Growth rates of nestling Egyptian Vultures Neophron percnopterus in relation to brood size hatching order and environmental factors.

Patterns of growth in weight, tarsus and feather (primary) are described for nestling Egyptian Vulture Neophron percnopterus in northern Spain. Maximum increase in weight and tarsus respectively occurred before 40 and 30 d. The primary growth rate was almost constant until fledging (75 d). Second-hatched nestlings either died before 14 d or grew in weight and tarsus at slower rates than first-hatched and single nestlings during the first development period (1-20 d). During the last period (40-60 d), however, this tendency reversed. Second-hatched nestling also suffered a relative delay in dates of primary emergence and achievement of feather fledging size. Hatching date and food habits were not related with growth patterns. A long period of rainy days seemed to affect to growth rates of second-hatched nestlings during the last development period favouring maintenance of feather growth in detriment of tarsus. The growth rates of the Egyptian Vulture seem to act as a fine-tuning mechanism of productivity.

Donazar J.A. & Ceballos O, ARDEA 77 (2): 217-226