Water and Wetland Bird Index Dataset

768

Observations

Series

Subjects

1975–2024

Period covered

What this looks like

One real series from the dataset, and real rows from the head of its published extract. Neither is a mock-up: the rows below are the same rows, unchanged, that are in the file you would download.

Water and wetland birds abundance index at United Kingdom

The longest single series this dataset holds — 48 annual values, one of 16. The dataset is not this chart.

Drawn to show the shape and resolution of what the dataset contains, not to make a point about United Kingdom. Gaps are breaks, never interpolated.

View the data behind this chart

Underlying data
Period	United Kingdom (index)
1975	103
1976	98.9
1977	102
1978	102
1979	94.4
1980	97.4
1981	99.5
1982	87.4
1983	85.8
1984	86.9
1985	89.3
1986	84.0
1987	85.5
1988	90.3
1989	94.6
1990	94.9
1991	87.1
1992	90.6
1993	91.0
1994	91.8
1995	108
1996	101
1997	95.1
1998	97.5
1999	101
2000	107
2002	108
2003	109
2004	106
2005	102
2006	103
2007	103
2008	108
2009	96.9
2010	104
2011	91.0
2012	91.6
2013	90.0
2014	93.9
2015	98.8
2016	101
2017	102
2018	89.8
2019	92.6
2021	96.3
2022	94.4
2023	98.3
2024	86.6

Sample rows

12 of 832 rows Taken from the start of observations-ecosystem-uk-defra-wild-birds.csv. These are sample rows, not the dataset.

Sample rows from the Water and Wetland Bird Index Dataset extract
`metric_id`	`subject_id`	`subject_kind`	`value`	`censored`	`censor_operator`	`censor_threshold`	`censor_limit`	`censor_reported`	`unit`	`period_start`	`period_end`	`period_kind`	`basis`	`confidence`	`source_id`	`source_ref`	`qualifier`	`superseded`	`retrieved`
bird-index-fast-flowing-water	country-gbr	geography	99.14	—	—	—	—	—	index	1975-01-01	1975-12-31	year	modelled	medium	uk-defra-wild-birds	Wild_bird_populations_in_the_UK_and_England.ods	—	—	2026-08-28
bird-index-fast-flowing-water	country-gbr	geography	101.64	—	—	—	—	—	index	1976-01-01	1976-12-31	year	modelled	medium	uk-defra-wild-birds	Wild_bird_populations_in_the_UK_and_England.ods	—	—	2026-08-28
bird-index-fast-flowing-water	country-gbr	geography	112.95	—	—	—	—	—	index	1977-01-01	1977-12-31	year	modelled	medium	uk-defra-wild-birds	Wild_bird_populations_in_the_UK_and_England.ods	—	—	2026-08-28
bird-index-fast-flowing-water	country-gbr	geography	114.96	—	—	—	—	—	index	1978-01-01	1978-12-31	year	modelled	medium	uk-defra-wild-birds	Wild_bird_populations_in_the_UK_and_England.ods	—	—	2026-08-28
bird-index-fast-flowing-water	country-gbr	geography	118.87	—	—	—	—	—	index	1979-01-01	1979-12-31	year	modelled	medium	uk-defra-wild-birds	Wild_bird_populations_in_the_UK_and_England.ods	—	—	2026-08-28
bird-index-fast-flowing-water	country-gbr	geography	121.29	—	—	—	—	—	index	1980-01-01	1980-12-31	year	modelled	medium	uk-defra-wild-birds	Wild_bird_populations_in_the_UK_and_England.ods	—	—	2026-08-28
bird-index-fast-flowing-water	country-gbr	geography	127.2	—	—	—	—	—	index	1981-01-01	1981-12-31	year	modelled	medium	uk-defra-wild-birds	Wild_bird_populations_in_the_UK_and_England.ods	—	—	2026-08-28
bird-index-fast-flowing-water	country-gbr	geography	110.45	—	—	—	—	—	index	1982-01-01	1982-12-31	year	modelled	medium	uk-defra-wild-birds	Wild_bird_populations_in_the_UK_and_England.ods	—	—	2026-08-28
bird-index-fast-flowing-water	country-gbr	geography	112.79	—	—	—	—	—	index	1983-01-01	1983-12-31	year	modelled	medium	uk-defra-wild-birds	Wild_bird_populations_in_the_UK_and_England.ods	—	—	2026-08-28
bird-index-fast-flowing-water	country-gbr	geography	114.52	—	—	—	—	—	index	1984-01-01	1984-12-31	year	modelled	medium	uk-defra-wild-birds	Wild_bird_populations_in_the_UK_and_England.ods	—	—	2026-08-28
bird-index-fast-flowing-water	country-gbr	geography	112.88	—	—	—	—	—	index	1985-01-01	1985-12-31	year	modelled	medium	uk-defra-wild-birds	Wild_bird_populations_in_the_UK_and_England.ods	—	—	2026-08-28
bird-index-fast-flowing-water	country-gbr	geography	99.12	—	—	—	—	—	index	1986-01-01	1986-12-31	year	modelled	medium	uk-defra-wild-birds	Wild_bird_populations_in_the_UK_and_England.ods	—	—	2026-08-28

