Swallows and mosquitoes

On the last night of the marine week Alison and I heard that there was going to be some bird ringing out at the Ilon Marsh which is a lake and wetland complex near to the A Rocha centre at Les Tourades. Once upon a time it would have been linked to the vast series of wetlands in the area that is now the Camargue but is now isolated from it by agricultural land. At this time of year migrating swallows arrive at the marsh, build up their energy reserves by eating vast quantities of mosquitoes and after roosting perhaps for several nights begin the long migration south across the Mediterranean and the Sahara. In conjunction with a number of local bird ringers (banders for Americans) A Rocha has been ringing here for many years with some impressive results.

Fastening the ring on the bird's leg

Fastening the ring on the bird’s leg

For the uninitiated, the point of bird ringing is to catch birds without harming them, identify, measure and weigh individuals and give them a unique band or ring around the leg and then release them. If you are lucky, the catching process will recover birds that are already ringed and so through well-established links you can find out where the bird has come from and so on. Ringing has given enormously useful information on migration paths and speeds, the health of birds and even how long they live. (It needs to be said that ringing is precisely regulated and licenced process and every effort is made to ensure that there is the minimum harm or stress inflicted on the birds.)

Setting up the nets

Setting up the nets

So with the light fading we joined the French team and made our way round on some extremely uneven tracks down to the marsh where the trapping nets (“mist nets”) were erected. Despite covering ourselves with the most effective insect repellent known to science mosquitoes immediately descended and began biting with the most extraordinary persistence. We later discovered bites in the most unusual locations, revealing that the mosquitoes had crawled up legs and sleeves and even bitten through shirts.

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Recorded sounds of swallows were played as the light faded and the sky became filled with the extraordinary spectacle of what must have been many thousands of swallows wheeling above us and slowly descending into the reeds to roost. As they did, many flew into the nets and were trapped. After perhaps forty minutes of waiting – and being repeatedly bitten – it was decided that all the birds had descended to roost and it was time to collect the birds in the nets.

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Freeing the birds while being as covered as possible against the mosquitoes!

Freeing the birds while being as covered as possible against the mosquitoes!

Not being licensed ringers we left the delicate task of disentangling the swallows from the nets to the experts. Each bird was carefully taken out and gently put in large cardboard boxes. Eventually, with the nets taken down, the car loads of boxes were taken back to Tourades where, fuelled by copious amounts of Coca-Cola, the birds were examined, measured, ringed and put back in the boxes to spend the night. The next morning they were all released. Apparently over two hundred were actually ringed: all swallows with a single house martin.

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Note the need for large amounts of coca-cola!

It was an impressive sight and definitely worth the bites. Full marks to all involved. It will be very interesting to see where the night’s records come from in the future. With climate change – yes there’s no getting away from that – and the draining of wetlands, the journey that swallows take is becoming ever more hazardous. The numbers of British swallows have certainly fallen dramatically over the last few years. It’s just possible that some of this ringing may actually throw a light on exactly why this is happening.

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