Influencing policy (training slides from Fast Track Impact)
PPt Modern Birds Info 2.ppt
1. Modern Birds
The other remaining Archosaurs are birds
given their own class Aves by traditional
taxonomists.
There are approximately 8,600 species of
birds ranging is size from the tiny bee
hummingbird to the ostrich.
3. Characteristics of the birds
Feathers a unique character among living
animals, but also found in dinosaurs.
Endothermic
Skeleton modified for flight. Bones hollow,
forelimbs support the wing, ribs with uncinate
processes, beak but no teeth, reduced tail.
Breathing by lungs and associated air sacs
Internal fertilization and hard-shelled amniotic
egg
4. Evolution of birds
Birds evolved from a group of theropod
dinosaurs in the Jurassic period. The oldest
known bird fossil is Archaeopteryx lithographica
which has a mix of “reptilian” and avian features.
Reptilian: long tail, teeth, long clawed fingers
Avian: feathers, ribs with uncinate processes,
avian shoulder girdle.
7. Feathers
Among living animals feathers are a
uniquely avian trait.
However, it is now well established that
feathers also occurred in dinosaurs. In the
1990’s feathers were described from
series of non-avian coelurosaurs, mostly
from the Chinese Liaoning deposits.
8. Feathers
Feathers are what enable birds to fly, but
originally are believed to have evolved as
a thermoregulatory device.
Feathers are lightweight, but strong. The
surface of the feather is made up of tightly
spaced, overlapping filaments that hook
together. Overlapping feathers form the
wings with which birds fly.
10. Feather structure
Feathers are made of keratin: an inert
substance that consists of insoluble
microscopic filaments embedded in a
protein matrix.
Keratin is the substance found in hair,
nails, claws and scales of other animals,
but bird keratin is unique and differs from
that of modern reptiles.
11. Feathers
There are two main categories of feathers
Plumaceous – downy for insulation
Pennaceous – linked , vaned feathers wing and
contour feathers.
Vane of a typical body feather consists of a
hidden downy base (for insulation) and an
exposed cohesive outer portion (for
streamlining).
13. Feathers
Body feathers of most birds include an
aftershaft that emerges from the underside
of the shaft where the first basal barbs of
the vane branch off.
The aftershaft is almost always downy and
functions to increase insulation. In
ptarmigan winter plumage the aftershaft is
¾ as long as the main feather.
15. Feather structure
A contour feather has a long central shaft and a broad flat
vane. The hollow base of the shaft (quill) anchors the
feather in a follicle under the surface of the skin.
The rest of the shaft, the rachis, supports the vanes.
Branching off from the rachis are barbs. Each barb has
barbules projecting to either side that interlock with the
barbules of adjacent barbs.
Barbs and barbules form an interlocking, but flexible
surface.
http://www.birdwatching-bliss.com/bird-feathers.html
17. Adaptations for flight
In general, the avian skeleton has been
lightened and strengthened for flight.
This has been achieved by eliminating
some structures and modifying others.
18. Adaptations for flight
Feathered wing.
Mass reduction
Wrist bones reduced to two
Bones hollow and supported by internal struts
or spongy bone
Reptilian tail lost. Fused tail bones (pygostyle)
support tail feathers
Teeth lost. Skull and bill light but strong.
20. Adaptations for flight
Skeleton strengthened
ribs have rear-facing uncinate processes that overlap
and strengthen walls of thorax
bones of wrist, pelvis fused
Sternum or breastbone enlarged with a large keel
(carina) for attachment of massive flight muscles --
pectoralis and supracoracoideus.
Fused hand bones support and maneuver primary flight
feathers.
Efficient lungs and powerful four-chambered heart power
flight.
25. Further skeletal modifications for
flight
Furcula The clavicles are fused to form a
structure called the furcula or wishbone.
The furcula flexs during flight and spreads
and contracts during each wingbeat. The
flexing may enhance gas exchange by
assisting in moving air through the air
sacs.
http://www.birdwatching-
bliss.com/bird-flight.html
27. Bernoulli’s Principle - “When the speed of a
fluid (air) increases, internal pressure in the fluid
decreases”
FLIGHT
28. Shape of bird’s wing = airfoil
The high pressure above the airfoil will be
greater than the low pressure above the
wing, causing the bird to “lift” causing the bird
to lift up.
29. Lift and thrust
In order to fly both horizontal thrust and vertical
lift are required.
Thrust is mainly generated by the primary
feathers (the long ones at the end of the bird’s
hand), which on the downstroke twist and acting
like a propeller push the air backwards.
