Multiple stressors in a top predator seabird: potential ecological consequences of environmental contaminants, population health and breeding conditions

Environmental contaminants may have impacts on reproduction and survival in wildlife populations suffering from multiple stressors. This study examined whether adverse effects of persistent organic pollutants (POPs) increased with poor population health and breeding conditions in three colonies (60–74°N) of great skua (Stercorarius skua) in the north-eastern Atlantic (Shetland, Iceland and Bjørnøya [Bear Island]). POPs (organochlorines [OCs] and polybrominated diphenyl ethers [BDEs]) were measured in plasma of incubating birds (n = 222), concentrations differing nearly tenfold among colonies: Bjørnøya (2009) > Bjørnøya (2010) > Iceland (2009) > Shetland (2009). Reproductive success (hatching success and chick survival) showed that breeding conditions were favourable in Shetland and at Bjørnøya (2010), but were very poor in Iceland and at Bjørnøya (2009). Biomarkers indicated that health was poor in the Shetland population compared to the other populations. Females whose chicks hatched late had high POP concentrations in all colonies except at Bjørnøya (2010), and females losing their eggs at Bjørnøya (2009) tended to have higher concentrations than those hatching. Moreover, there was a negative relationship between female POP concentrations and chick body condition at hatching in Iceland and at Bjørnøya (2010). Supplementary feeding experiments were conducted, and in Iceland where feeding conditions were poor, significant negative relationships were found between female POP concentrations and daily growth-rate in first-hatched chicks of control nests, but not in food supplemented nests. This suggests that negative impacts of POPs were mitigated by improved feeding conditions. For second-chicks, there was a strong negative relationship between the female POP concentrations and growth-rate, but no effects of supplementary feeding. Lowered adult return-rate between breeding seasons with increasing POP loads were found both at Bjørnøya (2009) and in Shetland, especially related to BDEs. This indicates stronger fitness consequences of POPs following seasons with very poor breeding conditions and/or high reproductive effort. This study suggests that the impacts of POPs may differ depending on population health and breeding conditions, and that even low concentrations of POPs could have ecological consequences during adverse circumstances. This is important with regard to risk assessment of biomagnifying contaminants in marine ecosystems

Antiparasite treatments reduce humoral immunity and impact oxidative status in raptor nestlings

Parasites are natural stressors that may have multiple negative effects on their hos as they usurp energy and nutrients and may lead to costly immune responses that may cause oxidative stress. At early stages, animals may be more sensitive to infectious organisms because of their rapid growth and partly immature immune system. The objective of this study was to explore effects of parasites by treating chicks of two raptor species (northern goshawk Accipiter gentilis and white‐tailed sea eagle Haliaeetus albicilla) against both endoparasites (internal parasites) and ectoparasites (external parasites). Nests were either treated against ectoparasites by spraying with pyrethrin or left unsprayed as control nests. Within each nest, chicks were randomly orally treated with either an antihelminthic medication (fenbendazole) or sterile water as control treatment. We investigated treatment effects on plasma (1) total antioxidant capacity TAC (an index of nonenzymatic circulating antioxidant defenses), (2) total oxidant status TOS (a measure of plasmatic oxidants), and (3) immunoglobulin levels (a measure of humoral immune function). Treatment against ectoparasites led to a reduction in circulating immunoglobulin plasma levels in male chicks. TOS was higher when not receiving any parasite reduction treatment and when receiving both endo‐ and ectoparasitic reduction treatment compared with receiving only one treatment. TAC was higher in all treatment groups, when compared to controls. Despite the relatively low sample size, this experimental study suggests complex but similar relationships between treatment groups and oxidative status and immunoglobulin levels in two raptor species

Changing distribution of flocking sea ducks as non-regenerating food resources are depleted

