The BOS covers a diverse range of habitats, from low level floodlands of the river Cherwell to the heights of Edge Hill and the Cotswolds. It also spans three major river systems of England - the Thames, Severn and Great Ouse. For a map of the area, see BOS area map.
As part of our fieldwork, we publish a detailed map showing the locations of recommended bird watching sites - see BOS Sites. The names of the sites are given in the BOS Guide for Observers.
Note that the BOS area will be affected by the construction of HS2 - see this article for details: HS2 Route Across the BOS.
The table below lists the top 10 sites ranked by the number of species observed, for the years 2007-2016. Many of these sites are reserves managed by the BOS and most are associated with water. Our reserves are listed here: BOS Reserves.
| Grid | Number of Species | Site Name | |
| 1 | SP4542 | 148 | Grimsbury Reservoir |
| 2 | SP4953 | 145 | Boddington Reservoir |
| 3 | SP3942 | 143 | Balscote Quarry |
| 4 | SP4451 | 139 | Wormleighton Reservoir |
| 5 | SP5721 | 119 | Bicester Wetland Reserve |
| 6 | SP4643 | 112 | Upper Cherwell Valley |
| 7 | SP3226 | 96 | Glyme Farm |
| 8 | SP4541 | 95 | Spiceball Country Park |
| 9 | SP4249 | 94 | Farnborough Park |
| 10 | SP3558 | 91 | Chesterton Pools |
The picture below shows the species density for each 1km square of the BOS area for the years 1982-2019 - the shading of the square reflects the number of species recorded. The figures in each square show the number of species recorded at that location. The numbers on the outside are the OS 1km grid references for the 100km square SP, shown as Eastings and Northings, just as they are on Ordnance Survey maps. The map shows there are many other good locations to observe birds, including the whole of the Cherwell valley.
