Reproductive biology of the roseate spoonbill platalea ajaja in Santa Fe, Argentina

Abstract

The reproductive biology of the Roseate Spoonbill Platalea ajaja was studied in the Ecological Reserve of the Universidad Nacional del Litoral, Santa Fe, (Argentina) in 2016. From September onwards, five nests were monitored in a mixed colony. The nests were built on curupí Sapium haematospermum and espinillo Acacia caven trees at 4.1 ± 0.7 m (mean ± SD) from the ground or the water surface. Clutch size was 3.6 ± 0.5 and hatching success 89%. Eggs had a maximum diameter of 64.6 ± 2.6 mm, a minimum diameter of 43.7 ± 1.3 mm, and an average volume of 62.9 ± 4.3 cm 3 (n = 16). Egg weight at the beginning of incubation was<br />69.4 ± 2.5 g (n = 9) but fell lineally to 59.6 ± 4.8 (n = 17) by the end of this period. The birth weight of nestlings was on average 43 g (n = 13). Most of nestlings died (6) or disappeared (4), presumably due to predation, and so fledgling success was low (1.2 chicks/nest).<br />Nestlings showed a sigmoid growth curve, with a marked increase in weight in the second and third weeks. The final body mass was reached at around eight weeks, somewhat later than the fledgling date at around day 27.<br />