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 :	Population development of the Herring Gull Larus argentatus in Denmark 1920-2012
Auteurs :	Thomas Bregnballe, Auteur ; Peter Lyngs, Auteur
Type de document :	Article
Dans :	Dansk Ornitologisk Forenings Tidsskrift (108(3) 2014)
Article en page(s) :	187-198
Langues:	Anglais
Résumé :	Based on more than 6000 counts, this paper describes the development of the population of breeding Herring Gulls in Denmark since the 1920s. As part of this review, all published as well as a large number of unpublished data concerning breeding numbers of all colonial coastal bird species recorded at individual sites were organised in a database. Furthermore, to ensure an updated overview of total breeding numbers in Denmark, a countrywide survey of these species was conducted in 2010 with the help of many volunteers. Based on the coverage of breeding sites censused in individual years we selected specific years where counts of Herring Gulls had been conducted at the most important localities as well as on a very large number of other less important breeding localities. For the sites that had not been covered in these selected years, we developed estimates of breeding numbers by using the average of the number of breeding pairs recorded in the two years before and the two years after the selected year (in case no counts had been conducted during these four years, we used the data from the nearest other year with a count, unless it had been conducted more than five years earlier or later than the selected year; Tabs 1 and 2).Using the data and estimates from the years with the most detailed and extensive countrywide counts, the Danish breeding population held in the order of 3000 pairs in 1920, 6600 pairs in 1940,17000 pairs in 1960, 76000 pairs in 1970, 66000 pairs in 1974, 60000 pairs in 1988, 62000 pairs in 1996 and 87000 pairs in 2010 (Tabs 1-4, Figs 1-3; see also the electronic Appendixes 1-4).The rapid growth of the Danish breeding population after 1940, and especially during the 1960s(16% p.a.), parallels the growth generally found in north-western Europe during this period. Like in other parts of Europe, the fast growth in Denmark is attributed to increased protection combined with periods of easy access to resources in the form of organic refuse from garbage dumps and discards from fisheries.The population development differed considerably between eastern and western Denmark. In 1974, almost 61% of the entire population bred in the eastern part of the country (eastern Zealand and Bornholm; regions 11-14). Most of these birds bred in two colonies: Grsholmen off Bornholm (at least 13000 pairs in 1974) and Saltholm off Copenhagen (some 43000 pairs in 1970). However, around 1974 the authorities initiated culling programmes at Graesholmen and Saltholm as well as in two smaller colonies in northern Jutland. These programmes ran until 1984, killing around 45000 adult Herring Gulls. At the same time, the large open dumps near Copenhagen and Malmo which especially during winter provided food for both the Saltholm and Graesholm birds were closed down. This resulted in a decline in the Danish breeding population as a whole, and a geographical shift in the growth centre from eastern to western Denmark. By 2010, only 19% of the population was breeding in eastern Denmark. Growth has especially taken place in the Lirrtord-area (region 3) in northern Jutland. In 2010, 25% of the Danish population bred here compared to 4% in 1974.No Danish studies of e.g. survival, breeding success or food selection of Herring Gulls have been undertaken, which hampers our evaluation of the reasons for the population development in Denmark, especially since the mid-1980s.

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+