Senescence of maternal effects: aging influences egg quality and rearing capacities of a long-lived bird

Senescence could depress prenatal and postnatal capacities of mothers to invest in offspring. Longitudinal observations on the blue-footed booby (Sula Nebouxii) revealed a quadratic effect of female age on fledgling production and cohorts differences in rate of reproductive decline. By swapping clutches between females of different ages, we tested whether reproductive senescence is due to decline in egg quality or capacity to care. As laying mothers aged, egg size, ulna length of 5-days old chicks, and ulna growth of second chicks up to age 30-days declined; and as rearing mothers aged, ulna growth and cellular mediated immune response of second chicks diminished. Oddly, the number of fledglings produced by senescent females (> 11 years) was greater rearing offspring of middle-aged females (8-11 years) than offspring of senescent or young females. Thus, senescence reduced egg quality and rearing capacities, and reproductive success of senescent mothers depended on
prenatal effects ...