Bird feeding and Digestion

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  • Bird feeding and digestion
    • Feeding
      • Diets
        • Carnivory
          • Inverts
          • Verts
          • PISCIVORY
          • INSECTIVORY
        • Herbivory
          • Various plants
          • Seeds
          • Fruits
          • Nectar
            • Niche separation, convergent evolution and alternative solution
        • Omnivory
      • Reflected in bill and feet morphology
        • Carnivores
          • Longer beak = potentially tearing prey up (avoids being soiled much)
          • Owl, short beaks, swallow prey whole- process bones (don't digests bones though)
        • Cranial Kinesis
          • Premaxillary bones of upper jaw articulated at craniofacial
            • Allows upper beak to move at the same time as the lower jaw (pincer movement- cranial kinesis)
              • Muscles opening lower jaw cause articular bone to pressurise the quadrate to rotate forward pushing palatine and jugal arches forward against the premaxilla
                • Muscles pull the premaxilla downwards whilst the lower jaw is pulled upwards
      • Competition for food resources is also reduced by prey selection on the basis of size
      • Specialisation in waders reduces competition for resources
        • Redshank probes mud and picks off food from the surface
        • Greenshank actively seeks fish and crustaceans in pools and water channels
        • Oystercatchers use bill skills that have to be taught by parents to young
          • Some smash shell with hammer blow; others open shell with sharp mandibles (by cutting through the muscle holding the two halves together)
            • Cannot easily switch methods and takes months to be taught (but prising open shells is less effort) e.g. going from smasher to priser don't work as being a smasher blunts beak.
    • Digestion
      • Some birds lack a crop
        • e.g. Ostrich have a proventriculus as storage structure rather than a crop
      • Gizzard typically muscular to grind materials using ingested grit
      • Variation in proximal alimentary tract associated with diet
      • Small intestine
        • Duoodenum; jejunum; illem
      • Cloaca
        • openings to large intestine, reproductive ducts and urinary ducts
        • Bursa of Fabricus-lymphoid tissue produces B-cells
      • Foregut fermentation in the Hoatzin
        • Huge crop for fermentation of leaves
      • Hindgut fermentation in Ostrich


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