L4 Redfern - Navigation

Question 1

What are the costs and benefits of migration?

Answer 1

Costs:

• energy loss
• increased mortality levels
• imperative to back to breed on time

Benefits:
- favourable conditions elsewhere may lead to higher survival rate and better breeding success

Question 2

What are true migrants?

Answer 2

birds that move long distances and , retain historical patterns of dispersal

Question 3

What do birds use as fuel for migration?

Answer 3

• mainly fat stores - small migratory birds can increase their body size by 150% due to sub cutaneous and abdominal fat stores pre migration

Protein is also metabolised as it is necessary for fat metabolism. Muscle must increase too to carry extra weight

Question 4

How is migratory behaviour stimulated?

Answer 4

Stimulated by changes in photoperiod which results in hormonal changes particularly an increase in TH (thyroid hormone - also stimulates moult)

Question 5

How do birds know where to go?

Answer 5

birds use cues to navigate - sun, visual landmarks, stellar compass ( + moon), olfaction, magnetic compass

Question 6

Describe how birds maintain a high aerobic metabolism

Answer 6

a highly efficient respiratory system, coupled to a powerful heart and circulatory system

Question 7

How do birds regulate their temperature?

Answer 7

• adequate cooling to remove heat in physical activity

- coupled with adequate insulation to maintain body temperature and good water economy

Question 8

What were the 2 main requirements for evolution of early reptiles into birds?

Answer 8

1. increased aerobic metabolism and ability to deliver

2. insulation required for endothermy

Question 9

Briefly describe a birds respiration

Answer 9

Inhalation - air enters the lungs and the posterior air sacs fill via trachea and the parabronchi

Exhalation 1 - the posterior air sacs act like bellows and force the air out of them through the parabronchi once more and into the anterior air space

Exhalation 2 - the anterior air sacs force the air back out the lungs via the trachea

Question 10

Why is the circulatory system in avian lungs very efficient?

Answer 10

Blood flows at right angles to the blood vessels, which maintains a high concentration gradient between the lungs and the bloods, meaning O2 transfer is very efficient.

Air flow is unidirectional

Question 11

What are the 2 types of parabronchi?

Answer 11

paleopulmonic

neopulmonic

Question 12

What 4 things effect the thermal ability of birds?

Answer 12

1. feather type - down is important for insulation, also feather position and quality
2. colour - important for reflectivity of light/heat
3. dissipating of heat - in flight via thinly feathered wings, and feet via vessels - brain is kept cool by cross current vessels
4. saving heat

Question 13

What is an avian syrinx used for?

Answer 13

Unique to avian, found at the junction of the trachea and primary bronchi

Song is achieved by changing the diameter of passageways and tension of typaniform membranes

Question 14

Describe from 2 days pre-hatching to hatching

Answer 14

1. 2 days before hatching, chick starts breathing with its lungs - makes a hole in the membrane to breathe through
2. vocalisation for parental awareness and sync with other eggs
3. egg tooth breaks shell

Question 15

After hatching, birds are either Precocial or Altricial, what does this mean?

Answer 15

Precocial - capable of moving, and don’t need much looking after other than warm and dry and food.

Altricial - unable to move, require intensive care and partially digested food