Module 1.4- Beaks and Bills

Question 1

What is the main factor that influences the evolution of beak shapes?

Answer 1

Diet.

Question 2

What factor other than diet influence the evolution of beak shapes?

Answer 2

Foraging habits

Question 3

A bird specialised in eating seeds would be expected to have what kind of beak?

Answer 3

A thick beak designed for crushing

Question 4

A wood pecking bird would be expected to have what kind of beak?

Answer 4

heavy, blunt beak designed to chisel

Question 5

A shorebird would be expected to have what kind of beak?

Answer 5

long, delicate beak designed for probing

Question 6

A raptor would be expected to have what kind of beak?

Answer 6

Sharp-edged, hooked beak designed for tearing skin, muscle and fur.

Question 7

Which bones make up the underlying structure of a beak?

Answer 7

premaxillary and mandibular

Question 8

How are the premaxillary and mandibular bones modified to form the beak?

Answer 8

local thickenings of the epidermis, made up of tightly packed keratinocytes that migrate outwards as they mature, cornifying as they progress outward.

Question 9

How do the keratinocyte cells that make up the beak epidermis change as they migrate outwards?

Answer 9

They transition from an actively growing germinative layer to a fully cornified layer

Question 10

Which direction do the keratinocytes in a birds beak migrate? What does this mean?

Answer 10

They migrate outwards, similar to that of human fingernails, meaning the beak of a bird is continuously growing.

Question 11

What comprises the outer layer of the beak?

Answer 11

A Laminae of cornified cells called corneocytes, which form a hard, horn like sheath.

Question 12

What is the name of the outer layer of the beak?

Answer 12

Rhamphotheca

Question 13

What is the type of the cell that comprises the outer layer of the beak?

Answer 13

corneocytes

Question 14

What is the type of cell that comprises the inner layers of the beak?

Answer 14

Keratinocytes

Question 15

how is the outer layer of the beak (Rhamphotheca) maintained?

Answer 15

It is continuously replaced via growth and maturation of the epidermis as it is worn down by use.

Question 16

What is the function of the outer layer of the beak (Rhamphotheca)?

Answer 16

provides a strong, durable structure for feeding, preening, breeding and defense

Question 17

What are the two types of sensory receptors that can be found within the beak?

Answer 17

Magnetoreceptors and mechanoreceptors

Question 18

What three functions other than feeding can the beak be used for?

Answer 18

May be used to perceive sensory information such as vibrations, temperature and pressure to assist with foraging and understanding the environment.

May function in orientation and migration with the use of magnetoreceptors located in the beak.

May assist with thermoregulation (Toco Toucans show vascular mechanisms for controlled heat exchange in the beak)

Question 19

What is the name of the structure at the tip of the premaxilla in a beak?

Answer 19

Rhinotheca

Question 20

What is the name of the structure at the tip of the mandible in a beak?

Answer 20

Gnatotheca

Question 21

Where is the external nasal opening usually located on a birds beak?

Answer 21

On the basal end of the premaxilla (close to the face on the top part of the beak)

Question 22

What one bird has external nasal openings located somewhere other than the normal position? Where are they located and why?

Answer 22

The New Zealand Kiwi has external nasal openings located on the cranial side of the Rhinotheca (tip of the beak) rather than the Premaxilla (close to the face). This is because they use it to detect prey in foraging.

Question 23

Name the layers of the ventral (bottom) beak, from deepest (innermost) to most superficial (outermost)

Answer 23

Mandible (bone), Dermis, Epidermis (stratum germinativum, stratum corneum)

Question 24

Name the layers of the dorsal (top) beak, from deepest (innermost) to most superficial (outermost)

Answer 24

Premaxilla (bone) and nasal cartilage, Dermis, Epidermis (stratum germinativum, stratum corneum), nasal passages

Question 25

Why is the Toucan (Ramphastos toco) beak special?

Answer 25

It makes up a third of the birds length but less than 5% of it’s weight because it is comprise of a specialised sandwich like layering and an outermost layer of keratin hexagonal scales, giving it lightweight but strong formation.

Question 26

What specialisation does the Monotreme bill contain to assist with locating prey?

Answer 26

They can detect electrical fields generated by the muscle contractions of their prey.

Question 27

Describe the overall structure of the Platypus bill

Answer 27

Soft, rubbery, well supplied with nerves, covered with thin, extremely sensitive skin.

Question 28

Roughly how many push-rod Mechanoreceptors are found in a Platypus bill?

Answer 28

46500

Question 29

Roughly how many mucous gland Electroreceptors are found in a Platypus bill?

Answer 29

40000

Question 30

Roughly how many sensory serous glands are found in a Platypus bill?

Answer 30

13500

Question 31

Where are the mucous gland electroreceptors of the Platypus bill located?

Answer 31

In rostrocaudal (“from the nose to the tail”) rows in the skin of the bill.

Question 32

Where are the push-rod mechanoreceptors of the Platypus bill located?

Answer 32

Distributed uniformly across the bill.

Question 33

How do the sensory serous glands help the Platypus find prey?

Answer 33

They assist with the detection of electrical signals at close quarters, when the mechanoreceptors are also being used. This allows the Platypus to distinguish between prey and riverbed substrates.