-Written by Jessé Roy-Drainville
Birds are an integral part of the marine world. They have been known for centuries by mariners to indicate the presence of land nearby or the approach of a storm. But do they know how to recognize them? Pelagic birds, which are relative to the open sea, are a world apart from continental birds. The adaptations that allow them to drink, eat and fly are really fascinating. In the open sea, an observation may last only a few seconds, rarely allowing time to get the camera. Also, identifying a bird in the middle of the Indian Ocean, thousands of miles away from home, is complex. Identifying the species can be difficult, but depending on the region and by elimination, it is often less complicated than it seems. Although pelagic birds come in a multitude of shapes, sizes, colours and behaviours, they have several obvious and unique characteristics that, when added together, make it really easy to identify the family to which they belong.
This short article will introduce you to three families of birds: Laridae, Procellariidae and Sulidae. It is possible to meet them on the open sea, whether you are on the Pacific, Atlantic, Indian, Arctic or Southern waters. These three families make up a good proportion of the birds that can be found offshore, but they are often difficult to differentiate for people who are new to ornithology. Of course, there are other families of seabirds, such as ducks, cormorants, penguins, murres and storm-petrels, but these birds have unique characteristics that often make them easy to identify.
Laridae
Everyone knows the Laridae, as this family includes gulls and terns. Larids also include noddys and skimmers, and there are 102 species of this family worldwide. Here are a few characteristics to help you recognize them.
Shape and size
Laridae have a wide size spectrum, ranging from just over 100 g and 60 cm of wingspan with the Little Gull, to the massive 1.6 kg and 1.65 m wingspan of the Great black-backed Gull. However, most species that spend more time in the open ocean have slim, more slender and smaller forms than land gulls, such as the Arctic Tern, the emblem of our team, or the Royal Tern, shown in the photo below. The wings are always angles and rather short in relation to their weight, if we compare with the other two families.
The angled wings, colourful bill, very pale plumage, and black wingtips are good clues to recognize a member of the Laridae, such as this Royal Tern. @Jessé Roy-Drainville.
Colour
Typically, Laridae are predominantly white as adults and in many cases the wing tips are black. Their beaks and legs are often coloured yellow, red and/or orange. It takes at least a year before adult plumage appears, so it is not uncommon to see immature birds in the open sea. They often have darker colours, in shades of brown and grey, like this photo of an immature Great Black-backed Gull.
Immature Great black-backed Gull. @Jessé Roy-Drainville.
Flight
These birds rarely glide. In just about any situation, Laridae will flap their wings almost continuously while flying. Their flight is often fast, combining agility and power, to capture their prey and escape from predators.
Diet
When they fly at sea, these birds are almost always actively searching for food, which consists mainly of fish. To capture them, they often make shallow dives, after spotting their prey, by flying a few metres above the water. They may also simply harvest their prey at water surface. Jaegers, also known as Skuas, close relatives to the Laridae, have a very different feeding strategy. Although they can get their food themselves, they often prefer to chase Laridae species to make them release or even regurgitate their prey. Being tireless flyers, they often end up winning the "cat and mouse" game. Knowing that regurgitating part of their dinner is a fairly effective way to get rid of the assailant, the victim will often opt for this option. Then, like a pirate, the Jaeger will retrieve its booty at to the surface of the water, that the hunted has delicately vomited in flight.
This picture shows a Long-tailed Jaeger. Jaegers are often regarded as pirates of birds because they steal other birds' food. @Mikaël Jaffré.
Procellariidae
This family is certainly the most pelagic of the three: they can spend months in the open sea and only return to land to reproduce. They are adapted for endurance and can travel very long distances using the least amount of energy possible. This family includes fulmars, shearwaters, petrels and prions. They all have the particularity of having external tubular nostrils, positioned above the beak, as shown in the photo of the Northern Fulmar below.
The Procellariidae have external tubular nostrils, above the beak, that give them an excellent sense of smell, like this Northern Fulmar.@Mikaël Jaffré.
There are 80 species of Procellariidae in the world. Here are some of their characteristics.
Shape and size
The majority of these birds range in size from 70 to 120 cm wingspan and 300 to 600 g. However, the small Diving-petrel can have a wingspan of 35 cm and weigh less than 100 g, while Giant Petrel have a wingspan of more than 2 m and can weigh more than 5 kg. In all cases, their wings are very long in relation to their weight and are much less angled than those of the Laridae. The photo of the Northern Fulmar below shows the very straight wings of Procellariidae. With their relatively short tails, we often notice that in flight, they have the shape of a "+".
