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Effects of vineyard management and fragmentation on Woodlarks and their invertebrate prey.

Author Laura BOSCO
Director of thesis Prof. Dr. Raphael Arlettaz
Co-director of thesis Dr. Alain Jacot
Summary of thesis

Due to increasing urbanization, industrialisation and agricultural intensification our natural landscapes have

changed dramatically in the last century. Many semi-natural and natural habitats have been destroyed, degraded

or fragmented, leading to pronounced biodiversity declines. Vineyards belong to those agricultural crops that

underwent rapid intensification, especially in the use of pesticides. The canton of Valais in southern Switzerland

represents an extreme case, as here still 80% of all vineyards are treated with herbicides and consequently do not

have any ground vegetation cover. As a result, the remaining 20%, which are managed with modern farming

practices allowing vegetated grounds, are often isolated from one another in the viticultural landscape. Yet,

depending on the management intensity, Valais vineyards can provide a suitable habitat for different animal

species, such as the Woodlark Lullula arborea. Around half of the Swiss Woodlark population breeds in this

intense agro-ecosystem. Woodlarks are ground-breeding birds and during the reproductive season they mainly rely

on invertebrate food. In the framework of this PhD thesis we studied habitat preferences of Woodlarks and the

distribution of their invertebrate prey in Valais vineyards. At a field scale we studied the effects of different ground

vegetation managements on occurrence patterns of Woodlarks and linked them with invertebrate abundance and

richness. In a next step, we explored nest-site selection of Woodlarks and predation risk of artificial nests in relation

to ground vegetation cover. At larger scales, we mainly aimed at disentangling the effects of habitat amount (area

covered by vegetated vineyards) and fragmentation (number of separated vegetated vineyards) on invertebrate

abundance and on Woodlarks’ habitat selection patterns. We found that Woodlarks prefer vegetated vineyards

with an enhanced plant species richness during territorial display and that nests are usually placed in dense and tall

vegetation patches. Likewise, in vegetated vineyards we observed a decreased predation risk. Invertebrate numbers

and taxonomic richness were also higher in vegetated vineyards harbouring a diverse plant community, likely

explaining the increased occurrence probability of Woodlarks in those fields. Habitat amount at local scales best

explained invertebrate abundance and habitat use of Woodlarks, revealing that around 60% of the surface should

be covered by vegetated vineyards. Fragmentation negatively affected invertebrate numbers and Woodlarks’ home

range selection, but the latter only in contexts where habitat amount was below 20%. Conversely, we even found

a preference for home ranges located in fragmented areas when habitat amount was high. This underpins the birds’

preference for heterogeneous landscapes, what might be explained through a more stable provision of resources in

complex systems, as compared to homogenized, simple landscapes. As a synthesis, we formulate precise

recommendations for practitioners in order to sustain and promote Woodlarks and their prey, what is likely to

favour overall biodiversity in Valais vineyards.

Status finished
Administrative delay for the defence 2018
URL http://www.iee.unibe.ch/cb/content/about_us/staff/bosco/index_eng.html
LinkedIn www.linkedin.com/in/laura-bosco-313339146