Grounded by the light

Skomer island has a massive part to play in the success of an enigmatic seabird often hailed as Wales' national bird. Every year half the world’s population of Manx shearwaters, that's around 700,000 birds, make the 7,000 mile journey from South America to breed on this tiny Pembrokeshire island. Thousands more breed on neighbouring Skokholm and Ramsey islands. It is a big responsibility to ensure these islands remain a safe place for these birds to rear their chicks. Biosecurity measures to prevent invasion by predators such as rats and mice is paramount. That is why we ask you to check your bags when you visit. It is also important that we give the young birds the best chance of fledging successfully so that in future years they will themselves return as breeding adults.

The Pembrokeshire islands: Skokholm (left) Skomer (centre) and Ramsey (far right)

Adult Manx shearwater gliding effortlessly over the sea 

700,000 birds come back to breed on this island every year

Research on Skomer by the OxNav group has shown that fledging birds can be significantly disorientated by light pollution which causes them to become grounded on-shore rather than heading far out to sea and safety. Unfortunately, the chicks having spent their entire life to this point in the darkness of an underground burrow have not yet learnt how to avoid the hazards of the bright lights. Everyone who stays overnight on Skomer uses red light to walk around at night so we don't disturb the birds.

During the fledging season (late August to late September) many chicks are blown off course by stormy weather and further disorientated by bright mainland lights. They become grounded inland or on off shore tankers. OxNav PhD student Martyna Syposz is currently researching this phenomenon on Skomer and her paper on the effect of light pollution on fledging Manx shearwaters in Scotland can be read here.

Martyna weighing a Manx shearwater chick on Skomer

Very young Manx shearwater chick being weighed (Photo Viv Hastie)

Manx shearwater fledgling exercising its wings before heading out to sea

Manx shearwater close to fledging in it's underground burrow (Photo taken from Skomer's burrow cam)

For the past two years, a joint project involving the RSPB and WTSWW has led to a campaign aimed at increasing public awareness about this issue. This campaign has also recruited volunteers across Pembrokeshire to rescue and release grounded birds back out to sea. Manx shearwaters should never be seen over land, let alone grounded, but many have been found stranded in gardens or on roads in Haverfordwest, Carmarthenshire and even as far as Ely in Cardiff! Highly adapted for a life at sea, once grounded on land Manx shearwaters struggle to take flight and without rescue would surely die. This has been an incredibly successful campaign and has led to the rescue of hundreds of birds and importantly highlighted the plight facing these young birds. 

Rescued Manx shearwater fledgling awaiting release at night (Photo: Thousand Islands Expeditions)

What we now need is to go one step further and we would love to see light pollution around the Pembrokeshire islands reduced during the fledging season. Those of you that have stayed overnight on Skomer this year will have noticed we now have blackout blinds in the hostel so that our birds are not affected by night time island lighting on the island. This simple intervention has led to a dramatic decrease in birds grounded in the farm courtyard.

Procellariifromes, the group of birds that include Manx shearwaters are amongst the most threatened of all seabird species, primarily due to climate change and over fishing and pollution. The last thing they need is another hurdle to get over. It really doesn’t have to be that difficult to fix this problem. For one month of the year surely we can turn those lights down for the fledglings.

Sarah Parmor (Skomer Visitor Officer)