Sources

• Natural Earth

  Country and region boundaries, lakes, river courses

  Public domain

• Copernicus DEM (GLO-30 / GLO-90)

  Elevation data for the country and region maps, and for refining the temperature layer on them

  Produced using Copernicus WorldDEM™-90 and Copernicus WorldDEM-30 © DLR e.V. 2010-2014 and © Airbus Defence and Space GmbH 2014-2018 provided under COPERNICUS by the European Union and ESA; all rights reserved. The organisations in charge of the Copernicus programme by law or by delegation do not incur any liability for any use of the Copernicus WorldDEM™-90 or the Copernicus WorldDEM-30.

• Copernicus Sentinel-2

  Land outline and synthetic elevation for the atoll maps of Tuvalu and Kiribati

  Contains modified Copernicus Sentinel data 2015–2026

• ETOPO 2022

  Elevation and bathymetry for the globe, the world map and the ocean floor, and the maps of Antarctica, Greenland, Alaska, Svalbard, Russia, Panama and the Azores

  Public domain (NOAA National Centers for Environmental Information)

• TerraClimate

  Monthly mean air temperature 1991–2020 for the climate layer on the globe and the country maps (Abatzoglou et al. 2018, Scientific Data 5, 170191). On country and region maps refined from about 4 km to 1–2 km with the Copernicus DEM, using the monthly decrease of temperature with elevation

  Public domain (CC0)

• HydroSHEDS / HydroRIVERS

  The river network drawn on each map

  Free to use with attribution (WWF)

• GeoNames

  City names, populations and marker positions

  CC BY 4.0

• geoBoundaries

  Administrative boundaries below national level

  CC BY 4.0

• OpenStreetMap (via Nominatim)

  Selected city outlines for Munich, Berlin and Hamburg

  © OpenStreetMap contributors, Open Database License (ODbL)

• GHS Urban Centre Database (R2024A V1.2)

  Urban area outlines worldwide, selected from centres with at least one million inhabitants in 2025 and generalised for display. Selected outlines use OpenStreetMap or US Census boundaries. In Bihar and Kerala, diffuse population clusters are omitted or restricted to compact built-up cores.

  © European Union, European Commission, Joint Research Centre (JRC). Reuse authorised with acknowledgment of the source.

• US Census Bureau — corrected 2020 Census Urban Areas

  Dallas–Fort Worth and Houston urban outlines, generalised from the 1:500,000 cartographic boundaries

  Public domain (US Census Bureau)

• GHSL — Global Human Settlement Layer

  Population grid behind the “people affected” figure; GHS-BUILT-S R2023A building surface for refining selected Indian city outlines (2020, 100 m)

  CC BY 4.0, European Commission, Joint Research Centre

• INDEC — Censo Nacional de Población, Hogares y Viviendas 2022

  Population of the Argentine provinces, used to scale the “people affected” figure on their maps (figures as tabulated in the Spanish Wikipedia article on the 2022 census, CC BY-SA 4.0)

  Creative Commons, reproduction permitted with attribution (Instituto Nacional de Estadística y Censos, Argentina)

• Wikipedia — Provinces of Turkey

  Population of the 81 Turkish provinces (estimates for December 2021, originally from TurkStat), summed to the twelve statistical regions to scale the “people affected” figure on their maps

  CC BY-SA 4.0

• Office for National Statistics — mid-2025 population estimates

  Population of the nine regions of England, used to scale the “people affected” figure on their maps (figures as tabulated in the Wikipedia article “Regions of England”)

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

• Wikipedia — Oblasts of Ukraine

  Population of the 24 Ukrainian oblasts (2022), Kyiv city counted with Kyiv Oblast, used to scale the “people affected” figure on their maps

