can easily take off from. The age of first breeding is usually five years, although this age is variable; a three-year-old tropicbird was once seen breeding. In some locations, breeding happens year-round, while in others, breeding occurs seasonally. For example, for islands in the California Current, breeding starts in November or December, while it occurs year round in the Galápagos. Breeding is influenced by the availability of food, with an increase in food generally causing an increase in breeding. Individually, this bird only breeds every nine to twelve months. A breeding bird usually returns to its partner and nest location from the previous breeding cycle. Courtship and pairing usually lasts three to five weeks, during which this bird performs aerial courtship displays to potential mates. The courtship displays include flying in the air which takes the form of gliding interspersed with short periods of rapid wing-beating. In one display, a pair glide together for , with one bird around above the other. The upper bird bends its wings down and the lower lifts its up, so they are almost touching. The two sink to about above the sea before breaking off. At nest sites, battles sometimes occur between two or more pairs before the original owners declare themselves as the owner of the nest. Red-billed tropicbirds are aggressive at nest sites, fighting with each other and ousting species such as shearwaters, petrels, and white-tailed tropicbirds. They have also been recorded taking over nests of white-tailed tropicbirds and raising their young if they failed to destroy their eggs. Vagrant red-billed tropicbirds have been implicated in egg loss in red-tailed tropicbird nests in Hawaii. This tropicbird usually lays a clutch of one white buff to pale purple egg with reddish-brown spots. The egg usually measures and weighs around —10% of the adult female's weight. It is incubated by both sexes for 42 to 46 days. If the egg does not survive the first few days in the nest, the female will usually lay a replacement egg. The chicks that hatch eventually fledge in about 10 to 15 weeks after hatching, although most fledge after about 80 to 90 days. Normally, the maximum weight of the chicks is about , but on years that are hotter than average, this can drop to about . Born helpless and unable to move around (nidicolous and semi-altricial), the chicks are constantly brooded by the parents until