Brood parasitism Flashcards
What is brood parasitism?
Individuals that exploit parental care
What are intraspecific brood parasites?
- Exploit individuals from same species
- Lay eggs in clutches on conspecifics (e.g. european starling, cliff swallows)
How have Masked weavers adapted to intraspecific brood parasites?
- They breed in large colonies - lots of opportunities to parasitise offspring
- 23-35% rate of parasitism
- Egg divergence and recognition
- Huge variation of patterns and colour of eggs within a colony, evolved as a way for parent to recognise own eggs
How has the american coot adapted to intraspecific brood parasitism ?
- 41% of pairs parasitised
- 43% of hosts reject at least one parasitic egg
- Egg colour variation between hosts
- Study showed that females were more likely to reject eggs that were different colour
what are Interspecific brood parasites?
Between species parasitism (e.g. cuckoo)
interspecific brood parasite examples
- Cuckoo catfish parasites cichlid fish brood
- Pin-tailed whydah - host common waxbill
Brood parasitism between cuckoo and their host
(Co-evolutionary arms race).
What is the natural history?
- female lays 15-20 eggs per season
- Always lay eggs in afternoon (most birds lay in morning)
- Lay small eggs very quickly
- Remove one host egg from nest and replace with own
- Females specialise on one host species and usually lay a mimetic egg
Have cuckoos evolved in repsonse to hosts? (how did the study show this?)
- Davies and Brooke
- Placed model egg in reed warbler nest
Have cuckoo behaviours evolved as co-evolution of host behaviours?
Why wait until host starts laying?
- Placed model egg in nest before and after start of laying
- 100% of eggs were rejected before host started laying
- 0% was rejected after laying
Have cuckoo behaviours evolved as co-evolution of host behaviours?
Why lay in the afternoon?
- 50% were rejected when placed in the morning
- 0% rejected in the afternoon
Not sure why, possibly due to increased bird vigilence in the monring
Have cuckoo behaviours evolved as co-evolution of host behaviours?
Why lay so quickly?
- Placed stuffed cuckoo by nest for 5 mins
- model egg and stuffed cuckcoo: 45% rejected
- Just model egg: 0% rejected
Have cuckoo behaviours evolved as co-evolution of host behaviours?
Why lay a small egg?
- Placed large model egg (expected size of cuckoo egg) in nest
- Large egg model: 40% rejected
- Usual model egg: 0% rejected
Have cuckoo behaviours evolved as co-evolution of host behaviours?
Why lay a mimetic egg?
- Placed model egg of different gens in reed warbler nests
- Varying levels of rejection for the other eggs
- lowest rejection was 44% because eggs were similar to host eggs
Why have cuckoos evolved these unusual behaviours?
- To overcome the host species defence
- Evolutionary arms race
What species has egg rejection evolved in?
- Parasitised species
- Non-parasitised species did not reject any eggs placed in their nests
