State-of-the-art technology used to monitor birds will allow experts to learn more about migration and how we can safeguard their future survival
WE ALL KNOW how easy it is to lose track of a bird. The elusive warbler that vanishes between one tree and the next; the unidentified seabird forever just disappearing over the horizon. So imagine how difficult it is to keep tabs on a bird – let alone dozens of birds – when it is heading out into the freezing expanses of the North Atlantic, or plunging into the steamy undergrowth of sub-saharan Africa.
How to solve the problem? Well, we can always ring birds, and see where they end up.
“There was only one recovery of a ringed Cuckoo in Africa,” points out Chris Hewson of the British Trust for Ornithology (BTO). “That was in 1928, recovered in Cameroon.” He adds that the finding actually set us off on the wrong track: for a long time it was thought that the birds wintered in Cameroon, when in fact the Cuckoo in question was probably already heading northwards, back to its European breeding grounds, when it was caught. Chris is heading up a programme of birdtracking projects designed to bring the latest in 21st Century technology to bear on this most enduring of problems. Since 2011, the BTO has been deploying satellite tags to monitor the movements of Cuckoos as they head to their African wintering territories. The tags transmit signals to the Argos satellite network, which relays the information to a ground-based component that is able to use a wavelength phenomenon known as the Doppler effect, which serves to calculate the birds’ approximate locations.
It’s a lot of trouble to go to for a handful of birds. What’s it all for?
“The main driver is the big decline we’ve seen in Afro-palearctic migrants,” Chris explains, “particularly those that go further south than the Sahel, those that go into the humid tropics of western and central Africa. In a lot of cases, we knew very very little about what our birds did, certainly once they left Europe and, in some cases, once they left Britain. “So, if we were to have any chance of finding out what’s going on with these birds in terms of their population decline, we really needed to know a lot more about what they were doing throughout the rest of the year when they’re not here on their breeding grounds.”
The summer of 2016 saw eight new birds – from Sherwood Forest, the New Forest, Thetford Forest and Dartmoor – joining the BTO’S corps of tagged Cuckoos, which now number 12 in total. The data sent back from the tags (which are fastened between the bird’s wings, ‘like a little backpack’) will help Chris and his team gain a more complete understanding of the threats facing the species. Twelve birds is a big enough sample for what the BTO’S Cuckoo Project is hoping to achieve, as Chris explains: “If you’re trying to get a general idea of what the overall migration strategy is, then the generally considered minimum is about four birds.”
There are different approaches to tagging birds
But other kinds of project require a more widescreen approach. The RSPB’S seabird tracking project, launched in 2010, has so far monitored the movements of some 1,200 individual birds from 27 breeding colonies. “The RSPB got European funding from the Future of the Atlantic Marine Environment (FAME) programme, and that allowed us to start the biggest tracking project that has ever been undertaken in the UK,” says RSPB Conservation Scientist Dr Ellie Owen. Ellie’s part of the project was designed to address the biggest data gap in our knowledge of seabird movements: where the birds go to feed during the breeding season. Before the advent of high-tech tags, researchers relied on indirect methods to estimate the birds’ foraging ranges – looking out for birds at sea carrying fish landwards, for instance, or timing the birds’ trips to and from the nest. Tagging has revolutionised the field. “The data was breaking all the rules straight away,” Ellie says. “Birds were foraging further from the colony than anyone thought possible, and seabirds of the same species at different colonies were travelling very different distances.
The data was breaking all the rules straight away,” Ellie says. “Birds were foraging further from the colony than anyone thought possible, and seabirds of the same species were travelling very different distances
“Some were able to feed on their doorstep, while others had to travel hundreds of kilometres, probably because of a failure of food resources near the colony.” The study – which initially covered Razorbill, Guillemot, Fulmar, Kittiwake and Shag populations at 30 UK colonies – found an inverse correlation between the distance birds had to travel and their rates of breeding success. After six years of study, the team now has what Ellie calls a ‘gap-free map’ of where four of the target species are likely to be active during the breeding season. It’s hoped that the map will be used in assessing the potential impacts of offshore developments – wind farms, say, or gas platforms – as well as in helping to identify optimum locations for Marine Protection Areas (MPAS). The missing species is the Fulmar. The tracking project used tags that had to be recovered, so researchers had to re-capture the target bird in order to access the data. Fulmar are tricky birds to catch, and not just because of their habit of vomiting fishy fluid over their capturers. “Once you’ve been working with Fulmars for a while, you work out how not to get covered,’ Ellie laughs. ‘But the problem is that they go on really long trips.”
