Surveillance collection thresholds for dead wild birds
Updated 29 September 2023
Applies to England, Scotland and Wales
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The Animal and Plant Health Agency (APHA) carries out year-round surveillance for highly pathogenic avian influenza (HPAI) in dead wild birds in Great Britain. This is part of their wild bird surveillance programme.
APHA investigates causes of unusual mortality other than HPAI in wild birds through the Diseases of Wildlife Scheme (DoWS) and Great Britain Wildlife Health Partnership (GBWHP).
They collect wild birds following reports from the public and warden patrols. All dead birds in Great Britain can be reported.
APHA triages reports and does not collect all birds. They will only collect birds:
- if the numbers reported meet the ‘collection threshold’ for each species group
- within their other collection limits
The collection threshold is the minimum number of dead birds that must be reported before APHA will collect carcases. The thresholds apply to birds reported in the same place.
APHA adjusts the thresholds to increase or decrease the sensitivity of the surveillance programme. England, Scotland and Wales set separate collection thresholds to adjust the sensitivity on a regional basis.
This document outlines the collection threshold for each species on dates when they have changed.
You should consider these collection thresholds and other limits set by APHA when reviewing the findings of HPAI in wild birds. The collection thresholds can affect the number of dead wild birds that APHA collects and therefore tests.
A separate collection threshold for birds of prey was first introduced on 29 December 2016.
England: collection thresholds
APHA is currently using the thresholds set on 29 September 2023.
| Date of threshold change | Birds of prey | Swans | Geese | Ducks | Gulls | Other wild birds |
|---|---|---|---|---|---|---|
| 29 Sept 2023 (week 39) |
1 | 1 | 1 | 1 | 1 | 5 |
| 1 Sept 2023 (week 35) |
1 | 1 | 1 | 1 | 5 | 5 |
| 12 July 2023 (week 28) |
1 | 1 | 1 | 1 | 5 | 5 |
| 15 Feb 2023 (week 7) |
1 | 1 | 1 | 1 | 1 | 5 |
| 8 Feb 2023 (week 6) |
1 | 3 | 3 | 3 | 5 | 5 |
| 12 Dec 2022 (week 50) |
1 | 5 | 5 | 3 | 3 | 5 |
| 4 July 2022 (week 27) |
1 | 3 | 3 | 3 | 3 | 5 |
| 25 Mar 2022 (week 12) |
1 | 1 | 1 | 1 | 1 | 5 |
| 6 Dec 2021 (week 49) |
1 | 3 | 3 | 3 | 3 | 5 |
| 4 Nov 2020 (week 45) |
1 | 1 | 1 | 1 | 1 | 5 |
| 9 July 2018 (week 28) |
1 | 3 | 3 | 3 | 3 | 5 |
| 29 Dec 2016 (week 52) |
1 | 1 | 1 | 1 | 1 | 5 |
| 7 Dec 2016 (week 49) |
No threshold | 1 | 1 | 1 | 1 | 5 |
Scotland: collection thresholds
APHA is currently using the thresholds set on 29 September 2023.
| Date of threshold change | Birds of prey | Swans | Geese | Ducks | Gulls | Other wild birds |
|---|---|---|---|---|---|---|
| 29 Sept 2023 (week 39) |
1 | 1 | 1 | 1 | 1 | 5 |
| 1 Sept 2023 (week 35) |
1 | 1 | 1 | 1 | 5 | 5 |
| 12 July 2023 (week 28) |
1 | 1 | 1 | 1 | 5 | 5 |
| 15 Feb 2023 (week 7) |
1 | 1 | 1 | 1 | 1 | 5 |
| 8 Feb 2023 (week 6) |
1 | 1 | 1 | 1 | 5 | 5 |
| 12 Dec 2022 (week 50) |
1 | 3 | 3 | 3 | 3 | 5 |
| 4 July 2022 (week 27) |
1 | 3 | 3 | 3 | 3 | 5 |
| 25 Mar 2022 (week 12) |
1 | 1 | 1 | 1 | 1 | 5 |
| 6 Dec 2021 (week 49) |
1 | 1 | 1 | 1 | 1 | 5 |
| 4 Nov 2020 (week 45) |
1 | 1 | 1 | 1 | 1 | 5 |
| 9 July 2018 (week 28) |
1 | 3 | 3 | 3 | 3 | 5 |
| 29 Dec 2016 (week 52) |
1 | 1 | 1 | 1 | 1 | 5 |
| 7 Dec 2016 (week 49) |
No threshold | 1 | 1 | 1 | 1 | 5 |
Wales: collection thresholds
APHA is currently using the thresholds set on 29 September 2023.
