Zusammenfassung der Ressource
Birds
- Water loss
- REWL (Respiratory evaporative water loss)
- Birds lack sweat glands -
rely on REWL for
thermoregulation
- Gullar Fluttering
- Rapid movement of flaps
in the throat to increase
evaporation
- TEWL (Transepidermal evaporative water loss)
- Bird skin permeable, allows
moisture through. Not very
waterproof
- Water Gain
- Drinking
- opportunistic - not
always available
- Specialist drinking
capabilities
- Ostrich
- Metabolic water
- 5 - 10 times higher in
than in invertebrates
and reptiles
- Diet
- Can feed on a high
water content
species of plants
- Ostrich
- Water re-absoprtion
- Nasal salt glands
- Produce concentrated salt
solutions which is then excreted via
the nose - 800 - 900mOsmol
- Small Birds =
Evaders
- Sand Grouse
- Males carry water
to the nest over
long distances
- Soaks specialised
breast feathers
- Can carry 40ml of
water over long
distance
- Keeps chicks away
from the habitats of
predators
- Larks
- Dunn's Lark
(ARABIAN DESERT)
- Annual rainfall - 90mm
- Air temperature in July = 40C
- Sky Lark/
Woodland Lark (NETHERLANDS)
- Annual rainfall - 750mm
- Air temperature in July = 22C
- Mesic VS Xeric
(balanced vs extreme)
- Higher Metabolic
rate, higher body
temperature
- Stratergies to reduce water loss
- Avoid the extremes of
hot and arid deserts
- Migration
- If small, able to evade the heat -
Larger birds must endure
(ostrich)
- Nitrogenous waste
- Urine
- Avian Nephrons
- Reptilian type -
Lack loops of
Henle
- Mammalian type = short and
sometimes long loops of henle
- better at reducing waste
- Production of uric acid
- Uricoetylic
- Renal Function
- Reabsorption of water
occurs in the colon and
cloaca - post renal
re-absorption
- Large Birds =
Endurers
- Ostrich
- Largest living bird -
flightless
- Reduced levels of
urination and urine
volume
- Urine more concentrated
than blood plasma (x2.7
plasma)
- Only expires 75%
saturated air via
REWL
- Water saving per
day - 200 - 500ml per
day
- Effective Nasal
counter-current flow
allows this
- Large and enhanced
nasal salt glands
- Lowered metabolic
rates, lowered body
temperature