Download these rows as CSV — the same twelve, with the column header, for testing a loader before committing to the full file.

Methodology

Collected from Defra’s official wild bird population statistics, published as a single OpenDocument spreadsheet under the Open Government Licence. The unsmoothed annual index is held for each group; the smoothed trend line published alongside is not, because it is a model with the year-to-year variation removed and it carries values for 2001 and 2020, when no survey took place. Tables are located by their published titles rather than by column position, so a table inserted upstream cannot shift a series into the wrong metric. Underlying schemes are the Breeding Bird Survey and the Common Birds Census for breeding groups and the Wetland Bird Survey for wintering groups.

What this dataset cannot tell you

Read before relying on these figures

An index is not a count and cannot be turned into one. Each series is 100 in its own first year and describes proportional change from that point; no population size can be recovered from it.
Levels are not comparable between indices. Wintering waterbirds stood at 195 in 2023 and water and wetland birds at 87 in 2024, which means one group roughly doubled from its 1975 level while the other fell — not that there are more of one than the other.
Each index is a composite of several species and can sit flat while some members collapse and others increase. The headline water and wetland index covers 26 species.
No value exists for 2001 or 2020. Foot-and-mouth disease closed the countryside in the first and the pandemic cancelled fieldwork in the second, so the surveys did not happen and the gaps are left as gaps. The publisher’s smoothed series does carry numbers for both years.
The published confidence intervals are not carried, because a Hydrionis series point holds a date and a value and has nowhere to put uncertainty.
Breeding indices are calendar years; the wintering indices run July to June and are labelled by the year they begin, so aligning the two, or either to a calendar-year hydrological record, is off by up to half a year.
Coverage is uneven across the UK. These are volunteer schemes, and upland and remote areas are less well surveyed than lowland England, so the national index is weighted rather than evenly observed.
The Wetland Bird Survey’s site-level counts are not held. They are available only through a data request service and are not openly licensed, so nothing here can be resolved to a particular wetland.

Coverage

Subjects	United Kingdom and England — 2 held
Period	1975–2024
Units	index
Update cadence	Annually
Identifier	`water-and-wetland-birds` v1.0.0

Fields

Data dictionary →

Every metric this dataset carries, with the unit it is stored in and the geography level it is reported at. Full definitions are in the data dictionary.

Identifier	Field	Unit	Reported at
`bird-index-water-and-wetland`	Water and wetland birds abundance index Abundance index for 26 species of water and wetland birds in the UK, relative to 1975 set to 100.	index	country
`bird-index-fast-flowing-water`	Birds of fast flowing water abundance index Abundance index for 4 species of birds of fast flowing water in the UK, relative to 1975 set to 100.	index	country
`bird-index-slow-standing-water`	Birds of slow and standing water abundance index Abundance index for 6 species of birds of slow and standing water in the UK, relative to 1975 set to 100.	index	country
`bird-index-wet-meadow`	Wet meadow birds abundance index Abundance index for 8 species of wet meadow birds in the UK, relative to 1975 set to 100.	index	country
`bird-index-reedbed`	Reedbed birds abundance index Abundance index for 4 species of reedbed birds in the UK, relative to 1975 set to 100.	index	country
`bird-index-wintering-waterbirds`	Wintering waterbirds abundance index Abundance index for 46 species and races of wintering waterbirds in the UK, relative to 1975/76 set to 100.	index	country
`bird-index-wintering-wildfowl`	Wintering wildfowl abundance index Abundance index for 31 species and races of wintering wildfowl in the UK, relative to 1975/76 set to 100.	index	country
`bird-index-wintering-waders`	Wintering wading birds abundance index Abundance index for 15 species and races of wintering wading birds in the UK, relative to 1975/76 set to 100.	index	country

