Our Approach
In the past, accepted practice was to remove dead trees and branches – research has shown that this has lead to a lack of natural nesting and roosting opportunities, contributing to declines in endangered dormouse and bat species. Artificial nest boxes help but have poorer thermal stability and higher visibility to predators than natural nest holes.
We design and carve nest holes for Hazel Dormice (Muscardinus avellanarius), Garden Dormice (Eliomys quercinus) and roosts for tree dwelling bats with exactly planned entrance and internal dimensions.
Minimally invasive carving of large nest chambers entirely through a single, narrow, precisely carved incision provides protection from weather and predation while minimising damage to the tree.
Design and location are based on the research of Goedele Verbeylen in Belgium and of Thomas Briner and Irene Weinberger in Switzerland and on our own statistical analysis. This maximises the value of ecological infrastructure created.
Our field study across 5 sites in in Belgium and studies with animals in rehabilitation by Susan Kerwin at Bat Rehabilitation Ireland and by Stiftung Wildstation Landshut in Switzerland monitor in detail how each species responds and have provided very positive initial results.
In 2025 field studies with dormouse and bat species in Switzerland and with the European Flying Squirrel (Pteromys volans) in Finland will strengthen our understanding of how these species respond.
Chainsaw Carving
We’ve developed new minimally invasive chainsaw carving techniques which cause no damage to the surrounding cambium, are very fast, very precise and can be deployed efficiently at very large scale but are technically demanding and require very high levels of strength, skill and athletic ability.
We carve bat roosts using powerful forestry chainsaws and nest holes for Hazel Dormice and Garden Dormice by making precise use of smaller arborist chainsaws and carving bars.
HSBS – High Speed Boring System
HSBS uses industrial boring heads with tungsten carbide tips together with specially made extenders, it achieves fairly high carving speeds, can be used by people without chainsaw experience and can be powered by an angle grinder and small generator.
LSBS – Low Speed Boring System
LSBS is powered by a battery powered hand drill, it is slower than chainsaw carving and HSBS but does not require a generator and can be used safely by people without chainsaw experience.
Hazel Dormouse (Muscardinus avellanarius) (National Priority: Very High and IUCN: Vulnerable in Switzerland)
For Hazel Dormice we carve an entrance of 16 mm width then cave a nest chamber of c. 100 mm width and height. All carving is done entirely through the narrow entrance. A precisely carved entrance allows Hazel Dormice in while at the same time blocking many predators and competitors for nest holes.
Garden Dormice (Eliomys quercinus) (IUCN: Vulnerable)
An entrance width of 20 mm and internal dimensions of c. 150 mm allow Eliomys to nest together in larger family groups.
Tree Roosting Bats (family Vespertilionidae)
Roosts with widths of 7 mm to 14 mm and up to 450 mm deep provide safety and thermal stability for small and large European bat species.
In the studies with bats in rehabilitation at Bat Rehabilitation Ireland, Swiss bat species (with IUCN status in Switzerland in brackets) Plecotus auritus (VU), Pipistrellus pygmaeus (NT), Pipistrellus pipistrellus (LC), Myotis nattereri (NT), Pipistrellus nathusii (LC), Myotis daubentonii (NT), Nyctalus leisleri (NT) and Myotis mystacinus (LC) showed a strong preference for carved roosts over other roosting options.
Forest Dormouse (Dryomys nitedula) (IUCN: Vulnerable in Switzerland)
Similar techniques to those used for Eliomys quercinus can be used for the isolated populations of Dryomys nitedula in Switzerland.
Western Jackdaw (Coloeus monedula, Syn. Corvus monedula)
Nest holes with larger entrances can be carved for Western Jackdaw (IUCN: Near Threatened in Switzerland)
Red Squirrels (Sciurus vulgaris), Great Spotted Woodpecker (Dentocopros major), European Green Woodpecker (Picus viridis), Black woodpecker (Dryocopus martius)
By providing nest holes with larger entrances we hope to protect these species while at the same time discouraging them from enlarging nest holes carved for smaller species.
Carved nest holes in our Belgian study are also used by birds: nuthatch (Sitta europaea), short-toed treecreeper (Certhia brachydactyla), marsh tit (Poecile palustris), green woodpecker (Picus viridis), great spotted woodpecker (Dendrocopos major), great tit (Parus major), blue tit (Cyanistes caeruleus), robin (Erithacus rubecula) and wren (Troglodytes troglodytes) and pigmy shrew (Sorex minutus) even crawled in.
Chainsaw carved bat roost and nest holes for garden dormouse (Muscardinus avellanarius) in Switzerland – for Muscardinus avellanarius the holes have a 16 mm wide entrance with an internal nest chamber c. 100 mm in all directions.
A garden dormouse (Eliomys quercinus) exploring a carved nest hole in our field study in Belgium. © Goedele Verbeylen
A chainsaw carved nest hole for red squirrel (Sciurus vulgaris) at Stiftung Wildstation Landshut in Switzerland cut open after carving.
References to research papers and other primary sources can be found here: References
“As climbing arborists, we exist at a unique confluence of art, science and athletics. Our profession has undergone a transformation from a dogmatic to a scientific era similar to that in medicine in the second half of the 20th century. As the challenges of biodiversity loss intensify, we find ourselves at a second turning point: we change from being consumers of research to leaders of the fundamental research and of the practical advances needed to ensure that trees remain homes to our most beautiful and endangered creatures.”
Blog
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From the tree crowns of an Irish forest I’d like to welcome you. At time of writing in July 2024 we’re focused on field studies, rehabilitation studies, bat counts and trying to work out what best to do after a devastating series of wildfires affecting Myomimus roachi in autumn 2023 and summer 2024 so this is just a basic site and we’ll be adding a lot more detail on species, people and techniques in English, German, French and Italian in autumn 2024. 🙂
Will 🌳🌲❤
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