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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	An atlas of bird ringing at the island of Helgoland. Part 2: Phenology in the trapping garden from 1961 to 2000.
Auteurs :	Kathrin Hueppop, Auteur ; Ommo Hueppop, Auteur
Type de document :	Article
Dans :	Vogelwarte (42(4) August 2004)
Article en page(s) :	285-343
Langues:	Allemand
Résumé :	At Helgoland, extensive long-term trapping data have been collected with very constant effort and methods (funnel traps). With up to 7 trappings per day throughout the year almost 468 000 individuals and 153 species could be registered from 1961 to 2000. The focus of this analysis are general phenological patterns. Changes of trapping totals throughout the 40-year-period are only discussed briefly. Taking all 153 species together, both, spring and autumn migration periods, can be divided into two bouts. The spring migration pattern of the short/medium-distance migrants has a maximum at the beginning of April, while that of the long-distance migrants peaks at the end of May. During autumn migration, long-distance migrants peak at the end of August and in the middle of September, while the maximum of short/medium distance migrants is in the middle of October. For 70 species with sufficient sample size, species-specific migration patterns could be analysed. For the 35 most abundant species, the presentation was further divided into four 10-year-periods (1961-1970, 1971-1980, 1981-1990 and 1991-2000). Our phenological data demonstrate the importance of all-year-round trapping effort: even between migration periods a considerable number of individuals was trapped. The method of "Binned Kernel Density Estimate" (BKDE-method) allowed the identification of the species-specific maxima and minima of migration and consequently the definition of migration times. Calculation of mean and median migration period and main mean migration time (range of 90 %) for the 70 species allowed a comparison with data from other stations. However, methodical problems, such as the use of different statistical features, different study periods and different geographical location of the stations (especially regarding different origin of the birds), influence of local factors and climate limit such comparisons. The migration patterns of the investigated species are to a large extent normally distributed in both migration periods. Only during autumn migration some short/medium-distance migrants with winter guests on Helgoland have positive skewness (longer right tail). Besides the majority of species with single-peaked passage, some frequently trapped species are characterised by multiple migration peaks. Several species could be analysed with regard to differential migration of sex (n = 15) and age classes (n = 25), and in some species differential migration explained multiple migration peaks. In most species males or adults migrate earlier in spring and later in autumn than females or young birds. As an exception the autumn migration pattern of the Sparrow Hawk shows two peaks, which is caused only by juvenile birds and can be explained as an adjustment to the two migration bouts of their avian prey.

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