by Anna Field (January 2023)
Last winter I was asked to estimate the number of breeding pairs of Red Kite Milvus milvus in the North Cotswolds for a presentation being given by Andrew Bluett. From a back of an envelope calculation based on breeding sites known to me and other local birders and suitability of habitat, I suggested there to be 100 breeding pairs of Red Kite in the thirteen 10km Ordnance Survey squares which make up the North Cotswolds. This generated some discussion amongst county birders, in part because of the lack of records submitted to the county recorder and in part because they only colonised the area around a decade ago, with the first confirmed attempted breeding recorded in 2012 on the National Trust’s Sherborne Park Estate (although earlier breeding attempts were suspected).
In order to derive a more reliable population estimate for the area, in the spring/summer of 2022 I set out to census (i.e. find all) breeding pairs of Red Kite in one 10km square, which could then be extrapolated to give a population estimate for the whole area. I selected SP11 as it is my local square and was easiest for me to survey comprehensively. In total I located 13 active nests, plus a 14th site near Windrush which is usually used but was not this year for some unknown reason. Seven nests were at sites where I had known them to breed in previous years. Three further sites were located by specifically surveying farm copses and woodlands in SP11 for Red Kite. One new site was discovered whilst carrying out a breeding bird survey for a local farm. One nest was discovered whilst watching my son play cricket as an adult Red Kite disappeared into some poplars on the edge of Bourton-on-the-Water carrying prey. The final nest was perhaps the most interesting find – I was checking on the Red Kite nest near Sherborne to estimate the age of the chicks for ringing and as I walked out of the woodland I happened to pass under the old nest used in the previous year. As I looked up, I was amazed to see three large chicks perched on the edge of the nest, almost ready to fledge. The nests were less than 200m apart – certainly the closest I’ve known them to nest. All chicks from both nests fledged successfully.
Figure 2 shows the approximate (but not exact) location of the 13 nests, plus the unoccupied Windrush site. Looking at the distribution of maps and knowing the landscape, I think it is quite possible that I have missed a 15th nest site to the south/east of Cold Aston. I have also shown the approximate location of three nest sites just outside SP11 which I happened upon by chance (although I did not thoroughly survey outside the boundary).
The North Cotswolds recording area consists of thirteen 10km squares (SO90, SO91, SO92, SP00, SP01, SP02, SP03, SP10, SP11, SP12, SP13, SP22, SP23), the majority of which are made up of similar habitat to SP11 and all of which are known to hold breeding Red Kite (with nearly 50 sites known, the majority of which have been located by chance during other surveys/activities by me or other local birders). To estimate the total number of breeding pairs in the North Cotswolds, an area equal to one 10km square was disregarded on the assumption that there would be few breeding pairs within urban areas such as Cheltenham and Cirencester. Otherwise, it was considered that the remaining area all consisted of suitable habitat for breeding Red Kite, with a mix of farmland for foraging and woodland/copses for nesting, and so each remaining 10km square is likely to hold 10-15 pairs of breeding Red Kite. The eastern squares are likely to hold slightly higher numbers than the western squares as these were colonised first from the Chilterns reintroduction. The whole North Cotswolds area is therefore estimated to hold between 120-180 breeding pairs of Red Kite. The North Cotswolds makes up approximately half of Gloucestershire but as the other parts of Gloucestershire are further from the reintroduction site and contain less suitable habitat for Red Kite, breeding numbers outside the North Cotswolds are currently much lower – but may well increase in time.