Presentation on theme: "Seabirds Procellariiformes, Gaviiformes, Sphenisciformes, Pelecaniformes, and Charadriiformes = 320 spp. Water > 67% Earth’s surface but seabirds ~ 3%"— Presentation transcript:
Seabirds Procellariiformes, Gaviiformes, Sphenisciformes, Pelecaniformes, and Charadriiformes = 320 spp. Water > 67% Earth’s surface but seabirds ~ 3% bird spp Some differences between sea and landbirds: - Most feed from the ocean - Nasal glands for expelling brine - Vary in their dependence of land, but all must return to land to breed - Others hardly ever settle on water (Sooty Tern, frigates) and continuously on wing away from land - Active at night
Distribution of seabirds is governed by: (1)latitudinal marine zones (2)distribution of food in the zone (3)nesting sites - safe nesting cliffs, islands, promontories (4) distance of nest to food sources Another difference between land and seabirds is distance flown to food – 100m to several km for landbirds to 10s, 100s, or 1000s km for seabirds Procellariiformes are the most pelagic and the capacity to exploit distant food supplies is aided by: (1)lower body temp (38 vs 41 degrees) (2)Subdermal fat and stomach oil (3)Flying style (dynamic and slope soaring) (4)Well-developed olfaction (5)Young resist chilling and become torpid
9 marine water zones (life zones) Cold water has more nutrients and O 2 and thus support more life Weak winds in the tropics means productivity is 1% that of temperate coastal water. The highest productivity being in polar areas and around continental shelves. Marine zones and productivity
Seabird distribution across marine zones The wide expanse and productivity cold southern oceans is where seabirds reach their max abundance of individuals. Procellariiforms, dominate this region – partially due to short food chains, krill, and loss of krill-feeding whales.
Auks, penguins, diving petrels are the only major seabirds that failed to colonize both hemispheres – and interestingly they also show the most striking evolutionary convergence. All spp hunt by “flying” underwater and this may explain their absence form cold water. A change in water temp of 5 to 15 degrees doubles the swimming speed of exothermic fish, but doesn’t change the speed of endothermic birds.
Foraging zones (2-dimensional) - Inshore (6-8 km from the sea) - Offshore (coast to edge of continental shelf) - Pelagic (over deep ocean) European Shag: 7 km trips of 6 hrs Wandering Albatross (Scotland) Common Tern: 30 km trips of 2 hrsS. Georgia to S. Brazil (Wadden Sea)(26°S to 67°S) Black-legged Kittiwake: up to 60 km and 6 hrsS. Chile to S. Indian Ocean (Alaska)(17°W to 85°W) Northern Gannets: 232 km (540 max) in 13-84 hrs (Scotland)6091 km/trip; 1534 km from nest gone for 11.6 days Fasting (for young and parent left behind) is associated with these trips Galapagos penguin: < 3 days Magellenic and King: 25-40 days Emperor: walk 150-180 km to open water, forage 500 km, fast for >110 days Foraging zones (3-dimensional) Species differ in whether they obtain food below the surface and the depths and length of time they can remain submerged Here, auks and penguins are the most marine spp. The best human diver can dive 100 m in 4 minutes. King and Emperor Penguins: 304 and 534 m, respectively and 7.5 and 15.8 min, respectively -----------------------------------------------------------------------------------------------
Most seabirds nest colonially and sometimes in great numbers, In general, nest-sites are of much greater biogeographic importance and limiting factor to population size than is the case for landbirds.
Breeding and life history Most seabirds are long-lived (30 or more years) and don’t breed until several years old. Breeding may take a long time (up to 1 yr in large albatrosses) and occurs only every other year. Many (Procellarids, Alcids) lay a single large egg (up to 25% of adult mass) Both parents incubate or otherwise care for young Most (Alcids are an exception) regurgitate partially digested food or provide stomach oil Pairbonds remain as long as both parents are alive, although divorce can occur, most frequently after unsuccessful breeding. This pattern of life history (reproductive and survivorship schedule) means that most populations are slow-growing and vulnerable to sudden collapses in population size (i.e., recovery is very long). Alternatively, their long life spans allow them to buffer short-term collapses in food supply that shut-down reproduction (e.g., El Nińo events).