250 800 460 1,336 1,440 1,400 2,100 3,200 8,834

Data from Lasiewski and Dawson, 1967; Altman and Dittmer, 1972; Gavrilov and Dolnik, 1982; Carey and Judge, 2000. Records for most wild birds are based on banding records from the field, and probably underestimate potential life span in captivity. Most longevities were validated using similar values from more than one large sample for a given species. Lifetime energy expenditures were calculated using published estimates of basal or resting metabolic rates.

of long-lived fliers (Finch, 1990; Austad and Fischer, 1991; Partridge and Barton, 1993). Evolutionary senescence theory predicts that organisms subject to natural selection in the form of high natural mortality rates from predation, disease, or accident will evolve life-histories characterized by rapid maturation, early reproductive investment, and relatively high fecundity (Medawar, 1952; Williams, 1957; Edney and Gill, 1968; Rose, 1991). Short life spans are a correlate of this evolutionary scenario, in which there is no long-term reproductive or genetic advantage to delayed or slow aging. Conversely, in the absence of high mortality rates and intense selection for reproductive investment early in life, natural selection should favor delayed maturity, repeated but smaller episodes of reproductive investment, and long-term somatic maintenance. In the latter scenario, organisms with effective defenses against predators and other sources of mortality, including the ability to fly, will also be expected to evolve long life spans and the molecular mechanisms supporting long-term somatic maintenance. In other words, effective antiaging adaptations—including, presumably, the ability to combat oxidative and glycoxidative damage—are most likely to be exhibited by organisms with naturally long life spans, including vertebrates like bats, mole-rats, and birds. A substantial amount of comparative data supports the idea that slow aging has accompanied the evolution of flight, in both birds and mammals (for reviews see Pomeroy, 1990; Partridge and Barton, 1993; Holmes and Austad, 1995b).

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