Ecosulis have recently completed a large scale infrastructure project in Lancashire. The primary focus of the job was to climb and inspect mature trees to assess the potential of tree cavities to support roosting bats.
The work was undertaken by Mark Anderton and Ben Mitchell (licensed bat ecologist) and once up in the tree canopy, the principle role of the inspection involved using an endoscope to inspect the full extent of the cavity. The first stage is evidently checking for the presence or absence of roosting bats, although no bats were recorded in this instance.
The majority of features inspected were woodpecker holes and knot holes. We found that a few of these cavities were inundated with nesting material from birds and arboreal mammals such as squirrels. In fact, we had an unexpected encounter with a roosting blue tit who was rather startled to find an endoscope in his house of residence. The first thought indicated that these cavities would be deemed unsuitable for roosting bats due to competition, predation and presence of unwanted parasites. However, bats roost can be found between periods where such residents use these cavities and may have still provided suitable roosting opportunities.
Some knot holes and woodpecker holes provided large, clean, smooth cavities which can be used as maternity roosts. In contrast, some cavities supported a damp interior, due to the presence of brown rot and in some cases were exposed to the elements, hence providing less potential.
A range of factors relating to other roost types were also considered, including hibernation and day roosts. Some trees featured small and tight crevices such as in hazard beams (longitudinal splits in lateral limbs) which provided good opportunities for single hibernating bats such as soprano pipistrelle’s. Or small knot hole cavities and in some cases cankers (changes in the texture of wood resulting from the death if the cabium) with cavities too small for maternity roosts but not too small for single bat day roosts.
Some features such as cavities resulting from tear outs (caused by branches tearing away from the trunk leaving a large open scar) provided large internal trunk cavities. In some cases these cavities were too extensive to fully inspect, however given the size, dry and smooth internal conditions, large maternity roost potential cannot be ruled out.
All in all, it was a rewarding project being in the tree canopy, of which so many of us don't experience.