Sea birds - feeding ecology and functional traits Flashcards
what are the major costs for seabirds
homeothermy (keeping warm)
flight
diving
= adaptations to reduce flight costs tend to increase dive costs and vice versa which explains by seabirds tend to be either specalised on flying or diving deep
what are the orders of seabirds
1) sphenisciformes = penguins
2)procellariiforms = albratrosses, pettrels,
3) pelecaniformes= cormorants, pelicans, frigate birds
4) charadriiformes = gulls, terns, auks, skimmers
why is homeotherm such as major cost for seabirds
- water conducts heat 25 times better than air so is much more effective at conducting heat away from the body whether the spp is sitting or diving on the surface
- wind chill = marine environments are more windy than terrestrial as mean wind speeds are greater at any given latitude
outline how air acts as an insulator in sea birds
plumage is much denser in seabirds compared to terrestrial
= heat loss is inversly proportional to the thickness of this plumage insulating layer = thicker the layer of air next to skin the more insulated you are
how can air which acts as a great insulator for sea birds come at a cost
air increases buoyancy and generates up thrust to overcome when diving
= it becomes compressed according to boyle’s law
= dive duration decreases with the more volume of plumage air
how does the volume of air in the plumage vary with feeding method
= diving birds have the least air in the plumage making it easier to diver compared to surface and air-feeders which have the highest values of air in thier plumage
what are the costs of diving birds countering upthrust and how are they overcome
= less insulation compared to surface or air feeders
1) higher feather desnity than non-diving spp
2) higher levels of body fat = incompressable so insulative capacity doesnt vary with depth but this means body density is greater in diving spp
how are diving bird adaptations, such as increased feather desnity and body fat, implications for flight
- not compatible with minimised flight costs
= as volume of air in the feathers decreases the wing load increases which, as a consequence, increases flight cost but decreases dive cost
what is meant by wing loading
how each unit area of the wing is loaded
= adding a heavier body means each unit area of the wing needs to generate more lift to stay airbourn (high wing loading) = less efficient
what are the different foraging stratergies for sea birds
1) fly well (and far) and dive poorly
2) dive well and fly poorly
what are some solutions to have the most efficient foraging strategy
1) dont fly
2) dive deep and dont fly far
3) plunge dive and possibly fly far
4) fly well and surface feed
outline the foraging statergy of just not flying
= means that they dont fly so can get even better at diving (large body size, high fat, dense feathers)
e.g. penguins have low dive costs and therefore deep divers
how are penguins adapted for efficient diving
1) rlly high feather density enables air to remain trapped even under high pressures
2) plumage air layer increases with increasing latitude
3)birds dont forage far from breeding colonies= this means there MUST be high prey densities close to colonies
outline the adaptations of diving deep but not flying far for a foraging stratergy
adaptation of relativley small wings to minimise the amount of air in the plumage
wetable feathers
low dive costs
outline the solutions and issues of diving deep but not flying far for a foraging stratergy
- deep diving only achieved by powered swimming so this wing mediated underwater propulsion needs small wings
= higher wing loading and therefore higher flight costs
