Gerber, A., W. Leuthold & M. Kéry
(* = Kurzbeitrag)
Der Bienenfresser Merops apiaster in der Schweiz: Durchzug und Bruten.
(von 1994 bis 2006 vergeben)
Durchzug, Brutkolonien, Verbreitung, Verhalten
The European Bee-eater Merops apiaster as a passage migrant and breeding species in Switzerland. During the last 50 years – partly even earlier – the European Bee-eater Merops apiaster has extended its breeding range, in repeated bouts, into central and even northern Europe. Observations of Bee-eaters in Switzerland have increased considerably since about 1980, and breeding was confirmed for the first time in 1991. Available records show a marked preponderance in south-western Switzerland (Cantons of Vaud, Geneva and Valais).
Along with the larger number of observations mean observed flock size has also increased, with a few flocks numbering up to 100 birds. Also, the seasonal distribution of observations has changed: records in autumn, relatively scarce until about 1995, increased notably in recent years. Presumably more birds migrate southward because of successful breeding in areas north of Switzerland. Spring arrivals and passage in Switzerland begin about mid-April, with a peak in May; in autumn, passage extends from about mid-August to early October. Earliest and latest observation dates in Switzerland were 15 March 2008 and 14 October 2004, respectively.
From 1991 through 2010 Bee-eaters bred in Switzerland every year. A total of 270 breeding attempts were recorded in 31 different locations, the maximum number in any one year being 34, in 10 different places. Many breeding sites were used only once or a few times and then abandoned. The only long-term colony is that of Penthaz (Canton of Vaud), where 130 cases of breeding were recorded over 15 years starting in 1996.
Breeding success is difficult to assess. Many breeding attempts by single, isolated pairs were unsuccessful. Of 145 breeding attempts sufficiently well documented 119 resulted in at least one fledged young. Breeding failures were due to predation (e.g. by foxes), inclement weather that caused flooding of burrows or a shortage of insects as food, and disturbances by human activities.
Most breeding sites were in sand or gravel pits. Occasional breeding attempts occurred in temporary heaps of sand or earth, or even in small vertical earth banks in a pasture. These breeding sites point to a major problem for Bee-eaters attempting to breed in Switzerland: The lack of natural locations suitable for successful breeding.
The future of Bee-eaters in Switzerland will depend on (a) the further course of climate change which is probably the main factor underlying the northward extension of the species’ breeding range, and (b) measures taken to protect existing breeding sites as well as to maintain and even (re)create suitable breeding habitats for this attractive bird species.
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