Seabird Characteristics

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Breeding
Breed in Colonies
A seabird colony can be defined as a group of birds nesting in close proximity and finding their food outside the breeding area. The colony may consist of 10 pairs along a cliff ledge or thousands of pairs of birds. Ninety five percent of seabird species breed in colonies (Löfgren 4).

Austroasian Gannet colony at Cape Kidnappers in New Zealand

This is a view of the Gannet Colony at Cape Kidnappers on the north island of New Zealand.

Despite the close proximity, Gannets defend a territory around the nest. You can see in this picture that the nest sites are evenly spaced.

Austroasian Gannets at Cape Kidnappers in New Zealand

Short-tailed Shearwater burrows on Phillips Island in Australia

Shearwater and petrels build their nests in underground burrows. The only evidence of a Short-tailed Shearwater colony in the day time are the burrow openings. An observer can tell it is an active shearwater colony and not just rabbit burrows by the smell.

Large colonies are vulnerable to attacks of predators. Leopard Seals patrol the shore near Penguin colonies and are assured that if the first bird gets away, they will have plenty of other chances. Tiger Sharks show up in the lagoon at Midway Atoll every year just which the baby Laysan Albatross are learning to fly. A fox will visit a colony regularly to obtain prey. Historically it was man that posed the greatest threats to seabirds in colonies stealing eggs, meat and even boiling seabirds to render the fat into useable oil. Most seabird colonies today are protected from men if not from their domestic animals.

While it seems only logical that seabirds would breed near the sea, the Snow Petrel may breed 200 miles inland and the Marbled Murrelet nests only in old growth forests.
Jaegers and Skuas breed on the tundra usually near colonies of kittiwakes, penguins, or puffins on which they prey.

Mate and Site Fidelity
Seabirds in general return to the site where they were raised to breed and raise their young. Once they start breeding at a site they return year after year to the same place and often breed within feet of where they bred the year before. When a colony becomes too large, individuals may prospect a new colony site.

Site fidelity supports monogamy and pairs tend to remain together as long as both live. Mate fidelity requires elaborate bonding rituals such as the dances performed by the Albatrosses. Since the birds depart the breeding grounds and roam the seas as singles, returning to the same site is necessary to re-establish pair bonds.

Pomarine Jaegers feed exclusively on lemmings during the breeding season and are an exception to the rule that seabirds show site fidelity and mate for life. Lemming populations fluctuate from year to year, but there are always places with large populations. A male Pomarine Jaeger will find a territory with sufficient lemmings and wait for a mate of opportunity.

The main advantage of colonial breeding for seabirds seems to be that it provides an opportunity for finding a suitable mate and for meeting up at the start of the breeding seasons for established pairs. Young unmated birds return to their natal colony after several years to find and bond with their life partner. The colony can be compared to a singles bar or a college campus.

After spending up to four years roaming the sea, young adult Albatrosses like these Laysan Albatross return to the natal colony. Here they work to find a mate.

Pair bonding is accomplished by performing elaborate dances. The Albatross on the left is performing the under the wing preen while the one on the right is standing at attention.

After forming a pair bond, the mates return to the sea. They return the following years at the start of the breeding season to meet up and renew their bond. Albatross spend only a few minutes together before copulating. Then both return to the sea separately. The female returns to lay a single egg. The male returns shortly after and takes the first incubation shift while the female returns to sea to feed and rebuild her body after laying the egg. Thereafter they take turns incubating, brooding, and guarding the chick until the chick is several weeks old. The chick is then left on its own while both parents go to sea to feed. Mated pairs spend very little time together during their entire life time.

Disruption of a breeding site has serious consequences. Mated pairs return annually to their nesting site to meet up. What happens if a bird returns to the site to find it has been turned into a new hotel?

Food Gathering
Depend on the Sea For Food
It seems only logical that seabirds would find their food in the ocean even during the breeding period and most do.

Many seabirds are scavengers feeding on dead whales, squid and fish. This leads many seabirds to following ships and fishing boats. One of the main reasons that seabird populations are declining so rapidly is that scavenging seabirds are accidentally caught by fishing hooks and nets. This is called the bycatch.

Dependent on the sea for food they are not helped by the depletion of fish stocks. Albatrosses are especially sensitive to the increased fishing for squid. Humans can live without squid. Boycott!

Pomarine Jaegers breed on the arctic tundra and depend on lemmings for their primary food source while breeding. Other Skuas and Jaegers also hunt lemmings, but can use other prey in years when the lemming population crashes. All skuas and jaegers except the Pomarine Jaeger exhibit mate and site fidelity. There are always sufficient populations of lemming in the arctic, but not always in the same place. The Pomarine Jaeger male must first locate a territory with sufficient lemmings and then attract a mate. Thus the Pomarine Jaeger is more like other land birds.

Some seabirds dive under the water and pursue prey either using their wings for locomotion of using legs only. Alcids are especially adept at swimming underwater with their wings. Loons on the other hand use only their feet.

Most seabirds rest on the water, but not all are able to dive under the water to pursue food or to escape predation. Notable examples of birds that do not usually dive are Storm-petrels, skuas, jaegers, and gulls. Frigate birds do not rest on the water.

Regurgitate Food to Young

Atlantic Puffin photographer on Skommer Island by Emmalee Tarry

A Puffin bringing 5-6 small fish back to its burrow is an endearing sight, but not typical of seabirds.

Since many seabirds fly long distances over the water to find food for their chicks, they carry the food in their intestine and regurgitate to the chick.

The chick of a Black-footed Albatross pecks on the parents bill to induce regurgitation. Photographed on Midway Atoll by Emmalee Tarry

Black-footed Albatross regurgitates food to chick on Midway Atoll.

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Page author: Emmalee Tarry