Herbivore foraging theory (2 Onderwerpen, alleen in het Engels)

1. Modeling the spatial distribution of Bewick's swans at the Lauwersmeer

General outline

This project relies on a lot of available data on the foraging behavior of Bewick's swans on pondweed tubers at the Lauwersmeer. Our aim is to understand the intensity of food depletion in different parts of the lake and the driving force behind habitat switches of the birds. For this purpose, an existing model should be adjusted, and validated with field data from the previous four years. An excellent opportunity for people who enjoy modeling and playing with datasets.

Project outline

Running simulations with different parameter settings on an existing model setup.

Duration (indicative)
Approximately 4 months, starting as soon as possible.

Contact
Abel Gyimesi, tel.: +31 (0)294 239 346, e-mail: a.gyimesi@nioo.knaw.nl

2. Tracking individual Bewick's Swans throughout their wintering range using GPS-loggers

Keywords
Fieldwork; Bewick's swan; GPS-loggers; avian spatial ecology.

General context
Within the Avian Spatial Ecology project we aim to understand spatial distributions of animals. We approach the problem from an individually-based angle and ask questions such as: where should animals feed in relation to the abundance of food, conspecifics and roosting sites. We hope to be able to disentangle 'rules of thumb' that animals follow in their daily whereabouts and we assume a key role for the individual's energy budget. Bewick's swans (Cygnus columbianus bewickii) are an ideal species to study these problems as many are individually coded by leg or neck band and attract a dense network of amateur observers. The recent miniaturization of global positioning systems (GPS) will allow us to study individual movements of Bewick's swans in even greater detail. Eventually, we hope to be able to quantify the outcome of movement-decisions in units of fitness, which will enable us to scale-up to dynamics in their population.

Project outline
Detailed field-observations on fuelling rates of GPS-equipped Bewick's swans. Estimates on fuelling rates can be obtained on a short-term scale by quantification of bite and dropping rates. Changes in the abdominal profile index (API) yield estimates on long-term average fuelling rates. After the field work, individual energy budgets will be reconstructed in combination with geographical analyses of movement patterns.

Remarks
Driving license is required.

Duration (indicative)
More or less 5-6 months during wintertime.

Contact
Jan van Gils (e-mail: j.vangils@nioo.knaw.nl; tel.: +31 (0)294 239 344).