The last order in our introduction to seabirds contains a mix of seabird, shorebird, and waterbird species – it can get a little confusing, so try and follow along.
Charadriiformes
This order is named after the nominal family – Charadriidae which contains the shorebirds plovers and lapwings. Although it is likely to change, for now certain seabird families are lumped into the Charadriiformes. Those families are Alcidae (the auks), Laridae (gull), Sternidae (terns), Rhyncopidae (skimmers), and Scolopacidae (sandpipers, phalaropes).
Alcidae
This family contains seabirds only – and 25 species of them. Of each genera, there are only a few species (or sometimes only one) – this relatively low diversity may be a reflection of their rather small geographic ranges, which in turn is limited by the distribution and behavior of their prey.
Auks are pursuit divers, and can only pursue and catch fish in cooler waters. In warmer waters, fish are physiologically able to swim faster and escape. Auks can all be found in the cooler northern ocean waters of Northern Hemisphere, and in many ways they fill the niche of penguins at the opposite end of the planet. In fact, the two murre species might easily be mistaken for penguins, with their upright posture and black and white coloration.
Murres can be found in a circumpolar distribution, in boreal and sub-arctic waters of the North Atlantic and North Pacific. Murres are excellent swimmers, able to quickly pursue fish and squid at a depth up to 180 m (590 ft). While they can fly, they are heavy and their wing loading is at right about the limit for birds of flight. If murres were any heavier or their wings any smaller, they would be flightless.
Like many seabirds, murres nest in dense colonies of up to thousands of individuals.
They are highly philopatric, returning year after year to the exact same nest site (about the size of one individual murre). Common Murres monitored on the Farallon Islands by biologists are pushing the upper limits for the life span of this species, with certain old birds pushing over 30 years – and still breeding!
They lay a single egg a year. These eggs are pyriform in shape, rounded at one end and pointed at the other – if disturbed they roll in a circle. This is highly advantageous as many populations nest on steep rocky cliffs, and part of the murres’ evolutionary strategy demanded an egg that would not roll off nest sites on cliffs. The eggs also vary individually in color and pattern – this is memorized by the parent birds so that they can identify their own egg amidst the hundreds surrounding them.
This is a family contains several species found in the North Pacific. Compact, stocky seabirds, they dive for fish and krill and nest on remote rocky islands. Most alcids are unique in that when on land, they walk using their entire foot, unlike most birds which walk on their toes. To human eyes, this looks like they are walking on their haunches but it is in fact foot-walking.
Genus Aethia – there are five species of auklets – Whiskered, Least, Crested, and Parakeet. The Cassin’s Auklet is in a separate genus Ptychoramphus. The Crested Auklet, in my opinion, should be more well-known as it is an incredibly charismatic species.
Highly social, they evolved a scent with which to communicate, build bonds, and perhaps mark their burrow with. This scent is strong, and pleasant, reminiscent of oranges, and the orange-y scent of a colony can be smelled from over a mile away.
They are incredibly goofy looking, and while excellent divers, their flying skills are limited and their return to the colony is often punctuated by flying into and bouncing off of rocks.
photo credit: ARRuss
There are three species of “true” guillemots (as murres are sometimes referred to as guillemots) in the genus Cepphus – Black, Pigeon, and Spectacled. They are unique among alcids in that they lay two eggs in a single brood. Perhaps as a consequence, they are shorter-lived than many other seabirds. Guillemots nest in loose colonies with their nests inside rocky crevices and will gather to socialize on the surface.
Murrelets are further divided into two separate genuses: Synthliboramphus and Brachyramphus. Brachyrhampus murrelets are rather unique within the auk family in that they nest far from water, individually. This makes them incredibly secretive and hard to study, and of the three Brachyrhampus species, two are near threatened and one – the Marbled Murrelet – is endangered.
The Marbled Murrelet relies on old growth forests in which to nest, requiring gigantic old trees. The staggering 90% loss of old growth forest to logging in the Pacific Northwest has decimated their habitat, and thus their populations.
Puffins are some of the most famous seabirds with the public – for good reason. During the breeding season they are stunning birds with a multicolored bill and sharp-looking plumage.
There are four species of puffin – the Atlantic, Horned, Tufted (genusFratercula), and the Rhinocerous Auklet aka Horn-billed or Unicorn Puffin (genus Cerorhinca). They all are piscivorous birds, stocky and pretty large in size for the order. All reside in the North Pacific, except for the Atlantic Puffin, which is the only puffin species found in the Atlantic Ocean.
Scolopacidae
This family contains plovers and phalaropes. The family is mostly comprised of shorebirds, although I am mentioning them here because two of the three species of phalarope are considered seabirds as they are oceanic – the Red-necked Phalarope and the Red Phalarope. When they are not breeding, their migration takes them over the ocean and across the equator. They also forage at sea.
Laridae
While most gulls are not considered seabirds, there are a couple of oceanic species – those being the kittiwakes. There are two species, the Black-legged and the Red-legged Kittiwake. They nest in the North Pacific, in the Aleutian and Pribilof Islands. They are the only gull species that nests on cliffs, and they form dense colonies during the breeding season. Similar to murre eggs, and as a response to nesting on cliff ledges, their eggs are pyriform.
Sternidae
Terns are contained in their own family. They are closely related to gulls, and can be found around islands, coasts, marshes, and wetlands worldwide. Some terns breed on remote oceanic islands, such as the white tern. Terns have long pointed bills, and often hunt for prey through plunge-diving, and often in association with tuna, sharks, and dolphins which will drive prey fish to the surface.
<a href=”http://www.public-domain-image.com/free-images/fauna-animals/birds/tern-birds-pictures/a-curious-white-tern-bird-gygis-alba-hovers-overhead.jpg”>source
Rhyncopidae
Skimmers belong in this family and are unique birds in their own right due to their feeding mechanism, although they are closely related to terns. Skimmers have an elongated lower mandible, and feed by skimming – while coursing through the air right above the water’s surface, the skimmers open their bills, dropping the lower mandible in the water. They fly along this way until their lower mandible hits a fish, which triggers the bird to snap its bill close, securing the fish. There are three species of skimmers, and there getting to watch one skim is a truly remarkable sight!
Charadriiformes is perhaps the most diverse order of seabirds, and hopefully by introducing this final order you now have a greater appreciation for the incredible natural histories that seabirds have evolved.