Behavioural ecology and optimality p. II

Question 1

How do small birds conserve energy?

Answer 1

• Build fat reserves under skin: do this when there is less food available

Question 2

What are the costs and benefits to small birds building fat reserves when there’s less food?

Answer 2

Costs: spend more time foraging
         -flying will take more energy
         -become slower and less agile
         -increased risk from predators
Benefits:
         -Avoid starvation
         -Fuel for breeding
         -Migration

Question 3

How can you measure how a bird’s fat reserves change over time?

Answer 3

Train bird to collect mealworms from an electric balance, and measure their weight throughout the day

Question 4

How will a small bird change its bodyweight if it weighs less at dawn?

Answer 4

It will eat more to increase its bodyweight quickly and intensely - vice versa if it has a high bodyweight at dawn

Question 5

How do we know that small bird will try and reach a precise bodyweight?

Answer 5

Bodyweight by dusk compared to dawn can fluctuate by 2 mealworms

Question 6

What are some explanations for dawn chorus?

Answer 6

• At dawn v quiet and less wind, high humidity = sound transmission is high at this time
• Foraging efficiency is low at dawn so have time to sing
• Fewer predators at dawn

Question 7

What are some of the explanations of low foraging at dawn?

Answer 7

• light intensity is manipulated
• across range of light - measured number of prey birds can find per minute
• dark so foraging success v low
• sky brightens, foraging success goes up

Question 8

What are stochastic dynamic programming (SDP) models?

Answer 8

• Take into account unpredictable variability
• Link short term decision making to long term fitness
• Identify optimal state at end of series of days

Question 9

What are ‘states’ in terms of animals?

Answer 9

Aspect of an animals biology that affects its long term fitness e.g., energy reserves, foraging success

Question 10

What do SDP models relate energy balance to?

Answer 10

Costs and benefits of different behaviours

At different times of day and night

Question 11

Why may the dawn chorus of bird be affected on colder nights?

Answer 11

Birds will build up bigger fat reserves on colder nights and therefore won’t need to forage in the morning. So may as well sing

Question 12

What are the different ways to test SDP models for behavioural routines?

Answer 12

1. Test key assumptions
2. Test predictions about how environment affects state and how state affects behaviour
3. Test predictions about daily routines

Question 13

Give an example of how you would test an SDP model in practise.

Answer 13

1. Testing key assumptions -
   - is singing costly? well robins found to sing more in response to unfamiliar song and so will lose bodyweight as not foraging. Energy costs
2. Measure song rate, bodyweight overnight temperature at dusk and dawn to see how much is lost

Question 14

How does overnight temperature affect the bodyweight of a bird?

Answer 14

• On warm nights birds use little body mass overnight

- On cold nights birds lose more body mass due to trying to keep themselves warm

Question 15

How many grams is lost per 10 degree drop in temperature?

Answer 15

0.5 g - CHECK

Question 16

How are birds able to prepare for the varying temperatures they may face?

Answer 16

Remember how cold night before was and expect it to be a similar temperature the next night to build up their fat reserves

Question 17

Even if they have low fat reserves what are certain things birds are guaranteed to sing for?

Answer 17

Protecting territory, mating etc.