Birds of Paradise

New Guinea is an extremely mountainous island. Its equatorial location results in a tropical climate near sea level, but cooler conditions higher in the mountains. In fact, the highest peaks have glaciers present. In addition, the prevailing oceanic winds carry moisture-laden air over the island, resulting in as much as 27 ft (8.5 m) of rain per year in some places. Sites on the lee side of mountains, however, may be quite dry. The great variations of climate in New Guinea result in numerous different habitats occurring. The various species of birds of paradise are rather specific to particular kinds of habitat. For example, the crested bird of paradise is only found in upper montane forest and subalpine shrubland, while the trumpet manucode is found only in lowland and lower mountain forests, and the blue bird of paradise prefers mid-montane forest.

In addition to inhabiting different ecological zones in New Guinea, the various birds of paradise use different food resources. The two basic kinds of foods eaten are fruits and insects. There are also two groups of fruits: simple fruits rich in carbohydrate, such as figs, and complex fruits with high levels of fat and protein, such as those of mahogany and nutmeg. Species of birds of paradise tend to eat mainly simple fruits (e.g., the trumpet manucode), mainly complex fruits (e.g., the raggiana bird of paradise), or complex fruits plus significant quantities of insects (e.g., the magnificent bird of paradise).

When animals eat tree fruits, they may also digest the seeds, or the seeds may pass through the digestive system intact. If seeds are not digested, a tree seedling may sprout from them, helping the forest regenerate. In most forest habitats worldwide, the main fruit-dispersing animals are mammals. In New Guinea, however, this role is largely played by birds of paradise, which eat fruits and distribute the seeds, helping to ensure the dispersal of important species of forest trees.