Birds and Theropods

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Birds and Theropods

• The Theropods had these traits that are similar
  in some ways to birds
• Elongate, mobile and S-shaped neck
• A foot with 3 toes pointed forward and one
  extending backward (tridactyl foot)
• Digitigrade posture (I.e. with toes bearing the
  weight of the body
• Ankle joint between tarsal bones (inter-tarsal
  joint) rather than between tarsals and tibia and
  fibula
• Hollow pneumatic bones
• Fused bone sternum
• A furcula (wishbone) formed from fusion of the
  clavicles

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Earliest Bird Archaeopteryx

• Archeopteryx is believed to be the the earliest
  known bird
• Oldest fossil belonging to the class Aves
• Dates to late Jurassic
• But its structures seem to be intermediate
  between Theropods and birds.
• Birds defined as Archaeopteryx extant birds and
  all descendants of their most recent ancestor

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Earliest Bird Archaeopteryx

• Flight feathers on wings had asymmetrical veins
  suggesting that they had been shaped by
  aerodynamics forces associated with flapping
  flight
• The retrices-(tail feathers) are arranged in 15
  pairs along the sides of the 6th thru 20th caudal
  vertebrae
• Had a large furcula
• Fused clavicle
• Rectangular sternum
• Wings very large, to contribute acceleration as
  it ran

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Earliest Bird Archaeopteryx

• Evidence suggest it could fly by taking off the
  ground and rapidly fly for several hundred
  meters
• Well defined as a ground dwelling cursorial
  predator that could leap into the air to seize
  flying insects and fly rapidly to escape from
  predators
• Could not land in trees due to its foot structure.

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Chapter 17 Extant Birds Characteristics

• Major characteristics of birds are modifications
  for flight which is the central trait of birds
• Feathers represent modified epidermal scales
• Are used for a variety of functions
• Insulation, airfoil, streamlining, waterproofing,
  reflecting/absorbing solar radiation, tactile
  senses and display

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Feathers and Flight

• In general, feathers grow in tracts called
  pterylae over the birds body.
• Unfeathered areas are called apteria
• A typical feather has a
• calamus, which is a short tube attached to the
  bird
• rachis, which is the main support in the middle
  of the feather
• vane, which is made up of barbs that are held
  together by barbules (Figure 17-2).

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Types of feathers

• contour feathers
• have a large vane and are found in the wing and
  tails
• Have interlocking barbs and barbules
• Used as airfoil, flight
• Remiges are the wing feathers
• Retrices are the tail feathers

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Types of feathers

• down feathers
• The rachis is shorter than the longest barb and
  there are no barbules,
• Thus the feather seems very disorganized.
• Soft and fluffy
• This feather is used for insulation and covers
  the body of the bird.

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Types of feathers

• Semiplumes (fig 17.4 a)
• are intermediate between a contour feather and a
  down feather . The base of the feather is like a
  down feather but the rachis is longer than the
  longest barb. Provides shaping and insulation

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Types of feathers

• powder down feather
• these produce an extremely fine powder as they
  break up. The powder helps to keep the feather
  dry.
• bristles
• have a stiff rachis and no barbs (figure 17.4 b).
  Generally used for protection around the eyes,
  nose, mouth and they are also tactile sense
  organs.
• filoplumes
• are very fine feathers with a few barbs at the
  distal end (figure 17-4 C).
• They are sensory in nature and provide
  information about the position of the flight
  feathers.

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Musculoskeletal system

• Bones have been lightened via inclusion of large
  air spaces (pneumatic bones)
• feathers may weigh more than skeleton
• Pneumatization better developed in large birds
  than small ones
• Diving birds have less pneumatization
• Skull is greatly pneumatic, sternum, pectoral
  girdle and pelvic girdles are all pneumatic

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Musculoskeletal system

• Skeleton is strengthened by extensive fusion of
  bones
• loss of teeth and heavy jaws replaced by horny
  beak -- lighter
• specialization of forearm bones to support flight
  feathers
• loss of tail pygostyle--fused 5 remaining caudal
  vertebrae platform for tail feathers.

