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A pair of common terns have nested on a raft built in the lake (summer 2007): a first for Wallonia!!!
Aquascope Virelles has the pleasure to announce that a pair of common terns are nesting on Virelles pond.
These magnificent birds are long-distance migrators that have never nested in Wallonia before. This makes it a first for our region, something that we are justifiably proud of, especially as the pair have built their nest on a raft that was put there specially to attract them!
Common tern: description and distribution :
 The common tern (Sterna hirundo) is a seabird about the size of a small gull. Its white underparts and pale grey back contrast with its black cap. The tail is long and forked, the wings narrow and pointed. The beak and legs are red.
When feeding it hovers above the surface of the water, watching for small fish close to the surface. It then dives, sometimes quite spectacularly, frequently managing to catch an unwary or sickly tiddler, in a selective cull that helps to keep the fish population healthy.
This “sea swallow” breeds in practically all European countries, mainly on the coasts and along large rivers and their tributaries. It is a migratory bird, overwintering on the coasts of Africa, from Senegal to South Africa.
In Belgium there are very few pairs that actually breed, and these are concentrated in the North of the country; in Wallonia we usually see them only during the migration period, and then only for very brief stays, usually no more than a stopover.
History of the project :
 Over the past few years various experiments have been carried out all over Europe, aimed at countering the loss of nesting habitats for the common tern, which likes to nest on gravel, shingle or sand. Coastal development, training of major water courses and disturbance caused by recreational activities have all led to the loss of suitable habitats. There are various ways of offsetting these threats, one of which is to build floating rafts.
Towards the end of 2005, after studying the various possibilities in relation to local conditions the Virelles Pond Scientific Commission gave the go-ahead for building a tern nesting raft on the site.
The raft measures 4 x 4 metres and weighs more than 2.5 tonnes.
This solution offers various advantages:
- It offers a favourable nesting environment (shingle).
- The raft rides up and down with the waves, preventing the nest from being swamped.
- The eggs and chicks are safe from land predators.
- The raft can be fitted with various special features such as an anti-drowning net, roosting boards etc.
In spring 2006 the newly installed raft only attracted a few more transient terns than normal. At the beginning of summer, however, a series of events raised the hopes of local naturalists. One day in July, two individuals started to get very territorial, mobbing a heron and a kite. They even appeared to be mating! But alas without result. Perhaps it was a young pair practising for the real thing in 2007?
Success !
 The hot, sunny weather at the start of summer 2007 was hardly likely to encourage migrating birds to stop for a breather at Virelles.
Not many terns were seen, and it was not until mid-June that first one individual and then another raised the expectations of birdwatchers.
Not only were the pair decidedly territorial in their behaviour, but they actually began courtship rituals, offering fish to one another, chasing each other through the air and actually scratching a small depression among the stones on the raft. To the observers, it looked very hopeful indeed.
On 1 July the female stayed sitting nearly all day on one of the scratched-out depressions: she was brooding. From then on the male constantly brought food for her. What little rest there was to be had on the raft was frequently broken off in defence of the nest, whenever some other bird dared to come to close. All birds that presented a threat, such as herons, kites, buzzards and jackdaws, were mercilessly driven off whatever their size.
Nouvelles fraîches:
We have been hoping for this moment since 1 July when
the female really seemed to be brooding on the raft.
On July 23 at least one chick was glimpsed in the early
hours of the morning during one of the feeds: a tiny
head poked out from underneath one of parents, beak wide
open in a plea for a morsel!
Later observations confirmed the presence of one chick.
The evening before, signs of hatching had been deduced
from the behaviour the pair. Never had they been seen to
be so diligent, with more frequent feeding, keeping busy
around the nest and fierce hostility to certain types of
bird flying over (hobby, osprey, grey heron etc.).
It looks as if the chick had actually hatched a couple
of days before, but weather conditions prevented from
being observed, as it remained hidden underneath one of
the parents.
At the end of July and the beginning August the chick
looked like a little ball of light brown feathers,
already gambolling around on the raft and enjoying the
sun. The adults shared the work, one of them always
staying on the raft to look after the chick while the
other went fishing or hunting for insects, occasionally
mobbing another bird that was getting too curious for
the anxious parent’s taste.
Epilogue: The first common tern hatched in Wallonia took
to the air on 14 August 2007. During the next few days
it was seen in flight accompanied by at least one adult.
One week later, all three birds left Virelles, bound for
Africa.
Why Virelles ?
An artificial platform by itself is not enough to attract a pair of common terns. There also have to be sufficient food resources, together with perfect peace and quiet. The absence of all water sports activities on Virelles pond certainly played a crucial role in the choice of site, but the availability of prey species probably played an even greater role. The constant efforts put into managing the pond by Virelles-Nature have paid off in this respect. In particular, the draining of the pond in Autumn 2006 made it possible to rejuvenate the fish population, while all the large carps were fished out; the latter stir up the mud while searching for food and so make the water cloudy. These measures followed on from the large-scale programme of restoring the quality of the water in Virelles pond, financed by the Walloon Region and carried out in collaboration with all the players in the catchment area. Dozens of measures were proposed and put into practice by the signatories of the Charter, to the benefit of the pond water quality.
As a result, when the terns arrived in June 2007 they found a young, diversified population of fish (they rarely take fish greater than 10 cm) swimming in clear water, thus enabling them to see their prey.
leur pitance.
Lessons learned
Birds are certainly one of the most marvellous spectacles offered by nature, constantly entrancing us with their mastery of the air, the diversity of form and shape, the variety of colours and their captivating song ... not to mention the feeling of liberty that the flight of birds inspires in us.
Birds are without doubt the best ambassadors of the natural world that too often is badly treated by us.
Faced the steady erosion of biodiversity in Wallonia, the arrival of a new breeding species is a hopeful sign.
This latest nesting demonstrates the great powers of adaptation and development of certain animal species. As long as this potential can be realised – or better still, given a helping hand – populations of these species will be able to establish themselves. But first we have to understand the requirements of rare species, as well as the threats facing them.
Finally, this nesting is proof if any is required of the great biological value of the Virelles site.
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