Social Behavior and Reproduction Colors, postures and vocalizations used to identify species, individuals and sex Vocalizations songs usually males

Transcription

1 Chapter 17. Avian Specializations Flight Upper limit to bird size Heavier bodies require more muscle power to lift Upper limit ~ 12-20kg? Flightless birds much larger Ostrich (150 kg); Elephantbird 450kg Feathers Contour feathers: body feathers and flight feathers (remiges and retrices wing and tail) These are vaned feathers Calamus (base of quill) Rachis (length of quill) Barbs form vane (interlocking barbules) Semiplumes long rachis downy feathers (insulation) Feathers (cont.) Down feathers short rachis downy feathers - insulation Bristles stiff rachis and few barbs Screen particles from eyes and nostrils Tactile sense organs, insect capture Filoplumes sensory structures show position of contour feathers Flight (again) Outer wing feathers (primaries) produce propulsion Inner wing feathers (secondaries) produce lift Pectoralis produces downward movement Supracoracoideus (over pulley) produces upward movement of wing

2 Wing Types Dynamic Soaring long, narrow, flat without slots in primaries Seabirds e.g. albatross Elliptical maneuverable with slots Sparrows, gamebirds High aspect ratio narrow, backswept, shorter without slots Falcons, swifts, swallows High Lift static soaring hawks, vultures Intermediate aspect ratio much slotting Body Form and Flight Streamlining to various degrees Skeleton not light, but changed weight distribution Shifted posteriorly (light skull) Pneumatic bones (less in diving forms) Pelvis fused to synsacrum pygostyle supports retrices Inflexible vertebral column boxlike structure Keeled sternum and fused clavicle (furcula wishbone) Dark vs white muscles Heart and Lungs 4 chambered heart 1-way parabronchus for gas exchange Air sacs anterior and posterior Air moves 1 way through parabronchus during inhalation and exhalation Cross-current flow efficient Vocal apparatus syrinx at base of trachea or upper bronchi

3 Feeding Digestive specializations Predatory actions by beak and feet Food stored in esophagus and crop Some produce crop milk for offspring (doves) Hoatzin does foregut fermentation of leaves Other herbivorous forms have ceca Proventriculus (stomach) acids and enzymes Gizzard (stomach) mechanical breakdown Cloaca stores products uric acid and feces Hindlimbs and Locomotion Terrestrial walking/running Runners have elongated limbs, reduced toes (ostriches) Hoppers feet together mostly perching birds Perchers have tendons under foot that contract around branch without muscles Climbers use toes and beaks Hindlimbs and Locomotion (cont.) Swimming surface Webbed feet Palmate ducks Totipalmate pelicans Lobed toes (rigid grebes) or flaplike Swimming diving Foot propelled (loons, grebes) Wing propelled (penguins) Ecology and Behavior of Birds Bills and Feeding highly specialized Insect catchers (pickers/nets) Mud/water strainers Tearing bills Seed crushing bills Fish catching bills (dip nets, grabbers, spears) Fruit plucking bills Hole boring bills Tongue specialization Nectar feeding bills and tongues

4 Foraging Behavior - Optimization Optimal foraging theory maximize caloric intake/cost Costs in time, energy, predation risk, etc. Food distributed in patches Marginal value theorem declining value with time Mobility allows switching to new patches when appropriate Food differs in quality/handling time Forage optimally with respect to abundance Good evidence for support of OFT Sensory Systems Well developed vision and auditory Vision large eyes Displace brain in some, tubular to fit into skull in some Unique pecten function unknown Vascularized, perhaps for nutrient supply to retina Oil droplets (filters) in cone cells Red orange yellow green function unclear Sensory Systems (cont.) Auditory well developed Large tympanic membrane, most sensitive to species calls Pneumatic skulls may help with sound location Owls parabolic sound reflector, asymmetrical skulls Allows horizontal and vertical discrimination Many sensitive to infrasound (below 20 hz) Sensory Systems (cont.) Olfaction not well-developed in most Highly acute in vultures Some ground and colonial nesting birds Seabirds Worm probers Others UV, polarized light, magnetic field, air pressure

5 Social Behavior and Reproduction Colors, postures and vocalizations used to identify species, individuals and sex Vocalizations songs usually males Song control region (SCR) of brain Larger in males generally Song is learned (sometimes prior to hatching - dialects exist) Colors and feathers often for displays involving female choice (sexual selection) Bright, cumbersome Females choose males with good genes Studies show better offspring survival from good males Potentially due to female investment in offspring though Social Behavior and Reproduction (cont.) Other stuff bowerbirds use objects to lure females Feather-produced sounds E.g. ruffed grouse, nighthawk Social Behavior and Reproduction (cont.) Mating Systems Monogamy most common in birds When resources uniformly spread out When biparental care necessary 93% of altricial species 83% of precocial species Polygamy multiple mates Resource defense polygyny Male dominance polygyny (lekking species) Polyandry Promiscuous mating next most common 6% Nesting and Brooding All oviparous probably due to endothermy and brooding No advantage for retention Nesting various degrees of design Brooding brood patch formed by feather loss or plucking Nest helpers kin selection (inclusive fitness) Shortage of territories helping kin best choice Gain access to territory and potential mate Learned behaviors for future success Nest parasites Imprinting and Learning Imprinting restricted (early) period Determines potential mates Movement important Learning of song

6 Migration Many do long-distance migration (40%) High site fidelity how to navigate? Smells, learning of route, magnetic cues Position of sun and stars Internal clock Hierarchical use of cues Daylength differences cue migratory behaviors