Sparrowhawk (Accipiter nisus) Science Article 4
Overall, female Sparrowhawks improved in the mean number of young they raised per year up to the 5th year of life, and then declined. An attempt is made to find to what extent this mean trend is caused by similar trends in the breeding of individual females, and to what extent to the progressive appearance and disappearance of high performing females among breeders of different ages. It is concluded that the mean trend could be attributed entirely to similar age-related trends in individual birds
Newton I. & Rothery P., ARDEA 86 (1): 21-31.