it reduces costs and risks of caring for young ants wasps birds fish Brood parasitism Cuckoo being fed by host Cuckoo catfish Cuckoo wasp Parasites can be generalists uncommon or specialists in regard to of host species ID: 719130
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Slide1
Brood parasites manipulate hosts to care for their young
it reduces costs and risks of caring for young.
ants, wasps, birds, fish
Brood parasitism
Cuckoo being fed by host
Cuckoo catfish
Cuckoo waspSlide2
Parasites can be generalists (uncommon) or specialists in regard to # of host species.
Brood parasitism
Over 200 species can be hosts
to cowbirds
Whydah
Finch host
specialistSlide3
Facultative brood parasitism
- parents build their own nests but will also “dump” eggs into others’ nests when nest sites are limited Some ducks, gulls, starlings, coots, othersOften
intraspecific
Brood parasitismSlide4
Obligate brood parasitism
- cuckoos, cowbirds, several other species parasites have lost nest building and parental abilities 1% of bird spp.
Brood parasitismSlide5
Parasite young often have great impact on host RS
cuckoo ejects host young
cowbird and wren chicks
honeyguide chickSlide6
Defenses against parasitism
Attack parasite adults Desert or bury nest Reject parasite egg Low intra-clutch variation
Reject foreign young “Arms race”
Coot attacking foreign
coot chickSlide7
Parasite eggs inner circle Host eggs outer circle
Low
intraclutch
variation with high
interclutch
variation
Parasite reduced to ‘guessing’ and suffer rejectionSlide8
Parasite counteradaptations
:Egg laying timingMimicry of eggs, chicks
“Arms race”Slide9
Common cuckoo ‘races’
– females that use redstart hosts lay blue eggs; those that use reed warblers lay spotted eggs. Egg color determined by genes passed from mom to daughter Fig. 4.18
Common cuckoo egg
Common cuckoo eggSlide10
Egg appearance influences rejection
wagtail
dunnock
R warbler
pipitSlide11
Presence of cuckoos selects for rejection
Variation of egg rejectionSlide12
Host rejection rate influences closeness of egg mimicry
Egg discrimination
Birds have enhancedcolor visionObjective measures of
reflectance show amountof overlap in appearanceSlide13
If egg mimicry is strong but parasitism is low, hosts may not evolve further defensesCosts of rejection errors
Imprinting on eggs vs. chicksArms race stages
Warbler ejecting a cowbird eggSlide14
Host feeding of parasite youngSlide15
Coots experience intraspecific parasitism. Eggs and chicks can be rejected.
Adults imprint on young with first broodSome parasite hosts can discriminate youngSlide16
Chick mimicry relatively rare
host
parasite
host
parasite
Mouthpart and body mimicrySlide17
Mimicry of host chick calls
Horsfield's
bronze-cuckoos
Superb fairy-wren
(don’t reject eggs, butabandon 40% of chicks)Shining bronze-cuckoos