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M. Ryan & G. Jones (In Press) "Bats Churches and the Landscape project, interim findings"

 

Surrounding habitat: Soprano pipistrelles preferentially feed on insects in wetland and woodland habitats (as found in previous studies) (Davidson-Watts et al., 2006, Nicholls and Racey, 2006, Bartonicka et al., 2008) but this study has found that the species is more mobile than previously thought. The average mean maximum nightly commuting distance was 4.46 km. This means that it is important to retain wetland, woodland and other trees in the landscape in areas surrounding soprano pipistrelle roosts and where opportunities arise, to recreate these habitats, to compensate for historic and ongoing losses.

Alternative roosts: Bats from three soprano pipistrelle colonies in churches in Essex, Norfolk and Peterborough were radio-tracked. These bats were found to use several alternative day roosts across large areas surrounding the church maternity roost, in a variety of structures, which supports the suggestion that this species is a generalist with respect to roosting habitat (Avery, 1991). However, although some individual bats switched roosts, the “main” church maternity roosts were always occupied during the radio-tracking periods. In total, for all three colonies, only four alternative communal roosts were located, three of which were in domestic houses and the fourth in a garage attached to a domestic house.

Bats use churches throughout the year: Soprano pipistrelles were present all year-round in three medieval churches monitored over 12 months. Activity peaked in mid-July, which coincided with the time juveniles were starting to fly. This indicates that without survey work to suggest otherwise, it should generally be assumed that where soprano pipistrelle bats are known to use a church in summer, that they may hibernate there too. The likely year-round use of medieval churches should be taken into account during building repair work (e.g. by consideration of whether a licence is needed and the timing of such work) and any mitigation should include provision to replace lost hibernation habitat as well as maternity roosting habitat.

Numbers of churches with pipistrelle bats: Surveys of 124 churches with previous records of common or soprano pipistrelle bat roosts, some of which were maternity colonies, indicated that although almost all of the visited churches still had evidence of these species, relatively few had obvious communal or maternity roosts present. A repeat of the National Bats in Churches Survey (Sargent, 1995) would allow a better understanding of the scale of issues caused by bats in churches. These surveys highlighted that church doors are frequently used for common or soprano pipistrelle species for their access into and out of churches, and that access over doors is sometimes threatened by draught exclusion and by restoration work.

Roost selection in churches: Within churches, soprano pipistrelle maternity and communal roosts are more likely to be situated in south-facing rather than north-facing areas. So to encourage bats to use less sensitive areas of the church building, it is important to identify other areas within the church with similar aspect and environmental conditions available for roosting.

Churches provide a range of temperature conditions for roosting during summer and winter. This is likely to help explain why churches are used so frequently by bats.

Can soprano pipistrelle bats be excluded from churches?

The preliminary findings show that:

  • Soprano pipistrelles may have access to some alternative roosts (four communal alternative roosts were used in the three church colonies studied by radio-tracking) and may be generalists with respect to roosting habitat. However, some individual bats remain very faithful to the church roost and did not use alternative roosts during the observed study period (up to one week per bat).
  • Medieval churches provide a range of temperatures and roosting conditions which may be important to bats and may not be straightforward to replace.
  • Medieval churches may also be used all year-round and used by more than one bat species.

All of these elements, along with practical difficulties, make whole-building exclusion from medieval churches complex compared to exclusions from domestic houses.

Bat Boxes - not a 'quick fix'

Electrically heated bat boxes can provide warm and stable temperature conditions throughout the day and night, when the heating unit is switched on and is working. However, for heated bat boxes installed in cool locations, such as church towers, the temperature regime will be unsuitable for soprano pipistrelle maternity roosts if the heating unit stops working (e.g. is accidentally turned off or blows a fuse).

Non-heated bat boxes in sunny positions outside a church can provide suitably warm daytime roosting conditions which mimic existing roost crevices, but they don’t provide the same amelioration of outside conditions (e.g. at night), that church buildings as a whole provide.

The installed heated and non-heated bat boxes were not used by bats within the first year after installation. It was difficult to find sites to install heated bat boxes, for a variety of reasons:

  • lack of electricity supply at some churches
  • some church wardens were not convinced it would work and had concerns about their operation, running costs and insurance restrictions.

A longer time frame is needed to test whether soprano pipistrelle bats ‘voluntarily’ take up heated or non-heated bat boxes in the absence of exclusion. However, the existing research suggests that heated bat boxes are not a ‘quick fix’. A fundamental concern would be how to guarantee the necessary maintenance and running costs required to keep a box in good working order for several decades.

Restricting roosting opportunities to parts of the church where the bats are unable to enter the church interior may be feasible in some cases. This approach is being trialled in one church in the near future.

References

AVERY, M. I. 1991. Pipistrelle. In: CORBET, G. B. & HARRIS, S. (eds.) Handbook of British Mammals, 3rd edition. Oxford: Blackwell Scientific.

BARTONICKA, T., BIELIK, A. & REHAK, Z. 2008. Roost switching and activity patterns in the soprano pipistrelle, Pipistrellus pygmaeus, during lactation. Annales Zoologici Fennici, 45, 503-512.

DAVIDSON-WATTS, I., WALLS, S. & JONES, G. 2006. Differential habitat selection by Pipistrellus pipistrellus and Pipistrellus pygmaeus identifies distinct conservation needs for cryptic species of echolocating bats. Biological Conservation, 133, 118-127.

NICHOLLS, B. & RACEY, P. A. 2006. Habitat selection as a mechanism of resource partitioning in two cryptic bat species Pipistrellus pipistrellus and Pipistrellus pygmaeus. Ecography, 29, 697-708.

SARGENT, G. 1995. Bats in Churches Project, London, Bat Conservation Trust.

 

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