Sutherland & Anderson (1993; J Theor Biol 160:223–230) considered how the distribution of consumers should change as prey resources fixed at the start of a period of exploitation are depleted by foraging activities. Their model predicts that consumers initially aggregate on a single or a few patches offering the highest feeding rate. As the prey density in those patches is reduced, the feeding rate declines to the level attainable at the next best patches, which are then also exploited. Therefore, an increase in the number of flocks and a decline in flock size should be observed as individuals spread out over the available feeding opportunities. Further, once occupied, a patch is exploited for the remainder of the winter. We tested these predictions with winter survey data on the number, size and location of flocks of common eiders Somateria mollissima and king eiders S. spectabilis wintering in Kvalsundet, a sound in northern Norway. Both species are benthivorous, and there is little or no growth or recruitment of their prey in winter at high-latitude sites. The green sea urchin Strongylocentrotus droebachiensis was the dominant prey of both species in Kvalsundet, and the density of this prey species declined over the winter in kelp beds, the preferred winter habitat of common eiders. Our data showed that both common and king eiders began their winter periods in Kvalsundet aggregated into a few large flocks. As the winter progressed, the distribution changed and birds gathered into more and smaller flocks. In the case of common eiders, flock locations remained fixed once a foraging location began to be exploited. King eiders formed a few large flocks early in the season which drifted in heavy tidal currents, but when these split up into smaller flocks in February, they started to exploit fixed locations. We interpret these results as consistent with the Sutherland & Anderson model

Dietary versus maternal sources of organochlorines in op predator seabird chicks: an experimental approach

We examined the relative importance of dietary sources and maternal transfer on organochlorine concentrations (∑OCs) in Great skua chicks (Stercorarius skua) in Shetland by food supplementing parents with known wintering area. We predicted that experimental chicks (whose parents were supplemented) should have (i) higher growth rates and, (ii) lower ∑OCs due to growth dilution effect and/or due to being fed with less contaminated food compared to control chicks. We also predicted a significant influence of maternal wintering area on chicks’ ∑OCs. Plasma ∑OCs of adults, assessed prior to the manipulation, significantly differed between wintering areas of birds. Chicks were weighed every 5 days and plasma ∑OCs were assessed at 20 days old. Based on nitrogen and carbon stable isotope analysis, the supplementary food contributed on average 20% of the dietary protein of the chicks. Although experimental chicks experienced better developmental conditions, supplementary food did not alleviate their organochlorine burden. Nevertheless, chicks whose mothers wintered in Europe showed ∑OCs 50% higher than chicks whose mothers wintered in Africa. Moreover, based on the positive relationship between ∑OCs of chicks and females, the contaminant load of Great skua chicks in Shetland appears to be more influenced by maternal transfer than by trophic transfer

SEAPOP. Et nasjonalt sjøfuglprogram for styrket beslutningsstøtte i marine områder

