Science - January 20, 2010

Big Brother spies on wading birds

Video camera makes fieldwork unnecessary.
Mobile radar recognizes bird species and records their flight movements

Martin Baptist surveys the screens with video and radar images in the control room.
A long pole carrying an ultra-modern video camera stands in the Balgzand mudflats in the Wadden Sea near Den Helder. Day and night, the camera records the activities of wading birds in the area.
The images are relayed to the control room at Imares Texel, a few kilometres away. There, student Harma Scholten of VHL Leeuwarden is meticulously updating the bird records. In other words, she is counting birds. Not just grallatorial birds like the oystercatcher, curlew, redshank and dunlin but also the eider duck for instance. The camera is the key element in a study, which started in December, of the foraging behaviour of waders in the Wadden Sea.
For strange though it may seem, there is little known about this subject, as Imares researcher (and Coastal and Marine Research reader at VHL Leeuwarden) Martin Baptist explains. 'We do count birds at their high tide flight locations but we don't know about their temporal and spatial movements at low tide. Where are they then? What food sources are they using? How much time are they spending on this and is there a difference between night and day? We just don't know this kind of thing.'
Office job
That is because the logistics of surveying birds on mudflats exposed when the tide is out are tricky. Baptist: 'It is difficult to get at the area. And when you are there, you disturb the birds'. The new camera turns tricky fieldwork into a comfortable office job.
The five-megapixel camera - 'a huge resolution, better even than HDTV; that is important in order to be able to recognize the species'- is in operation day and night. Images can be obtained at night thanks to infrared LED lights.
But that is not all. In addition to his video images Baptist also has live radar images of a large part of the Wadden Sea. A mobile radar system developed by TNO, the Robin Lite, is stationed in Den Helder harbour. The radar does not just show the birds' flight movements, in theory it can also be used to identify birds. Baptist says this is possible because there are vertical radar images as well as horizontal radar images. 'The vertical radar records flapping frequency, the mass of the object, the speed and the height at which it is flying. You can use this information to determine the bird species, but we still need to learn how to do this by making comparisons with visual observations. Identifying birds using radar is a completely new thing.'
Menu
The study is part of a larger project to determine the capacity of the Wadden Sea to support waders. 'That is, what is the Wadden Sea ecosystem's maximum production and how many fish, birds and sea mammals can the area support', Baptist explains. Imares is collaborating with SOVON Dutch centre for Field Ornithology, TNO, the Royal Netherlands Institute for Sea Research, Bureau Waardenburg and the University of Amsterdam in this project, which is funded by the Netherlands Organization for Scientific Research.
Information is being gathered not just about the foraging behaviour of waders but also about the menu of creatures on the bed of the west Wadden Sea. This is done by taking large numbers of samples from the seabed. Baptist says linking this information to the preferences of foraging birds should provide more insight into 'the wonderful world of the Wadden Sea'. 

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