Rights and access

Licence position

Open with attribution. Derivative use true; redistribution true; commercial reuse true.

Permitted uses

Public display
Derived analysis
API delivery
Bulk download
Commercial use

Available to: Public, Developer, Research, Professional, Enterprise. These follow from the rights of the contributing publishers, not from a Hydrionis pricing decision — no access tier can widen what a publisher withheld.

Contributing sources

Department for Environment, Food and Rural Affairs — Wild bird populations in the UK (Open Government Licence v3.0)

Attribution and citation

Cite and reuse →

Two different obligations, deliberately kept apart. One is a condition of somebody else's licence; the other is a request Hydrionis has no standing to enforce.

Attribution you are required to give

These are conditions of the licences the underlying data is published under. They are obligations to the publishers, not to Hydrionis, and they apply to you directly whether or not you mention Hydrionis at all.

Contains public sector information licensed under the Open Government Licence v3.0.

Department for Environment, Food and Rural Affairs — Open Government Licence v3.0 (licence text)

Suggested citation for Hydrionis

Hydrionis (2026), Water and Wetland Bird Index Dataset, version 1.0.0, accessed 2026-09-02, hydrionis.com/data/datasets/water-and-wetland-birds/

Cite Hydrionis where you rely on the compilation, the normalisation, the eligibility judgements or a chart. Where you use an unmodified published value, the publisher’s attribution is the one that is required; crediting Hydrionis as well is welcome and is not something Hydrionis can require of you.

Recommended, not required. Hydrionis does not claim rights over unmodified public data it relayed, and doing arithmetic on somebody else’s measurements does not make them Hydrionis’s. Cite the version and the access date: Water and Wetland Bird Index Dataset changes as publishers release and as methods are revised, and a citation without both cannot be checked later. Full guidance is on cite and reuse.

Changelog

Version 1.0.0 — 2026-08-28

First release.

Additions

Eight water and wetland bird indices for the UK and England, 1975 onwards.

Use this data

Download ecosystem observations from Defra (832 rows) (CSV)
Machine-readable JSON /api/v1/datasets/water-and-wetland-birds.json
How to cite this, and who you must credit
How these figures were produced
Request this at a different scale, format or geography

Every bulk extract ships with a companion metadata file carrying this dataset’s version, its sources, their licences, the attribution you are required to give and the suggested citation — so the terms travel with the file rather than staying on this page.

About this data

The fields a professional user needs to judge whether this is fit for a particular purpose. Deliberately not a score.

About this data

Everything below is a property of the data rather than a rating of it. There is deliberately no single confidence score: how much a gap matters depends on what you are about to do with the series, and only you know that.

Source	Department for Environment, Food and Rural Affairs — Wild bird populations in the UK · Open Government Licence v3.0
How the values came to exist	Mixed across the series — the basis is recorded on every individual value.
Period held	1975–2024
Known gaps	An index is not a count and cannot be turned into one. Each series is 100 in its own first year and describes proportional change from that point; no population size can be recovered from it. Levels are not comparable between indices. Wintering waterbirds stood at 195 in 2023 and water and wetland birds at 87 in 2024, which means one group roughly doubled from its 1975 level while the other fell — not that there are more of one than the other. Each index is a composite of several species and can sit flat while some members collapse and others increase. The headline water and wetland index covers 26 species.
Continuity	Version 1.0.0, released 2026-08-28. 1 recorded version; breaking changes and corrections are listed in the changelog above.
Last read from the publisher	2026-08-28 · publisher updates annually
Redistribution	Permitted by the upstream licences
Commercial reuse	Permitted by the upstream licences. No Hydrionis access tier can widen this.
Methodology	How this was produced