Vegetation structure and decreased moth abundance limit the recolonisation of restored habitat by the European Nightjar

Abstract

Woodland ecosystems of Europe have undergone major transitions in the last centuries. Changes in land use and the loss of natural forest dynamics have often led to structurally poor, uniform and dense stands. Not surprisingly, open forest species relying on a heterogeneous stand structure have suffered dramatic population declines. The European Nightjar Caprimulguseuropaeus, a nocturnal insectivorous bird, has undergone such a decline in its main Swiss stronghold in Valais. Despite the species’ potential to colonize new sites and habitat restoration measures implemented since 2001, recolonisation of restored sites has not taken place, suggesting problems with the current habitat restoration strategy. In order to refine management recommendations, we compared habitat structure and moth abundance, a key Nightjar food source, at sites that are still occupied and at sites that had been abandoned but have recently been restored. Vegetation structure was more heterogeneous and moth abundance greater at occupied than at abandoned sites. More specifically, occupied sites harboured a greater coverage of bare ground, while abandoned sites exhibited a higher amount of regeneration and intermediate shrub layer. The occurrence of natural perches was also higher in occupied sites. Abandoned sites are thus characterised by lower prey abundance and denser vegetation cover, the combination of which is likely to lead to lower prey availability for hunting Nightjars. Restoration action would benefit from maintaining snags and dead branches and by targeting unproductive habitats characterised by mineral soils, thereby slowing down regeneration and shrub regrowth. For future successful management of Nightjar habitats, it seems thereby essential trying to find the balance between actions that allow opening the lower and mid-strata of the forest while sustaining high moth populations.

Improved ecological insights commission new conservation targets for a crepuscular bird species

“…Nightjars used multiple habitat types indicating the importance of complementary resources to breed and to forage. Requirements to breeding habitats of the studied population are in line with previous findings (Sierro et al, 2001;Winiger et al, 2018), while (i) the preference for specific grassland types, alpine meadows and vineyards to forage and (ii) the requirement of a larger space, on average six times higher per individual compared with previous estimates (Sierro et al, 2001), shed new light on future conservation strategies. Furthermore, our results suggest that the land use changes, especially in potential foraging habitat, have contributed to the long-term population declines in Switzerland.…”

“…It has been suggested that nightjars would also stay within their breeding habitats to forage owing to sufficient food supplies (Sierro et al, 2001;Sharps et al, 2015a) or suitable micro-habitat structures to forage (Sierro et al, 2001;Wichmann, 2004). The lacking evidence of multiple habitat requirements, for the Swiss population, resulted in conservation measures mostly focusing on the management and restoration of lost breeding habitats (Sierro, 2013(Sierro, , 2016. However, almost all tracked nightjars (visual inspection of tracking data) in our study have been recorded foraging in extensively cultivated agricultural grasslands, alpine meadows or in vineyards.…”

“…Nightjars are an endangered bird species in Switzerland (Keller et al, 2010). The studied population has undergone a rapid decline in the last decades (Knaus et al, 2018), despite the local application of evidence-based restoration measures to create new breeding habitats (Sierro, 2013(Sierro, , 2016. By following a multi-scale approach, we characterized foraging behaviour and assessed local habitat use (i.e.…”

Living room conservation: a virtual way to engage participants in insect conservation

“…The Anthropocene epoch will bring unprecedented change to Earth's biodiversity (Pimm et al 2014;Lewis and Maslin 2015). Alarmingly, new studies have reported significant insect abundance declines over time (Dirzo et al 2014;Brower et al 2018), negatively cascading throughout the trophic community (Winiger et al 2018;Lister and Garcia 2018). We should be concerned because of four values: 1) utility -insects provide ecosystem services ranging from pollination to nutrient cycling that are worth billions (if not trillions) of dollars (Losey and Vaughan 2006) and also help scientists and engineers innovate new materials, structures, and systems through biomimicry (Gorb 2011); 2) aesthetics -many insects are admired for their beauty and sounds (Guiney and Oberhauser 2009;Sumner et al 2018), butterfly gardens are created to attract butterflies providing eco-therapeutic relief and admiration towards nature's beauty ; 3) intrinsic -collectively, biodiversity is important because species are connected in complex systems (Kim 1993), and species have the right to exist simply because they have the right to exist (Lockwood 1987), therefore, their success or extinction should be determined by their ability to adapt to Earth's natural processes, not human intervention (Lockwood 1987); and 4) unknown -due to the sheer numbers of species some components of insect services are currently unknown and unquantifiable; consequently, disastrous agricultural and ecosystem collapses could occur (Kim 1993;Losey and Vaughan 2006).…”

Habitat Selection by the European Nightjar Caprimulgus europaeus in North-Eastern Poland: Implications for Forest Management

“…In the context of this species' nesting preferences, we anticipated that certain microhabitat components, like the age and type of clearing, the type of undergrowth vegetation and the presence of seed trees, would play a significant role in its occurrence. Specifically, vegetation structure would enhance foraging efficiency on the one hand and create biotopes enabling the birds to remain concealed while nesting and roosting on the other [29]. We also hypothesized that more clearings and a younger tree cover in the immediate surroundings of the nesting territories would enlarge the birds' hunting area.…”