Seabirds are indicators of marine health, providing a window under the waves. Over the past 50 years, the world's sea bird populations have declined by 70%. One third of the EU's breeding sea birds are found in Scotland with over a million nesting on the Shetland isles. These populations mirror global trends with many species suffering dramatic crashes in past decades while a few are increasing in number. Scientists closely monitor big populations by collecting them from cliffs and burrows to be ringed and have GPS tracking devices attached. The results of these studies are showing why many species are struggling.
Guillemots can dive hundreds of metres in search of food yet more recently they've been recorded flying every further in search of scarce food. Numbers of one of their staples - the sand eel - have plummeted since heavy overfishing in the 1980s and continue to suffer due to climate change. The arctic tern is appreciated as a harbinger of summer yet its numbers too have dropped by almost two thirds in the past 30 years, also due to sand eel scarcity. The Tern undertakes the longest seasonal migration of any animal, some travelling nearly 50,000 miles in a year - from pole to pole - yet once landed they struggle to feed themselves and their young.
In an ironic twist, EU fishing quotas encourage a lot of trawlers to dump up to half of their catch in order to avoid fines. The northern gannet, fulmar petrel and great skua are adept at taking advantage of the discarded fish but are now threatened by EU proposals to scrap the system and allow larger catches to be kept.
The 100 odd islands that make up Shetland offer a unique 1,600 mile long combined coastline which becomes home to huge sea bird 'cities' in the summer time when the region enjoys around 20 hours of daylight. Warm currents allow for plankton blooms which feed the fish that in turn feed the birds.
The cliffs which house the myriad birds over the summer are a reflection of the birds' feeding and nesting behaviour and the structure of the food chain. Guillemots live in groups on lower rocks, gannets use much of the middle space up to the cliff tops where puffins burrow into the topsoil. On the moorland above, great skuas share the space with other birds from whom they pilfer eggs and regurgitated fish. And while the birds are protected in their nesting grounds, conservation needs to extend to the seas that feed them.
And Shetland is no isolated wildlife sanctuary. The islands lie at the heart of the UK's pelagic fishing grounds at the boundary between the Atlantic Ocean and the North Sea. The human population of 23,000 is outnumbered 40 to 1 by birds but fishing and the North Sea Oil industry put a heavy strain on the environment. While oil companies have become more careful about spills after enormous fines were levied on recent miscreants it is long-term and low-level pollution which is having an effect on the waters around Shetland. And despite assurances about deep water drilling's safety the risks of a spill from an oil tanker are serious and potentially devastating.
Over the past century a close link between fishing habits and agriculture on one side and bird populations on the other has been identified. When sand eel numbers started to plummet, a voluntary initiative by local fishermen to reign in their catches led to a partial recovery of numbers. Shetlanders also show their respect and care for their environment by organising the largest litter picking event in Europe each spring called 'ReddUp'. Undigestible waste such as plastics are known to cause starvation in birds who die with their stomachs full of man made plastics.
The distinctive green of fishing nets blankets some of the Shetland cliffs, collected by birds at sea who are feeding on discarded fish but often also get entangled in the nets, sometimes hanging themselves from the nest. Once again, their source of food can, in this instance, become their undoing. Man and bird live precariously side by side in some of these environments.