L14 Flashcards
Brood parasitism
- Individuals attempt to exploit parental care provided by others
- Same and different species
Co-evolutionary arms race
- Same and different species
Intraspecific brood parasites - Starling
- Egg on grass as a result of parasitism
- Female lays egg in nest which isn’t hers and removes an egg that was already in the nest
Intraspecific brood parasites - Burying beetles
- Find a carcass and lay eggs on it
- Female feeds larvae emerging
- Sometimes other beetles sneak into nest and bury eggs in carcass
- Parent unknowingly looks after larvae of another individual
- Quite difficult to observe as it is cryptic
- Many adaptations therefore to facilitate parasitism
Intraspecific brood parasites - Cliff swallows
- Marked eggs to identify them
- Often found eggs in the wrong nest
- Females would sometimes place eggs in other individuals nests
- Parasitism is tricky to observe
Intraspecific brood parasites - Masked weaver
- Marked eggs to identify them
- Often found eggs in the wrong nest
- Females would sometimes place eggs in other individuals nests
- Parasitism is tricky to observe
American coot, how many pairs are parasited? How many hosts reject at least one parasitic egg
- 41% pairs parasitised
- 43% of hosts reject at least one parasitic egg
How are parasitic eggs recognised in coots?
- Ranked colours of eggs on a scale (1-10)
- Look at other eggs
- Calculated difference between host and parasitic egg creating a colour rank difference value
How are parasitic eggs recognised in coots? Results
- Female more likely to accept eggs less different from its own
- Much higher rejection when more different from own
Interspecific brood parasites Cuckoo catfish
Cuckoo catfish
- Parasitises cichlid fish - Male stores eggs in mouth and looks after them - Catfish releases eggs into mouth whilst females are laying eggs into cichlid mouth - Cuckoo egg hatches first and eats true offspring - Just one cuckoo catfish emerges
How many bird species are obligate interspecific brood parasites?
100
Co- evolutionary arms race between cuckoo and host
- Arms races occur in virus and defence, predator and prey
- Brood parasites also are examples of co-evolutionary arms race
Natural history of cuckoos and hosts
- 10 main host species in Europe
- Female lays 15-20 eggs per season
- If all eggs are successful this is many more than cuckoo could rear her own
- Eggs can be laid and made because there is no investment in parental care
Female waits till host female lays eggs and lays her own egg in nest too
Egg laying behaviour:
- Always lay eggs in afternoon (most birds lay in morning)
- Small egg relative to body size
- Egg laying is very quick
- Remove one host egg and deposit their own
- Females specialise on one host species and usually lays a mimetic egg
Eg pipit cuckoos parasitise pipits
- Not a separate species but they specialise in a particular host species
Cuckoo egg variation
- Larger but mimetic to species
- Match those of host
- Make It harder for host to reject
When egg hatches it hatches quicker than rest of host:
Why do cuckoo eggs hatch quicker than the hosts actual eggs?
- Egg is more developed
- Gives advantage to kick out eggs and take over host eggs
- Monopolise parental care
- Mimics calling sound of mother
Much larger in size than host
