by: Eva Gruber
Some people might not be aware of the wonderful world of seabirds, and the fascinating life histories that this group of marine creatures have – I aim to briefly introduce this little-known yet strikingly diverse group so that we can all better appreciate, understand, and conserve some of the most intriguing animals on this blue planet. In the next four articles I will present the major taxonomic groupings of seabirds, and exactly what makes them so special.
If you think of a “seabird” – what do you think of? Most people think of a seagull* at the beach. Strictly speaking, gulls are not considered true seabirds as most species are not obligate marine birds and can in fact be found far inland, on lakes and around landfills.
Seabirds can be defined as a functional group of obligate marine birds – that is, they rely and reside on the oceans, and have evolved many unique adaptations to do so.
There are around 350 species of seabirds – many of them threatened or endangered – and while they are incredibly diverse in lifestyle, habitat, and behavior, many are generally similar in form – an example of convergent evolution in the face of similar selective pressure. Seabirds generally have dense, waterproof feathers, a considerable layer of fat for preventing heat loss in water, and efficient salt glands to be able to remove excess salt from their bodies.
Many seabirds spend the majority of their life at sea – if they do set foot on land it will only be for breeding, and even then it’ll likely be on a remote rocky island or sandy atoll in the middle of the ocean. Many species also nest in dense colonies, such as penguins and gannets.
Breeding & Lifespan
Most seabirds raise only one chick a year, and tend to delay breeding until they are older. Seabirds are also often much longer-lived than their terrestrial counterparts. The oldest known wild bird in the world is Wisdom, a female Laysan Albatross who has been nesting her entire life on Midway Atoll in the remote Northwestern Hawaiian Islands. She was banded at an estimated age of 5 years in 1952, which makes her at least 62 years old.
Most seabirds are also monogamous. These pairs are philopatric which means they will return to the exact same burrow or nest to breed, year after year.
So, how do seabirds make a thrive at sea? There are a variety of ways that they feed – from diving below the surface to pursue prey, to surface-feeding, to plunge-diving. Seabird diets are varied and often specialized. Some dive under the surface to chase after fish or squid. Others feed on plankton from the surface.
Some seabirds spend much of their life in the open pelagic, hundreds of miles from shore, while others remain close to shore. Some seabirds migrate thousands of miles a year over open ocean to feed and breed. There are seabirds in the tropics, at the poles, and nearly everywhere in between. But one thing joins them together – seabirds and humans have a long, storied history together – let’s make sure that it continues to be this way far into the future.
Order Sphenisciformes: Penguins
One of the most familiar seabirds to many people is the penguin. Penguins are highly adapted marine birds – so evolved to life in the ocean that they traded wings for flippers, losing their ability to fly (that is, through the air). Under the water’s surface, they are swift, hydrodynamic, fish-seeking torpedoes. To facilitate diving behavior, and in concordance with their loss of flight, penguin bones are dense and heavy, unlike the pneumatized bones of flying birds.
There are 16 species of penguin, ranging in size from the largest Emperor Penguin, to the smallest Little Blue (or Fairy) Penguin. While all penguins live in the Southern Hemisphere, they are not limited to the Antarctic – the Galapagos Penguin lives very near the equator. All penguins are countershaded with a dark back and white belly – the best sort of camouflage in the water, helping them hunt for prey, and to avoid being eaten themselves.
Most penguins nest in dense colonies ranging from a few hundred pairs to several hundred thousand. There are few spectacles on earth like that of a thriving penguin colony.
Seabirds are truly wonderful animals and I hope with this series of articles that you, dear reader, will begin to admire them just a little more. Stay tuned for the next order – Procellariiformes!