A huge white spot. This is what Rouzic Island usually looks like in the Sept-Îles archipelago (Côtes-d’Armor). Since 1939, this large pebble located off the Pink Granite Coast has been home to the only French colony of northern gannets with more than 20,000 pairs nesting there each year. Last year, however, the rock lost its characteristic white color. It was even transformed in the middle of summer into a giant cemetery. Blame it on the avian flu epizootic which wreaked havoc on poultry farms but also on seabirds.
The first corpse of a gannet was thus discovered on July 1 at the top of the island. From there, it was a hecatomb until the departure of the colony at the beginning of October with nearly 20,000 adult gannets who perished, more than half of the population of the island. “We can speak of a dark year as we have already experienced during the oil spills following the shipwrecks of the Torrey Canyon in 1967 or theAmoco Cadiz in 1978, says Pascal Provost, curator of the Sept-Iles national nature reserve. But here, the situation is unprecedented. »
The worst year for the birth rate
With his colleagues from the League for the Protection of Birds (LPO), the ornithologist watched helplessly at this carnage. “We felt completely helpless because we couldn’t do anything to curb this mortality,” he says. By decimating adults, the avian influenza epidemic also caused the birth rate to plummet on the island. “This is the worst year for the production of young people for thirty years”, underlines Pascal Provost. Before the start of the epidemic, 42% of gannet pairs present on the island had given birth to a chick. A figure which fell to only 10% at the end of the epizootic “and even to 3% in a specific sector where this rate was 77% at the end of the 1990s”, laments the curator.
For the past few days, however, Pascal Provost has felt a little relieved. After their migration, the gannets are indeed back on Rouzic Island. “The first landed on February 22, he says. We were quite worried because they usually arrive around January 27th. This year, they stayed three weeks at sea before landing. Amateur photographer Michel Prat flew over the area on February 24 and observed the presence of thousands of gannets on the island. “It is heartwarming to see this colony again after this cursed year 2022 for seabirds”, he writes on his Facebook page.
The colony will take time to repopulate
On the island, however, the devastation caused by the avian flu epidemic is still visible. “The colony is very sparse and many birds end up single,” says Pascal Provost. Of the 102 nests filmed live by cameras that were occupied by pairs in April 2022, only 15 are so to date. For the rest, 48 are empty and 39 occupied by a single individual. A depopulation that will take time to resolve, according to the scientist. “It will take decades to find this density of birds that we have known on the island, he estimates. But perhaps also that we will never find the level before. »
Because even before this dramatic episode of avian flu, the colony of northern gannets had already begun to decline for a few years under the effect of climate change and the decline in resources at sea. “All these pressures weaken the species and the threaten, underlines Pascal Provost. We just have to hope now that this avian flu epizootic awakens consciences and reminds us of the importance but also the fragility of this natural heritage. »