Credits & licences

This guide is built on public datasets and on media that are free to use. Below, first where the data come from — the checklist, the family tree, the measurements, the habitats and the distribution maps — and then the full list of photographs and recordings, giving the author, the licence and the source page for each file. Nothing is used under a non-commercial licence.

Where the data come from

The guide rests on a handful of public datasets. They are gathered here, with what each contributes and on what terms.

• AviListCC BY 4.0

  The sequence and arrangement of orders, families, genera and species. AviList is the global checklist that since 2025 has been maintained jointly by the major lists — the IOC list, Clements and BirdLife — so that there is one list instead of three. This guide follows version 2025b.

• B10K and the PhyloCode

  The clades above the level of the order, shown in the tree and in the side menu. They follow the family-level genome tree of the Bird 10,000 Genomes project (Stiller et al. 2024) and carry names established under the PhyloCode — a system that names a branch of the tree rather than a rank.

• AVONETCC BY 4.0

  The wing length and weight of every species. Eleven measured traits for all 11,009 bird species in the world, built from measurements of 90,020 individual birds in museums and in the field (Tobias et al. 2022). The wingspan is estimated from the wing length; how that is done is explained further down.

• EUNIS

  The habitats. EUNIS is the habitat classification of the European Environment Agency; this guide uses the A–J version, with ten main groups from open sea to built-up land and a few dozen formations beneath them. Each bird carries only the habitats where it genuinely lives and feeds, at most seven.

• GBIFCC BY 4.0

  The distribution maps. GBIF gathers records from museums, ringing stations and observer networks into one searchable whole; the maps in this guide draw the density of those records, not a drawn range boundary. Records from the Low Countries largely arrive through Observation.org, which regularly passes its validated records to GBIF and is one of its largest publishers.

• EURING Bird Migration Atlas

  What the guide says about migration. The Eurasian-African Bird Migration Atlas (Spina et al. 2022, EURING and CMS) brings together a century of European ringing for three hundred species: lines from ringing site to recovery, by region, by month and by age, with tracking data alongside. The route described in a species text rests on it. It is not drawn on the map: the atlas shows that migration is a fan of dozens of lines with wide scatter, not a single arrow. The data themselves have not been reused — the atlas was consulted as a reference work.

• IUCN Red List

  The status of each species, from least concern to critically endangered. The category appears in the summary box and colours the badge.

• Wikimedia Commonsvrije licenties

  All photographs and most of the recordings. Every file is CC0, public domain, CC BY or CC BY-SA; non-commercial licences are not used. Author, licence and source page are listed per file below.

• xeno-cantovrije licenties

  The open archive of bird sounds, built by volunteers. Most recordings in this guide were made there and carry an XC number, including those that arrived by way of Wikimedia Commons. Only recordings under CC0, CC BY or CC BY-SA are used.

Readers' photographs

Anyone with a freely licensed photograph of a free-living wild bird that the guide still lacks can submit it. The rules and the form are on a page of their own. Submit a photograph

Which birds are in the guide

The map decides the guide. The window runs from the Azores to beyond the Bosphorus and from northern Norway to the northern edge of the Sahara, and that edge is the edge of the list as well: a bird that occurs only outside it is not here.

For mainland Europe the guide includes, first of all, everything that is present every year: breeding birds, winter visitors and passage migrants, however scarce. Being rare is no reason to leave a bird out; being irregular is.

A vagrant is included once it has turned up more than ten times in the past ten years, and left out below that. A 'time' here is not a record but an occurrence: a distinct combination of year, month and quarter-degree square, counted from the records in GBIF. One lingering bird that a hundred people came to see thus counts once, and an inconspicuous species is not penalised for drawing fewer observers. Below that line a bird belongs in a reference work, not in a guide you take into the field: the hermit thrush (nine occurrences) and the Siberian thrush (ten) are not here, while Swainson's thrush and the Tennessee warbler (twelve each) are. A vagrant gets no distribution map and no chick photograph: it does not breed within this window, so a map would suggest a range that does not exist.

That measure applies only to vagrants on the mainland. A scarce bird that genuinely belongs somewhere in the region is not judged against that threshold but against the question of whether it occurs there every year. Monteiro's storm petrel has just seven records inside the window and is nonetheless an ordinary Azorean breeding bird; the same holds for the Barbary partridge and the small buttonquail in Morocco.

For Macaronesia, the Maghreb and Israel only the first part applies: the species included are those that occur there annually and fall within the map window. Vagrants to those regions are left out; otherwise the list would fill up with birds from the Sahel and the Middle East that have nothing to do with Europe.

Svalbard and Bjørnøya lie above the top edge of the window, at 74–81°N. They therefore appear as two small panels in the top left corner of the map, in the same seasonal colours — but only for the forty-odd species that actually breed there. Species that merely pass through or winter there get no panel, and neither do the many songbirds that turn up lost in June. Each panel has its own scale; they are not drawn to the scale of the main map.

