PHYLUM CHORDATA
SUBPHYLUM VERTEBRATA
CLASS AVES
Hummingbird Nest
California Condor
California Condor
Vulture
Nuthatch
Penguin
Chick
Emu
Rhea
Ostrich
Ostrich
OSPREY
Wood duck
Hummingbirds
Peregrine falcon and a flock of starlings
Phylum Chordata
Subphylum Vertebrata
Class Aves
Our favorite homeotherm??
Ducks Unlimited
Audobon Society
York Wildcare (raptor rehab)
The National Symbol
After fish, the most diverse vertebrate (9000 species)
And yet, birds are not diverse anatomically ….
WHY??
Flight places severe constraints on form
… most species have roughly equal
Wings
Muscles
Feathers
Aerodynamic profile
What are sources of anatomical
variability in birds??
BEAKS
FEET
Source of Variability:
SIZE
1.8 g bee hummingbird
450,000 g elephant bird of Madagascar (extinct)
ORIGIN OF BIRDS
19TH Century Zoologists saw similarities between reptiles and birds:
•
both have single OCCIPITAL CONDYLE
• both have only the STAPES in the middle ear
• both excrete uric acid
• both lay yolky eggs
Thomas Huxley (Darwin’s “bulldog”) wrote, “Birds are nothing
more than glorified reptiles”.
Mammal
Bird
Occipital Condyle
Meat-eaters
-Allosaurs
-Tyrannosaurs
-Velociraptor
FACT: New fossils are rapidly accumulating showing
that
1) Birds evolved from dinosaurs and
2) The line between dinosaurs and birds is fuzzy
2010 discovery:
Haplocheirus sollers
- 160 mya (late Jurassic)
- bird-like but no feathers
- 15 my earlier than Archaeopteryx
FEATHERS
Why would … why did dinosaurs develop feathers ??
-To have color (camouflage or mate attraction) ??
- Insulation ??
- Gliding ??
The Liaoning Province in
NE China is producing
amazing Mesozoic fossils
the feathered
Caudipteryx
Caudipteryx
Protarcheopteryx
2 years after publication of Origin of Species:
Archaeopteryx – strong mix of reptilian and bird
characteristics
Feathers
large
Archaeopteryx features
reptilian = blue
minimal
bird = red
fusion
NO
DOUBT
Archaeopteryx
Archaeopteryx
• probably not the first flier
• body-wing proportions bird-like
• feather patterns bird-like
• large furcula
• recent finding: rectangular sternum for muscle
attachment
• maybe roadrunner-like
FLEXIBILITY
RIGIDITY
Modern
Birds
Generate
Thrust
Types
of
Feathers
Generate
Lift
Frigate bird
7 foot wing span
4 oz skeleton !!!!!!!!!!!!!!
Skull and wings are light
Fallacy: All bird bones are light
Sternum and legs may be heavy
Feathers are dead
> 90% keratin !
Feathers are epidermal
(homologous to reptile scales)
with hooklets
1 barb may have 1200 barbules !
Preening?
Mammalian
Skin
MOLTING – following breeding season
Gradually & orderly
Feathers lost in left/right pairs
Symmetry permits flight
birds are
TETRAPODS
Wings are homologous to other pectoral
appendages
Wrist/digits reduced and fused
*
Sternum
**
**
Bracing
for rigidity
**
Side View
Location of
Flight Muscles
Upstroke Muscle
location??
NO !
Why
Here?
Antagonistic
Flight Muscles
25-35% of body
wt. in strong fliers
TUNA
Wild Bird: DARK MUSCLE
•Large capillary supply
•Many mitochondria
•Myoglobin
•Sustained aerobic metabolism
Thanksgiving Turkey: WHITE MUSCLE
Tergum
Indirect Flight Muscle
Direct Flight Muscle
Sternum
No Clavicle
No Coracoid
Small Sternum
Large Sternum
Clavicle
Coracoid
SOARING FLIGHT
Faster flow
Slower
Faster-moving air
Cambered Air Foils Really Work !!
Function??
Flapping Flight: Horrendously Complex …
Yet, fledglings do it perfectly the 1st time !
