The Brain and Senses. Birds perceive the world differently than humans. Avian intelligence. Novel feeding behaviors

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1 The Brain and Senses Birds perceive the world differently than humans Color and IR vision are highly developed Hearing is superior, owls track prey in total darkness Birds navigate using abilities to sense: The earth s magnetic fields Minute shifts in gravity Changes in barometric pressure Polarized light Birds can master complex problems Krushinsky experiment Counting Ravens Alex the amazing African Gray Parrot Birds use tools Galapagos Woodpecker Finches and Caledonian Crows Egyptian Vultures Japanese Carrion Crows Avian intelligence Bernd Heinrich s Ravens British Tits open milk bottles Novel feeding behaviors Galapagos Woodpecker Finches and Caledonian Crows use tools Alex Krushinsky experiment Carrion Crows use cars to crack nuts Green Herons use bait 1

2 Avian intelligence Bird brains are big Spatial memory Exceptional in seed caching birds, Corvidae, Sittidae, Paridae Associated with enlarged hippocampal complex in brain High performance vertebrates need a high performance nervous system and brain Bird brains are much larger relative to their body size than those of reptiles or mammals A) Monitor Lizard, B) Macaw Plain Titmouse Clark s Nutcracker Forebrain Cerebrum Olfactory lobe Midbrain Cerebellum Optic lobe Hindbrain Medulla The avian brain Birds are highly visual Large eyes used to search for food and avoid predators Eyes = 15% of head mass, humans = 2% Eagle and owl eyes are as large as human eyes Visual acuity 2X 8X that of humans Vision Vultures ride thermals to heights of 5,000 Visual acuity in some vultures may be 8X that of humans Center of retina (fovea centralis) magnifies vision in center of the field of view by 30 50%. 2

3 Visual acuity in Raptors What do birds see? Behind In Front Binocular Eye anatomy Owl eyes are like a fast telephoto lens Cornea Compton s muscle Iris Lens Brucke s muscle Sclerotic Ring Retina Foveae Pecten Nictating membrane 3

4 Visual pigments in cones allow color vision Abundant cones suggest good color vision Pigments convert light energy into electric energy (nerve impulses) Cones also have oil droplets (carotenoid pigments) that act as red/yellow filters, these may help birds see objects against a blue sky Many (all?) birds are sensitive to light in the near-ultraviolet spectrum (Honkavaara 2002). Used to detect; fruit, insects rodents Color perception Oil droplets in cones UV vision is well developed in many birds Absorbance spectra in Starling Highly developed Tympanum ear drum located below eye Facial feather discs focus sound Nerve endings in cochlea Echolocation SE Asian Cave Swiftlets South American Oilbirds Owl ears are offset Asymmetric ears allow owls to triangulate on prey Allows Barn Owls to hunt in total darkness and Great Grey Owls to catch mice under the snow Hearing The skin has nerve endings to sense touch, pain, heat, and cold More abundant in apteria (why?) Herbst Corpuscles Mechanoreceptors in bills, feather bases, tips of woodpecker tongues Touch 4

5 Poorly developed in birds Taste buds, birds = 20 60, humans =10,000 Food discrimination is mostly visual Need to capture food rapidly Birds like chili peppers Not sensitive to capsaicins May relate to seed dispersal Taste Poorly developed in most birds Small olfactory bulbs Exceptions are: Ducks, kiwis, snipe Procellariiformes Honeyguides Some vultures Smell Other sense abilities Barometric pressure Inner ear senses pressure systems (weather) and altitude Magnetic fields Magnetite (polarized iron) in brain Gravity Sensed in semi-circular canals of inner ear Polarized light The noble Rock Pigeon 5