Albatross: Ocean navigators par excellence.
I’ve spent many an hour of the deck of fishing boats, hauling and emptying nets, sorting fish and filling fish boxes. I’ve always been amazed at how, as soon as we start hauling the net, seabirds appear from nowhere across an empty sea. One of the joys of spending time at sea in the higher latitudes of the South Pacific, is watching albatross track across the ocean. On a couple of occasions, I have gone out in small boats specifically to watch albatross. Off the Kaikoura, on New Zealand’s South Island, large numbers of albatross congregate
Albatross are pretty much unmistakeable. Huge seabirds that appear to soar effortlessly at sea, hardly moving so much as a wingtip. They belong to the family Diomedeidae, and like their relatives the petrels and shearwaters, they have distinctive tube-shaped nasal passages, which scientists believe help them find food at sea through a keen sense of smell. Albatross are phenomenal travellers. Individual birds will circumnavigate the earth, travelling as much as 500 miles in a day and often flying at a steady 50 miles an hour. Once they are fledged, they remain at sea without ever touching land again for the next five or six years. They are found in the North and South Pacific, and in the South Atlantic, but not the North Atlantic. Quite why they don’t occur in the North Atlantic is still a subject of debate amongst scientists. We know they used to occur there from fossil records. Short-tailed albatross, which are now confined to the North Pacific, bred as recently as are 400,000 years ago in Bermuda. The current evidence suggests that a combination of factors may have been responsible. The closing of the Central American Seaway, connecting the Atlantic with the Pacific between North and South America, approximately 2.5 million years ago, and a period of global warming and interglacial sea level rise of several metres (some scientists suggest as much as 20 metres rise in Bermuda). The closure of the seaway effectively isolated the North Atlantic populations from others of the same species in the North Pacific, rendering smaller populations more vulnerable to extinction. It is also thought that sea level rise probably destroyed many nesting grounds. At this point you may be thinking ‘They fly vast distances, why didn’t they simply spread north from the South Atlantic?’ Unfortunately, it’s not that simple. While they appear to fly effortlessly, albatross need wind to generate lift and to steer. The sailors among you will be familiar with the doldrums, areas of ocean where only light winds or no wind at all occurs, and sailboats can be stuck for many days. The doldrums, more properly known as the Inter-Tropical Convergence Zone (ITCZ), forms a band that encircles the earth, extending roughly 5 degrees either side of the equator. Here the north-easterly and south-easterly trade winds collide, resulting in still, slowly rising air that leaves the sails of trans-Atlantic yachts gently flapping. In you are a bird designed to soar on the wind, this is no use at all. Albatross cannot sustain flight by flapping their enormous wings for long. At roughly 10 degrees of latitude wide, the doldrums form a band around 600 nautical miles wide. This is too far for albatross to travel without the aid of wind, and so those born in the southern hemisphere will normally remain in the southern hemisphere all their lives. Occasionally one does cross, perhaps during storm winds. They are then trapped in the northern hemisphere. The Bass rock, a small rocky remnant of ancient volcanos, off the east coast of Scotland, supports the largest colony of northern gannets in the World, but in May 1967 an unusual visitor nicknamed ‘Albert’ arrived. Albert was a black-browed albatross, a species that belongs in the southern hemisphere, more at home surfing the roaring 40s between New Zealand and Chile. It’s thought that Albert was blown off course during a storm in 1967, and was then marooned in the northern hemisphere. In subsequent years Albert was seen further north in the Shetland Isles, and in 2004 a black-browed albatross, believe to be Albert, took up residence among another gannet colony on the remote rocky outcrop of Sula Sgier. In recent years black-browed albatross continue to occasionally turn up around the British coast. In February 2019 one was spotted off Cornwall, while in July 2020 one was seen resting on cliffs amongst a gannet colony in Yorkshire.
This is still a very rare occurrence. The majority of albatross spend years at sea, traversing tens of thousands of miles, then successfully navigate back to the same colony. Wandering albatross, in particular, are famed for the vast distances they cover and their navigation abilities. Because raising chicks is such a long and demanding process for albatross, in most species the adults will breed only every second year, the intervening time being known as their sabbatical year. One study published in Nature (Weimerskirch Et al., 2015) found that some birds breeding in the Crozet and Kerguelen Islands (remote Antarctic and sub-Antarctic Island groups) will circumnavigate Antarctica twice or even three times, covering up to 120,000 kilometres during this sabbatical year, before returning to these remote specks of land in the Southern and Indian Oceans. The short answer is we really don’t know how albatross navigate so precisely. Sensitivity to the Earth’s magnetic fields has been suggested, but other studies have shown that disrupting these fields (by attaching tiny magnets to birds’ heads) make no difference to their ability to navigate. Using their sense of smell to detect traces of gases or compounds is another possibility. Albatross are tubenoses, they have distinctive tubular nostrils believed to help funnel smells as an aid to foraging. Studies have shown that wandering albatross are able to detect and follow faint food smells from at least 20 kilometres away. The olfactory bulbs, the part of the forebrain that processes information on smell, makes up around 37% of the brain space of albatross, so this sense is obviously hugely important in their interpretation of the world around them. Where smells are faint and patchy, albatross will fly upwind in zigzag patterns, presumably working out where the odours are strongest. Recent research is providing growing evidence that ocean-going seabirds may rely not on magnetic patterns but olfactory, or smell cues, and may be producing brain, odour maps of the oceans, possibly similar to our nautical charts of ocean currents, to successfully navigate across thousands of miles of empty ocean and return home.
Gabrielle A. Nevitt, Marcel Losekoot, Henri Weimerskirch. Evidence for olfactory search in wandering albatross, Diomedea exulans. Proceedings of the National Academy of Sciences Mar 2008, 105 (12) 4576-4581; DOI: 10.1073/pnas.0709047105
Anna Gagliardo, Joël Bried, Paolo Lambardi, Paolo Luschi, Martin Wikelski, Francesco Bonadonna. Oceanic navigation in Cory’s shearwaters: evidence for a crucial role of olfactory cues for homing after displacement. Journal of Experimental Biology 2013 216: 2798-2805; doi: 10.1242/jeb.085738
J. Mardon, A. P. Nesterova, J. Traugott, S. M. Saunders, F. Bonadonna. Insight of scent: experimental evidence of olfactory capabilities in the wandering albatross (Diomedea exulans). Journal of Experimental Biology 2010 213: 558-563; doi: 10.1242/jeb.032979
Reynolds Andrew M., Cecere Jacopo G., Paiva Vitor H., Ramos Jaime A. and Focardi Stefano 2015Pelagic seabird flight patterns are consistent with a reliance on olfactory maps for oceanic navigation. Proc. R. Soc. B.28220150468 https://doi.org/10.1098/rspb.2015.0468
Weimerskirch H, Delord K, Guitteaud A, Phillips RA, Pinet P. Extreme variation in migration strategies between and within wandering albatross populations during their sabbatical year, and their fitness consequences. Sci Rep. 2015;5:8853. Published 2015 Mar 9. doi:10.1038/srep08853