Birdsong and Foraging

Question 1

Which birds (order etc) usually sing?

Answer 1

Oscine family, order Passerifomes (perching birds)

Question 2

Singing vs vocalisation

Answer 2

Calls (vocals) - short, usually alarm response, year long

Song - complex, during breeding seasons

Question 3

Define repertoire

Answer 3

Variations of song types an individual can sing

Question 4

Features of a sonagram

Answer 4

Notes = individual elements
Syllables - components of an element / / / / 
Whistle = one long note
Trill = several short notes, syllables
Buzz = long note with varying frequency

Question 5

Why do dialects exist?

Answer 5

Allow territory distinctions between close geographic groups, avoiding costly altercations

Question 6

Drivers of the evolution of song (2)

Answer 6

Female choice

Male-male competition

Question 7

What can a song encode? (7)

Answer 7

Presence, identity, geographical origins, current location, whether territory is owned, breeding propensity, quality of mate

Question 8

When does song develop?

Answer 8

In absence of song when young, birds develop abnormal songs

Tutor tapes get close to normal, but must be present before sexual maturation i.e there is a time window

Question 9

Development of song (3 stages)

Answer 9

Subsong
Random sounds

Plastic song
Patterns like adults emerge, imitation and rehearsal

Crystallised song
Full sounds, volume and timing accurate

Question 10

Song learning (3 stages)

Answer 10

Sensory phase
Before subsong, exposure to adult males commits audio to memory within time window

Sensorimotor phase
Subsong and plastic song heard, practice and vocal diversity

Transition
(to crystallised song)

Question 11

Types of learners? (3)

Answer 11

Seasonal closed learners
Age-limited
Open ended

Question 12

Seasonal closed learners?

Answer 12

Sensory period occurs after hatching in spring into summer
Gap before sensorimotor in autumn
Crystallisation following spring
e.g. sparrows

Question 13

Age-limited learners?

Answer 13

Sensory period lasts 60 days after hatching, overlapping with sensorimotor (day 25 - 90)
Rapid crystallisation
e.g. zebrafinch

Question 14

Open ended learners?

Answer 14

Annual cycles with overlapping sensory and sensorimotor phases
Second sensorimotor phase = more plastic learning for greater song diversity
e.g. canaries

Question 15

How do swamp sparrows acquire song?

Answer 15

Overlap with song sparrow regions so juveniles have elements of both songs, before they are filtered out in crystallisation

Question 16

How do white-crowned sparrows acquire song?

Answer 16

Filter our alien sounds during sensory phase i.e. highly species-specific learning

Question 17

Proximate mechanisms of birdsong?

Answer 17

Hormonal/seasonal changes

Learning from conspecifics/adults

Question 18

Ultimate mechanisms of birdsong?

Answer 18

Adaptive function for mating, phylogenically passed on

Question 19

Example of hormone influence?

Answer 19

Testosterone - peaks correlate with a reduction of syllable types.
It inhibits plasticity = crystallisation

Question 20

Neural circuitry? (2)

Answer 20

2 circuits:

Song production nuclei e.g. HVc, RA and nXIIts

Anterior forebrain pathway
Area X, DLM, LMAN

Question 21

Seasonal/neuronal influences on brains

Answer 21

Certain regions of circuitry (HVc and RA) are larger in the spring
Neurogenesis of HVc also observed during new learning seasons

Question 22

Evolution of song learning

Answer 22

Occurred 2 or 3 times - recently reduced to 2 because parrots have been moved closer to songbirds

Question 23

Food choice model variables? (3)

Answer 23

Foraging time/encounter rates
Energy derived from food
Handling time of food e.g. digestion rate

Question 24

What does the model assume? (3)

Answer 24

Animals maximise energy intake per unit time i.e. to leave time for other activities
Decisions are simple i.e. to attack or not
Animals will select the best food option available

Question 25

What is Ts in the model?

Answer 25

Time spent looking for food

Question 26

λi in model?

Answer 26

Encounter rate (with food type i)

Question 27

Ri in model?

Answer 27

Reward from food i, in joules

Question 28

hi in model?

Answer 28

Handling time of food type i

Question 29

What does the unsimplified model state?

Answer 29

A second food type will only be included if the reward from both types is greater than that of one alone

Question 30

What is the optimal decision rule?

Answer 30

Simplified inequality to determine whether or not a food type will be included in an animals diet
-i.e. the animal will make the best decision for them

Question 31

Conclusions of optimal decision rule (2)?

Answer 31

Whether an item is included in the diet does not depend on commonality

Poorer items are included only if better items are rare

Question 32

Role of uncertainty in foraging?

Answer 32

2 feeders dispensing every 30s, one with the same amount each time and one variable.
Low average number of seeds = birds gambled on variable one as risk of food loss was already present

If expected food is greater than amount needed to survive, they will play it safe - uncertainty invites risk.

Question 33

How does danger affect foraging behaviour?

• prey
• predators

Answer 33

Less effective foraging (compromising growth rate) may occur to avoid predation, often seen in juveniles

Predators may also avoid more dangerous pray - spiders can either wrap prey in a web or attack, switching to the wrapping strategy when prey have weapons of their own

Question 34

Learning in foraging?

-finches

Answer 34

Darwin looked at this in finches - different food sources have the same rewards and encounters, but varying handling times.
Each bird learns the best strategy (e.g. insects from branches, nectar in flowers) and selectively hones this for one food type over time.

Question 35

Three bird groups showing song?

Answer 35

Passerines, parrots and hummingbirds