Cahow (Bermuda Petrel) what chance of seeing one off Ireland?

Cahows – Hope Springs Eternal

Paul Moore

 

“BERMUDA PETREL  seen from Celtic Voyager over Porcupine Bank c 170nm WNW of  Slea Head today. Per Niall Keogh”   As texts go it was a bit of a shocker,  kind of a …where were you when you heard moment, a  JFK shot,  Roy Keane walking out of the World Cup, kind of  shock.

It shouldn’t have come as a major surprise really , in recent years there has been a growing tendency  for the accessibility of rarities in Ireland to be in inverse proportion to their status; generally the rarer they are, the harder they have been to see. Kinglet, Kingbird, Skimmer, Slaty backed , Bulwer’s, Purple Gallinule have all been untwitchable or effectively so. Thus if one of the rarest seabirds in the world was to be seen in Irish waters then you could be pretty sure there’s unlikely to be a second chance; or at least that seems to be the consensus.

Globally Bermuda Petrels are very rare indeed, just over one hundred pairs breed, and amazingly, outside of Bermuda it seems there have been no sightings from land  anywhere. . According to Bob Flood of Scilly pelagics  http://www.scillypelagics.com/index.html  young birds disperse to no one knows where and return to the breeding colonies anywhere between two to seven years after fledging.  Presumably they take this opportunity to locate favoured feeding areas to which they can return to in subsequent years. Adults spend the breeding season north of Bermuda and the non breeding season  in waters around the Azores. But even that is a bit of a generalization, unlike Petrels, Pterodromas appear to make an entirely personal choice as to where they forage at any time of the year, during the breeding season some stay in waters close to home while others travel vast distances to forage.

Anyone with an interest in seabirds and seawatching in Ireland would have been aware of the results of a  Data logger study of  the  Cahow which showed that at least one bird had come within a couple of hundred km of the Irish coast in Spring 2011. Of course as the data loggers can be out by as much as 150km there was the possibility it wasn’t quite that close but now one has been seen and suddenly it’s a whole new ball game.

The two birds tracked to waters off western Europe appear to have been failed breeders, in April and May, as adults they should have been feeding chicks. Given how rare they are it’s even possible Niall Keogh’s Celtic Voyager bird could be the same data logged  bird back again to a favourite spot.

If occurrences of Cahow in Europe are limited to failed breeders then it doesn’t bode well for anyone hoping to see one, though as the population hopefully continues to recover the chances are slowly improving. It’s a sobering thought for anyone trying to see a Cahow here that  your chances may depend on the failed breeding attempt of a critically endangered bird – hopefully the observers of the Celtic Voyager Cahow were suitably muted in their celebrations with this knowledge  J,  though I wouldn’t bet on it!

Pterodromas appear to like feeding  in upwellings, where currents collide or where deep canyons meet underwater shelves forcing nutrients to the surface; returning to that  map from 2012,  all  6 dots in Irish waters are near the shelf, one quite near Niall’s sighting, one apparently over shallower waters to the east but the other four are  intriguing, clustered around an amphitheatre shaped  ‘scoop’ out of the shelf known as the Porcupine Seabight.

 

map1

Above: 2011/2012 Breeding Season Report Cahow Recovery Program Jeremy Madeiros

Map from the excellent Bermuda  Dept of Conservation Services  Cahow Recovery Programme      http://www.conservation.bm/cahow-recovery-programme/

 

This area measures approximately 300 km X 200 km and is well-known for it’s biodiversity. The first Irish Blue Whale to be photographed was here in 2008 with more since then and it was also the approximate destination for some of the pioneering Irish  pelagics in the late 1980’s when birders logged good numbers of Wilson’s Petrels north of the area. The reasons for the Seabight’s richness is the complex underwater geography causing numerous upwellings over a large area and also the fact that it is sufficiently close to land to receive  nutrients washed from the  land into shallower waters. One  marine ecologist speculated it may be one of the great seabird hotspots, you just need to get there.

The nearest point of the Bight to the SW Irish coast is approx 60 miles from the south western peninsulas of Ireland and as far as I can find out just a few birders have made the trip in recent decades. One Cork birder has been twice with the Irish whale and Dolphin Group (IWDG),  in his desire to see Blue Whales in Irish waters. He reported the area teeming with life, Great Shearwaters were the commonest  bird, a flock of over 30 Wilson’s Petrels and  many many Cetaceans, 9 species on one trip with Humpbacks surfacing beside the boat, (apparently their breath stinks) though no Blue Whales yet.

