds, which migrate altitudinally in response to shifts in food abundance and availability. [5]
Assisted migration is a specific type of species introduction. Species introduction is any act of establishing a species in a habitat it does not currently occupy. It often refers to a long-distance relocation, such as the accidental introduction of an invasive species from one continent to another, or the intentional relocation of a species in decline to a habitat where it can persist.