Ardea
Official journal of the Netherlands Ornithologists' Union

login


[close window] [previous abstract] [next abstract]

Platteeuw M., Koffijberg K. & Dubbeldam W. (1995) Growth of Cormorant Phalacrocorax carbo sinensis chicks in relation to brood size, age ranking and parental fishing effort. ARDEA 83 (1): 235-245
Growth parameters of Cormorant hatchlings are described in relation to brood size and age ranking of each chick within individual broods. Growth rates, expressed as body mass increment per day over the period of linear growth (5-30 days), ranged from 56.4-102.8 g d-1 and were found to be independent of brood size and age ranking. Asymptotic fledgling mass, logistic growth rate coefficient and age at point of inflection were estimated for 14 chicks measured up to ages of over 30 days. Estimated body mass and age at fledgling (twice the age at point of inflection) were further used to estimate the energetic needs. The fastest growing chicks would require peak energy needs of 3022 kJ d-1, the slowest growing of about 2050 kJ d-1. Total energy needs throughout the nestling period ranged from 46 000 to 69 000 kJ, implying average daily requirements of 1300-1800 kJ. Individual energy needs were on average 40% higher and at the peak 47% higher in fast growing chicks than in slow growing ones. However, slower growth, as a means of energy saving, does not seem to be chosen for voluntarily by younger chicks in larger broods. Parental fishing effort (expressed as total amount of time spent on fishing trips) increased with brood size. Maintaining a foraging uptake of 3 g min-1 of fresh fish, found in the field, 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 needs 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 uptake level of 3 g min-1 of fresh fish. A range of other flying distances and uptake levels is also presented to indicate the margins.


[close window] [previous abstract] [next abstract]