Intégration du lien consommateur-ressource dans l'étude de l'influence des activités humaines sur l'hivernage des bernaches cravant dans un écosystème littoral fortement anthropisé

• Main Author: Desmonts, Diane
• Other Authors: Centre d'études biologiques de Chizé (CEBC), Centre National de la Recherche Scientifique (CNRS), Université de Bretagne occidentale - Brest, Hervé FRITZ
• Format: Thesis
• Language: French
• Published: HAL CCSD 2007
• Subjects: envir; geo; Branta bernicla; brent geese
• Online Access: https://tel.archives-ouvertes.fr/tel-00286376/file/Desmonts.pdf; https://tel.archives-ouvertes.fr/tel-00286376

Human activities can modify animal behaviour and distribution which ultimately can have a significant effect at the population level. For migratory species, a site may become unsuitable for wintering due to high levels of disturbance. As a consequence, individuals will winter on other sites, increasing the level of interference and potentially decreasing feeding efficiency. However, to well estimate the influence of human activities on wintering species, food resources have to be taken into account. The aim of this work was to account for the link between consumer and food resource when studying the influence of human activities on wintering Brent geese Branta bernicla. The study area was in South Brittany (France), where Brent geese feed mainly on eelgrass species such as Zostera noltii. We characterised the relationship between the distribution of Brent geese and Z. noltii at three spatial and temporal scales. We found that food resources determined Brent geese distribution, from the broad scale of the gulf during thirty years to the position in relation to tide edge during a tidal cycle. We also demonstrated that human activities can modify this relationship. Indeed, the potential energy cost they lead to (depending on their type, their position and geese flock size) could make Brent geese avoiding some Z. noltii beds. Through this approach of energetic costs of human disturbances, this work also contributed to a more general and robust classification of the possible costs of human activities on wintering birds. This work helps to better understand the importance of food resources for wintering Brent geese distribution, as well as the way human activities may modify this relationship. This study also shows that the behaviour and distribution of wintering Brent geese can serve as a reliable, although coarse, indicator of the state of Zostera beds at the site scale as well as the regional scale. Les activités humaines peuvent entraîner des modifications de comportement et de distribution spatiale chez les ...