Bibliothèque Tour du Valat

Se connecter

Mot de passe oublié ?
Pas encore inscrit ?

La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Détail

Ajouter au panier

Ajouter au panier

Lien vers la notice

Titre :	The rise and fall of an Eurasian Tree Sparrow population. (2002)
Auteurs :	Christiaan Both, Auteur ; Marcel E. Visser, Auteur ; Hans van Balen, Auteur
Type de document :	Article
Dans :	Limosa (75(2) 2002)
Article en page(s) :	41-50
Résumé :	Eurasian Tree Sparrows established themselves as breeding birds in nestboxes in the Hoge Veluwe area in 1966, and the population grew strongly during the next 15 years. In the early eighties population numbers crashed in just a few years, and have not recovered since. In this paper we aim to explain the demographic causes of this observed population growth and crash. Population growth rate was strongly related to the annual number of fledged offspirng per pair, and the four years in which reproductive success was experimentally reduced, support the idea that the observed population fluctuations are a result of variation in the number of fledged offspring. During the population growth phase, the reproductive success of first broods was equal to that in the period of decline, but the probability to produce a second and third brood as well as their success were higher during population growth than after the crash. The population crash coincided with three years in which reproductive success was experimentally reduced. In a simple simulation model we showed that the population dynamics could be the result of the observed fluctuations in reproductive success, without any additional change in mortality, suggesting that reproduction and not mortality is the cause of the observed dynamics. We consider different hypotheses that can account for the observed rise and fall of this Eurasian Tree Sparrow population. Intensification of agriculture and its subsequent reduction in seeds seems not important because that would mostly affect survival aid not so much reproduction. Adverse effects of pesticides on reproduction were considered unlikely, since the sparrows increased during the period when the most persistent pesticides were used, and the effect was not found on the first broods. An increase in Sparrowhawk predation can in principle explain both the decrease and the increase of the Eurasian Tree Sparrows, but our results point in the direction of reproduction, and not mortality, being the most important factor driving the population dynamics. We discuss the possibilities that insect food abundance during the late breeding season may have declined, or that diseases or parasites have increased. Our results are in contrast to what happened in Britain, where the Eurasian Tree Sparrows probably declined as a result of decreased survival, and where reproduction increased simultaneously.

FAQ

Infos pratiques

Heures d'ouverture et contact

Lundi , mardi et jeudi de 9h à 12h et de 13h à 17h00 : ouverture au public ...

Liens utiles

A-
A
A+