Brownsea Island's bird and mammal box project

Red squirrel kits in a nest box, Brownsea Island, Dorset | © National Trust / Brian Whitlock

The National Trust staff and volunteer team look after nearly 400 nest boxes across Brownsea Island, which provide homes for a variety of birds, red squirrels and bats. Here we explain a little more about what the rangers and volunteers find on their yearly rounds.

Yearly round-up

Each year, all of the nest boxes are checked in May and September to see if they are in use, and then any repairs are carried out in February.

This was another successful year for the project, which has been running since 1997.

Our usual box checks were once again carried out in May and September during 2022. We were unable to check bat boxes during the pandemic (in line with national guidance on bat surveys) so this was the first time all boxes in the project were able to be checked since September 2019.

Birds

126 tit nests, including 23 blue tit, 19 great tit and 5 coal tit, plus a high number of ‘unknown’ tit nests were found. Treecreeper, robin and wren nests were also found this year.

Tawny owl nest records for 2022 were down compared to 2019. Only 1 box had definite signs of use in May (1 egg) and no adults or chicks were seen.

Blue tit chicks in nesting box at Ravenscar, Yorkshire — Blue tit chicks in nesting box | © National Trust Images/Zoe Frank

Red squirrels

Although squirrel boxes are clearly identified (with little porches on the side), squirrels will quite happily hijack any other box they can lay their paws on.

They have been catered for with 55 purpose-built wooden boxes which have proved very popular. As in previous years, we found that red squirrels made use of the owl boxes too, along with various types of bird boxes. During the 2022 checks, 62 boxes in total showed signs of use by red squirrels, including most of the purpose-built squirrel boxes provided for them, as well as owl boxes and bird boxes.

Bats

The project also includes around 140 bat boxes, over half of which are hand made from untreated timber.

Many of our bat records are based on the presence of droppings, which indicate that bats have used the boxes. Since 2015, we've found that large numbers of pipistrelle bats congregate in some of our specially-designed wooden bat boxes to form maternity roosts.

Bat results during 2022 were similar to 2019 with the usual species recorded. Pipistrelle bats were found in 38 boxes across the island, including a large maternity roost in a purpose-built box. Brown long-eared bats were found in 4 boxes and good numbers were seen hanging from the ceiling again in one of the island's hibernaculums (a hibernaculum is a shelter of sorts, where animals hibernate for the winter). Natterer’s bats were also found in 7 boxes and Noctules in 3 boxes.