Aerial insectivorous birds depend highly on favourable weather conditions for successful foraging because flight activity of insects is constrained by daily weather. Thus, the variation in weather conditions during reproduction, mediated by prey limitations, should be mirrored in annual reproduction performance, and finally in annual breeding success. We analysed the effect of local weather conditions on the availability of airborne insects and on the variation in brood size and nestling condition of European bee-eaters Merops apiaster at the northern edge of their range where years with adverse weather frequently occur. The availability of large flying insects, the common prey of bee-eaters, increased with air temperatures and duration of daily sunshine. As predicted, local weather conditions affected reproductive performance with annual breeding success (mean 3.7 nestlings per breeding pair, range 1.7-4.9 nestlings) being up to 32 % higher in extraordinary dry and hot summers. Additionally, a nestling's body condition (residual mass) was also affected by sunshine duration during their growth period and internally was co-affected by the number of siblings and the individual rank within the sibling hierarchy. Thus, a prolonged duration of daily sunshine causes a cascade from higher insect flight activity, and, thus, higher food availability for chick-rearing bee-eaters, which finally translates into better chick body conditions and higher annual breeding success. Consequently reproduction and population development of European bee-eaters might be especially susceptible to regional changes in weather and climatic conditions. ZusammenfassungDeutlicher Dominoeffekt der Witterungsbedingungen auf Nahrungsverfü gbarkeit und jährliche Reproduktionsleistung beim Bienenfressern Merops apiaster Für einen erfolgreichen Nahrungserwerb sind Jäger von Fluginsekten stark von Wetterbedingungen abhängig, da die Flugaktivität der Insekten maßgeblich durch die lokale Witterung beeinflusst wird. Deshalb sollten sich Witterungsschwankungen während der Brutzeit in einer Reduktion der verfügbaren Beute und damit in der Reproduktionsleistung und dem jährlichen Bruterfolg widerspiegeln. Wir analysierten die Auswirkung der lokalen Witterungsbedingungen auf die Verfügbarkeit von Fluginsekten sowie die Brutgröße und die Kükenkondition von Bienenfressern Merops apiaster am nördlichen Rand des Verbreitungsgebiets. Die Verfügbarkeit von großen Fluginsekten, der Hauptbeute von Bienenfressern, stieg mit Communicated by F. Bairlein. Electronic supplementary material The online version of this article (

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SummaryCorncrakes Crex crex mainly breed in grassland, where they are threatened by mowing. Conservation requires delayed mowing or modified mowing methods. In large fields, it has been suggested that leaving strips of uncut grass may reduce mortality, especially of unfledged chicks. We attended mowing operations (2012–2015) in the Lower Oder Valley National Park in north-eastern Germany, where 10-m refuge strips were introduced. We documented the escape behaviour of adults and chicks and their use of refuge strips by observations and radio-telemetry. Flightless chicks crossed significantly shorter distances of mown area (< 20 m) than adults. When mowing from the outside inwards, chicks were not able to successfully escape to the field edge at > 31 m, adults at > 60 m distance to the edge and returned to the unmown block. Twenty-three percent of adults, 30% of families and 49% of independent chicks survived in 10 m-wide strips until such strips were either mown or left as refuges. Whereas adults departed the strips the next day, independent chicks stayed for up to 22 days after mowing in 15–30 m wide refuges. We recommend refuge strips for breeding sites where more effective measures cannot be applied. Farmers face less additional effort and lower financial losses compared with delayed mowing. A width of 10 m should be considered as the absolute minimum, because most birds left the cover already > 10 m for the first time and only wider refuges served as temporary habitat for young.