Niklaus Zbinden

Patches of Bare Ground as a Staple Commodity for Declining Ground-Foraging Insectivorous Farmland Birds

Conceived to combat widescale biodiversity erosion in farmland, agri-environment schemes have largely failed to deliver their promises despite massive financial support. While several common species have shown to react positively to existing measures, rare species have continued to decline in most European countries. Of particular concern is the status of insectivorous farmland birds that forage on the ground. We modelled the foraging habitat preferences of four declining insectivorous bird species (hoopoe, wryneck, woodlark, common redstart) inhabiting fruit tree plantations, orchards and vineyards. All species preferred foraging in habitat mosaics consisting of patches of grass and bare ground, with an optimal, species-specific bare ground coverage of 30–70% at the foraging patch scale. In the study areas, birds thrived in intensively cultivated farmland where such ground vegetation mosaics existed. Not promoted by conventional agri-environment schemes until now, patches of bare ground should be implemented throughout grassland in order to prevent further decline of insectivorous farmland birds.

Identifying habitat suitability for hazel grouse Bonasa bonasia at the landscape scale

Abstract The hazel grouse Bonasa bonasia is declining in many areas within its European distribution, particularly in managed forests. Adequate habitat management may thus be crucial for the regional survival of the species. So far management activities have tended to focus on the local scale. However, for the sustainable management of the hazel grouse and its habitat, the landscape scale also needs to be considered. We therefore evaluated whether habitat suitability for hazel grouse can be quickly, but adequately, modelled at the landscape scale with information obtained from aerial photographs. We mapped hazel grouse records in a forested area typical of large tracts of the Swiss Jura mountain range, and extracted data on habitat composition from infrared aerial photographs applying a bird-centred sampling approach. We then used the hazel grouse records together with an equal-sized data set of non-grouse plots to build predictive habitat suitability models using a generalised linear model (GLM) and a classification tree (TREE). The models were evaluated and then applied spatially explicitly to the 25 km2 study area to compare their predictions for hazel grouse distribution. Hazel grouse preferred vertically and horizontally richly structured forest stands. Forest edge density, shrub and herb cover, stand structure and development stage were essential habitat variables. The resulting 5-fold cross-validated predictive habitat models performed well, having a kappa of 0.62 (GLM) and 0.8 (TREE), and a correct classification rate of 0.81 (GLM) and 0.90 (TREE). This suggests that predictive modelling based on a bird-centred analysis is an efficient way to assess habitat suitability for hazel grouse habitat management at the landscape scale.

Habitat use and foraging ecology of the nightjar (Caprimulgus europaeus) in the Swiss Alps: towards a conservation scheme

The European nightjar is one of the most endangered bird species in Switzerland. As its ecology in the country is poorly understood, we collected data on resource exploitation in the upper Rhone valley (Alps). The diet of two adult birds and one nestling consisted primarily of moths (81 and 93% of biomass), which were also the most abundant prey sampled at the study site. Three radiotracked nightjars selectively exploited oak scrubland compared to vineyards and pine forests; vineyard monocultures harbour presumably insufficient moth populations, whereas dense pine stands probably do not provide the flying and foraging requirements of nightjars. The survival of nightjars in Valais probably depends both on the existence of sufficient populations of moths and on the availability of semi-open natural habitats, such as oak scrubland, which seem to offer the best suitable foraging and nesting places.

Mortality of birds of prey following field application of granular carbofuran: A case study

The death of buzzards (Buteo buteo) found in fodder and sugar beet fields treated with granular carbofuran was investigated. To determine if there was a causal relationship between carbofuran treatment and bird mortality, earthworms of a specific fodder beet field as well as the crop contents of dead buzzards were analyzed for carbofuran contamination. Earthworms of the fodder beet field contained carbofuran concentrations up to 3.2 mg/kg, while remains of earthworms and carbofuran were detected in all buzzard crop contents. The carbofuran concentrations found in the earthworms as well as in the crops of the buzzards corroborate the suspicion that the buzzards found on fodder and sugar beet fields treated with granular carbofuran had died of secondary poisoning with carbofuran via contaminated earthworms.

