of the eggs hatch. Hatching success can drop to about 35% in unusually hot conditions. Egg shell thinning, a potential cause of egg mortality, can be caused by pollutants. About 78% of chicks fledge in normal years, with that percentage only dropping slightly, to 77%, in abnormally hot years. Most egg and chick mortality during periods of normal climate is caused by nest fights between the parents and other birds. Breeding adults usually survive the year, with only about 18% dying every year. The young have a lower survival rate, with about 29% dying each year. The lifespan of this bird is anywhere from 16 to 30 years. References Books cited External links Red-billed Tropicbird BirdLife International Phaethontidae Birds of Ascension Island Birds of Cape Verde Birds of the Caribbean Birds of the Indian Ocean Birds of the Middle East Birds of Saint Helena Island Birds described in 1758 Taxa named by Carl Linnaeus