GROWTH OF CORMORANT PHALACROCORAX-CARBO-SINENSIS CHICKS IN RELATION TO BROOD SIZE, AGE RANKING AND PARENTAL FISHING EFFORT

Growth parameters of Cormorant hatchlings are described in relation to brood size and age ranking of each chick within individual broods. Gr owth rates, expressed as body mass increment per day over the period o f linear, growth (5-30 days), ranged from 56.4-102.8 g . d(-1) and wer e found to be independent of brood size and age ranking. Asymptotic fl edging mass, logistic growth rate coefficient and age at point of infl ection were estimated for 14 chicks measured up to ages of over 30 day s. Estimated body mass and age at hedging (twice the age at point of i nflection) were further used to estimate the energetic needs. The fast est growing chicks would require peak energy needs of 3022 kJ . d(-1), the slowest growing of about 2050 kJ . d(-1). Total energy needs thro ughout the nestling period ranged from 46 000 to 69 000 kJ, implying a verage daily requirements of 1300-1800 kJ. Individual energy needs wer e on average 40% higher and at the peak 47% higher in fast growing chi cks than in slow growing ones. However, slower growth, as a means of e nergy saving, does not seem to be chosen for voluntarily by younger ch icks in larger broods. Parental fishing effort (expressed as total amo unt of time spent on fishing trips) increased with brood size. Maintai ning a foraging uptake of 3 g . min(-1) of fresh fish, found in the fi eld, and a flying distance of 20 km, a bottleneck is expected to occur at the period of maximum energy needs. In order to cover maximum need s a chick should be fed with an average of 632 g of fish per day. Such a food provisioning level can be achieved for three chicks at an upta ke level of 3 g . min(-1) of fresh fish. A range of other flying dista nces and uptake levels is also presented to indicate the margins.