A resampling-based method for effort correction in abundance trend analyses from opportunistic biological records

Capsule Resampling data from biological records databases yielded abundance trend estimates better corrected for increasing observation effort. Aims To correct population trend estimates for the effects of annually changing observation effort in analyses of opportunistic data. Methods We developed a resampling-based abundance index for analysis of population trends based on opportunistic citizen-science observations. To correct for the huge recent increase in observation effort every year, we resampled (with replacement) a species-specific constant number of records from the data and computed our index. To validate our standardized index, we used counts from the national waterbird census as a benchmark. Results Over 22 winters (1991–2012), trend estimates based on resampled indices were substantially more similar to waterbird census-based trend estimates than were raw index-based trends. Raw index trends were off by 648% (se 72%) and typically overestimated trends, while trends computed from standardized indices were off by only 125–131% (se 12–13%) and over – and underestimated trends about equally frequently. Hence, our method of effort correction reduced the bias in trend estimates by a factor 5. Conclusion Our resampling method may be useful for improving trend analyses from collections of opportunistic biological records, as they become increasingly available, especially via the internet.

Evidence for an additive effect of hunting mortality in an alpine black grouse Lyrurus tetrix population

In the Canton of Ticino in southern Switzerland data from the monitoring programme for black grouse from 1981 to 2016 (population density, lek size, sex ratio in chicks and adults) were analysed together with information on bag statistics and hunting regulations to evaluate if mortality from hunting had an additive effect. In the study population the proportion of cocks at the beginning of the study period was only 23%. As hunting regulations for black grouse were tightened in the late 1970s the observed proportion of males showed an increase in particular during the first years but remained much lower than what would be expected from the sex ratio among chicks assuming equal survival between the sexes. The observed low proportion of adult males indicates a lower survival rate and as a consequence a smaller than natural lek size. High reproductive success two years before had a positive effect on lek size. The correlation coefficient between hunting bag and population size index increased with increasing hunting pressure and showed a decline over the years. Bag size in the period with a high hunting pressure (1981–1999, many hunting days) was driven by population density whereas in the second period (2000–2016, few hunting days) it was driven by hunting regulations. Our analysis showed that hunting affects population structure and presents indirect evidence that mortality due to hunting is additive. The study also shows that hunting management has to be continuously adapted to changes in the size and structure of the population as well as changes in habitat conditions. It is therefore essential to continue long-term monitoring of population size and of demographic parameters.

Amateure in der ornithologischen Grundlagenforschung: Viele Daten — wenige Veröffentlichungen?

Since many years, amateurs have played an important role in scientific ornithology. In this paper which is based on a symposium convened by Dachverband Deutscher Avifaunisten (DDA) on the meeting of the German Ornithologists Society in Leipzig in 2000 we give examples of significant contributions to basic scientific research by amateur ornithologists. The contributions of amateurs to scientific ornithology range from casual observations (we propose common aims and quality criteria for annual bird reports) to sound and comprehensive population studies. We review some problems amateurs face during their work. Difficulties are often related to publishing results in scientific papers. We suggest solutions: ornithological societies, editors of journals, libraries and the ringing centres support the work of amateurs. We invite readers to discuss further promotions of scientific ornithological work of amateurs. Amateure spielen in der wissenschaftlichen Ornithologie seit langer Zeit eine wichtige Rolle. In diesem Artikel, der auf einem vom Dachverband Deutscher Avifaunisten (DDA) auf der Jahrestagung 2000 der DO-G in Leipzig veranstalteten Symposium basiert, wird die Bedeutung von Amateur-Ornithologen für die ornithologische Grundlagenforschung anhand einiger Beispiele aufgezeigt. Die Beiträge von Amateuren reichen von Gelegenheitsbeobachtungen — hierzu werden Ziele und Qualitätskriterien für avifaunistische Jahresberichte vorgeschlagen — bis zu umfassenden populationsbiologischen Studien. Probleme bei der wissenschaftlichen Arbeit von Amateuren — oft die Veröffentlichung der bereits gesammelten Daten betreffend — werden genannt und Lösungsmöglichkeiten angegeben. Ornithologische Vereinigungen, Schriftleitungen von Zeitschriften, Bibliotheken und die Vogelwarten leisten wichtige Beiträge zur Unterstützung der Arbeit von Amateuren. Die Autoren laden zu einem Dialog über weitere Fördermöglichkeiten ein.