In flight, Procellariidae often have this "+" shape, with straight wings, like this Northern Fulmar. @Mikaël Jaffré.
Colour
These birds often have white underwings, usually paler than the top. Even for a species with very dark pigmentation, such as the Sooty Shearwater shown in the next photo, the underside of the wings remains lighter than the top. The white throat and the dark top of the head are also good signs that it is a Procellariidae.
This Sooty Shearwater, certainly one of the darkest species among the Procellariidae, has a very pale underwing compared to the upperside, a good indication that it belongs to this family. Procellariidae will also ʺwalkʺ on the water to take off. @Laurie Maynard.
Flight
The flight is probably the most peculiar thing about these birds, since they are true wonders of the air. Much like albatrosses, Procellariidae fly hundreds of kilometres a year. So, they have a flight that greatly minimizes energy losses. They flap their wings as little as possible and, thanks to their large wingspan, use the wind, and in particular the air movements formed by the waves, to glide easily over very long distances. They are often recognized by their undulating flight when they are on the move, which takes the form of an inclined "S" (~). Note also that many of these birds will "walk" on the surface of the water when they take off.
Diet
Procellariidae mostly seek their food on the surface of the water without ever diving from the air. Fish, squid and crustaceans make up the bulk of their menu. They are often in association with underwater predators, such as tuna and dolphins, which make their prey reachable by pushing them against the surface of the water. However, some species are known to be very good divers, using their wings to propel themselves underwater.
Sulidae
They are certainly among the birds best known for their aerial dives. Their body is fusiform and adapted to diving, allowing them to reach 100 km/h during dives. This family includes the boobys and gannets. Although there are only 10 species in the world, they are found in both warm equatorial waters and cold northern waters. They are less frequent in open sea than Procellariidae, but being excellent pilots, it is not uncommon to see them far offshore. Here are a few tips on how to recognize them.
Shape and size
boobys and gannets are all fairly large birds. The Red-footed Booby, the smallest, has a wingspan of about 1 m and weighs less than 1 kg on average. The Northern Gannet, on the other hand, can have a wingspan of up to 2 m and weigh more than 3.5 kg. However, regardless of the size of the species, these birds all have the same shape: very long, straight wings, with a long beak carried by a large head and a long neck. A bit like Procellariidae, in flight, they have the shape of a "+". However, their wings and head give them a much more fusiform appearance than the other two families. This picture of Northern Gannets shows these last two characteristics.
Sulidae will often fly in a line, as these gannets show. Moreover, their "+" shape, with their very elongated head and neck are also very good clues that they are Sulidae. @Jessé Roy-Drainville.
Colour
In general, adult Sulidae are highly contrasted, possessing both white and dark colours and the transition zones are always well defined between the two. Immatures are usually darker in colour than adults and will not acquire adult plumage until they are 3 or 4 years old. The following photo shows two Brown Boobys: the immature on the left is dark all over the body, while the adult on the right has a very contrasting chest and belly. It can therefore be difficult to determine the species, if the bird observed is an immature one. But as this family has only ten species, the region where the observation is made always gives a good clue as to the species that can be seen and very often reduces the choices available.
Adult Sulidae always have contrasting colours, often sharply cut off from each other, on the wings, head or chest. Immatures can make the task more difficult and are often darker. Can you recognize the immature and adult in these Brown Boobys? @Jessé Roy-Drainville.
Flight
Sulidae have a rather peculiar flight. They will also use marine air currents to make undulating and graceful flights, like the Procellariidae, but as they move, they will repeat a sequence of a few wing beats followed by a glide. In addition, it is not uncommon to see the gannets moving in groups, following each other in a line, as shown in the photo of several gannets above, which the other two families almost never do.
Diet
Their spectacular diving is certainly the most unique thing about this family. They can spot their prey from over 60 metres above the surface. A dive from this height allows them to reach a depth of more than 10 m and then swim down to 25 m. During their dive, they will gradually stick their wings to their bodies, and will then have the shape of a missile when they hit the water. The next picture shows a Northern Gannet about halfway down a dive.
Sulidae make spectacular dives to feed and this is one of the main characteristics that makes them easily recognizable, like this Northern Gannet, halfway through a dive. @Jessé Roy-Drainville.
Conclusion
These three families, although having unique and particular characteristics, can be challenging to identify, especially if the observation lasts only a few seconds. Hopefully, these little tips can help lovers of the open seas recognize these bird families. But what about Tropicbirds, Frigatebirds, Albatrosses and Pelicans? More in an upcoming article!