Transcript Document

Birds and Theropods
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The Theropods had these traits that are
similar in some ways to birds
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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
Earliest Bird: Archaeopteryx
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Archeopteryx is believed to be the the earliest
known bird
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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
Earliest Bird: Archaeopteryx
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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
Earliest Bird: Archaeopteryx
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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.
Chapter 17: Extant Birds:
Characteristics
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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
Feathers and Flight
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In general, feathers grow in tracts called pterylae
over the birds body.
Unfeathered areas are called apteria
A typical feather has a
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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).
Types of feathers
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contour feathers
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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
Types of feathers
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down feathers –
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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.
Types of feathers
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Semiplumes (fig 17.4 a)
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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
Types of feathers
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powder down feather –
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bristles –
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these produce an extremely fine powder as they
break up. The powder helps to keep the feather
dry.
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
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are very fine feathers with a few barbs at the
distal end (figure 17-4 C).
Musculoskeletal system
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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
Musculoskeletal system
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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.
Musculoskeletal system
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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
Musculoskeletal system
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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)
Avian Wing
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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..
Flight terminology
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Reaction:
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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
Flight terminology
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Cambered airfoil
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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
Flight terminology
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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
Flight terminology
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Alula
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The tuft of feathers on the first digit of a
bird’s wing that reduced turbulence in
airflow over the wing
Flight terminology
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Aspect Ratio: ratio of wing length to width
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Long narrow wings
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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 = 40:1
Short broad wings
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Have low aspect ratio
Slow flight speeds without stalling
Good maneuverability
E.g. pheasants, woodland dwelling birds
Flight terminology
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Wing Loading
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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
Flight terminology
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Induced drag
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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).
Flapping Flight
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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.
Flapping Flight
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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.
Flapping Flight
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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.
Four Types of wings
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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
Four Types of wings
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dynamic soaring birds have –
long narrow, flat wing, no slots in the
outer primaries; very high aspect ratio
(18:1)
Albatrosses and shearwaters (figure
17.12)
Four Types of wings
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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.
Four Types of wings
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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)
The hind Limbs
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Hind limbs are adapted for walking,
running (cursorial adaptation) as follows
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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
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Usually birds have three toes forward and one back (called
ansiodactyl) : produces a large grip
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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
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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
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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
Feeding & digestion
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Feeding habits are reflected in beak
morphology
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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)
The digestive system
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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
Esophagus & Crop
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crop is basically a pocket in the esophagus.
The function is
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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
Stomach: Has two parts
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Proventriculus: anterior
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Secrete enzymes and acid
Large in spp that swallow whole fruits
Gizzard: Posterior muscular stomach
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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
Intestines, Ceca, Cloaca
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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
Intestines, Ceca, Cloaca
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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).
Mating Systems, Reproduction
& parental care
Colors & Patterns
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Colors of patterns are determined by a
combination of pigments and structural
characteristics
Three types of pigments
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Eumelanin: produces black, gray, dark
brown color
Phaeomelanin: reddish brown & tan shades
Carotenoid pigments: red, orange, yellow
Vocalizations
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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
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Series of notes with intervals of silence
More than one song type for many spp
Show regional dialects
Individual variation
Spp specific
Mating systems
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Monogamy
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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
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Male and female share responsibility for a clutch
of eggs but do not demonstrate fidelity
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Extra-pair copulation
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Polygamy:
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See advantages on page 470-471
Second most common mating system for
birds, accounts for 6% of the extant birds
2 types
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Polygyny: a male to many females
Polyandry: a female to many males
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Resource defense polygyny
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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
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Males compete for females by establishing
patterns of dominancy, or displays
Reproduction & Parental Care
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Oviparous
Sex determination is genetic
Heterogametic sex chromosomes
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Female is heterogametic: WZ
Male is homogametic: ZZ
Sex Biased Broods
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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
Reproduction & Parental Care
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Nesting
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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
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Shallow holes in the ground
Cup shaped nests made from plant materials woven
together
Stems of aquatic plants- floating nests
Reproduction & Parental Care
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Incubation is by
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Burying eggs in sand as in megapodes, or
the Egyptian plover
Use of metabolic heat by most birds
Time of incubation varies
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Some soon after laying the first egg
Others wait until last egg has been laid
Reproduction & Parental Care
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Brooding
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Females and males have brood patchesareas 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
Reproduction & Parental Care
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Brooding Temperature & Period
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Temperature should be 33-37 degrees
Celsius
Period varies from 6-8 days and 60-80
days
Larger birds have longer incubation time
Reproduction & Parental Care
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Parental Care
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Precocial young
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Altricial young
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Feathered and self sufficient
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