The count is an aid to the decision, not an official tally: GBIF is far better filled in north-western Europe than in the south-east, and an escaped cagebird counts just as heavily as a genuine vagrant.

Measurements: wing, weight and wingspan

The wing length and weight in each bird's summary box come from a single source: AVONET, a dataset of eleven measured traits for all 11,009 bird species in the world, built from measurements of 90,020 individual birds in museums and in the field. One source for every species, so that two birds in this guide can genuinely be compared. Wing length is the ringer's measurement: from the carpal joint — the bend halfway along the wing — to the tip of the longest primary. The weight is the mean of the birds weighed; a bird's weight varies a great deal over the year, so one figure says more here than a range from another source.

The wingspan is not in AVONET, nor in any other series of measurements: it is hardly ever taken from a living bird, and the figures in the handbooks are estimates that differ from book to book — by twenty per cent in the case of the roller. This guide therefore estimates it from the measured wing length, using a ratio calibrated per family. That ratio varies widely: in a swift, which is almost all hand, the wingspan is 2.6 times the wing length; in a grebe, with its long arm, 4.5 times. A check leaving each species out of its own calibration gives a median error of four per cent, with four in five species within ten per cent. Hence the c.: it is an estimate, and the guide would rather say so than print a precise-looking figure that the next handbook contradicts.

The bird's length does not come from AVONET but from the field guides, checked per species against its source.

• Tobias, J.A. et al. (2022), AVONET: morphological, ecological and geographical data for all birds. Ecology Letters 25, 581–597. CC BY 4.0.

The Red List categories

The status in each species' summary box is the global assessment of the IUCN Red List, as carried by AviList — not the European or a national Red List. A species on a national Red List can be “least concern” globally, and the reverse also occurs. The IUCN assesses every species against fixed criteria: rate of decline, size of range, population size and probability of extinction. The nine categories, from lowest to highest risk:

LC Least Concern

Assessed and not in any of the threatened categories: usually a widespread and numerous species.

NT Near Threatened

Does not currently meet the thresholds for Vulnerable but is close to them, or is expected to meet them in the near future.

VU Vulnerable

High risk of extinction in the wild: for example a decline of 30 percent or more over ten years or three generations, or fewer than ten thousand mature individuals.

EN Endangered

Very high risk: for example a decline of 50 percent or more, or fewer than 2,500 mature individuals.

CR Critically Endangered

Extremely high risk: for example a decline of 80 percent or more, or fewer than 250 mature individuals.

EW Extinct in the Wild

Survives only in captivity or as an introduced population outside its original range.

EX Extinct

There is no reasonable doubt that the last individual has died.

DD Data Deficient

There is too little information on distribution or population to assess the risk.

NE Not Evaluated

Not yet assessed against the criteria.

• IUCN (2012), IUCN Red List Categories and Criteria, version 3.1, second edition. The thresholds below are the outline; the full criteria are in that document.

The scientific name

At the foot of every species page stands the full zoological name: the species name, followed by whoever first described the bird and in what year. Where that author and year stand in brackets, the species has since been moved to a genus other than the one it was described in — the brackets are not a detail but a rule of the code of nomenclature, and the guide observes it.

The guide follows the arrangement and the naming of AviList. Author, year, the original name and the type locality come from its extended edition, which gives the first description and its locality for every species. The type localities have been shortened and rendered in present-day place names: 'in Europae apricis lapidosis' is simply Sweden here.

GBIF, the database behind the distribution maps and the Red List categories, is sometimes behind on naming or follows a different arrangement. For the fifty-eight species where that is the case, the GBIF name stands after it, without further explanation — enough to find the bird again in other sources.

The meaning of the names comes largely from the species accounts of the English Wikipedia, and above all from the passages that cite Jobling, The Helm Dictionary of Scientific Bird Names; where those were missing, the name is explained straight from the Latin or the Greek. Some of the species are still waiting for a second check.

• AviList Core Team (2025), AviList: The Global Avian Checklist, version 2025b, extended edition. — Jobling, J.A., The Helm Dictionary of Scientific Bird Names, cited through the Wikipedia species accounts.

Arrangement and sequence

The arrangement and sequence of orders, families, genera and species follow AviList, the unified global checklist of the birds maintained jointly by the major checklists. Above the level of the order stand clades: those follow the family-level genome tree of the B10K project and carry names from the PhyloCode.

• AviList v2025b
• Stiller et al. 2024, Nature 629, 851–860 (B10K)

Texts

The texts on this site were written for this guide. Factual data on measurements, distribution and status draw on standard field guides and the IUCN Red List.

Typeface

The running text is set in IBM Plex Sans, the headings in Cormorant Garamond and the small labels in IBM Plex Mono — the typefaces of vorstman.com. Only the title of each page is set in Antonio, a narrow, tall grotesque in the spirit of the classic field guide covers. All four are under the SIL Open Font License 1.1 and are served from this site itself, so no request goes to an outside server.

The maker