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 MATING. 65 permanent residents of the tropics, where seasonal changes are less marked, could nest at any time. Nevertheless, the breeding season in the tropics is as well defined as it is in more northern regions, and occurs with the return of summer, or the season of rains. It is therefore at a time of the year when food is most abundant. There is an obvious necessity for this regularity. Old birds can wander over large areas in search of food, but the young of many species must be fed in the nest, and their food supply should be both exliaustless and con- venient of access. Among our birds, the Hawks and Owls, whose young are fed on animal food, are the first birds to nest, while those which feed their young on fruit or insects wait until later in the year. Mating. — Birds are ardent lovers. In their effort to win a bride the males display their charms of song and plumage to the utmost, and will even enter the lists to do battle for the possession of a mate. It is not possible to describe hei-e the many pecul- iar customs of birds during the season of courtship. It may simply be said that every bird will then re- pay the closest observation. For the scientific-minded there is opportunity to secure evidence bearing upon the theory of Natural Selection ; for every one there is endless entertainment in the human traits which l)ird8 exhibit. The Nes.t. — The first step in nest-building is the selec- tion of a site. There is almost no suitable location, from a hole in the ground to branches in the tree-tojDS, in which birds may not place their nests. Protection seems to be the chief desideratum^ and this is generally secured through concealment. Most birds hide their nests. Many sea birds, however, lay their eggs on the shores or cliffs, with no attempt at concealment ; but, as a rule.