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Musculoskeletal system

• furcula - fused clavicles, only in birds and
  theropods--"wishbone" provides extra bracing
  for shoulder girdle
• synsacrum fused pelvis
• Hind legs used for body support and locomotion
  (bipedal walking, hopping, perching)
• Fore-limbs modified as wings

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Musculoskeletal system

• Thoracic vertebrae are joined by strong ligaments
  that are often ossified- immobile
• Resists collapse during flight
• Sternum bears an enlarged process keel for the
  origin of the flight muscles (the Pectoralis)
• Furcular and procoracoids brace the sternum and
  prevent it from collapsing the chest during
  contractions of flight muscles
• Ribs overlap, forming light, strong cage
  protecting heart, viscera, during contraction of
  flight muscles

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• Femur is robust to support major muscles
• Bones of shank, ankle, foot elongated for
  efficient locomotion
• Ankle joint is mesotarsal ( inside the
  tarsals)5th toe is lost
• Tarsometatarsus formed by fusion of distal
  tarsals and metartasals of the remaining toes
• Knee is between thigh and drumstick and is hidden
  between contour feathers of the body
• The tibiotarsus is the lower leg (drumstick)

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Avian Wing

• Serves as an air foil (lifting surface) and
  propeller for forward motion
• Equipped with primary feathers that propel the
  bird and the secondaries that provide lift.
• Primary feathers responsible for flying..

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Flight terminology

• Reaction
• Force produced by flow of air and composed of
• Lift vertical force opposed to gravity
• Drag backward force opposed to forward motion
• Angle of attack the angle above the horizontal
  of the leading edge of a bird,s wing. A larger
  angle ideal for generating lift

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Flight terminology

• Cambered airfoil
• A structure of a wing that is convex dorsally and
  produces lift when air flows across it or
• The degree to which the ventral surface of the
  wing is concave.
• The more camber the more lift that is developed
  at low speed.
• Can compensate for high wing loadings, low aspect
  ratios

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Flight terminology

• Angle of attack
• The angle that the wing is tilted above
  horizontal as is moves into the air.
• If the angle of attack is too high, turbulence
  results across the wing and the lift decreases to
  the point that it can not keep the bird in the
  air. At this point the bird stalls.
• The angle at which this occurs is called the
  stalling angle.
• See figure 17.8

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Flight terminology

• Alula
• The tuft of feathers on the first digit of a
  birds wing that reduced turbulence in airflow
  over the wing

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Flight terminology

• Aspect Ratio ratio of wing length to width
• Long narrow wings
• have high aspect ratio and high lift to drag
  ratios (L/D)
• These wings allow fast flight and dynamic soaring
• E,g sailplanes, albatrosses AR 18 1 L/D
  401
• Short broad wings
• Have low aspect ratio
• Slow flight speeds without stalling
• Good maneuverability
• E.g. pheasants, woodland dwelling birds

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Flight terminology

• Wing Loading
• Mass of bird divided by wing area
• The lighter the load, the less power is needed to
  sustain flight (e.g in small birds)
• The larger the load, the more power needed to
  sustain flight ( as in larger birds)
• See table 17.1
• Heavier birds, in general, have higher wing
  loadings than lighter birds

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Flight terminology

• Induced drag
• is the result of airflow from beneath wing
  around the distal tip to the upper surface of the
  wing. (picture an airplane landing on a dusty
  runway).

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Flapping Flight

• The shoulder joint of a bird involves the
  Humerus, scapula, and Coracoid.
• The muscles that power the wing are on the
  ventral surface.
• The muscles on the dorsal surface are very weak
  and are not used to power the wing.
• The downstroke is powered by the Pectoralis major
  (largest breast muscle).This muscle originates on
  the keel of the sternum and inserts on the
  ventral surface of the Humerus.

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Flapping Flight

• The upstroke is powered by the supracoracoideus.
  This muscle also originates on the keel of the
  sternum and is deep (or beneath) to the
  pectoralis major.
• A tendon runs from the supracoracoideus, though
  the foramen triosseum and inserts on the dorsal
  surface of the humerus.

