Filling the groove: energy flow to seabirds in the Beagle Channel, Tierra del Fuego, Argentina

Abstract

We assessed the energy requirements and the food consumption of the seabird community of the Beagle Channel in summer. We evaluated differences in energy flow among a priori established zones in the study area and among species. We converted data on densities of seabirds in the channel (February and March 1997) into energy demands. Energy flow to seabirds in shallow waters was twice that of in deep waters. Average energy flow in the whole study area was 9.46×104 kJ.km-2.day-1. Energy intake rates ranged 4-13×104 kJ.km-2.day-1, being higher in zones that include breeding sites or close to them. Imperial Cormorant was the major contributor to energy flow in all the zones followed by the Black-browed Albatross. Kelp Gull was the major contributor in areas where food from human origin was available. Energy flow was similar in four zones, which may represent a saturation point for seabird biomass in the Beagle Channel. The factors that explain the observed energy flow distribution deal with the distribution of shallow water areas in the channel, the presence of seabirdís colonies, the proportion of diver and surface feeders, and the possible segregation of, at least, the most abundant species. Finally, food consumption varied from 1.71-3.42 ton/day, being higher near breeding colonies and lower in areas with more open waters.