Migratory birds need considerable energy reserves to fuel long-distance flights to their breeding grounds in spring. To attain sufficient energy deposits before departure, birds require high daily intake rates, which can be reached by utilizing high-quality food. During such periods of high energy demand, animals often track changes in the nutritious value of their food, for example by switching to a more profitable habitat or diet. Pre-migratory Barnacle Geese Branta leucopsis staging along the Wadden Sea coast are known to switch from pastures to salt marshes during spring. Previous studies have suggested that Barnacle Geese switch habitat to track changes in protein levels, which drop in pastures as spring progresses, and to avoid high levels of disturbance. Here we made use of detailed information on pre-migratory habitat use of individual Barnacle Geese tracked by GPS/accelerometer tags to assess which factors may drive a habitat switch. We analysed habitat use and time budgets of individual birds and combined this with data on food quality in two habitats to analyse differences in food intake. We found large individual variation in pre-migratory habitat use, both in the extent of salt marsh use, as well as in the timing of a switch from pastures to salt marshes. In salt marshes, geese spent more time grazing and made fewer flight movements, potentially as they experienced lower levels of disturbance compared to geese in pastures. By increasing grazing time and reducing flight movements, geese in salt marshes may compensate for reduced food quality. Our results show that Barnacle Geese trade-off high intake rates and high costs in pastures with low intake rates and low costs in salt marshes.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 107 • No. 2