Marine Birds & Their Biological Role in the Marine Realm



The animal group of birds (Aves) can be characterized by some typical distinguishing features. These include feathers (for thermoregulation and flight) and wings. Both can be seen in all birds, and only in birds. Also, all birds are ovipar, meaning that all birds lay eggs, and they walk on two legs (bipeds).


Their skeleton is usually adapted for flight; the bones can be filled with air (pneumatic bones). Other characteristic features include the crop (to store food), the sternum, and the pygostyle (the bone that forms the posterior end of the spine).


From an evolutionary perspective, birds most probably evolved from a small theropod dinosaur (R. Wehner, W. Gehring, 2013). It is thought the first birds appeared around 160 million years ago, and today scientists believe there are between 9,000 and 10,000 known species, around 350 of which are seabirds.


Birds are endothermic, so, to lay eggs, the seabirds must return to land. This means that most seabirds are found in the Southern Hemisphere, and they obtain nearly all their food from the ocean.



The best adapted birds to the pelagic world are the tubenoses (albatrosses and petrels) and the penguins. The great albatrosses are wonderfully adapted to the ocean sky, they have a long body with thin wings and are extremely aerodynamic.


The wandering albatross (Diomedea exulans) is the largest of them - their wings can span up to 3.6 m. Albatrosses can fly for months across the ocean in conditions of high waves and strong winds, and are therefore true masters of the ocean skies!


Penguins are another group perfectly adapted for the seas. They cannot fly, but they use their wings for swimming. The largest penguin species, the emperor penguin, can dive to depths up to 275 m (T. Garrison, R. Ellis, 2019).



You may have seen that seabirds often nest on cliffs and rocks. Puffins, gannets and rockhopper penguins are among the best known to show this behaviour.


Puffins, are also known for their typical yellow beak, which is there to reinforce the bond between monogamous pairs, and shows countershading as a protection from predators. Gannets also mate and pair for life and are known to breed in large colonies.



Rockhopper penguins, as the name suggests, have feet perfectly suited for movement from rock to rock.


They have an extremely streamlined body and paddles like other penguins for swimming. Their spine is also more vertical than that of other birds and their legs are lower on the body, giving them an upright standing position.


Another interesting behaviour seen in some marine birds is plunge diving. The brown pelican is a perfect example of performing this movement.


When plunge diving, the bird folds its wings back from a height of up to 20 m and dives vertically to catch fish like sardines and anchovies in upwelling areas (The Science of the Ocean, 2020).



Now, unfortunately, several of these marine bird species mentioned in this article are threatened with extinction (IUCN, 2021). Climate change, fisheries (longline), bycatch and invasive species are all major threats to seabirds.


The wandering albatross (Diomedea exulans) is especially vulnerable. The wandering albatross population on Macquarie Island in the southwestern Pacific Ocean has declined to an average of only five breeding pairs each year. Their breeding probability has also been seen to decrease, as well as their survival.


Heavy rain and dense invasive rabbit populations has caused reductions in albatross breeding success, due to habitat degradation. Survival was nevertheless higher following La Niña southern oscillation events in three other albatross species. Higher winds also have had a positive effect on survival.


Black-browed and light-mantled albatrosses show increasing populations, while grey-headed albatrosses are stable on Macquarie Island. This is why it is so important to take management action for globally threatened species such as albatross (J. Cleeland et al., 2021).



How Can You Help Protect Seabirds?

  • Be aware of MPA sites where birds usually nest.

  • Keep 1,000 feet away from nesting and resting seabird colonies.

  • Never chase seabirds.

  • Always take your litter home with you, especially when visiting the beach.

  • If you are a keen fisher, use barbless fishing hooks, artificial lures, and weighted fishing lines to avoid a seabird getting hooked or caught in the line.

  • Support organisations such as the RSPB, BirdLife International, or your local wildlife trust.





Written by Adriana Giger












Resources


Jaimie B. Cleeland et. al., Disentangling the Influence of Three Major Threats on the Demography of an Albatross Community, frontiers in marine science, February 2021, Vol. 8


Rüdiger Wehner, Walter Gehring, Zoologie, 2013, p. 687-688


The Science of the Ocean – the secrets of the seas revealed, natural history museum, 2020, p. 54-59, p. 242


Tom Garrison, Robert Ellis, Oceanography – an Invitation to Marine Science, 2019, p. 441-443


https://www.iucnredlist.org/search?query=albatross&searchType=species



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