Breeding Ecology of the Black Redstart Phoenicurus ochruros at a Tibetan Site, with Special Reference to Cooperative Breeding

摘要

ThispaperprovidesdataonthebreedingbiologyandsocialsystemoftheBlackRedstartPhoenicurusochrurosataTibetansite(4300melevation).Egg-layingoccurredbetweenearlyMayandearlyJulyduringwhichpairsbredonce(10outof12markedpairs)ortwice(2).Clutchsizevariedbetween4and5eggs(4.56?±0.51SE),butaseven-eggclutchwasrecorded.Incubationbythefemalelasted12a€“14d(13.0?±1.0SE).Nestlingswereprovisionedbybothparentsfor13a€“18d(16.7?±1.6SE).Nestlingsfledgedwhentheywereslightlyheavierthanadultfemales.ComparedtotheirEuropeancounterparts,thehigh-elevationredstartshadsimilarclutchsize,incubationornestlingperiodsandtendedtoproducefewerclutchesoflargereggs.Thissuggestsalifehistorystrategyadaptedtomaximizeoffspringsurvivalintheharshhighlandenvironments.Mostnestswereattendedbyonemaleandonefemale,whileatseveralneststhepairwasaccompaniedbyathirdindividualinfemale-likeplumage.Oneofthesehelperswasmolecularlysexedasamaleanditsplumagepatternindicatedittobeayearling.Suchcooperativegroupsoccurredintwoofthe12closelymonitorednestsandtwoadditionalnestsbasedonopportunisticobservations.Oneofthefourtrioswasconfirmedtoraisetwobroodsduringasinglebreedingseasonandanotherproducedtheseven-eggclutch.Thisisthefirstconfirmationofcooperativelybreedingamongthe11Phoenicurusspecies.