Posted by: orcaweb | May 9, 2017

Musings on Migration

Hi, it’s Andy here on the Pont Aven.

We’ve had marginally better weather conditions this week and have had some great days travelling through Biscay.  Monday gave us distant pilot whales and wake riding bottlenose dolphins in the northern Bay, hundreds of common dolphins all the way across, and a brief close up of a female Cuvier’s beaked whale, along with a handful of the mighty fin whales in the southern Bay.

The fin whales aren’t here in huge numbers yet but they are certainly around. It may be that these are the first wave of the summer’s great whales to pass through before the usual much larger second movement that fills the Bay in August and September.

Passengers often ask us if these whales are migrating?  The answer is somewhat ambivalent as we don’t really know yet.  Certainly movement is taking place, driven in part by food sources, but so little is understood about the fin whale population in the North Atlantic that it’s hard to be certain.  We have yet to identify where their calving grounds are but their distribution ranges from Greenland and Svalbard in the north down to the Canary Islands and the Antilles in the south.  Whether there is a definite north-south migration similar to that of the humpback whales in the N. Atlantic is uncertain and fins can be found across their range at all times of the year.  But we do have some understanding of some of their foraging grounds and Biscay is clearly a hugely important one to the North Atlantic population.  It may well be that we are seeing a northern shift in summer fin whale distribution as we are starting to see good numbers of them feeding around Southern Ireland and the numbers seen in the Bay may be slightly less than the massive figures that were being recorded over a decade ago.  But that is anecdotal, speculative and cautionary and is exactly why the work that ORCA does, establishing a record of long term baseline data, is so important.

A week spent on the Pont-Aven sees us travel between four different countries (UK, France, Spain, Ireland) and that sense of continuous movement reminds me that both the history and the rhythm of the world is one of constant movement and migration.  Whale watchers and birders are regular companions for us on the upper decks, many travelling to Spain at this time of year to catch the raptor migration.  Others are heading south to take part in mammoth trips like walking the pilgrimage routes to Santiago de Campostella or starting or ending cycle tours that can cover huge areas of Europe and take months or even years to complete.  Some are solitary travellers, a few travel with just their dog as a companion, often in a trailer towed behind a bicycle.  Many passengers are returning to the UK after spending the winter in Spain or Portugal in their camper vans, others are bikers off on a big ride or emigrants leaving the UK and moving to Europe in search of their dreams.  And the same tales can be found on the Roscoff-Cork crossing with lots of French and Irish travellers using the ferry service for very similar reasons.

It is that crossing to Ireland that has given us so many sightings of basking sharks this year.  They also migrate in search of rich pickings and follow the plankton shoals north up the coasts of the UK and Ireland throughout the summer.  It is thought that some basking sharks winter off the coasts of West Africa, whilst others stay in the vicinity of the UK but move to deeper, warmer water.  So it seems that basking sharks migrate both through the water column and spatially.

We saw yet another shark sedately feeding on Saturday morning but before that we arrived on deck at 6am to find lots of swallows, swifts, house martins, a grey plover, and even a little egret – all using the slipstream of the ship to aid their migration north.  Swallows have been ever present friends since I started on the ship at the beginning of April.  When I left home they had yet to arrive from their southern African winter retreats but I soon found them in Spain en-route to northern Europe – despite the fact that Aristotle believed that the reason for their winter disappearance must have been that they hibernated underground!  We have enjoyed their company across the Bay of Biscay, the Channel and the Celtic Sea in recent weeks and I know that they will be swooping around the fields of my Devon home when I return in a few days time.  Like me they have been chasing Spring.  It’s wonderful to see the swifts returning too; I first picked them up flying high above Roscoff a couple of weeks ago.  We also found a group of travelling wheatears resting in the park on the seafront at Roscoff last week and I have been hearing those early migrants the chiffchaffs with their distinctive song around the Brittany town for some time.

Turnstone, Roscoff harbour, April, 2017.jpg

Turnstone, Roscoff harbour

 

 

 

The last late groups of lesser black-backed gulls have been moving through the Bay the past week from their wintering grounds off the Portuguese and west African coasts.  I’ve seen these heading through Biscay as early as mid-February before, accompanied by huge strings of adult gannets powering north through the late winter gales, driven by the unstoppable instinct to head to the breeding grounds to reproduce.  We’ve spotted osprey, mixed flocks of bar tailed godwits and whimbrels, herons and various wagtails in the middle of the Bay this year.  A wind beaten chiffchaff hitched a ride on the ship for quite some time on a Channel crossing.  Sadly we’ve not picked up any turtle doves this year but we have had three collared doves paying us a visit on the Pont-Aven.  That might not seem strange if it wasn’t for the fact that they aren’t really known to migrate so we have been surprised to find them on the ship so far out to sea.  So we’ve had a good range of moving species so far this Spring – perhaps not enough to make a twitcher twitch but more than enough to excite us.

Collared dove on Pont Aven 2017

Collared Dove visiting the Pont-Aven

chiffchaff, Pont Aven, Channel, early May 2017

A windswept chiffchaff sheltering on the ship

Maybe our favourite bird, that has been with us since the start of the Wildlife Officer season, is the amazing and beautifully two-toned manx shearwater.  We first found them in the Bay and on the northern shelf as we started the season and they have since largely moved on from there and can now be found in large numbers in the Celtic Sea as we cross to Ireland.  This tiny, 400g, trans-equatorial and trans-Atlantic migrating seabird can travel an immense 10,000 km from their primary wintering grounds off the coasts of Brazil and Argentina to spend around three months mainly off the coasts of Britain and Ireland – which host two thirds of the world’s Manxie breeding population.  That makes our waters and islands a globally significant habitat for these birds.  It’s likely that a majority of those that we spot in the Celtic Sea are nesting on the Welsh Islands of Skomer or Skokholm which accommodate around 170,000 of these shearwaters each year for their brief but essential, once a year visit to land, in order to nest. They do this in burrows below the ground which they access at night so as not to get predated on by great black-backed gulls and raptors.  This highlights the huge costs that migration incurs as species have to battle storms, predation and mortality but still the rewards – generally better food resources for raising their offspring – are worth the hardships endured.

Yesterday, Heather and I spent eleven hours on deck with passengers, sea watching and surveying within the Bay of Biscay in reasonable conditions.  It was a most enjoyable day for us all with hundreds and hundreds of dolphins sighted.  What was slightly strange was that we came across only a handful of birds and no other cetacean species at all.  No fin whales, sperm whales, pilot whales, beaked whales, bottlenose dolphins, just short-beaked common dolphins.  We diligently checked pod after pod and couldn’t find any striped dolphins until we found some in the very last couple of groups of dolphins that appeared at dusk.  Just large numbers of commons, many starting to amalgamate into groups of a hundred or more.  Have the fin whales and sperm whales moved on and the Bay is empty before the next wave of animals moves in or are they simply in another part of the Bay?  We don’t know yet but one thing I do know is that the movement of peoples and animals is absolutely fascinating and is an integral aspect of life on this earth.  Keep an eye on the blogs from my fellow wildlife officers over the coming weeks to find out where all the whales have gone.

Striped, biscay northern shelf, May 2017.jpg

Striped dolphins on the northern shelf

commons, biscay, May 17, Heather.jpg

Common dolphins in the Bay

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