Productivity in nest boxes at Townthwaite Beck

My Pied Flycatcher next boxes are in a north-facing limestone ghyll woodland overlooking the Solway near the Caldbeck mast. The site is cold and exposed at 250 metres, with westerly winds blowing across the face of the hill. There are currently 31 boxes, and I have been observing and ringing there for ten years now. On average, I usually have about 12 Pied Flycatcher nests, with variable numbers of Blue and Great Tits.

The 2000 and 2001 seasons were poor with a very high casualty rate, only 10 flycatcher chicks being fledged in 2001.

From the start of 2002, things did not look good, with only 15 boxes occupied by my second round of visits, of which only four were by Pied Flycatchers. Blue Tit numbers were also down to three, although Great Tits were about the usual eight nests.

With nice weather in early April and May things looked promising. However, from mid-May the weather turned cool and wet and stayed that way for the rest of the breeding period. Consequently one Pied Flycatcher deserted eggs, and of the three which hatched young, only one nest box fledged a full brood of seven, a second box fledged three out of seven, and in the fourth box all eight chicks died at about ten days old. The Blue Tits had mixed fortunes, with one desertion following a very wet day, although both the remaining broods fledged about seven chicks. The Great Tits also did badly, with all six boxes on the west side of the ghyll losing all their chicks. The two more sheltered boxes fledged all chicks.

The low productivity at this site appears to be a problem of altitude and exposure, because there were no problems in any of my boxes or hole-nesters at Finglandrigg Wood, where occupancy and fledging rate was again very high. The problem in 2001 was not all due to the weather as several boxes were predated, probably by Great Spotted Woodpecker. At least three male Redstarts were on territory and one, possibly two, Nuthatches.

Frank Mawby