  CC BY-SA 4.0

• EOD — eBird Observation Dataset (Cornell Lab of Ornithology), via GBIF.org

  Animal migration: reports with counts, 2015–2024, set against all bird reports of the same place and week. White stork: 500,000 reports in Europe and Turkey (GBIF Occurrence Download https://doi.org/10.15468/dl.qzwcas). Snow goose: https://doi.org/10.15468/dl.j2jbcw. Sandhill crane: https://doi.org/10.15468/dl.rg29df. Canada goose: https://doi.org/10.15468/dl.nyj655. Rufous hummingbird: https://doi.org/10.15468/dl.8vg7xa. Tree swallow: https://doi.org/10.15468/dl.n28eme. Demoiselle crane: https://doi.org/10.15468/dl.q4feb3. Bar-tailed godwit: https://doi.org/10.15468/dl.hvr6wu. Broad-winged hawk: https://doi.org/10.15468/dl.35np4z. Barn swallow: https://doi.org/10.15468/dl.enum2s (with the datasets below). Common swift: https://doi.org/10.15468/dl.dguqfr (with the datasets below). Common crane: https://doi.org/10.15468/dl.gxp8bk (with the datasets below). Amur falcon: reports of the species and of all birds per area and day from the GBIF occurrence API (with the Southern African Bird Atlas Project 2, accessed 6 November 2026), without counts. Own analysis and migration model; not endorsed by the Cornell Lab of Ornithology, GBIF or the other data publishers

  CC BY 4.0

• Movebank Data Repository

  White stork migration in Africa: GPS tracks of 400 storks (1991–2023) from Flack et al. 2015 (doi:10.5441/001/1.78152p3q), Berthold et al. (doi:10.5441/001/1.k29d81dh), Fiedler et al., LifeTrack Oberschwaben (doi:10.5441/001/1.c42j3js7_2) and Bavaria (doi:10.5441/001/1.v1cs4nn0_2), Maxhuni et al., Kosova (doi:10.5441/001/1.s367rd3k), Grasso et al., Sicily (doi:10.5441/001/1.4v8q16qf), Acácio et al. 2023, Portugal (doi:10.5441/001/1.137cn005)

  CC0 1.0

• Artportalen (SLU Artdatabanken), via GBIF.org

  Common crane, barn swallow and common swift migration: bird reports from Sweden, part of GBIF Occurrence Downloads https://doi.org/10.15468/dl.gxp8bk, https://doi.org/10.15468/dl.enum2s and https://doi.org/10.15468/dl.dguqfr

  CC0 1.0

• NABU|naturgucker, via GBIF.org

  Common crane, barn swallow and common swift migration: bird reports, part of GBIF Occurrence Downloads https://doi.org/10.15468/dl.gxp8bk, https://doi.org/10.15468/dl.enum2s and https://doi.org/10.15468/dl.dguqfr

  CC BY 4.0

• Norwegian Species Observation Service (Norwegian Biodiversity Information Centre), via GBIF.org

  Common crane, barn swallow and common swift migration: bird reports from Norway, part of GBIF Occurrence Downloads https://doi.org/10.15468/dl.gxp8bk, https://doi.org/10.15468/dl.enum2s and https://doi.org/10.15468/dl.dguqfr

  CC BY 4.0

• U.S. Fish & Wildlife Service — Waterfowl Population Status 2025

  Snow goose migration: the greater snow geese (St. Lawrence, Atlantic coast) are held at their share of the population, 428,000 of 9.5 million

  Public domain (work of the U.S. federal government)

• Wikipedia — White stork

  Breeding pairs per country from the 6th International White Stork Census 2004/05 (NABU), used to share the breeding storks between the countries

  CC BY-SA 4.0

• Wikimedia Commons — A White Stork Flying Over Temara, Morocco

  Photo of the white stork in the migration view (Moroccan spotter, cropped)

  CC0 1.0

• Wikimedia Commons — A Solitary Snow Goose on Lake Andes (U.S. Fish & Wildlife Service)

  Photo of the snow goose in the migration view (L. Julian, USFWS Mountain-Prairie, cropped)

  Public domain (work of the U.S. federal government)

• Wikimedia Commons — Kraanvogel - common crane - Grus grus 2

  Photo of the common crane in the migration view (Bouke ten Cate, cropped)