Lift is mainly generated by the secondary
feathers (the inner portion of the wing), which
form an airfoil.
http://www.youtube.com/watch?v=p-_RHRAzUHM
(Peregrin Falcon with camera attached in flight)
31. Avian lungs
The one-way flow of air is achieved by using a
system of air sacs and a two breath cycle.
On inspiration air flows down the trachea to air
sacs below the lung. On expiration the air mass
flows into the lung where gas exchange takes
place.
With a second inspiration the air mass in the
lung flows into anterior airsacs and with a
second expiration exits the body via the trachea.
37. Bird’s digestive tract and other internal organs
http://www.dkimages.com/discover/previews/824/80016755.JPG
38. Feeding and digestion
Because birds lack teeth they can’t process food
much in the mouth so that is left up to the gastric
system.
Birds can frequently gather food faster than it
can be processed. This food is usually stored in
the birds crop, an enlarged part of the
esophagus.
The crop is also used to store food that will later
be regurgitated to chicks.
39. Stomach
A bird’s stomach has two parts the anterior
glandular proventriculus and the posterior
gizzard.
The proventriculus contains glands that
secrete digestive enzymes. In birds that
swallow whole foods such as fruits the
proventriculus is often very large.
40. Gizzard
The gizzard’s main function is to
mechanically process food.
The walls of the gizzard are thick and
muscular and the gizzard often contains
small stones, which the birds swallow to
assist in grinding the food. The gizzard
thus fulfills the same role as the teeth in
mammals.
41. Gizzard
The gizzard can exert significant pressure.
For example, a turkey’s gizzard can
process two dozen walnuts in about four
hours.
It can also crack hickory nuts, which
require 50-150kg of pressure to break.
42. Seasonal changes in gut
morphology
Birds often change their diets over the course of a year
and gut morphology changes too. Insects are more
easily and quickly digested than plant food (e.g. berries).
When starlings switch to eating more plant material in
the fall their intestines increase in length by about 20%
and decrease by a similar amount in spring when their
diet switches back to animal prey.
Accompanying the morphological changes are changes
in the types and quantities of digestive enzymes
produced tailored to match the composition of the diet.
43. Sensory systems: vision
Most birds have excellent vision and this is
reflected in the structure of the brain.
There are large optic lobes and the
midbrain which processes visual
information is enlarged.
In contrast, in most birds olfaction is
unimportant and the olfactory bulbs are
small.
44. Hearing
Birds have hearing that is comparable in
sensitivity to that of humans even though their
heads are much smaller.
However, they have proportionally much larger
tympanic membranes which enhances sensitivity
to sound. In addition, the cochlea has about 10x
as many hair cells per unit length than a
mammalian cochlea does.
45. Puerto Rican Screech owl Saw –whet owl
http://www.fs.fed.us/r8/caribbean/wildlife-facts/2003/
wildlife-facts_images_2003/pr_screech_owl.jpg
46. Hearing
Owls possess the most acute hearing among
birds (comparable to that of a cat) and can
isolate sounds very accurately even in complete
darkness.
Owls possess a distinctive facial ruff of stiff
feathers that acts as a parabolic sound reflector,
which focuses and amplifies sounds.
Some ruffs are asymmetric and the ruff’s
asymmetry (as well as asymmetry in the vertical
placement of the ears) enhances the owls ability
to isolate sounds in three dimensional space.
48. Hearing
The asymmetries in the ruff and ears cause
delays in the time at which sounds reach each
ear that can be interpreted by the brain and
used to identify precisely the source of a sound.
A barn owl’s ability to do this is so good that it
can isolate sound to within 1º in three
dimensional space. If you envisioned yourself
surrounded by a sphere with a radius
approximately equal to your arm length 1º would
be about the area covered by a fingertip.
49. Olfaction
Most birds have a poorly developed sense
of smell, but a few groups do have a good
sense of smell.
These include kiwis which have their
nostrils at the end of the bill and use odor
cues to find prey when they probe in the
earth.
50. Brown Kiwi hatched at the Smithsonina National Zoo 2006:
http://news.nationalgeographic.com/news/2006/02/images/060217_kiwi.jpg
Kiwi’s ,the flightless birds that are the national symbol of New Zealand,
appear to sniff out their earthworm prey. (nocturnal)
51. Olfaction
Other birds with a good sense of smell are
the various “tubenoses” the petrels,
shearwaters and albatrosses, which are
attracted to the scent of chummed fish and
fish from a considerable distance.
In addition, turkey vultures have a well
developed sense of smell and can find
even covered carcasses very quickly.
52. Sooty Shearwaters and Nothern Fulmars are
attratcted from downwind to the smell of fish oils,
squid, and krill.
