L9 - Seabird Biology

Question 1

Give examples of birds that feed in each of these methods:

a) surface feeding
b) aerial feeders
c) plunge diving
d) benthic feeders
e) pursuit divers
f) klepto parasitism

Answer 1

a) surface feeding - skimmer (lower jaw is longer than upper)
b) aerial feeders - turns, kittiwakes
c) plunge diving - shearwaters and gannets
d) benthic feeders - cormorants, shags, ducks
e) pursuit divers - puffins, guillemots
f) klepto parasitism - penguins steal from pelicans

Question 2

What 2 methods do we use to monitor what birds do at sea?

Answer 2

• TDR

- satellite transmitter

Question 3

What percentage of seabirds are colonial?

Answer 3

98%

Question 4

Give an advantage and disadvantage to foraging from a colony

Answer 4

advantage - information giving, birds follow other birds

disadvantage - increased competition

Question 5

Give 3 advantages and 1 disadvantage to living in a colony and the effect on predation

Answer 5

advantages:

• safety in numbers
• synchronised breeding - short time for predator
• colonies are usually in a safe place

disadvantage - colonies are very conspicuous

Question 6

Give 2 advantages and 3 disadvantage to living in a colony and the effect on socialising

Answer 6

advantages:

• increased chance of meeting a mate
• increased competition

disadvantages:

• increased competition for a mate
• disease
• territorial disputes

Question 7

In offspring production, describe what is common in r-selected bird species

Answer 7

• high adult mortality - to combat this they produce lots of small young
• population size can change rapidly

Question 8

In offspring production, describe what is common in k-selected bird species

Answer 8

• Produce few but large young (high juvenile mortality, low adult)
• stable population size - usually at carrying capacity

Question 9

What is Lacks Hypothesis?

Answer 9

• Starvation in winter is the main density dependent factor
• population size is greatest after breeding season
• food amount in winter is the reason

Question 10

What is Ashmoles Hypothesis?

Answer 10

Based on tropical birds that have food all year round

Regulation occurs during the breeding season because:

• this is when food requirement is highest
• local food depletion due to competition

Question 11

What is the Wynne-Edwards Hypothesis?

Answer 11

Birds regulate their population size via social interactions, but this is UNLIKELY

Question 12

What happens to the population if a density independent factor mortality dominates?

Answer 12

The population wont ever reach a size where density dependent factors are important

Question 13

What factor is dominant appears to be dependent on the species, state what affects each:

a) Shags
b) Fulmars
c) Kittiwakes
d) Peruvian seabirds

Answer 13

a) Shags - density dependent nest site quality
b) Fulmars - density-dependent food supply
c) Kittiwake - density-independent food supply

d) Peruvian seabirds over the last 100y
- Initially unregulated
- Then regulated by nest site availability
- Now regulated by food shortage