Another occasional observer is Ronan McLaughlin, an Irish Naval officer.  Ronan has been in the area a number of times and he prepared the map below, it probably deserves an article in it’s own right as he has been keeping notes whenever he can, (off duty obviously!) He also takes his camera with him and has photographed most of the main sightings mentioned below eg http://www.irishbirding.com/birds/web/Display/sighting/59121/Feas_type_Petrel.html

 

map 2

 

(As a complete aside, with that number of Wilson’s Petrels being seen in the area then Madeiran or White – faced is surely on the cards, and what else might be out there is purely the stuff of  imagination.  The Gulf Stream washes against the south and west coasts of Ireland having originated from Florida where it greatly assists pelagic trips from Hatteras. Check out the Seabirding Blog and dream  http://seabirding.blogspot.ie/  )

 

So to cut to the chase, at least some Bermuda Petrels appear to like spending time in the waters off south-western Ireland in Spring, what are the chances of seeing one?  Infinitesimally  small probably, there’s only a few hundred Cahows and a lot of Atlantic Ocean, and yet if the Atlantic Voyagers got lucky so could someone else. It’s an unfortunate accident of geography for sea birders that the edge of the continental shelf is so far from land around the UK and Ireland, it’s not easy to get there and if you don’t fancy joining the navy or crewing on a Spanish trawler then your options are limited. The whale watching trip costs £1000 per head and it’s too far out for a normal charter.  Unless someone starts drilling for oil out there then the only stable base for a scope is on a headland.

If a Bermuda Petrel is going to be seen on a seawatch off SW Ireland then the first requirement is that someone needs to be looking and by and large this rarely happens. There are virtually no spring pelagics in Ireland, and almost nobody seawatches from the extreme SW in spring any more.  Spring seawatching would have been carried out occasionally on Cape Clear up to the early 2000’s and sometimes off Dursey Island and no Cahows were noted though the population would have been even smaller back then.

Another limiting factor is the lack of suitable conditions , you just don’t get many big blows from the SW in spring. Add in the species rarity and that the nearest  record to land so far seems to be about 100 miles and it would be easy to feel pessimistic. It’s not totally hopeless though, the species has been logged covering 500 miles in a day so a 100 mile diversion on the wind to within sight of land should be no great  exertion.

The relevant seawatching points off SW Ireland – the toes of the Teddy bear as I would have been taught in school – (if that doesn’t make any sense have a look at the shape of the whole island and use your imagination) are Cape Clear, Mizen Head, Dursey Island, Valentia Island and possibly Brandon Point.

Cape and Dursey are islands, with very differing access issues. Cape is only accessible by boat, Dursey by cable car, so neither is good for an opportunistic seawatch.

      Brandon is probably too far north and sheltered and only good in a west or north west wind, though nobody seems to have seawatched from there in spring anyway according to the local birders.

So that leaves Mizen and Valentia Island. Valentia isn’t a ‘proper’ island being accessed by a bridge and has had little seawatching carried out from it, but see this post on the Kerry Birding Blog highlighting a new area’s potential

http://kerrybirding.blogspot.ie/p/fantastic-new-seawatching-spot-in-co.html

 

Mizen Head in west Cork has long been known as a seawatching spot.  Access is no longer possible from the lighthouse, at least not legally, but there are a number of other areas. Galley Cove on the south side of the peninsula involves a clamber over rocks, Brow Head requires a walk through fields, or there’s the car park  at the lighthouse if you like your comfort though this is very high up.  These last two seem the best bet for a Spring Bermuda or who knows even a Black – Capped Petrel seawatch.

So to summarise this speculative piece, the chances are slim though slowly improving, nobody’s really looking at the right time of year and as Niall Keogh showed, blind optimism can pay off. Future planned data logging studies will be fascinating in what they reveal, in the meantime the first big blow next Spring I know where I’ll be going, and if by some miracle I do connect, rest assured my celebrations will be every bit as muted as the Celtic Voyagers.

 

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