Secondary feathers – lift
Primary feathers - thrust
Source
of Lift
Source of
Thrust
Downstroke
More
Thrust
Upstroke
HOVERING FLIGHT
Extreme Shoulder Rotation
Nature … Hummingbirds: Magic in the Air
http://video.pbs.org/video/1380512531/
2:30 – 6:00
Aspect Ratio = wing length
mean width
Maneuverable
low ratio
Speed
high ratio
Soaring
high ratio
High lift
medium ratio
strong camber
Peregrine
Falcon
Q: Does flight impose size limitations on birds??
Upper limit: 15 kg?? buzzards, swans, condors ?? Why??
Argument: as size increases, volume increases faster than surface area
1) Volume = length3
Surface area = length2
2) As bird size increases, volume (and weight) increase fast
3) Surface area and (wing area) increase less fast
4) Wing SA must increase faster than other surfaces
5) But, driving very large wings requires much heavy muscle
VIDEO
Wild Moves
Birds: Flying and Gliding
DVD QL 6
Chps 2-5 ~ 17 min
The amazing FRIGATE BIRD
Nonstop fliers (except for parental care)
Fly 24/7 … sleep??
Exceptionally HUGE respiratory system ??
TIDAL VENTILATION in Amphibians, Reptiles and Mammals
OUT
IN
Observations about tidal ventilation
* alveoli never fully empty
* alveolar air is a mix of fresh
and stale
* air in alveolus is motionless
O2 Partial Pressures
Air = ~ 159 mm Hg
Alveoli = ~ 100
(location of parabronchi)
• No diaphragm
• Rigid lungs
• Rigid rib cage
Gas-exchange Site
Chicken – 400 parabronchi/lung
Duck - 1800
O2 Partial Pressures
Air = ~ 159 mm Hg
Parabronchus = ~ 159
1
*
SEM of a Chicken Lung
Note Numerous
Air Capillaries
Whooping Crane Trachea
(huge anatomical dead space)
Oxygen Consumption in a Anna Hummingbird
24 h
O2
BEHAVIOR
Perching
Flying/hovering
HOURS
mL/hr
10.5
75.4
794
2721,2
639
12.6
140
2.4
Roosting/Torpor 11.1
1heart
2may
Daily
rate may reach 1200 beats/min!!
eat 100% of its body wt./day!!
mL O2
HOW FAST TO FLY??
HOW FAST TO FLY??
Which animals are bipedal ??
NO NO
What other amazing
animals are bipedal ?
MATING
Copulation looks “normal” but …
Penis-less (?!)
(Cloaca to Cloaca Sperm Transfer)
BIRD
REPRODUCTION
Single
Fertilization
region
Albumen glands
coat egg with
“egg-white”
Egg Shell (Chicken)
94% CaCO3
1% MgCO3
1% CaPO4
3-4% protein
6,000-17,000 pores/egg
Birds are Homeotherms … Eggs are not !!
Interspecific Brood Parasitism
Lay your eggs in another species’ nest!!
Brilliant: transfers the task of parenting to the host
Common among birds: 1% of all bird species lay their
eggs in another species nest.
Examples: Honeyguides, cuckoos, finches, cowbirds.
European great spotted cuckoo disposing
of eggs from a host nest
Blind cuckoo chick ejecting host egg …
Later, host chicks are similarly ejected.
Cowbird (a brood parasite)
Host
Chick
Parasitic
Chick
Vocal Mimicry !!
Birds may be relatively MONOGAMOUS … Why??
1) Males fully capable of parental care.
2) Offspring success may depend on male help.
EXAMPLE:
Female penguin can't do it all -- male sits
on eggs/warm chicks while the female is foraging.
Male has to stay … or his young will die.
BONUS: Long-term monogamy eliminates the need to acquire
a new mate each breeding season (e.g., bald eagle)
Seasonal Fluctuations in
Testes Size in Birds
Mate-guarding by male warbler
Male is tricked
by model eggs
Alternative to Monogamy: POLYGYNY
Example: LEKS in birds
Leks are aggregations of males for the
sole purpose of displaying to females
Sage Grouse
Black
Grouse
Black Grouse: Male Mating Success
Most Successful Males Over 5 Years
# copulations
Bird Reproduction:
SEXUAL SELECTION!
Long-tailed widow bird …. MALE!!
BOWER
Adornments