Survival Rates of Black-Tailed Godwits Limosa limosa Breeding in the Netherlands Estimated from Ring Recoveries

摘要

TheNetherlandsholdsinternationallyimportantnumbersofBlack-tailedGodwitsLimosalimosa,andreportsofasubstantialpopulationdeclinehavepromptedconcern.Onewayofnarrowingthelistofpossiblecausesofthisdeclineistoidentifythedemographicprocessesresponsible.Forthisreason,weconductedasurvivalanalysisfortheperiod1960to2000basedondeadrecoveriesofgodwits.Althoughdecliningsamplesizesandfallingreportingratesreducedtheprecisionofestimatesinlateryears,weconcludedthatadultsurvivalhaddroppedsignificantlyinthelate1990sfrom0.77to0.40.Dataweretoosparsetoestimatejuvenilesurvivalinthisperiod.Apartfromthissharpdrop,wefoundnoevidenceoflong-termtrendsineitherfirst-yearoradultsurvival.Wefoundnoevidenceforeffectsonsurvivalestimatesofshiftsinthespatialdistributionofrecoveriesorinthereportedcausesofdeath.Theselarge-scaleanalysesofbirdsrecovereddeadcomplementmoreintensivemark-resightingstudiesatindividualsites.Giventhefallingreportingratesofdeadbirdsandconsequentlossofprecisionofsurvivalestimates,intensivemark-resightingprogrammeshaveanincreasinglyimportantroletoplayinthestudyofsurvivalrates.