FeedingSlide 2Slide 3Slide 4Slide 5MigrationTrue Migration vs. Continuous MigrationNotes on MigrationNavigationSlide 10Feeding•Surface feeding while flying (sometimes with pursuit plunging) Storm Petrels Flit back and forth, lowering the feet and pattering the surface of the water, and dipping the head down to feed on zooplankton and small fish.FrigatebirdsSkim the surface at full speeds and a downbent head, plucking food from the surface layer, a method facilitated by their long neck and long, sharply hooked bill. Terns Pick off fish or squid that are running away from larger predators, either by pattering, plunging or catching flying fish in the air.Feeding•Surface feeding while swimming (sometimes with pursuit-diving)–Feed by sitting on the surface or forcing themselves slightly below•Albatrosses and Shearwaters–Feed mainly on fish, squid, cuttlefish, crustaceans and offal, but also eat jellyfish.–Usually feed at night by dipping their heads into the water, though they sometimes plunge dive. »They feed at night because many fish and zooplankton surface at night.–Nomadism allows these birds to take advantage of rich, but widely separated food sources.Feeding•Plunge diving- could be truly deep divers, or merely surface–Deep plunge divers = Gannets and Boobies»Heavy birds, they may begin dive with either wing beats, or just falling. Go at most 10 meters deep and last for less than 10 seconds.»Air sacs cushion against the impact and occluded nostrils prevent water up the nose–Shallow plunge divers= Brown pelican»Pouch opens rapidly to surround the fish, while the upper mandible closes rapidly»Pouches hold 10liters of water (~3 gallons)Feeding•Diving from the surface and underwater pursuit–Difficult to fly well in air and in the water=Puffins, Auks, Guillemots, –Penguins- Feed mostly on fish, squid and crustaceans found at the surface•When traveling large distances, King Penguins ‘porpoise’ through the water, traveling 3-4 m in the air and 6-12 underwater•Emperor penguins can diver for up to 9 minutes to depths of 265m•Better divers than mammals because they carry more oxygen in their blood. –Good divers and flyers tend to be big and use feet as well as wings for propulsion= Cormorants and Shags•Water absorbent feathers reduce buoyancy and help with diving. •Forage singly or in loose groups, rarely diving deeper than 10m for 3 to 4 minutes•Eat mostly fish, but will also eat freshwater crustaceans, insects and tadpoles•Forage within 8 to 16 km of homeFeeding–Scavenging and Piracy-Less important and usually only used as a supplement to regular foraging•Classic scavengers- gulls (Herring Gulls), Fulmars and Gannets»Feed on leftovers, either human or from other feeders»Usually strenuous competition amongst scavengers•Pirates- Skua, Frigatebirds, Terns»Attack other birds in order to steal their food. May also attack and feed on the young.»Frigatebirds and Skuas circle above their victims and then surprise them by dive-bombing.Migration–A clear, seasonal shift in the center of a population from locality A to B and back again. It is different from dispersal and nomadism. Usually one location is a breeding area and the other is only a feeding area.•Dispersal- Movement is more random and preference for a particular location is weak.•Nomadism - Birds keep moving, perhaps randomly, as an adaptive response to covering vast areas.True Migration vs. Continuous Migration•True Migration- –Breeding area empties and refills next breeding season.–Migration along fixed route, usually rapid and extensive•Continuous Migration-–Birds leave breeding area on a migration so extensive that most of the period between then and the return next breeding season is spent following the variably fixed migration route.Notes on Migration–Seabirds migrate in order to utilize seasonally abundant food sources.•In a-seasonal environments (e.g. the Mediterranean) migration is not necessary–Migrants tend to always return to the same breeding and winter grounds year after year, though eruptions do occur.•Eruption- a mass emigration to areas not normally reached, depends on conditions at the time such as food shortages.–Migrants may, or may not, feed en route. •The greater the distance of migration, the greater the tendency for a quick migration, with few stops along the way.Navigation–Visual Landmarks–Used first and foremost –Follow watercourses, coastlines and mountain ranges–Causes birds to be ‘funneled’ by bays, channels and straits–Solar Compass–Use the position of the sun as a mark by which to set their path. When it’s cloudy birds tend to just wander randomly.–The position of the sun in the sky changes 15 degrees/hr, so the solar compass must be time compensated, i.e. they can keep track of the time.•Stellar Compass–Nocturnal birds use stars to navigate instead of the sun. –Don’t know if nocturnal birds compensate for the movement of stars over time.Navigation• Olfaction–Olfactory clues supplement other navigation systems–Petrels and pigeons can smell their way back to their nests•Geomagnetism–The geomagnetic fields of the Earth provide a map of horizontal space, just as gravity and barometric pressure give information about vertical space. –The intensity and dip angle- or inclination of the magnetic field-change with latitude in ways that provide reliable, omnipresent information about geographical position.–Special photoreceptors appear to be sensitive to a bird’s orientation relative to these fields. •Internal Maps–A compass isn’t enough to get you home. You need a map to which you can apply it. A bird must know its own position relative to its goal.–It is not known how birds solve this