Feeding I: Overview

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Feeding I Overview Beak

• JodyLee Estrada Duek, Ph.D.
• With much assistance from Dr. Gary Ritchison
• http//people.eku.edu/ritchisong/avian_biology.htm

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Because of their high metabolic rates

• Birds must consume more food in proportion to
  their size than most animals.
• a warbler might eat 80 percent of its body weight
  in a day.
• birds consume just about any type of food
  amphibians, ants, buds, carrion, crustaceans,
  fish, fruit, grass, insects, larvae, leaves,
  molluscs, nectar, other birds, pollen, reptiles,
  rodents, roots, sap, seeds, suet, snails, wax,
  worms
• To meet their metabolic needs while remaining as
  light as possible (to be efficient flyers), the
  digestive system of birds has to be
• light as possible
• efficient as possible
• Weight has been minimized by
• loss of teeth
• limited jaw musculature.

http//www.nps.gov/cebr/naturescience/images/Orang
e-crowned_Warbler.jpg
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Efficient Feeders
Magnificent hummingbird, SWRS, Chiricahua Mtns.,
AZ

• Must keep weight as low as possible
• Limited amount of fat can be stored
• except perhaps prior to migration
• 'Efficient' means birds locate, ingest, digest
  food quickly and efficiently
• Next slide Retention time (in hours) for fluid
  particulate digesta markers in gastrointestinal
  tracts  of representative reptiles, birds,
  mammals (Stevens Hume 1998)

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In general, typical mean retention times are 30 -
50 minutes for avian nectarivores, 40 - 100
minutes for granivores, and 15 - 60 minutes for
frugivores (Karasov 1990, Klasing 1998).
Species Body mass Fluid retention time (hr) Particle retention time (hr)  
Iguana - lt48 207
Broad-tailed Hummingbird1 3.3 gm 1.2 -
Rock Ptarmigan 460 gm 9.9 1.9
Sooty Albatross 2.5 kg 6.3 15
Rockhopper Penguin 2.5 kg 3.8 17
Emu 38 kg 3.9 4.7
rabbit 2.1kg 39 27
pig 176 kg 39 48
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Typical Avian Digestive System
Source http//numbat.murdoch.edu.au/Anatomy/avian
/fig4.1.GIF
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A bird's bill
http//www.bbc.co.uk/tyne/content/image_galleries/
northumbria_icons_farne_puffin_gallery.shtml
http//www.tropicalbirding.com/tripReports/TR_Nort
hernAndesEcuador_Jan07/tripreportnorthernandesjan0
7.htm

• consists of a bony framework
• covered by tough layer of keratin
• keratin layer continuously worn down by eating
  and manipulating hard objects
• keratin layer continuously replaced
• cutting edges of the beak tomia
• critical in food acquisition, shape varies with
  food

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Bill examples

• Flamingos use a series of projections, or
  lamellae, to filter tiny food items from debris
  in the water.
• Swifts are aerial insectivores use their wide
  gape to help capture flying insects.
• Eagles (and hawks) are diurnal raptors use
  their hook-like bills to tear apart large prey.
• Shovelers use their spatula-shaped bills to
  filter food from mud water.
• Crossbills use their 'crossed-bill' to extract
  seeds from pine cones.
• Herons use their bills to spear small fish and
  amphibians.
• Avocets sweep their long up-curved bills from
  side-to-side through the water to capture small 
  invertebrates (or use it like a forceps to pick
  up prey).
• Woodpeckers use their chisel-like bills to chop
  away wood expose insects and insect larvae.
• Wrens use their thin, probing bill to capture
  small insects. 
• Curlews use their long bill to probe mudflats for
  small invertebrates.
• Hawfinches are seed-eaters use their bills to
  crack open large, hard seeds.
• Macaws use their strong hook-like bills to feed
  on nuts. 
• Mallards other waterfowl use their bills to
  filter small invertebrates from mud and water.
• Skimmers use their elongated lower mandible to
  skim the surface of the water capture small
  fish and invertebrates.

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A kingfisher capturing prey!
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Toucan beak
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Toucan beak

• outer shell is hexagonal keratin tiles cemented
  together with organic glue and piled in several
  staggered layers
• The interior is rigid "foam" composed of bony
  fibers and drum-like membranes sandwiched between
  outer layers of keratin
• The "foam" is covered with overlapping keratin
  tiles, each about 50 µm in diameter and 1 µm
  thick, glued together to form sheets. The closed,
  air-filled spaces reduce overall weight without
  loss of rigidity.

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Bill
 

• A bony framework covered by a tough layer of
  keratin
• keratin layer is continuously replaced throughout
  the life of a bird is just as continuously worn
  down by eating and manipulating hard objects
• cutting edges of the beak are the tomia
• The bill plays a critical role in food
  acquisition , of course, bill morphology varies
  with food habits

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Finch eating seeds

• lower mandible is moved toward the tip of the
  bill in a slicing motion.
• When most of the coat has been cracked or
  removed, the lower mandible is moved from side to
  side to remove the rest of the shell, releasing
  the kernel

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Hummingbird catching insects

• Hummingbirds have bendy lower beaks to help them
  catch insects (Yanega and Rubega 2004).
• The flexibility allows long-beaked birds to open
  their mouths wide enough to hunt on the wing.
• Hummingbirds use their long, narrow beaks to
  probe flowers for nectar, but they also need
  insects for essential nutrients.
• birds that hunt flying insects usually have short
  beaks to help them open their mouths wide. -
  Helen R. Pilcher, Nature Science Update

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Cape Gannet Capturing Prey
plummeting from up to 30 m into the water, where
they seize fish with their razor-sharp beaks.
Ropert-Coudert et al. (2004)
Photo source http//www.homepages.mcb.net/wormwel
l/Gannet130604.htm
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Kingfisher

• http//ww3.osf.co.uk/ftg_runclip.html?clip_id9348
  file_type_id2 from above
• http//www.youtube.com/watch?vkgrRD4ono6k from
  below

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Birds Feeding

• Hyacinth Macaw eating palm nuts
  http//www.youtube.com/watch?vNLh6u587I8E
• Black Skimmers http//www.youtube.com/watch?v5Q8u
  nR8XEZQ
• Red-tailed Hawk eating a Red Squirrel (graphic!)
  http//www.youtube.com/watch?vlNnrb5sX6uk
• Foraging Wilson's Petrels  The Bird That Walks On
  Water - video powered by Metacafe
• Pale-billed Woodpecker (Mayflower Bocawina
  National Park, Belize) http//www.youtube.com/watc
  h?viwFOmwBXHmo
• Vultures move in on lion kill Video
• Corys Shearwaters Common Dolphins
  http//www.youtube.com/watch?vozTlQzzw-8A
• Red-necked Phalarope http//birdcinema.com/view_vi
  deo.php?viewkeyfeedfdeaab192ead4ac0