| Date of threshold change | Birds of prey | Swans | Geese | Ducks | Gulls | Other wild birds |
|---|---|---|---|---|---|---|
| 29 Sept 2023 (week 39) |
1 | 1 | 1 | 1 | 1 | 5 |
| 1 Sept 2023 (week 35) |
1 | 1 | 1 | 1 | 1 | 5 |
| 12 July 2023 (week 28) |
1 | 1 | 1 | 1 | 5 | 5 |
| 15 Feb 2023 (week 7) |
1 | 1 | 1 | 1 | 1 | 5 |
| 8 Feb 2023 (week 6) |
1 | 1 | 1 | 1 | 5 | 5 |
| 12 Dec 2022 (week 50) |
1 | 3 | 3 | 3 | 3 | 5 |
| 4 July 2022 (week 27) |
1 | 3 | 3 | 3 | 3 | 5 |
| 25 Mar 2022 (week 12) |
1 | 1 | 1 | 1 | 1 | 5 |
| 6 Dec 2021 (week 49) |
1 | 1 | 1 | 1 | 1 | 5 |
| 4 Nov 2020 (week 45) |
1 | 1 | 1 | 1 | 1 | 5 |
| 9 July 2018 (week 28) |
1 | 3 | 3 | 3 | 3 | 5 |
| 29 Dec 2016 (week 52) |
1 | 1 | 1 | 1 | 1 | 5 |
| 7 Dec 2016 (week 49) |
No threshold | 1 | 1 | 1 | 1 | 5 |
Highly pathogenic avian influenza (HPAI) risk level and strain
The following table outlines the HPAI risk level and strain detected in the wild bird population in Great Britain on dates of threshold change.
| Date of threshold change | HPAI wild bird risk level | HPAI strain |
|---|---|---|
| 29 Sept 2023 (week 39) |
High | H5N1 |
| 1 Sept 2023 (week 35) |
High | H5N1 |
| 12 July 2023 (week 28) |
High | H5N1 |
| 15 Feb 2023 (week 7) |
Very high | H5N1 |
| 8 Feb 2023 (week 6) |
Very high | H5N1 |
| 12 Dec 2022 (week 50) |
Very high | H5N1 |
| 4 July 2022 (week 27) |
Medium | H5N1 |
| 25 Mar 2022 (week 12) |
Very high | H5N1 |
| 6 Dec 2021 (week 49) |
Very high | H5N1 |
| 4 Nov 2020 (week 45) |
High | H5N8 |
| 9 July 2018 (week 28) |
Low | H5N6, H5N8 |
| 29 Dec 2016 (week 52) |
High | H5N8 |
| 7 Dec 2016 (week 49) |
Medium | H5N8 |
H5N1 and H5N5 were later detected in wild birds during winter 2020 to 2021.
Other collection limits
If a collected dead wild bird tests positive for HPAI, APHA will not normally collect more wild birds from the same location for 14 days. The same location is defined as within 3 kilometres of the reported wild bird.
APHA will only collect a maximum of 5 birds from the location of a mass die-off.
Testing becomes unreliable as carcases decompose. APHA will not collect carcases once 4 days have passed since the report.
The collection thresholds do not apply to reports of dead wild birds made:
- through the Wildlife Incident Investigation Scheme (WIIS), which investigates death or illness of wildlife that may result from pesticide or rodenticide poisoning
- as part of a report of wildlife crime