Storms taking a toll on Jersey’s seabirds

For north-west Europe, the winter of 2013/2014 will be remembered for its persistent and severe storms. Sustained wind speeds of over 140 km/h and gusts over 190 km/h, combined with extreme rainfall and spring high tides, the storms have caused extensive damage and some loss of human life. People have been evacuated from their homes, roads and railways damaged, agricultural land flooded. The cost of repair to private property owners, businesses, infrastructure, and coastal defences will reach into the billions. It’s not just people that have been impacted by this stormy season. Across Europe, there is evidence that some of the wildlife has also taken a beating, arguably most notably its seabirds.

Jersey and its associated offshore reefs may be small but with relatively mild winters it is both home and a stopover location for numerous waders and seabirds.  When the winter storms hit the Island, reports of seabird live strandings and mortalities along the coast rocketed in local wildlife groups.  With these reports persisting throughout January and early February, Cris Sellares – a bird researcher who also works for the National Trust for Jersey and Birds On The Edge – lead a team of some 30 volunteers from the ‘Jersey Wildlife’ Facebook group on 3 Island-wide seabird mortality (known as a wreck) surveys.

 Part of Jersey's 2014 seabird wreck. Credit Samantha Andrews/Ocean Oculus

Part of Jersey's 2014 seabird wreck. Credit Samantha Andrews/Ocean Oculus

The first survey - held mid-February, resulted in some 212 birds being collected off the beaches in just a few hours.  The collection comprised of 13 different species including kittiwakes (Rissa tridactyla), razorbills (Alca torda), guillemots (Uria aalge), curlews (Numenius arquata), European Shags (Phalacrocorax aristotelis), great northern loons (Gavia immer), and Atlantic puffins (Fratercula arctica).  With the storms lessening, the second survey held the following week saw fewer birds being collected – a total of 139.  The final survey, conducted on early March came after a week of more favourable weather.  This survey produced the lowest count of the series with just 27 birds collected – just 13% of the first survey.

 Razorbills and guillemots dominated the mortaility count in 2014. Credit: Samantha Andrews/Ocean Oculus

Razorbills and guillemots dominated the mortaility count in 2014. Credit: Samantha Andrews/Ocean Oculus

Only a small number of the birds were ringed so it is difficult to confirm if the majority of the birds collected were locals/regular visitors to the Island, or washed in from farther afield.  Birds that were ringed were primarily done so in the Channel Islands/north-west France area, though one – a razorbill - came from as far north as Sanda Island, Scotland.  Apart from the final survey, most of the birds collected were in good condition, indicating that they had likely perished within the region – and recently too.  The news that many of the European shags in the wreck likely came from local populations is particularly troubling.  Since 2007 the shag population on the Island has been dwindling, with few reported breeding pairs in recent years.  The causes for this decline remain unknown, but the recent storm mortalities may very well push the population into a steeper decline. 

Concerns about Jersey’s Atlantic puffin population have also been raised.  Jersey supports the remnants of the most southerly population of Atlantic puffin in the British Isles.  Unfortunately, the population has dwindled substantially over the last century - from an estimated 200-200 pairs to 6-10 -pairs, perhaps even less.  Sadly in recent years there has been no evidence that any of the pairs are breeding.  The primary cause of the decline appears to relate to the increasing number of rats and cats on the Island, which prey upon the eggs and young chicks in the Puffin’s burrows.  As yet there is no evidence that the Island’s puffin population has been hit by the recent barrage of storms, but with so many puffins been found across the Channel Islands and France, it is highly plausible that the Jersey population has been impacted, perhaps resulting in the extirpation of the birds from the Island. 

 Many of the birds appeared to be in good condition. Credit: Samantha Andrews/Ocean Oculus

Many of the birds appeared to be in good condition. Credit: Samantha Andrews/Ocean Oculus

So what caused these birds to die?  Both preliminary findings of postmortems carried out on a few of the birds, and assessment at the survey drop-off point indicates that drowning as a result of malnutrition and/or exhaustion was the most likely cause of mortality for the majority of the wreck.  The continuing storms of the past winter has likely made feeding very difficult for seabirds - particularly pelagic species like Alcids, which only come ashore during the breeding season.  Increasing energy expenditure of having to swim in very rough seas and fly in very high winds coupled with low prey captures over a sustained period leads to exhaustion, and eventually drowning.  A small number of the birds have evidence of light oiling, and some showed evidence of broken bones, but it is unclear if these occurred before or after mortality.

Since the last Island-wide survey, a small number of seabird mortality continues to be reported to local wildlife groups but for now at least it seems that the worse of the wreck is over.  The true impacts of the storms on local populations are will only become evident as we move into the breeding season, and continue to monitor the health of the population.

 

This article originally appeared in Marine Scientist.  Marine Scientist is only available in print format.