Aging in birds

Abstract

The class Aves is a diverse group consisting of approximately 9600 species of birds in 29 orders [1–3] which, on the whole, are remarkable for their longevity. Body weights of birds vary from smallest to largest by a factor of about 40 000-fold [4, 5], and the range of variation in avian metabolic rates, life histories, life spans and aging patterns is equally striking [6–9]. Birds can live three to four times longer than mammals of equal body mass (Table 1). A 20 g laboratory mouse, for example, rarely lives over four years, but documented maximum life spans of small songbirds often exceed 10 years. The most paradoxical examples of avian longevity by far are the hummingbirds. They are the smallest of all birds, with the highest metabolic rates, yet individuals of some species have survived up to 14 years in the wild (Calder, personal communication) [10, 11].