Brood parasitism Brood parasitism Parasites can be generalists (uncommon) or Brood parasites manipulate hosts to care specialists in regard to # of host species. for their young it reduces costs and risks of caring for young.

ants, wasps, birds, fish Finch host specialist

Whydah Cuckoo catfish Over 200 species can be hosts Cuckoo wasp Cuckoo being fed by host to cowbirds

Brood parasitism Brood parasitism Facultative brood parasitism - parents build Obligate brood parasitism - their own nests but will also “dump” eggs into cuckoos, cowbirds, several other species others’ nests when nest sites are limited parasites have lost nest building and Some ducks, gulls, starlings, coots, others parental abilities Often intraspecific 1% of bird spp. “Arms race” Parasite young often have great impact Defenses against parasitism on host RS  Attack parasite adults Quick Time™ and a Cinep ak dec ompr esso r ar e nee ded to see this pic ture.  Desert or bury nest cowbird and wren chicks cuckoo ejects host young  Reject parasite egg  Low intra-clutch variation  Reject foreign young

Coot attacking foreign honeyguide chick coot chick

“Arms race”

Parasite counteradaptations: Low intraclutch  variation with high Egg laying timing interclutch variation Mimicry of eggs, chicks  Parasite reduced to ‘guessing’ and suffer rejection

Parasite eggs inner circle Host eggs outer circle Egg appearance influences rejection Common cuckoo ‘races’ – females that use wagtail dunnock R warbler pipit 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 egg

Egg discrimination Variation of egg rejection Host rejection rate influences closeness of Presence of cuckoos selects for rejection egg mimicry

Birds have enhanced color vision

Objective measures of reflectance show amount of overlap in appearance Arms race stages Host feeding of parasite young If egg mimicry is strong but parasitism is low, hosts may not evolve further defenses Costs of rejection errors Imprinting on eggs vs. chicks

Warbler ejecting a cowbird egg

Some parasite hosts can Chick mimicry relatively rare discriminate young Mouthpart and body mimicry Coots experience intraspecific parasitism. Eggs and chicks can be rejected. Adults imprint on young with first brood host parasite

host

parasite Mimicry of host chick calls

Horsfield's bronze-cuckoos

Superb fairy-wren (don’t reject eggs, but abandon 40% of chicks)

Shining bronze-cuckoos