L17-vision and diving energetics of birds, cormorant problem

Question 1

The cormorant problem

Answer 1

cormorants are killing fish
see as a big problem
– Annual cull 2000 – 3000 birds(around 12-15% of current population)
– perception Greedy, gluttonous birds than injure as many fish as they kill, and they kill a lot of fish
theory that each a ton of fish= 550 g bird-1day-1 that is not sustainable

Question 2

We need to know how much fish they need, and how they get it

Answer 2

• Energetics of avian divers:
– Macrophysiological variation in the energy expenditure of birds
– Flight-foraging and buoyancy-thermoregulation trade-off
– The cormorant paradox (a tropical bird in the arctic)
• Visual performance of avian divers:
– Consequences of crossing the air-water interface
– Visual acuity, visual fields, and eye movements
• The predatory strategy of cormorants: integration of vision and energetics

Question 3

• Energetics of avian divers:

Answer 3

– Macrophysiological variation in the energy expenditure of birds
– Flight-foraging and buoyancy-thermoregulation trade-off
– The cormorant paradox (a tropical bird in the arctic)

Question 4

Visual performance of avian divers:

Answer 4

– Consequences of crossing the air-water interface

– Visual acuity, visual fields, and eye movements

Question 5

Cormorants distribution

Answer 5

widely distributed-australia to uk and iceland
subspecies have been moving into the UK
means encounter variety of environmental conditions
more heat needed to produce more heat so more food

Question 6

Residual BMR with temp

Answer 6

as species get bigger less metabolic rate
in warm areas less energy expenditure
animals in cold places have higher relative rate of energy expenditure
high BMR higher cold tolerance

Question 7

FMR

Answer 7

energy expenditure as animal goes about its life

Question 8

Why is cold a challenge?

Answer 8

• High thermogenic capacity
– High rates of basal metabolic
– High rates of field metabolism
– High food requirements
• The additional problem of water
– Buoyancy-thermoregulation
– Flight-foraging

Question 9

problem with flight,diving and insulation?

Answer 9

can’t have blubber as to heavy
use air layer but means very buoyant can’t dive
thicker the air layer the warmer but also more buoyant
as dive air layer decreases in size but also means it is less warming

Question 10

Cormorant origins

Answer 10

come from warm ocean waters near aus have expanded all the way to greenland water gets to near negative temperatures
death to hypothermia no serious threat

Question 11

Cormorant buoyancy and feather structure

Answer 11

feathers to wick of water
feathers get wet
great for warm waters not great for cold waters
buoyancy and heat retention abilities decrease as go down

Question 12

Diving birds: depth and buoyancy

Answer 12

metabolic rate in water twice that as in air
metabolic rate increases again when diving
reduction in warmth cost more energy than an increase in buoyancy would

Question 13

Dive:pause ratio

Answer 13

how long do they stay on surface vs in water

more energy they used the longer they need to spend on top of water

Question 14

Field Metabolic Rate,energy expenditure

Answer 14

cormorants have fairly low daily energy expenditure much higher catch needed compared to other bird species
catch per unit effort worst when dark
also catch lots of fish for time diving
energy expenditure highest when cold,dark