Editing Seabird (section)

==== Pursuit diving ====
[[File:African Penguin Skeleton.jpg|thumb|An [[African penguin]] skeleton, showing the sternal keel that makes the species a strong diver and swimmer]]
Pursuit diving exerts greater pressures (both evolutionary and physiological) on seabirds, but the reward is a greater area in which to feed than is available to surface feeders. Underwater [[Marine propulsion|propulsion]] is provided by wings (as used by penguins, auks, [[diving petrel]]s and some other species of petrel) or [[Bird feet and legs|feet]] (as used by cormorants, [[grebe]]s, [[loon]]s and several types of fish-eating [[duck]]s). Wing-propelled divers are generally faster than foot-propelled divers.<ref name="Burger" /> The use of wings or feet for diving has limited their utility in other situations: loons and grebes walk with extreme difficulty (if at all), penguins cannot fly, and auks have sacrificed flight efficiency in favour of diving. For example, the [[razorbill]] (an Atlantic auk) requires 64% more energy to fly than a petrel of equivalent size.<ref name="Auk">Gaston, Anthony J.; Jones, Ian L. (1998). ''The Auks'', Oxford University Press, Oxford, {{ISBN|0-19-854032-9}}</ref> Many [[shearwater]]s are intermediate between the two, having longer wings than typical wing-propelled divers but heavier wing loadings than the other surface-feeding [[procellariidae|procellariids]], leaving them capable of diving to considerable depths while still being efficient long-distance travellers. The [[short-tailed shearwater]] is the deepest diver of the shearwaters, having been recorded diving below {{convert|70|m|ft}}.<ref>{{cite journal|author1=Weimerskirch, H. |author2=Cherel, Y. |year=1998|title= Feeding ecology of short-tailed shearwaters: breeding in Tasmania and foraging in the Antarctic? |journal=Marine Ecology Progress Series |volume=167|pages= 261–274|doi=10.3354/meps167261|bibcode=1998MEPS..167..261W |doi-access=free }}</ref>

Some albatross species are also capable of limited diving, with [[light-mantled sooty albatross]]es holding the record at {{convert|12|m|ft|sigfig=1}}.<ref>{{cite journal|author1=Prince, P. A. |author2=Huin, N. |author3=Weimerskirch, H. |year=1994|title=Diving depths of albatrosses|journal=Antarctic Science |volume=6|issue=3|pages= 353–354|doi=10.1017/S0954102094000532|bibcode=1994AntSc...6..353P|s2cid=129728675 }}</ref> Of all the wing-propelled pursuit divers, the most efficient in the air are the albatrosses, and they are also the poorest divers. This is the dominant guild in polar and subpolar environments, but it is energetically inefficient in warmer waters. With their poor flying ability, many wing-propelled pursuit divers are more limited in their foraging range than other guilds.<ref name="Ulanski">{{cite book |last1=Ulanski|first1=Stan|date=2016|title=The California Current: A Pacific Ecosystem and Its Fliers, Divers, and Swimmers|publisher=UNC Press Books|page=99|isbn=978-0070294219|url=https://books.google.com/books?id=iWM3CwAAQBAJ&pg=PT99}}</ref>