Dans le cadre de la mise en oeuvre de la directive europeenne Habitats, le Museum National d'... more Dans le cadre de la mise en oeuvre de la directive europeenne Habitats, le Museum National d'Histoire Naturelle a ete amene a mettre au point une methode d'evaluation d'espaces naturels d'interet communautaire. Cette methode, simple et synthetique, cadre au plus pres avec les criteres definis par la directive (annexe III) mais integre egalement des criteres complementaires tels que la vulnerabilite, la typicite des habitats et la presence d'elements rares ou remarquables. Cependant, les auteurs soulignent les difficultes d'utilisation de ces criteres definis au niveau europeen. La demarche a permis dans un premier temps, d'evaluer chaque type d'habitat au sein des sites puis chaque site au sein d'une region. Il a ainsi ete possible de hierarchiser plus de 1600 sites selectionnes au niveau national en quatre categories : sites remarquables, tres interessants, interessants et secondaires. La methode ne permet cependant pas d'emettre un jugement ...
We studied regulation of the food supply to black-browed albatross chicks at Kerguelen by simulta... more We studied regulation of the food supply to black-browed albatross chicks at Kerguelen by simultaneously recording the provisioning rates achieved by individual parents and satellite tracking foraging birds during two seasons, by studying changes in adult mass, and by experimentally manipulating the food requirement of chicks. In 1994 black-browed albatrosses had a higher breeding success and produced heavier chicks that grew faster than in 1995. They spent a rimilar time foraging but brought heavier meals to their chick in 1994. Satellite tracking indicated that in both seasons birds foraged in the same oceanographic area, 250 km from the colony. Travel times to and from this area remained unchanged, and similar times were spent foraging there. In our study area, black-browed albatrosses appear to rely on a food resource that is predictable in location, but whose availability varies from one year to the next. The principal difference between yean of differing food availability was that birds brought larger meals when food was more abundant Costs of commuting to nearby feeding areas are probably low and allow the delivery of energy to the chick at a high rate. A study carried out in 1991 indicated that there was no relationship between the changes in adult mass from one trip to the next and the duration of foraging trips or feed mass, suggesting that adult body condition had little influence on the provisioning strategy of this species. An experiment whereby some chicks were deprived of food and others received supplementary food showed that parents of underfed chicks spent the same time foraging and brought slightly larger amounts of food to their chicks as control parents. We suggest that parents are searching for food to the maximum limits of their ability and thus cannot reduce further foraging time, but underfed chicks can swallow more food. Parents of overfed chicks delivered less food and increased the time between feeds. The reduction in provisioning frequency is interpreted as the capacity of parents to modify their foraging behavior according to the nutritional status of the chick, but the reduction of feed mass is probably the result of chicks being close to their maximum assimilatory capacity. Comparison between Procellariiform species indicates extensive differences in the degree to which parents can regulate the supply of food to their chicks. Neritic species like black-browed albatrosses appear to have a reduced ability to regulate, and especially to increase provisioning rates, whereas more pelagic species may have a greater regulation ability. Kty words: black-browed albatross, chick growth, Diomtdta mdtmophris, experimental manipulation, satellite tracking. [Bthav Ecol 8:635-643 (1997)]
Dans le cadre de la mise en oeuvre de la directive europeenne Habitats, le Museum National d'... more Dans le cadre de la mise en oeuvre de la directive europeenne Habitats, le Museum National d'Histoire Naturelle a ete amene a mettre au point une methode d'evaluation d'espaces naturels d'interet communautaire. Cette methode, simple et synthetique, cadre au plus pres avec les criteres definis par la directive (annexe III) mais integre egalement des criteres complementaires tels que la vulnerabilite, la typicite des habitats et la presence d'elements rares ou remarquables. Cependant, les auteurs soulignent les difficultes d'utilisation de ces criteres definis au niveau europeen. La demarche a permis dans un premier temps, d'evaluer chaque type d'habitat au sein des sites puis chaque site au sein d'une region. Il a ainsi ete possible de hierarchiser plus de 1600 sites selectionnes au niveau national en quatre categories : sites remarquables, tres interessants, interessants et secondaires. La methode ne permet cependant pas d'emettre un jugement ...
We studied regulation of the food supply to black-browed albatross chicks at Kerguelen by simulta... more We studied regulation of the food supply to black-browed albatross chicks at Kerguelen by simultaneously recording the provisioning rates achieved by individual parents and satellite tracking foraging birds during two seasons, by studying changes in adult mass, and by experimentally manipulating the food requirement of chicks. In 1994 black-browed albatrosses had a higher breeding success and produced heavier chicks that grew faster than in 1995. They spent a rimilar time foraging but brought heavier meals to their chick in 1994. Satellite tracking indicated that in both seasons birds foraged in the same oceanographic area, 250 km from the colony. Travel times to and from this area remained unchanged, and similar times were spent foraging there. In our study area, black-browed albatrosses appear to rely on a food resource that is predictable in location, but whose availability varies from one year to the next. The principal difference between yean of differing food availability was that birds brought larger meals when food was more abundant Costs of commuting to nearby feeding areas are probably low and allow the delivery of energy to the chick at a high rate. A study carried out in 1991 indicated that there was no relationship between the changes in adult mass from one trip to the next and the duration of foraging trips or feed mass, suggesting that adult body condition had little influence on the provisioning strategy of this species. An experiment whereby some chicks were deprived of food and others received supplementary food showed that parents of underfed chicks spent the same time foraging and brought slightly larger amounts of food to their chicks as control parents. We suggest that parents are searching for food to the maximum limits of their ability and thus cannot reduce further foraging time, but underfed chicks can swallow more food. Parents of overfed chicks delivered less food and increased the time between feeds. The reduction in provisioning frequency is interpreted as the capacity of parents to modify their foraging behavior according to the nutritional status of the chick, but the reduction of feed mass is probably the result of chicks being close to their maximum assimilatory capacity. Comparison between Procellariiform species indicates extensive differences in the degree to which parents can regulate the supply of food to their chicks. Neritic species like black-browed albatrosses appear to have a reduced ability to regulate, and especially to increase provisioning rates, whereas more pelagic species may have a greater regulation ability. Kty words: black-browed albatross, chick growth, Diomtdta mdtmophris, experimental manipulation, satellite tracking. [Bthav Ecol 8:635-643 (1997)]
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