  CC BY 4.0, https://creativecommons.org/licenses/by/4.0/

• Wikimedia Commons — Sandhill Crane (Grus canadensis pratensis) (U.S. Fish & Wildlife Service Southeast Region)

  Photo of the sandhill crane in the migration view (Keenan Adams, USFWS, cropped)

  Public domain (work of the U.S. federal government); also CC BY 2.0

• Wikimedia Commons — Canada goose on Seedskadee NWR (USFWS Mountain-Prairie)

  Photo of the Canada goose in the migration view (Tom Koerner, USFWS, cropped)

  CC BY 2.0, https://creativecommons.org/licenses/by/2.0/

• Southern African Bird Atlas Project 2 (FitzPatrick Institute of African Ornithology), via GBIF.org

  Barn swallow, common swift and Amur falcon migration: bird reports from southern Africa, part of GBIF Occurrence Downloads https://doi.org/10.15468/dl.enum2s and https://doi.org/10.15468/dl.dguqfr and of the GBIF occurrence API (Amur falcon) (Brooks M, Ryan P, Southern African Bird Atlas Project 2, https://doi.org/10.2989/00306525.2022.2125097)

  CC BY 4.0

• EEA / DG ENV — Article 12 Birds Directive reporting 2013–2018 (tabular public version)

  Barn swallow and common swift migration: breeding pairs per EU member state, used to share the breeding birds between the countries

  CC BY 4.0, https://creativecommons.org/licenses/by/4.0/ (Directorate-General for Environment, European Environment Agency)

• Wikimedia Commons — Landsvale (barn swallow)

  Photo of the barn swallow in the migration view (Malene Thyssen, cropped)

  CC BY 2.5, https://creativecommons.org/licenses/by/2.5/

• Wikimedia Commons — Selasphorus rufus1 (U.S. Fish & Wildlife Service)

  Photo of the rufous hummingbird in the migration view (Dean E. Biggins, USFWS, cropped)

  Public domain (work of the U.S. federal government)

• Wikimedia Commons — Tree swallow (50007800177) (U.S. Fish & Wildlife Service Alaska)

  Photo of the tree swallow in the migration view (Lisa Hupp, USFWS, cropped)

  Public domain (work of the U.S. federal government)

• Dryad — Alerstam T, Bäckman J, Grönroos J, Olofsson P, Strandberg R (2019): Data from: Hypotheses and tracking results about the longest migration: the case of the arctic tern

  Arctic tern migration: light-level geolocator positions of terns breeding in the Baltic Sea; the routes of six terns tracked for a whole year give the flow on the map. Own route estimate and migration model, not endorsed by the authors

  CC0 1.0 (public domain)

• Wikimedia Commons — Arctic Tern (Sterna paradisaea)

  Photo of the arctic tern in the migration view (Billy Lindblom, cropped)

  CC BY 2.0, https://creativecommons.org/licenses/by/2.0/

• Dryad — Wellbrock AHJ, Bauch C, Rozman J, Witte K (2017): Data from: ‘Same procedure as last year?’ Repeatedly tracked swifts show individual consistency in migration pattern in successive years

  Common swift migration south of the Sahara: geolocator tracks of ten swifts from one colony in western Germany; around the equinoxes bridged on straight lines. Own analysis and migration model, not endorsed by the authors

  CC0 1.0 (public domain)

• Wikimedia Commons — Common swift 2024 04 21

  Photo of the common swift in the migration view (Alexis Lours, cropped)

  CC BY 4.0, https://creativecommons.org/licenses/by/4.0/

• Wikimedia Commons — Amur falcon male in flight

  Photo of the Amur falcon in the migration view (Sumeet Moghe, cropped; the crop is licensed under the same licence)

  CC BY-SA 4.0, https://creativecommons.org/licenses/by-sa/4.0/

• Copernicus Marine Service — Global Ocean Physics Reanalysis (GLORYS12, GLOBAL_MULTIYEAR_PHY_001_030)

  Loggerhead hatchlings: daily surface currents and monthly sea temperature for a drift model of about 26,000 virtual hatchlings from Florida's nesting beaches, July 2023 to June 2024. Generated using E.U. Copernicus Marine Service Information; https://doi.org/10.48670/moi-00021

