Trying to help Pied Flycatchers at Coed y Bedw, near Cardiff

Pied Flycatchers are a distinctive and attractive migratory bird which is very characteristic of open Welsh woodlands. They winter in sub-Saharan West Africa before making the long journey back to the UK in spring.

Pied flycatcher by Margaret Holland

Pied flycatcher by Margaret Holland

The species are Amber-listed in the UK due to a steep (25-50%) decline in their numbers between 1994 and 2009. It is not certain what the cause of the decline is but it could be changes to their wintering grounds or migration routes. Making conditions as ideal as possible in their breeding grounds would hopefully benefit the species by providing as many healthy new adults as possible to make the migration back in the autumn.

Pied Flycatchers breed on a number of our reserves across the patch; one of these is Coed y Bedw near Cardiff. The recently-retired former voluntary warden, Cliff Woodhead, has long been involved in a nest box monitoring scheme in the woodland, in which time he has noted a distinct decline in breeding pairs there (see Figure 1 below).

The species is a cavity-nester which shows a distinct preference for using nest boxes so the installation of these is an effective method of helping the species by providing nest sites which are relatively easy to monitor. As Figure 1 shows, the species reached a high of 20 breeding pairs in 1989 but hasn’t successfully bred at the reserve since 2010, despite there now being over 120 nest boxes of various sizes and materials on site.

Figure 1 Changes in numbers of breeding pairs of Pied Flycatchers at Coed y Bedw

Figure 1 Changes in numbers of breeding pairs of Pied Flycatchers at Coed y Bedw

Due to Cliff’s excellent work over the years, we have detailed information on where and when Pied Flycatchers have bred on the reserve so before the return of the birds in spring we set out to improve the species’ chance of breeding successfully here. Due to the SSSI status of the reserve we are unable to carry out extensive habitat management specifically for the species but we could alter their potential nesting habitat.

The first step was to use Cliff’s records to establish areas that the Pied Flycatchers have favoured over the years. Figure 2 below illustrates this with black dots representing boxes which have never been used by the species and red dots increasing in size depending on how frequently they had been occupied by Pied Flycatchers.

Figure 2 Pied Flycatcher nesting frequencies

Figure 2 Pied Flycatcher nesting frequencies

Using this information we decided to try to target some nest box manipulation for the species’ benefit. The species has been extensively researched and it has been found that they prefer new nest boxes with small (28mm) nest holes and that they also prefer nest boxes high up in the trees. One of the problems that the species also faces is that, due to their migratory nature, by the time they are looking to set up territories resident species, especially Blue and Great Tits, have already occupied the best sites.

Female Pied Flycatcher L Maiden

Female Pied Flycatcher L Maiden

All of this information led us to attempt a number of alterations: firstly, some new boxes were installed in the most favoured areas, some of the previously favoured boxes had the smaller nest box hole installed, some boxes were installed higher up in the trees than is standard and finally some of the box holes were blocked up (after ensuring they were empty!) until mid-April when the Pied Flycatchers begin returning from migration to prevent other species occupying them.

We will now be closely monitoring these boxes over the coming months in order to see whether any of these altered or new boxes are taken up by Pied Flycatchers. If so, we will try to expand any of the successful modifications across the reserve to try to give this charismatic species the best chance of establishing territories and increasing the breeding population on this site. If Pied Flycatchers do successfully breed this year, we will let you know!