SOS Survey Strategy
Updated: June 2026
Martin Flores & James Aldridge (Surveys & Projects Officers), Ken Smith & Mark Mallalieu
Background
The SOS continues to have an excellent track record in supporting national bird surveys and following its own programme of surveys. Recently completed surveys are in Table 1 below. The SOS organises the annual Sussex Winter Bird Survey, which is coordinated by Christine George (sussex.wbs@gmail.com) and supports ongoing annual surveys such the Wealden Heaths Breeding Bird Surveys (WHBBS) and South Downs Farmland Bird Surveys. The information below does not cover these or the regular BTO surveys such as the Breeding Bird Survey (BBS) and the Wetland Bird Survey (WeBS) – see the SOS and BTO websites for further details or contact the Sussex BTO representative Dr Helen Crabtree (hcrabtree@gmail.com) on BBS and WeBS inland sites and Dave Boddington (davebodds@yahoo.co.uk) for coastal and estuary sites. Helen is also the contact for the South Downs Farmland Bird Survey and other BTO surveys including Woodcock and heronries. Alan Perry (aledgehill@outlook.com) leads on the WHBBS.
Table 1. Recent surveys completed by SOS/BTO volunteers. Note all species are colour coded in the tables according to their Birds of Conservation Concern 5 (BoCC) status – red, amber and green.
| Year | Species/group | Narrative |
|---|---|---|
| 2020 | Honey-buzzard Marsh Tit | SOS survey completed in 2021 As above |
| 2021 | Chiddingfold Forest Turtle Dove National seabird census Breeding Waders of Wet Meadows | Joint with Surrey Bird Club. Started 2021, completed 2022. Turtle Dove & Nightingale RSPB survey Urban gull survey completed in 2022 National BTO/RSPB survey of LWG waders – Lapwing, Redshank and Snipe. Completed 2022. |
| 2022 | Nightingale | SOS survey completed |
| 2023 | Nightjar | SOS survey completed |
| 2023 | Woodcock | National BTO survey completed |
| 2024 | Corn Bunting | SOS survey completed |
“Stanbury, A., Eaton, M., Aebischer, N., Balmer, D., Brown, A., Douse, A., Lindley, P., McCulloch, N., Noble, D. & Win I., 2021. The status of our bird populations: the fifth Birds of Conservation Concern in the United Kingdom, Channel Islands and Isle of Man and second IUCN Red List assessment of extinction risk for Great Britain. British Birds, 114, pp.723–747.”
| Year | Species/group | Narrative |
|---|---|---|
| 2023/24 & 2024/25 | Wintering gulls | BTO national survey (WinGS) was completed. The primary aim was to obtain new population estimates for the principal gull species that winter in the UK and assess how populations have changed since the last survey in 2003/04–2005/06. |
| 2025 | Heathland Birds Survey | BTO survey completed. |
| 2026 | Lesser Spotted Woodpecker | Survey using passive acoustic recorders in sample of monads with wet woodland. |
Survey Strategy
In October 2023 a subgroup of the SOS Scientific Committee met to update the SOS surveys strategy. This group consisted of Pete Hughes, Ken Smith and Mark Mallalieu. The 2025 strategy was then reviewed in January 2026, alongside previous surveys in Sussex Bird Reports back to 2001, and with consideration of possible priorities for future survey by James Aldridge, Martin Flores, Mark Mallalieu and Ken Smith. A further update was made in June 2026. The revised programme of surveys, up to winter 2027/28 at the start of the next BTO Atlas 2027-2031 survey period, is shown in Table 2.
This list forms a framework but is brought to the Scientific Committee annually for consideration and to ensure it continues to fit in with national surveys. We will also consider whether any species should be added or removed from the list, for example a species that had declined to the extent that it dropped off the BTO BBS trends would be a strong candidate for addition.
The species proposed in Table 2 are those which we believe are suitable for surveys using SOS volunteers. Some additional notes on the proposed groups and species are included in the table. It is suggested that species surveys are repeated on a roughly ten-year cycle.
Table 2. SOS surveys up to the next BTO atlas period.
| Year | Species | Narrative |
|---|---|---|
| 2026 | House Martin | Last BTO survey 2015. The 2026 methods involve one reconnaissance visit in mid to late-May and two further visits in June and July. The survey has been designed to sample 182 1km squares, all of which have supported Occupied Nests of house martin previously. By targeting known sites, it will likely be more enjoyable for surveyors with less nil returns, track abundance at previously monitored nests, as well as potentially provide a more accurate minimum count of known Occupied Nests for the county. |
| 2026 | Hawfinch | Trial survey using passive acoustic recorders attached to well-fruiting cherry trees in June to test viability as a technique for surveying species where it occurs at low densities. |
| 2027 | Rook | County rook surveys completed 1975, 1996 & 2011. Some coverage by BBS, but separate survey to count rookeries should be an attractive option for membership. An early season (March/early April) survey. |
The BTO will be organising the next national atlas from the winter of 2027/28. In coordination with the BTO representative, SOS will aim to ensure that there are Timed Tetrad Visits (TTVs) to all tetrads in the county in the breeding season and in winter with a view to producing a new Avifauna, either printed or online, or some combination.
The SOS should pause most or all other single species survey work during the next Atlas but will include special survey design measures for certain species, e.g. those hard to detect and/or are most easily detected outside the main survey periods, such as Goshawk, Long-eared Owl and Hawfinch. These special measures will be detailed in the County Atlas Survey Strategy where considered necessary to complement the BTO methodology (which is expected to include some new techniques, such as use of passive acoustic monitoring, which will help in detection of some of these species).
The 2025 Tree Pipit survey was not fully completed, unfortunately, and this remains on the agenda for future surveys. It is likely that this species will be included in the special measures of the Atlas, to detect singing birds during the breeding season.
Whilst moderately difficult to detect, Spotted Flycatcher, is a declining and red listed bird of conservation concern, and has not been subject to county survey in the reviewed period from 2001. The Birds of Sussex did not provide a population estimate of this species. A July visit to detect family groups or recently fledged young, as well as ideally an earlier visit from end of May to June, would likely increase detectability of Spotted Flycatcher, particularly if sampling areas known to have supported previous breeding. This would aim to inform population trends and potentially a population estimate for the county.
Issues and species meriting further investigation
It may be possible to use the SOS database to monitor trends and estimate population size for a few species thus reducing the priority they might otherwise merit for single species surveys.
Martin Flores
James Aldridge
Ken Smith
Mark Mallalieu
June 2026
