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 volunteer led project has been running since 1997.

The team check 400 bird, bat and squirrel boxes in May and September. They have reported back that plenty of active squirrel nests were found, along with a maternity bat roost containing around 200 bats, three of the owl boxes were being used by tawny owls. There were plenty of bird nests in all stages from eggs to almost ready to fledge young, on the whole it was a good year.

Birds

Our volunteer team recorded 106 tit nests, including 27 blue tit, 8 great tit and 3 coal tit nests and 1 treecreeper nest. The overall number of nests was similar to last year but more of them were recorded as ‘unknown’ because they were either empty or had eggs or young chicks that could not be identified to species.

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. Red squirrels made use of nearly all the purpose-built squirrel boxes, as well as some owl boxes and bird boxes. We found signs of red squirrel use in 62 boxes overall.

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.

Pipistrelle bats were found across the island, including a large maternity roost near Rose Cottage where more than 200 bats were seen emerging at dusk in May. Brown long-eared bats and natterer’s bats were also recorded in May and September. We also found noctule bats found in 4 boxes in September – an exciting result as none were seen last year.