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Flapping Flight

• Strong fliers have as much as 20 of their body
  weight made up by breast muscle (pigeons),
• Some birds have the breast muscle make up only
  10 of the body weight (owls).
• During takeoff birds usually strongly power both
  the upstroke and the downstroke.

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Four Types of wings

• high-speed wing fast flying birds such as
  pigeons and falcons moderately high aspect ratio
  tapered to a point at the distal end
• very little camber (almost flat on the ventral
  surface)
• no slots in the outer primaries

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Four Types of wings

• dynamic soaring birds have
• long narrow, flat wing, no slots in the outer
  primaries very high aspect ratio (181)
• Albatrosses and shearwaters (figure 17.12)

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Four Types of wings

• elliptical wings
• Low aspect ratio (length to width ratio is
  small). E.g in pheasants grouse
• highly cambered slotting in the outer primaries
• highly maneuverable wing, relatively slow speed,
  commonly found in woodland species, constantly
  flapping to produce lift.

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Four Types of wings

• slotted high-lift wing
• Highly maneuverable wing, with high lift at slow
  speed. intermediate aspect ratio, deeply cambered
• These birds engage in static soaring where they
  ride thermals or other air currents while
  gliding.
• marked slotting in the outer primaries (the
  slotting reduces induced drag and provides lift
  at slow speed with each feather acting as an
  airfoil)

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The hind Limbs

• Hind limbs are adapted for walking, running
  (cursorial adaptation) as follows
• an increase in the length of the distal elements
  of the leg
• a decrease in the surface area of the foot that
  makes contact with the ground
• a decrease in the number of toes (for example,
  ostriches have 2 toes)
• See figure 17.13

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• hopping This is a specialization in which both
  feet move together. A succession of jumps
• This is typical of smaller birds (songbirds)
• In larger birds hopping becomes energetically
  unfavorable (for example among the corvids, blue
  jays hop but ravens walk).

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• Perching on trees/ branches
• Usually birds have three toes forward and one
  back (called ansiodactyl) produces a large grip
• Typical of passerines which perch on their limbs,
• Parrots woodpeckers have two toes forward and
  two toes backward (called zygodactylus)
• Special arrangements of tendons creates a pulley
  system such that the weight of the perching bird
  tightens the tendons and curls the toes tightly
  around the perch
• Means no muscular energy expended, bird will not
  fall of when off when it sleeps

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• Climbing
• Relatively short legs for climbing
• Feet often with 2 toes in front and 2 to rear
• Often accompanied by tail with especially stiff
  feathers to act as prop

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• Swimming
• Feet either webbed or lobed
• webbing or lobbing between the toes
• legs positioned toward the back of the bird
• muscle mass for the limbs is more streamlined
  into the body
• wide body for stability when floating
• dense plumage for buoyancy and insulation
• preen gland that produces oil that waterproofs
  the feathers

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Feeding digestion

• Feeding habits are reflected in beak morphology
• Short, deep curved beaks seed eating
• Short pointed shallow beaks insects
• Long slender pointed beaks fish spears
• Spoon bills flattened with broad tips for
  aquatic feeding
• Long broad, flattened bills with ridges along the
  sides Filter feeding (water strainer, mud sifter)

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The digestive system

• The digestive tract of birds has some interesting
  adaptation for holding food and for mechanical
  digestion
• teeth are absent, hence no processing of food in
  mouth

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Esophagus Crop

• crop is basically a pocket in the esophagus.
• The function is
• to hold food,
• transport food to nest, adult regurgitates food
• Produces crop milk in doves that is fed to the
  young. Rich in lipids and proteins

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Stomach Has two parts

• Proventriculus anterior
• Secrete enzymes and acid
• Large in spp that swallow whole fruits
• Gizzard Posterior muscular stomach
• Has a thick lining and is very muscular.
• Birds eat small bits of gravel and the gizzard
  grinds the food with the gravel.
• The function is for mechanical digestion of the
  food and basically replaces the chewing as birds
  do not have teeth, Also food storage chemical
  digestion