  Copernicus Marine Service licence (free of charge, for any purpose, with the credit above)

• Wikimedia Commons — Loggerhead Sea Turtle Hatchlings (U.S. Fish & Wildlife Service, National Archives 166702360)

  Photo of the loggerhead hatchlings in the migration view (USFWS, Back Bay National Wildlife Refuge, cropped)

  Public domain (work of the U.S. federal government; National Archives: use unrestricted)

• Movebank Data Repository — Studies “1000 Cranes” (2024): Ukraine (Andryushchenko Y et al.), Southern Kazakhstan, Russia. Transbaikalia, Russia. Taman. Azov, Russia. Volga-Ural Interfluve, Russia. Altai (Ilyashenko EI et al.)

  Demoiselle crane migration: GPS tracks of 64 cranes where eBird has next to no reports (Sudan and Chad, Arabia, the Caucasus, Central Asia, Tibet and the Himalaya); https://doi.org/10.5441/001/1.590, https://doi.org/10.5441/001/1.591, https://doi.org/10.5441/001/1.592, https://doi.org/10.5441/001/1.594, https://doi.org/10.5441/001/1.595, https://doi.org/10.5441/001/1.596. Own analysis and migration model, not endorsed by the authors

  CC BY 4.0, https://creativecommons.org/licenses/by/4.0/

• U.S. Geological Survey — Gill RE, Tibbitts L, Battley PF, Warnock N, Douglas DC (2023): Tracking Data for Bar-tailed Godwits (Limosa lapponica)

  Bar-tailed godwit migration: satellite tracks of the Alaska-breeding godwits, used for the shares of Alaska, East Asia and New Zealand per week. Not endorsed by the USGS

  Public domain (U.S. Geological Survey data release, no use constraints)

• Movebank Data Repository — Battley PF, Lisovski S, Conklin JR (2024): Data from: Study “Bar-tailed Godwit geolocator tracking New Zealand 2013-2014”

  Bar-tailed godwit migration: geolocator tracks of godwits from New Zealand. Own analysis and migration model, not endorsed by the authors

  CC BY 4.0, https://creativecommons.org/licenses/by/4.0/

• Movebank Data Repository — Andrews-Goff V, Gales N, Childerhouse SJ et al. (2023): Data from: Australia’s east coast humpback whales: satellite tag derived movements on breeding grounds, feeding grounds and along the northern and southern migration

  Humpback whale migration: satellite tracks of 44 east Australian humpback whales; the stretches without tags (the way north from the Antarctic, the breeding season) are modelled. Own analysis and migration model, not endorsed by the authors or the Australian Antarctic Division

  CC0 1.0 (public domain)

• Wikimedia Commons — Demoiselle Crane in Tal Chhapar Sanctuary November 2025 by Tisha Mukherjee 04

  Photo of the demoiselle crane in the migration view (Tisha Mukherjee, cropped; the crop is licensed under the same licence)

  CC BY-SA 4.0, https://creativecommons.org/licenses/by-sa/4.0/

• Wikimedia Commons — Bar-tailed Godwit in flight

  Photo of the bar-tailed godwit in the migration view (Wayne Butterworth, cropped)

  CC BY 4.0, https://creativecommons.org/licenses/by/4.0/

• Wikimedia Commons — Broad-winged hawk (54475730551) (U.S. Fish & Wildlife Service Midwest Region)

  Photo of the broad-winged hawk in the migration view (Courtney Celley, USFWS, cropped)

  Public domain (work of the U.S. federal government)

• Wikimedia Commons — 001 Humpback whale breaching in Ballena Marine National Park Photo by Giles Laurent

  Photo of the humpback whale in the migration view (Giles Laurent, cropped; the crop is licensed under the same licence)

  CC BY-SA 4.0, https://creativecommons.org/licenses/by-sa/4.0/

The maps themselves are computed from these datasets in house. How the result is meant to be read, and what it deliberately leaves out, is described under Method.