I signed up for the British Trust for Ornithology’s Tawny Owl Point Survey. The BTO is concerned that tawny owl populations may have declined but it needs evidence from nocturnal surveys. This one is being done in selected areas, where BTO has carried out surveys in the past (most recently 1989 and 2005), so that it can monitor the changes.
The Chilterns are included so I opted for two tetrads in Buckinghamshire: SU89B near the village of Wheeler End, and SU89C immediately to the north, on the northern side of the A40. I am familiar with this area because it falls within my Ramblers’ path-checking parish of Piddington and Wheeler End.
The requirement is for at least two visits in each tetrad, preferably separated by less than a fortnight, within two hours of sunset, between 15 August and 15 October. You have to stand as near to the middle of your tetrad as you can, and listen for owls for two consecutive spells of ten minutes, recorded hoots and calls. From this you can estimate the number of territories in each tetrad.
Fortunately, with plenty of paths here, I could walk very close to the centre of my tetrads.
To reach the site for SU89B, I followed the footpath through the gate installed under the Chiltern Society’s Donate a Gate scheme, by the Ramblers’ Wycombe and District Group in honour of John Esslemont’s long service (grid reference SU805929).
I crossed a field
and went into Denham Wood, where I found a spot I would be able to identify again, where two beech-trees are growing close together.
On the first visit on 7 September I started at 20.06, and during both the first and second point counts heard one owl calling. My second visit was on 17 September (starting at 20.00). I heard one owl hooting during each count. I hope I haven’t mixed hoots and calls, but it can be quite difficult to distinguish them despite the helpful recordings on the BTO website. I think sometimes I was hearing young birds.
Matters were made more complicated by the constant chunterings, from pheasants I presume. When I walked back through the wood they flew noisily out of the trees.
The second tetrad to the north has conveniently at its centre a crossroads of footpaths: from Ham Farm to the south, Green End Farm to the west, Chorley Farm to the north and Great Cockshoots Wood to the east. I found a spot where the footpath goes through a gap in the hedge at the top of the hill, a good vantage point.
On my first visit, 1 September, I started at 20.28 and heard nothing in the first ten minutes, and then a call in the second. On my second visit, on 7 September at 21.03 (after visiting the Wheeler End tetrad), I heard one hoot in the second ten minutes; both times the owls were in Chawley Wood to the north.
So my conclusions so far are that there is one territory in each tetrad. I shall repeat the exercise in February or March, and again in autumn 2019 and spring 2020.
It is not too late to sign up for a tetrad, so take a look at the BTO website. Also, there is a tawny owl calling survey which starts from 30 September and is very flexible. As we have owls close to home I shall do that one too, from my doorstep.
It has been delightful on these warm autumn evenings to be out listening for owls.