Migration

Despite the dangers of long-distance travel, many different animals have developed migration strategies, presumably as a defense against the greater dangers of environmental uncertainty and competition. The breeding range of migratory animals is likely to cover a region whose environment becomes increasingly inhospitable after the breeding season is over (i.e. there is less food available in the winter), so it is advantageous to travel elsewhere. The wintering ranges will have food available year-round, but also many more animals competing for that food, as well as increased competition for shelter in which to raise their young. Hence the advantage of returning to the breeding grounds, where competition is less severe.