Up Close and Personal With… Seabirds

Seabirds may not be the first creature that comes to mind when we picture the ocean but there are in fact over 300 different species of bird which roam the skies above our open waters. These species can be found around the world crossing Arctic icesheets, nesting on balmy Hawaiian islands, floating on the surface of the Pacific Ocean hundreds of miles from shore or, of course, strutting up and down our local beaches in search of the odd titbit. Some, such as the Arctic tern, can actually be found in all climes as they complete the longest migration in the animal kingdom: a 22,000 mile round trip from the Arctic to Antarctica. Unfortunately however, it seems our incredible seabird populations have been especially hard hit by human actions and as a result, many are rapidly declining. Let’s take a closer look at some of our amazing seabird species before unveiling the threats they face in the 21st century.  

Seabirds vary dramatically, not only in what climate they live in but also in size, with the smallest of our ocean-going birds being the northern storm petrel which can be as little as 13cm high. In comparison, our greatest seabird is the wandering albatross whose wingspan is an incredible 11 feet! Despite their obvious physical differences, all seabirds have clever adaptions which allow them to live successfully out in the open sea. For example, many have salt glands near the base of their bills which act as a mini desalination system. This means that these creatures can drink seawater and remain perfectly healthy as their glands pump the salt out of their blood. Arguably, they even have built in sunglasses as a special red oil in their eyes is believed to act as a filter, protecting their eyes from the harsh glare of the sun on the sea whilst helping them spot schools of fish under the surface. 

Not only do seabirds need to battle with cold waters, storms, harsh winds and isolation but they must also be able to find food underwater. Birds must be light to allow them to fly long distances and also buoyant so they can float on the water when resting but these two qualities mean that some birds struggle to dive very far beneath the surface. To solve this problem, some species, such as gannets, have turned to gravity. Gannets are famous divers and often dive like an arrow from 40 metres in the air and hit the water at an incredible 50mph as they use momentum to help them reach tasty fish up to 35 metres under the water. Their ribs and lungs are designed to compress a little when they hit the water to handle the pressure whilst they also have extensions of their respiratory system which act as an airbag.

Once hunting trips are over, many birds head back to land to either breed or feed their growing young. Birds tend to nest in colonies whose size can range from a couple of dozen birds to hundreds of thousands of individuals from different species all living together on rocky outcrops. Parent fulmars are just one species which leave their young behind in the warm nest whilst they head out to hunt. The parents eat the fish they catch and their digestive system separates the oil from the protein and stores the oil in a special gland. Once back in the nest, they regurgitate this sticky oil for their young to eat as it is highly nutritious and helps the chicks grow quickly. However, this strange oil also has another very important purpose. With fulmar chicks left alone unable to fly, they are open to predators which include larger birds such as skua. If one of these greater birds tries to attack the nest, the chick can spit up a jet of warm oil onto the predator which cools into a waxy substance. Fulmar oil and feathers do not mix well and can cause the predators’ feathers to lose their warm and waterproof qualities, leaving them open to the risk of hypothermia. 

Feathers are very important, particularly for Antarctic penguins which live in some of the harshest conditions in the world. Temperatures often drop below -40C, whilst the sea is below freezing, yet they must maintain their core body temperature of 38C. These birds therefore have the densest feathers in the bird world, allowing them to sit on their eggs for weeks on end and head out into the freezing sea to hunt for just as long. Whilst their torpedo shaped bodies make them terrible flyers, they allow them to swim at 15-20mph underwater whilst diving to astonishing depths of 450 metres!

Sadly however, despite our seabirds holding all these amazing superpowers, they are struggling to cope with the plethora of human-induced threats which are facing them. One of the largest comes from our fishing industry and it seems we have become so efficient at catching fish that we are now outcompeting birds which have spent millions of years evolving to do just that. With fewer fish to feed on, seabirds have been seen to have a much slower growth rate, leaving them more susceptible to predation.

Long line fishing sees almost invisible lines which can stretch for up to 80 miles covered in thousands of sharp baited hooks. Birds such as albatrosses, petrels and shearwaters which dive to catch food on the surface fall prey to these as they swoop down to catch a tasty morsel and end up trapped on the hook where they eventually drown. It is hard to know exactly how many birds are killed this way each year as most fishing takes place in the high seas but it is thought 300,000 seabirds die as bycatch from long lines each year whilst 400,000 more die entangled in gill nets, also aptly known as ‘curtains of death’. Currently, conservationists are working with fishermen to find cheap and easily applicable solutions which so far include tying colourful streamers on the lines to scare birds, fishing at night when most birds do not hunt and adding weights to long lines so they sink deep beneath the waves more quickly, reducing the time that birds have to steal bait.

Yet even nets which have long since been abandoned can cause seabirds major strife as ghost nets form a major part of plastic pollution and can still trap and entangle our sea creatures which then struggle to fly, hunt or escape predators. Plastic as a whole provides a huge danger to seabirds which often mistake fragments of trash for food. Soon after plastic enters the sea, algae attach to its surface and this means that our waste can easily smell the same as natural food sources. Additionally, birds like albatrosses often skim the water, meaning microplastics are easily picked up alongside fish and krill. Once inside the body, sharp edges can puncture internal organs whilst plastic often leaves animals feeling full despite having no real nutrients to survive on. As we get more acquainted with the perils of plastic, we are also learning that the chemicals coated around many plastic items such as water bottles and shopping bags are being stored in birds’ tissues and organs and the effect of this on fertility is yet to be fully understood. So it seems here is yet another reason for you to swap out that single-use bottle, say no to straws and avoid plastic shopping bags.

If this wasn’t enough, humans have also, sometimes unwittingly, introduced invasive species to the areas where seabirds mate and raise young. For example, the introduction of rats and livestock to small islands which have historically been isolated and left to nature is causing huge problems. Rats and cats prey on chicks and even full grown adults whilst livestock can trample nests and eggs. Even seemingly harmless species such as ants can cause physical damage to defenceless chicks whilst invasive plant species can often take off, growing so densely that nesting areas and burrows are lost. If this disturbance continues over a long period of time, seabirds may abandon their colony but where do they turn when our world is becoming increasingly busy, connected and polluted? 

Seabirds are an incredibly important group of animals; not only do they play a key role in the food chain and fill people around the world with joy when they are spotted swooping overhead but they are also an important indicator of the overall health of our oceans. Scientists are increasingly studying seabird populations as a way to determine the health of fish stocks far out at sea. Sooty terns on Ascension Island have been found to regurgitate a diet of low quality food such as squid, snails and tiny crabs but the small fish that comprised the majority of their diet 100 years ago has not really been seen. This indicates that something greater is happening in our oceans, leading scientists to look closely at the effects of climate change and overfishing. It is essential that we better understand these worldwide events if we are to better protect our seabird species; can we really imagine a world without the distant squawking of a gull or the elegant outline of a gliding gannet?

By Neve McCracken-Heywood