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Intestines, Ceca, Cloaca

• small intestine primary site if chemical
  digestion and absorption of nutrients.
• Enzymes produced by small intestine pancreas
• large intestine is short and is for storage of
  wastes and water absorption.
• Pair of ceca at the junction of the small and
  large intestines. small in carnivores,
  insectivorous seed eating spp, large in
  herbivores
• Contain symbiotic microorganisms that ferment
  material

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Intestines, Ceca, Cloaca

• cloaca is the very last section and receives
  wastes from the excretory system as well.
• Water absorption also occurs in cloaca
• In birds, the feces is composed of urate salts
  from the excretory system (the white stuff) and
  indigestible matter from the food (the dark
  stuff).

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Mating Systems, Reproduction parental care
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Colors Patterns

• Colors of patterns are determined by a
  combination of pigments and structural
  characteristics
• Three types of pigments
• Eumelanin produces black, gray, dark brown color
• Phaeomelanin reddish brown tan shades
• Carotenoid pigments red, orange, yellow

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Vocalizations

• Birds use color, vocalizations and posture for
  sex, spp, and individual identification
• Bird songs are long and complex
• In many spp, songs are produced by males only and
  during the breeding season
• Song is a learned behavior controlled by many
  song control regions (SCRS) in the brain

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• PROPERTIES OF BIRD SONG
• Series of notes with intervals of silence
• More than one song type for many spp
• Show regional dialects
• Individual variation
• Spp specific

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Mating systems

• Monogamy
• A pair bond between one male and one female
• Pairing may last for a part or entire breeding
  season, or for a lifetime
• Both parents care for the young
• Infidelity may still occur (extra-pair
  copulation)
• Social monogamy
• Male and female share responsibility for a clutch
  of eggs but do not demonstrate fidelity

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• Extra-pair copulation
• See advantages on page 470-471
• Polygamy
• Second most common mating system for birds,
  accounts for 6 of the extant birds
• 2 types
• Polygyny a male to many females
• Polyandry a female to many males

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• Resource defense polygyny
• Males control access to females by controlling
  critical resources such as nest sites
• Its it a high quality territory, females settle
  for a male with other mates already.
• Male dominancy polygyny
• Males compete for females by establishing
  patterns of dominancy, or displays

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Reproduction Parental Care

• Oviparous
• Sex determination is genetic
• Heterogametic sex chromosomes
• Female is heterogametic WZ
• Male is homogametic ZZ
• Sex Biased Broods
• Sex biased hatching is not well understood
• Females hatch first the sex that is a higher
  chance of survival
• Eggs hatch in the sequence of laying

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Reproduction Parental Care

• Nesting
• Nests protect eggs not only from physical
  stresses as heat, cold and rain
• But also from predation
• Most birds nest individually but a few are nest
  in colonies, many nests put together at a
  distance of two necks
• Nests vary in quality and materials
• Shallow holes in the ground
• Cup shaped nests made from plant materials woven
  together
• Stems of aquatic plants- floating nests

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Reproduction Parental Care

• Incubation is by
• Burying eggs in sand as in megapodes, or the
  Egyptian plover
• Use of metabolic heat by most birds
• Time of incubation varies
• Some soon after laying the first egg
• Others wait until last egg has been laid

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Reproduction Parental Care

• Brooding
• Females and males have brood patches- areas of
  bare skin- no feathers
• May be produced by prolactin plus estrogens or
  androgens
• Some may be produced by plucking as seen in ducks
  and geese

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Reproduction Parental Care

• Brooding Temperature Period
• Temperature should be 33-37 degrees Celsius
• Period varies from 6-8 days and 60-80 days
• Larger birds have longer incubation time

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Reproduction Parental Care

• Parental Care
• Precocial young
• Feathered and self sufficient
• Altricial young
• Naked and entirely dependent on parents for food
• Guarded and fed by both parents
• Open their mouths wide upon the noises of parents
  
• See table 17.3 and table 17.4

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• Structural colors due to melanin particles in
  cells on the surface of feathers that reflect
  specific wavelengths of light
• Blue is reflected by small particles
• Green is reflected by larger particles
• Combinations of pigments and light reflections

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