SEAPOP (Seabird population management and petroleum operations) er et nasjonalt, kunnskapsoppbyggende program om sjøfugl tilrettelagt for å gi styrket beslutningsstøtte for marine områder. Konseptet ble først utviklet for oljeindustrien i et samarbeid mellom Norsk institutt for naturforskning (NINA) og Den norske stats oljeselskap as (Statoil), men er senere videreutviklet i samarbeid med Norsk Polarinstitutt (NP), Tromsø Museum — Universitetsmuseet (TMU) og Direktoratet for naturforvaltning (DN) for også å innbefatte miljøforvaltningens kunnskaps-behov. Visjonen er å gi oljeindustri, forvaltningsmyndigheter og andre aktører et nødvendig grunnlag for beslutningsstøtte i miljøspørsmål relatert til sjøfugl og petroleumsvirksomhet eller andre aktiviteter på kysten og offshore. Om programmet gjennomføres etter planen vil det sikre oppdatert kunnskap om utbredelse, tilstand og utvikling for norske sjøfuglbestander, og koordinere ulike aktiviteter og deltakende institusjoner. Det vil spesielt fokusere prosessorienterte studier og overvåkning for å forstå effektene av så vel naturlige som menneskeskapte faktorer. Etter en generell introduksjon (del A) gir rapporten først en utredning av de ulike målgruppenes kunnskapsbehov som ramme for en evaluering av eksisterende kunnskap og datagrunnlag (del B). På denne bakgrunn utformes programmet etter et godt nok-prinsipp hvor klare prioriteringer og hensyn til ansvar, kostnadseffektivitet og beslutningsrelevans leder fram til en anbefalt plan for gjennomføring (del C). Videreføring av eksisterende overvåkingsaktiviteter og databaser er integrert så langt det er funnet formålstjenlig. Avslutningsvis gis en enkel illustrasjon av hvordan innhentet kunnskap og data tenkes gjort løpende tilgjengelig for deltakerne (kapittel C4), samt en grov beregning av kostnader og nødvendige behov for tilskudd for å realisere programmet (kapittel C5). Målt i 2005-kroner trenges det omkring 12 mill. kr friske midler årlig over en tiårsperiode for å realisere programmet på nasjonalt nivå, gitt at tidligere etablerte aktiviteter videreføres på samme måte som før med uavhengig finansiering. To tredeler av tilskuddsbehovet ligger i området fra Lofoten og nordover, som både har landets desidert største forekomster av sjøfugl og byr på de største logistiske og personellmessige utfordringer for programmet. Den sentrale begrunnelsen for programmet er at oljeindustri, annen maritim virksomhet og offentlig forvaltning har overlappende kunnskapsbehov om sjøfugl. Utredningsbehov knyttet til olje og andre faktorer som påvirker sjøfugl krever faglig forsvarlig prediksjon av skadeomfang og restitusjonsevne. Bedre sikkerhet i slike analyser vil blant annet gjøre det lettere å identifisere de minst konfliktfylte områder og tidsperioder for et eventuelt inngrep. Uansett påvirkning vil tilstrekkelig presise beregninger av potensielt skadeomfang forutsette oppdatert kunnskap om sjøfuglenes utbredelse i antall, tid og rom, og om bestandenes tilstand og geografiske opprinnelse. Beslutningsrelevante vurderinger av restitusjonsevne fordrer også relevante mål for bestandenes dødelighet og rekruttering, og de viktigste andre faktorene som bestemmer disse. Denne type kunnskap er også nødvendig for å kunne skille effekter forårsaket av menneskets virksomhet fra den naturlige dynamikken i bestandene. For å oppfylle dette, søker SEAPOP å innhente nødvendig kunnskap om sjøfugl i et helhetlig program, tilrettelegge alle relevante sjøfugidata for aktørenes utrednings- og forvaltningsformål i en base på internett, og sikre at disse dataene til enhver tid er standardisert, tilstrekkelig oppdatert og av god nok kvalitet. Dette vil blant annet gjøre det mulig å fylle viktige kunnskapshull på en kostnadseffektiv måte og utvikle mer formålstjenlige verktøy for ulike typer av analyser relatert til effektene av ulike typer inngrep på sjøfugl. SEAPOP vil dermed gjøre det lettere å utarbeide mer helhetlige og målrettede miljøutredninger knyttet til petroleumsvirksomhet og andre naturinngrep, og forbedre samordning, standardisering og kvalitetssikring av utredningsoppgavene

Wintering areas of Great SkuasStercorarius skuabreeding in Scotland, Iceland and Norway

Capsule Great Skuas Stercorarius skua breeding in Scotland, Iceland, and Norway, winter in different areas. Aims To assess the winter distribution of adult Great Skuas breeding in different countries. Methods Geolocation data-loggers were deployed on breeding adults at colonies in Shetland (Scotland), southeast Iceland, and Bjørnøya (Norway) in 2008. Loggers were recovered when birds returned to breed the next year and downloaded data were processed to indicate the location of each individual throughout the winter period. Results Adult Great Skuas from Scotland wintered off northwest Africa and southern Europe. Adults from Iceland mostly wintered off Canada, with small numbers visiting northwest Africa and Europe. Although adults from Bjørnøya (Norway) migrated to similar areas to birds from Iceland, a slightly greater proportion wintered off Europe, and most used areas further north than birds from Scotland. Although three birds studied over consecutive winters used the same small area in consecutive years, four moved between different areas within one winter. Conclusion Great Skuas show clear variation in migrations among breeding regions, and some evidence of individual consistency