Month: August 2017

Back in the winter I went to an absolutely fascinating talk by Chris Redfern at the Natural History Society of Northumbria. Chris has been studying arctic terns on the Farne Islands for the past 20 years or so (and they had been well-studied by others before him), and in 2015 managed to fit little geolocators to more than 20 of them.  With their main breeding areas in the Arctic and their wintering grounds in the Antarctic, it has long been known that of all birds, arctic terns are probably the greatest long-distance migrants. This has been confirmed in recent years by fitting geolocators to arctic terns in Greenland, Iceland and Holland which showed them following the expected route down through the Atlantic, some tending to follow the African coast and others crossing over to Brazil and then down the coast of South America before heading down further to the edge of the pack ice around Antarctica.

It might seem, then, that tracking arctic terns from the Farnes would be superfluous but ‘Steely’, the National Trust’s irrepressible former head ranger on the islands, got the BBC interested and they and the geolocator manufacturer (Migrate Technology) stepped in to provide the required kit.  Data from the first of the returned birds was downloaded in June last year and showed that after heading down the Atlantic it had flown far to the east of the Cape of Good Hope before turning south to Antarctica, in the process giving itself the record for long-distance avian migration, duly reported on Springwatch.

However it turned out that this bird wasn’t really trying.  Once the data from all of the returned terns was downloaded it transpired that fully five of them had not only followed the same route out into the middle of the ocean east of South Africa (something out there leads them to linger for a while), but had carried on to the south coast of Australia and then to New Zealand, before finally heading down to Antarctica.

On reflection, it is not actually that surprising that the terns made that easterly change of direction after passing the Cape of Good Hope.  Those latitudes are, after all, the Roaring Forties, where strong westerly winds sweep around the globe almost uninterrupted by landmasses.

One bird had flown so far around the perimeter of Antarctica before it started back along its return migration that its journey would actually have been shorter if it had carried on a little bit further and then turned north directly into the South Atlantic rather than retrace its steps.  As Chris noted, this tends to suggest that the arctic tern’s mental map is based on a flat Earth.

While on their long journey the birds generally stay well away from the coast, which prompts me to ponder the energetics of their journey.  Terns mainly hunt by plunge-diving and while they will splash about while bathing and preening I have never seen them sitting or swimming on the water surface for more than a few seconds at a time, although their webbed feet indicate that they should be perfectly competent paddlers if they have to be.  Also they are active flyers rather than soarers and gliders which must put them at an enormous energetic disadvantage when compared to those great ocean wanderers the albatrosses, petrels and shearwaters.  Do they regularly sit on the water when they are out of sight of land, or do they base themselves on ice floes when they reach the Antarctic?

One does wonder how such astonishingly long migrations first come about.  Most other terns seem content to confine their journeying to a single hemisphere.  There are several tern species very similar to the arctic tern that breed in the sub-antarctic islands and limit their wanderings to the Southern Oceans.  Did our arctic tern evolve from one of these that strayed north of the Equator? or did some arctic terns ‘turn’ their backs on the long-distance migrant lifestyle and settle to breed in their wintering grounds?  Maybe modern molecular genetics will shed light on this.

I also wonder if there is a link between the arctic tern’s lifestyle and its extraordinary feistiness.  At various times I have been bashed on the head by bonxies, by arctic skuas and by great black-backed gulls, but arctic terns are the only ones to have drawn blood while bashing me, and the only ones cunning and agile enough to defeat the stratagem of wearing a cap by going for my ears.  I have come to rely on a wide-brimmed Australian-type leather bush hat while servicing my bat detectors on the Farnes – which may explain the latest tern tactic of an infantry attack – waddling over and tugging at your trouser leg!

Is the aggression used in defending their breeding colonies underpinned by high levels of adrenalin which are then the source of the chutzpah, drive and recklessness needed to push them into global explorations?  Or was it the other way around – has the challenge of their global adventurer lifestyle given them the self-confidence and swagger to take on all comers on their breeding grounds?

