Marine Birds SEA BIRDS

Diet  Seabirds evolved to exploit different food resources in the world's seas and oceans, and to a great extent, their physiology and behavior have been shaped by their diet. These evolutionary forces have often caused species in different families and even orders to evolve similar strategies and adaptations to the same problems, leading to remarkable convergent evolution. There are four basic feeding strategies, or ecological guilds, for feeding at sea:  1. Surface feeding: Many seabirds feed on the ocean's surface, as the action of marine currents often concentrates food such as krill, forage fish, squid or other prey items within reach of a dipped head.  2. Pursuit diving: Pursuit diving exerts greater pressures on seabirds, but the reward is a greater area in which to feed than is available to surface feeders  3. Plunge diving: Gannets, boobies, tropicbirds, some terns and brown pelicans all engage in plunge diving, taking fast moving prey by diving into the water from flight. Plunge diving allows birds to use the energy from the momentum of the dive to combat natural buoyancy and thus uses less energy than the dedicated pursuit divers, allowing them to utilize more widely distributed food resources.  4. Kleptoparasitism, scavenging and predation: This catch-all category refers to other seabird strategies that involve the next trophic level up

Breeding  Ninety-five percent of seabirds are colonial, [2] and seabird colonies are among the largest bird colonies in the world, providing one of Earth's great wildlife spectacles. [2]  Seabirds are one of the only avian families that include ritualized dances in their courtship. These dances are complex and can include displays and vocalization that vary greatly between families and orders, a few examples are: - The wandering albatross (Diomedea exulans), sky pointing is accompanied with “sky calling” where the displaying individual spreads its wings, revealing his massive 12 foot wingspan while pointing and vocalizing skyward. - the brown booby, sky pointing is described as a display where the male throws his head backwards, stretches his neck out, and usually gives a whistling vocalization - Frigratebirds are known for their unusual displays and breeding system. Unlike other seabirds, frigatebirds have a lek-breeding system where displaying males aggregate in groups of up to 30 individuals with prospecting females flying overhead. However, unlike classic leks, the pair then builds a nest on the male’s display site. The male then participates fully in nest defense, incubation, and chick-rearing

Habitat  Seabirds and shorebirds, some of the most threatened animals on Earth, are dependent upon and contribute to robust ocean and coastal ecosystems. Invasive predators on seabird islands reduce their breeding success. Endangered seabirds, like albatrosses and petrels, are caught inadvertently in fishing gear on the high seas. And wetland reclamation and human disturbance have eliminated habitats important to shorebirds. With our grantees and partners, we are working to reduce these threats and strive to restore seabird and shorebird populations by supporting a range of initiatives in island restoration, seabird bycatch mitigation, and shorebird habitat conservation.  Seabirds are an excellent species for studying the question of how animals share the limited supply of food in their habitat. Seabirds must live on land during the breeding season, and over this period they have to share space and food with many other animals. The birds breed in nesting colonies, often in confined spaces that provide protection from predators -- the food supply, however, is widely distributed throughout the sea off the coast. The birds must leave the colony to find food and then return to the islands to feed their chicks.

Population  The study linked the decline in seabird populations to a slew of factors, including over-fishing — which caused a decline in the fish the birds rely on for food — and ecological and environmental changes caused by climate change. The researchers also point to the introduction of invasive predators, plastic and oil pollution, and dangerous fishing gear as potential causes for the decline. All told, the study found that seabird populations globally have declined by 69.6 percent in the last 60 years, representing a loss of some 230 million birds.  Seabirds tend to travel long distances foraging for food, but often return to the same colonies to breed. A change in colony populations can be an indication that coastal and marine ecosystems might be off — but a drop in colony populations also can have a negative impact on the ecosystems, as seabirds eat (and are eaten) by a variety of species, and help fertilize food webs with their waste.

Life History & Facts Northern gannet pair "billing" during courtship; like all seabirds except the phalaropes they maintain a pair bond throughout the breeding season.  Seabirds' life histories are dramatically different from those of land birds. In general, they are K-selected, live much longer (anywhere between twenty and sixty years), delay breeding for longer (for up to ten years), and invest more effort into fewer young. Most species will only have one clutch a year, unless they lose the first and many species like the tubenoses and sulids, only one egg a year.  Because of the greater investment in raising the young and because foraging for food may occur far from the nest site, in all seabird species except the phalaropes, both parents participate in caring for the young, and pairs are typically at least seasonally monogamous.  Due to the extended period of care, breeding occurs every two years rather than annually for some species. This life-history strategy has probably evolved both in response to the challenges of living at sea, the frequency of breeding failures due to unfavourable marine conditions, and the relative lack of predation compared to that of land-living birds.

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