Numerous long-lived species have a monogamous mating pattern (Black 1996). This observation is somehow puzzling: why would males prefer to mate with a single instead of several females, while the latter would allow them to increase their fitness? How are individuals choosing their mates? How can they control the fidelity of their mate?
Since the late 70s, many socially monogamous species have been shown to be behaviourally and genetically polygamous, with various rates of extra-pair parentage (Birkhead & Moller 1992). Extra-pair copulations may allow females to pair with the genetically best males, without loosing the advantages (such as parental care) linked to their normal mate. In these socially monogamous species, 11% of the offspring appears to result from extra-pair copulations, and such extra-pair relationships may concern 90% of bird species, the group with the highest rate of social monogamy (Griffith et al. 2002).
However, some species (and especially seabirds) are strictly monogamous (0% of extra-pair paternity). Why don't males look for extra-pair partners to increase their reproductive success? Why don't females look for extra-pair males to increase the genetic quality of their offspring?
Males may reduce their parental care according to their faith in the fidelity of their mate. Females may thus avoid extra-pair copulations in order to avoid parental care reduction (Møller 2000, Møller et Cuervo 2000). This hypothesis may explain the behaviour of females with low extra-pair paternity rates, such as Albatrosses (Pheobastria irrorata) or Adelia penguin (Pygoscelis adeliae) (Huyvaert et al. 2000, Pilastro et al. 2001), but it is not sufficient to explain the case of strictly monogamous species, such as black-legged kittiwakes (Rissa tridactyla).
Black-legged kittiwake is a common seabird of arctic and sub-arctic regions of both Atlantic and Pacific oceans. It winters in the vicinity of the sea, where it fishes. Easy to observe and follow, kittiwakes populations are well monitored and are thought to be an important index of global oceanic characteristics (Aebischer et al. 1990). Behavioural studies have focused on many life-history traits, such as habitat selection (Danchin et al. 1998). Strictly monogamous (Helfenstein 2002), males are also unable to guard their mates during the fertility period, since they have to forage and let their female alone in the vicinity of sexually active males during the pre-incubation period. However, despite such opportunities, extra-pair copulations have never been observed (25000 hours / individual / nest, 119 genotyped chicks with microsatellite markers).
During my thesis, I considered different problems:
1) Since black-legged kittiwakes form long-term pair bonds, how are individuals recognizing each other after the winter separation? What is the role of vocal parameters (such as long-calls, Danchin 1987) in this recognition?
2) What are the bases of mate choice in this monogamous species? (different indices of individual quality have been investigated)
3) What are the links between mate choice and genetical characteristics? Do females choose males that are highly heterozygous, or individuals that have a highly dissimilar genotype (according to microsatellites or to MHC loci)?
4) What is the role of divorces in monogamous species?
The main studied population is located on Middleton Island, in the gulf of Alaska (USA). This population has been monitored since the late 70s by the Scott Hatch's team, of the US Geological Survey of Anchorage. Birds are nesting on an old radar tower equipped with one-way windows that enable easy observations and captures. All birds nesting on the tower have been banded, and their history is recorded.
A second population located on Cape Sizun (Brittany, France) has been studied by E. Danchin and collaborators from 1979 to 2002, and I also analyze these observations.Short bibliography
N.J., Coulson, J. C. , & Colebrook, J.M. 1990. Parallel
long-term trends across four marine trophic levels and weather. Nature
Birkhead, T.R., and Møller, A.P. 1992. Sperm competition in birds. Evolutionary causes and consequences. Academic Press, London.
Black, J. M. 1996. Partnerships in Birds : the study of monogamy. Cambridge University Press : Cambridge.
Danchin, E., Boulinier, T. & Massot, M. 1998. Conspecific reproductive success and breeding habitat selection : implications for the study of coloniality. Ecology 79, 2415-2428.
Griffith, S.C., Owens, I.P.F., & Thuman, K.A., 2002. Extrapair paternity in birds : a review of interspecific variation and adaptative fonction. Molecular Ecology 11 : 2195-2212.
Helfenstein, F. 2002. Stratégies de reproduction et conflits sexuels. Le cas d’une espèce coloniale, la mouette tridactyle Rissa tridactyla. PhD, Paris : UPMC, Paris VI.
Huyvaert, K.P., Anderson, D.J., Jones, T.C., Duan, W. & Parker, P.G. 2000. Extra-pair paternity in waved albatrosses. Molecular Ecology 9 :1415-1419.
Møller, A.P. 2000. Male parental care, female reproductive success and extrapair paternity. Behavioral Ecology 11 : 161-168.
Møller, A.P., & Cuervo, J.J. 2000. The evolution of paternity and parental care in birds. Behavioral Ecology 11 : 472-485.
Pilastro, A., Pezzo, F., Olmastroni, S., Callegarin, C., Corsolini, S. & Focardi, S. 2001. Extrapair paternity in the Adélie Penguin Pygoscelis adeliae. Condor 143 : 681-684.
During my master internship at the Mediterranean Institute of Ecology and Paleoecology of Marseille (J.-L. de Beaulieu), I studied the impact of human populations in montanaeous areas, using technics of palynology. The studied area was in the vicinity of an archeological site dated from early Middle-Age (Fangeas site, L'Argentière valley, Ecrins), and we were able to show the different phases of occupation of the site and their impact on vegetal communities (such as christmas tree, chestnut tree, olive tree and certain herbs),