The first time I went to the Farnes was as a kid, with my father, Philip.  On that occasion Dad had forgotten to wear his cap, so he protected himself by holding a newspaper over his head.  Undaunted, one of the terns just went for his hand which bled quite prolifically for a while.  Nevertheless, Dad always liked terns.  Anyway, he died in April at the ripe old age of 93, and I thought it would be a fitting tribute to the memory of a kind and gentle bird-lover to respond to Chris Redfern’s appeal for funds to sponsor the purchase of additional geolocators to fit to Farnes arctic terns so that the research can continue.  I have a sneaking hope that that at least some arctic terns have figured out that the world is actually round and that one of them will be the first bird ever to be proven to have circumnavigated the entire planet.  I shared this thought with Chris and asked him to pick a tern for Dad’s geolocator that hadn’t been tracked before and looked as if it might be a potential global circumnavigator.  Chris duly obliged, writing on 10th June:

‘Green-64 photo attached; this is a bird with no ‘logger history’. This bird (metal ring SV63945) was first ringed as an adult on Inner Farne on 28 June 2003, so it is at least 14 years old. Nesting in a fairly competitive part of the colony so should be a ‘good’ bird! Not sure about the sex though (we can only really tell by watching them mating, or DNA). The geolocator is attached to the green leg ring, as you can see. The ring with device rotates quite freely and does not seem to impede the bird in any way that we have been able to measure. Incidentally, yesterday I managed to recover a geolocator from a bird that I couldn’t catch last year. The logger (and bird) were in good condition and the logger was still functional and had recorded data for a full 18 months (the maximum time that they are programmed, by the manufacturer, to collect data for), so we are well pleased!’

This is Chris’ photo of Green-64, Philip’s Tern. The object it is standing on is a stone font that sits in the courtyard on Inner Farne amongst the old monastic buildings.

I went out to the islands myself on 22nd June to check on the bat detectors and spent some time in the courtyard.  Philip’s Tern soon appeared, with a tiny sand eel in its bill, and perched briefly on the font before dropping down into the long vegetation where its chick(s) must have been lurking.  It returned, minus sand eel, to the top of the font where it spent the next half hour preening, loafing and driving off any other tern that tried to perch on the rim.

 

The Farnes belonged to the Church from the 7th century, when the kings of Northumbria gifted them to St Cuthbert and his successors, through till the late 19th century, and the font seems to be a leftover from the extensive restoration works undertaken to the buildings on Inner Farne by the eminent Victorian churchman and social reformer Charles Thorp.  Thorp was the archdeacon of Durham and the first person to take steps to protect the birds of the Farnes. (St Cuthbert, who seems to have been a prime exemplar of the Celtic monkish tradition of showing respect for all forms of life, is particularly associated with otters and eider ducks, so it’s possible he’s the one who actually deserves the gold medal!).  Thorp refurbished St Cuthbert’s Chapel with fittings scavenged from Durham Cathedral and the font, which was perhaps surplus to requirements, came from a church in Gateshead.  This explains why, despite its age (15th century) and current outdoor location it is only lightly weathered.

 

 

 

As my brother Nick reminded us at Dad’s funeral, Dad was never baptised.  His parents had unusually advanced ideas for the 1920s and thought a person should have the opportunity to make their own mind up about their religion, and in the event Dad never seemed to feel the need to have one.  Not that this ever stopped him from accepting invitations to be a godparent (‘just don’t tell the vicar!’) and I like to think he would appreciate the irony of his tern being the boss of a font!

By the time of my next visit to the Farnes, on the 16th August, the terns had all gone. Unlike the other tern species which dawdle down the east coast after breeding, the arctics head off soon after the young have fledged, taking a direct route over land to the Irish Sea and then out into the Atlantic.  They have, after all, a very long way to go.  But I am already looking forward to May 2018 when, hopefully, Green-64 will return once more to the courtyard on Inner Farne and Chris will find out where it has been.

Go Green-64, Philip’s Tern, Monarch of the Font!