Effet du pétrole de l'"Amoco Cadiz" sur les oiseaux de mer. Bilan provisoire

Immediatly following the AMOCO CADIZ oil spill, the S.E.P.N.B. carried out health centers for oiled birds from Finistère, and estimated the impact of the oil spill on seabirds. In the whole, 15 to 20 000 birds are dead because of the AMOCO CADIZ oil spill. 41 species have been oiled, among which 35 usually live in marine environment. The species most stressed belong to alcidae. The mortality rate (0,1 bird/ton of oil) seems to be, at. present day, the lowest rate never mentionned in the litterature.Dans les jours qui ont immédiatement suivi l'échouement de l'AMOCO CADIZ, la S.E.P.N.B. a été chargée de coordonner l'activité des centres d'accueil et de soins aux oi­seaux mazoutés du Finistère et de dresser, pour l'ensemble des côtes bretonnes, le bilan de la marée noire sur l'avifaune. Au total, 15 à 20 000 oiseaux sont morts dans la marée noire de l'AMOCO CADIZ. 41 espèces ont été touchées par le pétrole, parmi lesquelles 35 vivent ha­bituellement en milieu maritime ou marin. Les espèces les plus touchées ont été les repré­sentants de la famille des alcidae. Le taux de mortalité (0,1 oiseau par tonne de pétrole) semble être, à ce jour, le plus faible taux jamais enregistré dans la littérature

Régulation par le recrutemet, la fidélité et la non-reproduction chez un oiseau colonial, la mouette tridactyle (Rissa tridactyla)

A long term study of the Kittiwake colonies of Cap Sizun (Brittany, France) shows that, even though Kittiwakes usually recruit at the age of 4, the population growth rate from year to year is highly correlated with the breeding success of the previous year. This is due to a strong recruitment, a large proportion of breeders, and a high adult fidelity after years of high fecondity. Furthermore, for a given individual breeding performance (breeding success or failure), adult fidelity to the colony and the proportion of breeders in the following year increase with the breeding success of the colony in which they bred in the previous year. This leads us to propose a mechanism of population regulation through Attraction, Recruitment, Non-breeding, and Adult Fidelity, in which breeding success and social context — two characteristics which reflect environmental quality — play prominent roles. These two parameters are the main components of the attraction exerted by a breeding site, i.e. its capacity to recruit new breeders (young or adults) and to retain its own adults as breeders. Breeding success and social context are assessed by potential recruits when prospecting different breeding places. If fecondity and social context are good, prospectors may settle there and recruit in the following year. Prospectors are attracted to nests with chicks, on which they squat when they are momentarily left unattended by the parents after the middle of the rearing period. These squatters are mainly prebreeders or failed breeders ; both are actively looking for a breeding site. Males are more prone to squat on chicks. Prebreeding squatters on chicks show a high proportion of recruitment in the following year : 34 % of prospecting males recruit on one of the nests they have squatted during the previous year, and 24 % on the most consistently squatted nest. Thus, squatting is an appropriation behaviour of a breeding site. The density of parasites influences the colony breeding success : breeding groups with high densities of parasites on the chicks have the lowest fecondity. The appearence of parasites is correlated with a drop in fecondity of the kittiwakes and parasites are likely to be the cause of this reduced fecondity. This acts on the numbers through prospectors’ and adults’ behaviour which in turn can explain the positive correlation between the fecondity in a given year and the rate of population increase in the following year.Cadiou Bernard, Danchin Etienne, Monnat J.Y., Boulinier Thierry. Régulation par le recrutemet, la fidélité et la non-reproduction chez un oiseau colonial, la mouette tridactyle (Rissa tridactyla). In: Revue d'Écologie (La Terre et La Vie), tome 48, n°2, 1993. pp. 163-174

Oiseaux marins nicheurs de la facade atlantique francaise

CNRS-CDST / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc