Characteristics edit
Seabirds have evolved a variety of adaptations to survive and feed in the ocean. The niche into which a particular species or family has evolved has shaped its wing morphology, so a scientist can learn about a species’ life-feeding habits by examining the shape and loading of its wings. More pelagic species tend to have longer wings and lower wing loading, whereas diving species have shorter wings. [15] Because of their diminished ability to fly by powered means, certain species—like the wandering albatross—that feed over vast stretches of ocean are reliant on slope soaring and a form of gliding known as dynamic soaring, in which lift is produced by the wind being deflected by waves. [16] Additionally, webbed feet are nearly universal in seabirds, helping with surface mobility and, in certain species, diving. The Procellariiformes are unique among birds in that they have a keen sense of smell, which they use to locate widely dispersed food in a large ocean[17] and to help them discriminate between familiar and unfamiliar nest odors. [18] Cormorants, like this.
Seabirds use their salt glands to help them osmoregulate and to deal with the salt they ingest through drinking and eating, especially crustaceans. [20] Almost pure sodium chloride is expelled from these glands, which are located in the birds’ heads and emerge from the nasal cavity. [21].
Like the majority of other birds, seabirds have waterproof plumage, with the exception of cormorants and certain terns. But they have far more feathers covering their bodies than land birds do. The bird’s thick down layer keeps the cold out and its thick plumage helps to keep it from getting wet. Compared to other diving birds, cormorants have a special layer of feathers that allow them to retain less air, but they still absorb water. This keeps enough air in the feathers to keep the bird from losing too much heat when it comes into contact with water, but still enables them to swim without fighting the buoyancy that comes from keeping air in them. [22].
Most seabirds have less colorful plumage than land birds, mostly limited to shades of black, white, or grey. [15] While some species—like some penguins and tropicbirds—have colorful plumes, the majority of color in seabirds is found on their bills and legs. Many times, the plumage of seabirds is assumed to be used for camouflage, both aggressive (many seabirds’ white undersides help conceal them from prey below) and defensive (US Navy battleships’ color is the same as that of Antarctic prions,[15] and both reduce visibility at sea). Because the typically black wing tips are made of melanin, which darkens the feathers, they help shield the feathers from wear and tear. [23].
Away from the sea edit
Although the term “seabird” implies that the birds in question live near the ocean, many seabird families contain a variety of species that live partially or entirely inland from the coast. The most remarkable thing is that many species breed thousands, hundreds, or even tens of miles inland. Certain species, like the snow petrel, whose nests have been discovered 480 kilometers (300 miles) inland on the Antarctic continent, still make their way back to the ocean to feed. This is because they are unlikely to find any food near their breeding sites. [63] The marbled murrelet builds its nests inland in old growth forests, looking for massive conifers with voluminous branches. [64] Some species, like the California gull, breed and feed on lakes farther inland before migrating to the coasts for the winter. [65] Individuals of some species of cormorant, pelican, gull, and tern live entirely on land that is not near the sea; instead, they inhabit lakes, rivers, swamps, and, in the case of some gull species, cities and agricultural areas. In these instances, it is believed that these freshwater or terrestrial birds descended from marine ancestors. Certain seabirds will also migrate over land, mainly those that nest in tundra, like phalaropes and skuas. [3][66].
Although their habits are more restricted, more marine species like gannets, auks, and petrels are occasionally spotted inland as vagrants. This typically affects young, inexperienced birds, but it can also happen in large quantities to weary adults following powerful storms—a phenomenon known as a wreck. [67].
Regional Seabird Conservation Efforts
Since 1989, the Alaska region has been actively addressing the bycatch of seabirds in longline fisheries off the state. Previously, the groundfish fisheries off Alaska alone would hook up to over 20,000 seabirds annually. A whopping 75% of Alaska’s hooked birds are gulls and northern fulmars. However, the endangered short-tailed albatross’ bycatch receives the majority of regulatory and conservation attention. With the use of seabird avoidance measures (e. g. seabird bycatch by four times thanks to fisherman’s use of paired and single streamer lines.
Learn more about reducing seabird bycatch in Alaska:
Shearwaters trapped in nets were frequently used as bait in handline fisheries by fishermen on the Georges and Grand Banks in the late 19th century. Seabirds still interact, both directly and indirectly, with the commercial fishing industry even though it is no longer a practice. A variety of seabird species inhabit the Northeastern Atlantic region.
Learn more about reducing seabird bycatch in New England/Mid-Atlantic:
Seabird bycatch mitigation measures are mandatory for pelagic longline fishermen based out of Hawaii operating in the Pacific Islands. By taking these precautions, unintentional encounters with seabirds—mainly North Pacific albatrosses—have decreased by more than 90%.
According to NOAA Fisheries estimates, there were 2,433 unintentional interactions between the Hawaiian longline fisheries and albatrosses in 2000. The number of albatross-human interactions has decreased by roughly ten times annually since the seabird mitigation measures went into effect in 2002.
Learn more about Seabird Interactions in the Pelagic Longline Fishery.
The West Coast Region prioritizes research to gain a better understanding of seabird populations off our coast and employs mitigation strategies to lessen seabird interactions in our fisheries. Although seabird bycatch is less frequent than in other areas, groundfish and highly migratory species fisheries on the West Coast occasionally interact with seabirds that are endangered. Mitigation strategies for seabird bycatch, both required and voluntary, have been effectively employed to lower the likelihood of unintentional encounters with North Pacific albatrosses in particular. These precautions include putting out gear at night, using streamer lines for hook-and-line boats, coloring pelagic longline bait blue, and continuing research into strategies to lessen interactions with wires on trawl vessels. Seabirds are significant components of marine ecosystems, and both the Northwest and Southwest Fisheries Science Centers conduct research on them. This includes surveys of seabird distribution and abundance, evaluations of seabird productivity and diet, and analyses of seabird bycatch in groundfish fisheries on the West Coast. Furthermore, a workgroup under the Endangered Species Act was constituted by the Pacific Fishery Management Council to discuss concerns related to seabird bycatch.
Learn more about reducing seabird bycatch on the West Coast:
FAQ
What percentage of birds are marine species?
How many seabirds are extinct?
What is classified as a marine bird?
What are the four groups of marine birds?