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Pied Flycatcher

                                            

Strid Wood

Strid Wood straddles the River Wharfe in a deep sided valley cutting through the Milstone Grit and Carboniferous Limestone of the Skipton Anticline between Bolton Abbey and Barden. Situated at an altitude of 110 metres, the woodland covers some 146 hectares and contains the largest area of acidic Oak woodland and the best remnant Oak wood pasture in the Yorkshire Dales National Park. Designated as a Site of Special Scientific Interest (SSSI) in 1985, the woodland has long been noted amongst naturalists for its botanical interest, including lichens, and the diversity of its birdlife.

Nest boxes were first introduced to the east bank of the River Wharfe in Strid Wood in 1989, between Posforth Bridge and the upper extremity of the wood below the Barden aqueduct, when 21 boxes were erected. Fourteen of these were of the Small Hole type and introduced to encourage the nesting of Pied Flycatchers. By 1993 the numbers of this type of nest box had been increased to 52.  
In 1999, boxes were introduced for the first time to the woodland on the west bank of the river in the vicinity of Strid Cottage, where 17 Small Hole boxes were installed. This number was subsequently increased to 22 in 2002. All the nest boxes were positioned on the north side of suitable mature Oaks with the exception of three, which were attached to mature Sycamores. Where practical, boxes were placed away from paths at a height of three metres and any branches below the boxes were removed to minimise disturbance and to avoid any likelihood of vandalism. Due to the narrowness of the woodland and the outcropping of rock, some boxes were inevitably located close to the paths but experience has shown that the vast majority of visitors fail to see them and disturbance has been minimal.

Although some monitoring of boxes was undertaken between 1989 and 1996 for the express purpose of ringing the chicks, it was not until 1997 that details of clutch size and hatching and fledging success were undertaken as part of the BTO nest record scheme. It was in 1997 that the ringing of both chicks and adult Pied Flycatchers trapped at the nest commenced.

Table 1 provides a breakdown of the number of nest boxes that have been available each year and the number and percentage of those occupied by Pied Flycatchers. The majority of the remaining boxes are occupied by Blue Tits, Great Tits and occasionally Nuthatch. Although there are a number of pairs of Redstart breeding in the wood each year, only on one occasion have they utilised one of the nest boxes. In any one year there are also a small number of nest boxes which remain unoccupied.

No adults or pulli were ringed in 2007 but there were 12 males singing at nest boxes at the start of the season.

	Year
	97	98	99	00	01	02	03	04	05	06	07	08
Boxes available	51	51	68	68	68	73	73	74	74	74	74	74
Boxes occupied	8	14	14	18	12	22	19	15	10	12	10	15
% occupied	15.7	27.5	20.6	26.4	17.6	30.1	26.0	20.2	13.5	16.0	13.5	20.3

Table 1. The number of nest boxes available and occupancy rates at Strid Wood 1997 - 2008
Note: Information for all occupied nest boxes in 2001 not available due to foot and mouth restrictions

Over the years 1989 to 1996 the prime objective was to ring the chicks. Nest boxes were examined each spring to check for the presence of Pied Flycatchers. If birds were incubating they were not disturbed and nests were not revisited until the presence of chicks was indicated by the feeding activity of the adults. Consequently a full set of data of clutch sizes and hatching success is not available. With the commencement of the trapping of adult birds in 1997, the decision to monitor the nests in more detail was taken as part of the BTO nest record scheme.

The majority of Pied Flycatchers (88.5%) laid clutch sizes of between six and eight eggs, with clutch sizes of seven occurring most frequently (43.4%). The overall mean clutch size was 7.0 for the range 2 to 9. The mean number of young per successful pair was 6.0 for the range 1 to 9, with annual mean figures varying between 5.2 and 6.6 per successful pair.

         
Pied Flycatcher nestlings                                    Ringing a chick

There appeared to be no correlation between frequency with which individual nest boxes were used and the number of fledged young.

No. adults	No. Pulli	Total	Re-trapped	Recovered
146	661	807	96	7

Table 2: Ringing, retrap and recovery totals for Strid Wood 1997 - 2008

The number of birds re-trapped includes a number which were caught on more than one occasion, often at the same nest box in consecutive years. The longest recorded use, to date, is four years. A proportion of Strid Wood ringed pulli also subsequently return as adults to breed.

The decline in the number of Pied Flycatcher pairs would appear to have bottomed out at 10 to 12 pairs although the small number of fledged chicks, due mainly to the weather, gives cause for concern regarding the long term future. Things improved in 2008 with 14 pairs rearing 93 chicks.

The most interesting recovery was a bird ringed as a pullus on 12th June 1999 which was recovered in Doiras Cervantes, Lugo, Spain on 22nd August as a road casualty. The bird had travelled a distance of 1294km over a period of 71 days.

West Tanfield

 

Year	New (adult)	Pulli	Retraps	Controls
1998	4 (1 )	20 (4)	2	-
1999	2 (2)	7	1	-
2000	4 (3)	19	2	-
2001	1	24	4	1 (5)
2002	1	16	3	-
2003	0	0	0	-
2004	0	14	3	-

(1) One male running two sites  (2) One adult not caught  (3) Two adults not caught  (4) Three later dead  (5) Barningham Co. Durham