Transfer to release sites
At 45 to 55 days old the birds are boxed individually and transported to one of the project release sites at Sandringham and Ken Hill Estates in West Norfolk. The release sites were chosen for their proximity to the intertidal mudflats and saltmarshes of the Wash, one of Britain’s most important feeding areas for waders.
The birds spend a short period in the release pen in order to acclimatise. On release day the end panel is removed, and the birds are free to explore their environment.
Release pen at Ken Hill
Fitting GPS tag
GPS and radio-tracking
To monitor the movements of young birds post-release, a subset are fitted with either GPS or radio tags by BTO scientists. GPS tags are fitted with ‘backpack’ harnesses and provide detailed locations multiple times per day, and sometimes as frequently as every 30 minutes. Tags upload data over the mobile phone network daily.
These devices are somewhat heavy (about 12 grams), and not all released birds are yet of a size to carry them, so a different subset of birds are fitted with glued-on radio tags. Scientists can them revisit release sites with a radio receiver and ‘listen’ for tags which are still in the vicinity. Radio tags will fall off naturally after about 3-6 months, while GPS tags will stay on anywhere from 12-18 months.
Fitting radio tag
BTO scientists analyse the movement of GPS tagged birds in the days, weeks and months following release to get an idea of how birds explore their surroundings and what habitats they prefer to use. Because relatively few young Curlew fledge each year, and juveniles are quite difficult to catch and fit tags to, very little is known about how wild juvenile Curlew behave and move around the landscape at this stage of their lives. Being able to track headstarted Curlew can provide a real opportunity to study the behaviour of Curlew of this age.
Curlews waiting to be released at Sandringham
Much more needs to be done
This is a hopeful project. With low breeding success and a lack of fledging of chicks in the wild becoming ever more apparent, the aim of this project is to increase the number of breeding adults and assist in the long-term recovery of the species. It is important however not to see it as a panacea for curlew recovery. Such projects can produce a short-term boost to populations but are expensive and challenging. They are a crucial tool that can only work as part of a wider programme that ensures suitable habitat and protection from predators. It is vital that long term solutions are found that help curlew chicks survive when hatched in the wild.