Tags are problematic and many are liable to be lost
The tags used on the birds are only temporary, and are liable to fall off; the window of opportunity for
capturing a returned Fulmar before the tag comes loose can therefore be very small. In some cases, as many as two-thirds of tags go uncollected. Ellie talks me through the capturing process for cliff-nesting species. It’s actually very similar to the method used for centuries by the people of St Kilda, who relied on seabirds for their survival – “we use the newest technology, but the oldest techniques,” Ellie says. A researcher, safely roped, will approach the cliff-edge and lower a long pole towards the target bird. The pole has a loop on the end, which is used to ensnare the bird. It’s tricky, painstaking work – especially for recaptures, when the bird has been through the same process just days before. “They know exactly what you’re doing,” Ellie said, though the advance of technology promises to make life easier for both the researchers and the birds. GPS tags that relay data to a radio basestation – and therefore needn’t be recaptured – have been successfully used on Puffins and also Black Guillemots. But progress comes at a price: the new tags can cost up to 10 times more than the old ones, while satellite tags like those used in the BTO’S Cuckoo project can set you back more than £2,000. New ground is always being broken, especially with regard to miniaturisation. Tiny geolocators, which are small enough to fasten to a leg-ring and monitor light levels to provide a location to a precision of around 150km, have long been in use, but now GPS – which is up to 10,000 times more precise – is catching up. Devices weighing just 0.23g have been attached to 10g Wood Warblers; Ellie’s team has been Gps-tagging Storm Petrels, which is the UK’S smallest seabird. Chris Hewson is passionate about the wider impacts of the BTO’S tagging programmes. “It’s been really important for public engagement, raising awareness of migrant declines,” he says. “In doing that you’re removing impediments to future research and also the conservation action that needs to be taken. “People aren’t going to care about what they don’t know about. It’s part of the process of trying to raise the profile of migrants and migrant declines,” he added. The Cuckoo project, he said, has been the Trust’s most important so far. The advanced technology in use has been a game-changer.
Data is king for monitoring birds
Almut Schlaich, a researcher at the University of Groningen who works on tracking the threatened Montagu’s Harrier, is another evangelist for satellite tagging. “[Satellite] bird tagging is the tool to follow birds year-round,” she says. “With monitoring and radio-tracking you can gain important information on populations and movement during the breeding season, but where birds spend the rest of the year,
Devices weighing just 0.23g have been attached to 10g Wood Warblers; Ellie’s team has been Gps-tagging Storm Petrels
which routes they use for their migrations, where they stop over, where they winter, can only be followed by using tracking devices,” she added. “The data that we retrieve gives us information on population-specific routes, connectivity between breeding and wintering areas, stop-over sites. Another very important thing is that we see where birds die during the annual cycle.” Almut says this is very important to infer bottlenecks for a population. But Gps-logging tags which link to a groundbased antenna system rather than a satellite also have their uses. “Normally, we build up a network of antennas in the breeding area that tagged birds connect to when they arrive back,” Almut says. “The advantage of these data is that you collect very detailed movement and behavioural data (up to a position every three seconds), and with this we can analyse habitat use on a much smaller scale,” she added. “This is needed to understand how birds use the landscape and to investigate which measures could help them survive and breed successfully.” The emphasis on technology might suggest that bird researchers risk becoming desk-bound laptop-jockeys, forever chained to data feeds and satellite link-ups. Far from it! Almut’s research has taken her far from the UK and the Netherlands, to the harriers’ regular wintering grounds in the Sahel region of Africa. “It’s one thing to see the tracks on a map, which is already amazing, but another to see the birds from so close by, follow them down to their stop-over sites in eastern Morocco and their wintering areas in Niger, Burkina-faso, Mali and Senegal, and seeing the same birds you held in your hand some months before flying over the savannah landscape hunting grasshoppers! Just amazing,” she says. “The combination of tracking data and fieldwork is the key to finding out more about the requirements of the species.” Similarly, Ellie Owen from the RSPB first experienced the wonders of tracking data at one of the UK’S wildest spots, the island of Copinsay, east of Orkney. “Incredibly exciting,” she recalls. “Just an amazing place: there are enormous waves right next to you, and you’re right below thousands and thousands of Razorbills and Guillemots and Kittiwakes, and add to that the fact that the data we were getting back was showing something completely new… “Every time we went through the turmoil of ‘will we catch this bird back?’, ‘did the tag work?’ – then you finally get this data popping up – and it’s pretty cool.” For more about the BTO visit bto.org and for the RSPB visit rspb.org.uk
Which routes they use for their migrations, where they stop over, where they winter, can only be followed by using tracking devices
BACKPACK COMPACT A total of 12 Cuckoos have been tagged by the BTO. The tags are fastened between the bird’s wings Technology used to transmit information to the BTO is packed into a device no larger than a 50p piece
BIRD TRACKING Chris Hewson of the BTO is heading up a programme of projects using the latest technology to track birds, such as the Cuckoo
ON THE MOVE A Puffin in flight has been fitted with a tag and is being monitored by the RSPB
LIGHTWEIGHT Some tags weigh as little as 0.23g and have been fitted to 10g Wood Warblers
TAGGING Puffins are tagged to help researchers monitor population and movement