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Of course, in the southern hemisphere, the directions are reversed, but there is less land area in the far south to support long-distance migration. [ 19 ] The primary motivation for migration appears to be food; for example, some hummingbirds choose not to migrate if fed through the winter. [ 20 ]
A few hundred species migrate long distances, in some cases of thousands of kilometres. About 120 species of fish, including several species of salmon, migrate between saltwater and freshwater (they are 'diadromous'). [23] [24] Forage fish such as herring and capelin migrate around substantial parts of the North Atlantic ocean.
The mallard has hybridised with more than 40 species in the wild, and an additional 20 species in captivity, [13] though fertile hybrids typically have two Anas parents. [14] Mallards and their domestic conspecifics are fully interfertile; many wild mallard populations in North America contain significant amounts of domestic mallard DNA. [15] [16]
Most hummingbirds migrate in the winter to Central America or Mexico, but some hummingbirds spend the winter on the Gulf Coast and may be found in South Texas and South Louisiana during mild winters.
Mallards, both domestic and wild in particular are notorious hybridizers, know to frequently hybridize within the mallard complex and even outside of Anas. The willingness to hybridize has concerned conservationists as the gene flow from the mallard may pollute pure populations of more vulnerable species such as the Mexican duck. [ 2 ]
A wild mallard weighs some 1.1 kg (2.4 lb), but large breeds like the Aylesbury may weigh 4.6 kg (10 lb) (and hybrids even more), while small breeds like the Appleyard may be only 0.7 kg (1.5 lb). Those breeds are raised for meat and eggs, [ 2 ] while other breeds are purely ornamental, having been selected for their crests, tufts, or striking ...
The males migrate directly to the shallow water of fjords, where spawning will take place, while the females remain in deeper water until they are completely mature. Once the females are mature, they migrate to the spawning grounds and spawn. [6] This process usually takes place at night. [3]
What do orioles eat? A Baltimore oriole stopped off at a bird feeder in Portsmouth. Ripe fruit is a favorite of orioles, so cutting oranges in half and hanging them from trees is a reliable strategy.