Chick development and parental care in the northern gannet

Kirkham, I.R. (1980) Chick development and parental care in the northern gannet. Masters thesis, Memorial University of Newfoundland.

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Abstract

Parent-young interactions in Northern Gannets (Morus bassanus) were studied at three North American colonies in 1978 and 1979. Nestling behavioural and morphological development were investigated using wild and hand-reared chicks. During the first month post-hatch, certain body parts grow faster than others. Rapid growth of tarsi, midtoes, culmen, and associated muscles aid in eventual thermoregulatory activities and in increasing the efficiency of food reception. Metabolic rate (VO2) of nestlings between 5 and 10 days was high and variable and declined in magnitude and variability to near adult levels by 21 days. When endothermic, chicks had low metabolism and thermoregulation did not appear to require much of the available energy, most of which was allocated to growth. -- Chick dependence on adults requires continuous attendance and care (brooding and feeding). Relative parental investments by males and females were determined by observation of time spent incubating, brooding, foraging and feeding chicks. Daily nest attendance by both parents was similar during egg and chick stages. Females incubated, on average, for significantly longer periods than males. Chick brooding and attendance spells were shared about equally by males and females. Males fed chicks more often than females, during post-hatch weeks 1 through 3; thereafter chick feeding was shared about equally between parents. -- The food energy requirements of nestlings peaked at about week 6 and declined slightly after week 9. Mackerel, which has a high fat content and caloric value, was the most common food feed to chicks. Mackerel is an ideal food type for gannets, because of its large size (fewer foraging trips) and its high levels of fat which nestlings require for post-fledging survival. The gannets mode of development is discussed tin terms of nestling behaviour and energetics, parental time and energy investments, and with comparisons to other avian development patterns.

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