{"refrec":{"BRefID":6251,"RR":"<b>Ratcliffe, N.; Hughes, J.; Roberts, F.A.</b> (1999). The population status of Sooty Terns <i>Sterna fuscata</i> on Ascension Island = De status van Bonte Sterns op Ascension. <i>Atlant. Seabirds 1(4)</i>: 159-168","BEntID":6251,"PublicFlag":1,"CheckedFlag":0,"wosflag":null,"vabbflag":null,"RefStringPartII":". <i>Atlant. Seabirds 1(4)</i>: 159-168","DocTypID":8,"DocType":"Journal article","MarineFlag":1,"FreshFlag":0,"BrackishFlag":0,"TerrestrialFlag":0,"Authorstring":"Ratcliffe, N.; Hughes, J.; Roberts, F.A.","OrigTitleTranslFlag":0,"Authorstringtrunc":"Ratcliffe, N. <i>et al.</i>","Englishabstract":"Feral cats were introduced to Ascension Island in the 1800s and extirpated all seabirds with the exception of Sooty Terns <i>Sterna fuscata</i> to inaccessible islets, stacks and cliffs. Sooty Terns continue to breed in reduced numbers on the south-west plains of the island and are still subject to cat predation, so monitoring of their population trends is important. Measuring the impact of cat predation upon seabird populations depends on having reliable baseline data; censuses of Sooty Terns on Ascension were conducted in 1990, 1996, 1997 and 1998 and involved sampling clutch densities in sub-colonies and then extrapolating to the total colony area. The population varied significantly over the study period, with 176 000 pairs in 1990, 202 000 pairs in 1996, 151 000 pairs in 1997 and 207 000 pairs in 1998. The 22% decline in 1997 compared with increases in 1996 and 1998 is thought to be due to a large proportion of mature birds deferring breeding because of reduced food availability induced by oceanographic perturbations. Such variability in breeding population size in relation to stochastic events means that censuses need to be undertaken frequently to ensure trends can be detected with confidence.","AbstractOtherLang":"Zoals op zoveel afgelegen eilanden bleef ook voor de zeevogels van Ascension Island (Centrale Atlantische Oceaan, juist onder de evenaar) de komst van de mens niet onopgemerkt. In de 19e eeuw werden katten op het eiland geintroduceerd en daardoor werden de zeevogels van het eiland uitgeroeid, of op zijn minst naar enkele afgelegen rotspunten en kliffen teruggedrongen. Alleen de Bonte Stern <i>Sterna fuscata</i> wist zich (tot op de dag van vandaag) op het hoofdeiland te handhaven,ondanks de aanhoudende predatie door katten. Een populatie die zo sterk onder druk staat moet nauwkeurig gevolgd worden en in dit artikel worden de resultaten van in in de jaren 1990,1996, 1997 en 1998 gepresenteerd. De tellingen bestonden uit precieze tellingen van de aantallen legsels in vaste gedeeltes van de kolonies, gevolgd door extrapolatie van de dichtheden voor de totale met vergelijkbare dichtheden bezette oppervlakte. Het bleek dat de aantallen broedvogels enorm van jaar tot jaar verschilden: 176,000 in 1990, 202,000 in 1996, 151,000 in 1997 en 207,000 paar in 1998. Het kleine aantal broedvogels in 1997 werd vermoedelijk veroorzaakt doordat veel volwassen vogels dat jaar wegens slechte voedselomstandigheden van broeden hebben afgezien. Het voedselaanbod staat onder invloed van oceanografische fluctuaties. Indien de populatie zodanig kan variëren, is het aan de hand van een klein aantal tellingen onmogelijk om lange termijn trends op het spoor te komen. Een dergelijke populatie moet dan ook regelmatig geteld worden.","BibLvlCode":"AS","StandardTitle":"The population status of Sooty Terns <i>Sterna fuscata</i> on Ascension Island = De status van Bonte Sterns op Ascension","OrigTitleLangCode":null,"OrigTitleLangCodeExtended":null,"OrigTitleLangID":null,"DateLastModified":{"date":"2024-12-10 01:33:17.368041","timezone_type":1,"timezone":"+01:00"},"UserAccessRight":null,"UserAccID":null,"AuthorKeywords":null,"OtherDescriptors":null,"Notes":null,"AnaPub":1999,"MonPub":null,"DateUpdate":"2017-09-05","DateCreate":"2001-02-21","SecASFANote":null,"ConfID":null,"PeerRev":1,"VlizCoreFlag":1,"WoScode":null,"VABBcode":null,"OpenAcc":1},"refs":null,"anarec":{"AnaID":6251,"PubliDate":1999,"Pagination":"159-168","XtraPublOfAnaID":null,"ISBN":null,"Volume":"1","Issue":"4","BRefMon":null,"BRefMonRR":null,"BRefXtra":null,"BRefXtraRR":null,"SerBRefID":45223,"SerRR":"Atlantic Seabirds. Seabird Group and Dutch Seabird Group: Sandy, Bedfordshire.  ISSN 1388-2511","StandardTitleSer":"Atlantic Seabirds","ISSN":"1388-2511","AbbrevSer":"Atlant. 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