| Titre : | Population dynamics of an expanding passerine at the distribution margin |
| Auteurs : | Juhani Karvonen, Auteur ; Markku Orell, Auteur ; Seppo Rytkönen, Auteur ; Juli Broggi, Auteur ; Eduardo Belda, Auteur |
| Type de document : | Article |
| Dans : | Journal of Avian Biology (43(2) MAR 2012) |
| Article en page(s) : | 102-108 |
| Langues: | Anglais |
| Résumé : | Individuals may be maladapted to novel environments at the species distribution margin. We investigated population dynamics in a marginal habitat where reproduction has been proven poor. Survival, population growth rate (?) and its components, breeding and natal dispersal were studied in great tits Parus major breeding at the northern margin of its distribution in northern Finland. We used long term capturemarkrecapture data sets. Study area size and population density were used to explain adult survival rates. The average annual estimates of adult survival rose from 0.371 to 0.388 between the periods of 19711984 and 19992009. The estimates are slightly lower than estimates of small passerines in Europe. Low local survival rate of fledglings (0.0500.055) probably reflects intensified emigration from this low quality area. Temporal variation in ? was large (0.4981.856). Despite of low adult survival and recruitment rates, the mean estimates of ? (1.008 and 1.033) indicate an overall stability in the population size. Indeed, our results suggest that the immigration has an important role in the population dynamics of northern great tits. Thus the population is demographically and genetically dependent on core habitats which may cause adaptive problems due to intensive gene flow. Given those limitations, options for evolution of local adaptations in northern distribution margins are discussed. |



