The postdoc will contribute to the development of a data-assimilation system which combines different monitoring techniques and dynamic models of bird movements to predict bird distribution over various spatio-temporal scales in the Western Wadden Sea.

Project description: In the Wadden Sea, a relatively small number of bivalve species represent the majority of the macrobenthos biomass (Blue mussels, Cockles, Soft-shelled clams, Baltic Tellins, Pacific oysters and Razorshell clams). During the last decades, the occurrence and abundance of these species as well as benthivorous birds has changed dramatically. However, the exact causal relations between abundance and species composition of shellfish and benthivorous birds are not clear. Yet, there is an urgent need to understand these relations in order to enhance the management and conservation of the Wadden Sea ecosystem. To help in achieving this aim, this project will monitor the macrozoobenthos species composition, distribution and abundance over the intertidal and subtidal areas of the Western Wadden Sea and as well as the community dynamics of the benthivorous birds on the tidal flat of Balgzand. The abundance of bivalve species is established by regular grid bed-sampling. Biogenic structures of mussels and oysters are mapped with aerial photography analysis and sonar. Bird movements and the composition of the bird community are observed with a combination of radar, video cameras and field-observations. By combining the observations it will be possible to enhance our understanding of the relations between the macrozoobenthos and benthivorous bird community compositions and abundance and create better prediction models.

Monitoring the distribution of birds will be carried out by combining different observation techniques and integrating these with a suitable data-assimilation framework. Our approach focuses on the spatio-temporal behaviour of birds at various scales. Central in the project is the use of radar to monitor flying bird movements and a video system to monitor foraging activities. The radar observations cover an area of maximum 300 km2. These observations will quantify timing and intensity of bird movements between roosting and feeding sites, as well as movements of birds due to disturbance. Video camera observations will be used to study the micro-distribution on the tidal flats. Bird counts during high and low tides will complement the data set with validation data.

On the basis of the observations and existing theory, data-based models and a data assimilation system will be developed to link the continuous observations with radar and video to high tide and low tide bird counts, abiotic variables and benthic surveys. The end-goal of the modelling system is to reconstruct the continuously changing bird distribution (during both day and night) over the monitoring area as well as the entire Western Wadden Sea.

Tasks:

•  Supervise the collection and conduct the processing of radar observations of flight movements. The radar-surveys will be carried out in selected time slots of three times fours weeks (28 days) at minimum
• Supervise the collection and processing of video observations of the micro-distribution at the tidal flats. These observations will be carried out continuously throughout the monitoring program
• Process counts by human observers during low tide from a hide
• Develop a data-assimilation system to combine the above observations with an existing dynamic state-space model describing bird movements
• Construct state-space models (either continuum based or individual based) to describe the movement of the most important bird species at the appropriate spatio-temporal scales
• Calibrate the models with observational data
• Create a reanalysis data set of bird abundance by applying the constructed models to the study area as well as the Western Wadden Sea