What is the definition of cooperative breeding?
breeding pair assisted by helpers in caring for young
Who are the helpers?
-birds of the same species, usually children from previous years
What are the eight cooperative families?
1. babblers *
2. fairy-wrens *
5. scrubwrens/thornbills *
Which is the cooperative family not in Australia?
What four cooperative families are endemic to Australia?
-babblers -fairy wrens -scrubwrens/thronbills -honeyeaters
How many bird species are cooperative worldwide?
-3% -Australia is a hotspot
How many species are cooperative breeders in Australia?
-68 (out of 800 and when only counting the ones evolved here then that is 22% of old endemics are cooperative breeders)
What evolutionary history do the cooperative bird species have in Australia?
-all are old endemic Gondwanan in origin -no record of cooperation in breeding in recent arrivals (15-20mya)
What are the functional explanations of cooperative breeding? (concept)
-benefits that improve survival or fitness (number of offspring)
What are the evolutionary explanations of cooperative breeding about? (concept)
-evolutionary history/ancestry -common themes among cooperatively breeding species
What was the old idea about what favoured cooperative breeding in Australian birds?
-humid aseasonal climate -no migration -long life-spans -small clutch sizes -the climate: not that much support -contradicted by study showing a species of birds more likely to be cooperative when seasonal -none well supported
What is the monogamy hypothesis?
Monogamy (low levels of promiscuity) -high relatedness in family groups -helping those that share your genes can help spread your genes -favours the transition to cooperative societies.
What is the counter-evidence to the monogamy hypothesis?
-the superb fairy wren is a cooperative breeder but is the most promiscuous bird
Is the monogamy hypothesis correct?
-on the large seems to be
-cooperative breeding is much more common in species with low promiscuity
Is there a correlation in distribution of cooperative breeders and cuckoos?
-yes -very strong -about half of cooperative breeders are cuckoo hosts whereas only 11 percent of them are non-cooperative.
What sort of cooperative breeders are superb fairy wrens?
-facultative (some are and some not) -get parasitised by Horsefield's Bronze-cuckoos -when the chick hatches it kicks out the eggs of the host
Do cuckoos target cooperative breeders?
-YES, cuckoo chicks raised by groups of superb fairy-wrens weigh more than those raised by pairs
Do birds breed cooperatively to deter cuckoos?
YES, large groups mob adult cuckoos near their nests more than small groups -large groups of superb fairy-wrens get parasitised less often than small groups
Did cooperative breeding and cuckoo parasitism co-evolve?
What are the two evolutionary explanations for cooperative breeding?
1.More likely to evolve in less promiscous species 2.More likely to evolve where there are cuckoos
Why do helpers stay?
Habitat saturation or Shortage of mates
With super fairy wrens why do the helpers stay?
-both shortage of territories and mates -the bigger the shortage of territories or mates(usually females) the more juveniles stay with their parents
What is more important for staying as helpers in superb fairy wrens?
-create vacancy by removing a pair, later add female -helpers initially stay at home but all dispersed when female added -so shortage of mates more important!
Why do helpers help?
i.Indirect benefits - enhanced production of relatives (who share your genes) ii.Direct benefits - enhanced survival or reproduction, either immediately, or in the future
What are the indirect benefits for helpers for helping?
-idea of inclusive fitness or kin selection - individuals can propagate genes without reproducing -in monogamous species relatedness is high Why? Because relatives share genes parents with offspring: r = 0.5 brothers/sisters with their siblings: r = 0.5 grandparents with grand-offspring: r = 0.25 uncles/aunts with nieces/nephews: r = 0.25
What is the cooperative breeding in purple-crowned fairy wrens?
-groups of 2-10 individuals, so help feed nests that are not their parents' too -riparian specialist endemic to northern Australia -low rates of extra-pair mating(low promiscuity unlike superb fairy wren)
Who do the purple-crowned fairy wrens help feed more (higher rate), chicks with r= 0.5 or r=0.25?
-r=05 -full siblings more than half siblings
In purple crowned fairy wrens do more helpers mean more offspring?
-yes as they bring more food (possible alternative explanation is that the territory is that good but not the case as proved by the babblers experiment)
How did the grey-crowned babbler experiment prove the helpers help?
-reduced number of helpers and the survival of chicks drops despite being in the same environment
What is the cooperative breeding like with Bell Miners?
-clans consisting of several pairs and numerous helpers -helpers may help at more than one nest, differing in relatedness -within the clan, helpers help more with the related chicks than unrelated =support for indirect benefits of helping