How are bird migrations visualized?

A comprehensive review of the history, measurement methods, and visualization patterns of our migratory flying friends

Fig 1. National Geographic’s interactive map illustrating migration patterns for birds in the American continent. From ‘Billions of Birds Migrate-Where do they go?’ (borrowed from: ( Accessed on: 6:00 PM (EST), December 2, 2018)


Bird migration is the annual, large scale movement of birds from locations of lower food and nesting resources to locations with higher resources. Bird migration is important to study because it gives us insights on bird movements, their behavior, and relevant concepts such as bird evolution, climate change, habitat, and species conservation. Bird migration charts are tools to visualize these complex bird movements across the globe which are relevant for scientific as well as general public consumption. Collecting data to create these visualizations is difficult and is done by using different methods like bird ringing, counting, radio and satellite tracking, geo-logging, radar tracking. The data collection method used has an impact on how the bird migration chart is visualized. This report summarizes current state-of-the-art tools used for the data collection on bird migration and the visualization tools that support the discovery and advancement of the field.


Bird migration is the annual large scale movement of birds between their summer breeding grounds and winter non-breeding grounds across the globe [6]. This migration is largely from a location low in resources such as food and nesting sites to a location rich in these resources. Bird migration can be classified in four types depending on the distance the birds cover — permanent residents, short distance, medium distance and long-distance migrants. Permanent residents don’t migrate at all. Short distance migrants fly short distances, for instance, from higher to lower elevation on a mountainside. Medium distance migrants can distances that scale several states. Long-distance migrants can cover distances as large as across continents. For instance, birds migrate from United States and Canada to wintering grounds in Central and South America.


Birds have always captured the fascination of mankind. In his book, A Concise History of Ornithology, Michael Walters, talks about how birds’ abilities to communicate and travel in the skies is that makes them distinct [1]. And, there are references to personifying them with supernatural abilities in many ancient myths and religions. The author gives examples of how the Hindu god, Vishnu had the eagle Garuda as his heavenly steed. In fact, in many Native American legends, the Thunderbird is described to be so humongous that it could swallow whole whales and its voice felt like the tempest. Additionally, the Egyptians of the ancient times saw God Horu as a gigantic falcon whose wings stretched from one end of the universe to the other. Birds also appear in a semi-mystical guise in old stone-age paintings in the caves at Lascaux, France. In some instances, they can be of use in historical documentation of the birds themselves. For instance, from the frescos in Egyptian tombs (fig 2.) we can observe that the Red breasted Goose (Branta ruficollis) formerly wintered in the Nile delta, although they no longer do so. However, there have been debates questioning the authenticity of these paintings, only reinforcing the relevance of studies related to our ornithological cousins[4].

Fig 2. Fresco depicting two Egyptian Geese of Meidum 2650 BC Egyptian Museum of Antiquities Cairo Egypt. (borrowed from: ( Accessed on: 1:13 PM (EST), December 2, 2018 )

History of bird migration


Origins of bird migration date as back as the eighth century BC. Written records for migration have been found from the ancient Greek scholars, including Homer and Aristotle [2]. Homer, in his epic, Iliad, talks about cranes being at war with pygmies at the ends of the world, pointing towards the possible movement of these birds. Four hundred years later, Aristotle proposed that cranes might have migrated from the Scythian steppes (north and east of the Black Sea and the Caspian Sea) to the headwaters in modern-day Egypt. It is believed that Aristotle brought ornithology to mainstream science by providing a scientific description of bird migrations listing 140 species [2]. However, Aristotle also initiated the long lasting myth that swallows and other birds hibernate in the winter this story was believed by some europeans till the nineteenth century. He also incorrectly noted that the Common Redstart (a common summer visitor to Greece) transformed into a European robin during fall. This was probably due to the disappearance of Redstarts at the same time Robins appeared in Greece. We now know that Redstarts migrate south from Greece to sub-Saharan Africa, while Robins arrive in Greece from the mainland Europe.

“Even the stork in the sky knows her seasons

And the turtledove, swift, and crane

Keep the time of their coming.”

Pliny the Elder, a Roman writer of the first century BC repeated many of Aristotle’s writings on the subject. Meanwhile, the myth of bird hibernation grew in Europe. Olaus Magnus, bishop of Uppsala in Sweden, told his readers that both fishes and swallows hibernate in the mud in winters. In fact, in his book A history of northern nations he has a woodcut (from 1555) of a fisherman catching both fish and swallows (fig 3.).

Fig 3. A net full of swallows by Olaus Magnus (1500s). (borrowed from: ( Accessed on: 1:47 PM (EST), December 2, 2018)


The eighteenth-century ushered more scientific explorations on why birds disappear during autumn. Von Pernau in 1702 defined migration as it is known these days, the seasonal movement of birds. He described the reason for migration to be an intrinsic restlessness in birds which tells them when is it the correct time to migrate. Carl Linnaeus listed 500 species and initiated a modern approach to natural history studies and is called the “father of modern taxonomy”. In 1822, evidence of long-distance migration came in the form of a white stock which was spotted in central Europe with an arrow of African origin embedded in its neck. 25 such storks were spotted after that and were called Pfeilstorch, German for “Arrow stork”.

Nineteenth Century

Direct field studies of migrating birds began in the nineteenth century. Arrival and departure dates of birds were marked and observations like species, their behavior, count were made. The second half of the nineteenth century saw the founding of ornithological journals and unions like the World Ornithological Congress. Their first congress was hosted in Vienna 1884 with coordination of migration as one of its primary agenda. This gave access to the world of ornithological knowledge and helped collect migration data of birds that fly across countries and continents. The origin of journals would have also encouraged independent rational inquiries across various domains of ornithology.

Ringing method

Ringing, also known as bird banding was started by Hans Martensen in 1890s by attaching zinc bands to birds. It started as a method to recognize migration destinations and bird routes. Small birds are trapped in mist nets, funnel traps or cannon nets so that they can be ringed. The bands are very light (they can weigh 0.04 grams) and are made of aluminum these days. The US Bird Banding Laboratory has twenty-three standard sizes of bands for small birds like hummingbirds and large birds like Trumpeter Swans. The bands are designed such that they fit snugly in the legs and don’t hamper the bird’s flight as that could bias the collected data/observations.

Counting method


The counting method refers to physically counting the birds using visual or audio aids. Birders often spend hours at a given location and keep a note of their bird observations. These observations include a point-in-time count of birds seen at a particular location on earth. There are estimation methods like counting the first ten birds of a large flock in flight and then multiplying it by in proportion with the size of the flock [7]. Bird counting does not cause any harm or interference to the bird populations. Sometimes when the bird is not visible, the sounds are recorded and processed that can give an estimate of the number of birds in the area.


Mapping refers to dividing the land into subdivisions (viz. continent, country, estuary, field) and then counting for that subdivision. Mapping requires large manpower to cover large areas.


Moonwatching is another counting method in which a number of nocturnal birds can be observed flying in front of the moon in a near-full moon or full moon night. The fact that it only works during full moon nights is a limitation.

Infrared Detectors

In recent times infrared detectors are being used to observe birds. Birds give out body heat, which can be captured (fig 4 ). This, however, has to be noise-free so that other objects like bats and planes are not captured. This process can be automated to capture continuous shots and can prevent observer fatigue. This method, however, can only count the number of birds and cannot be used to differentiate between the species.

Fig 4. Thermal images showing (a) sequence of female Barn Owl Tyto alba in flight (AGA 782), (b) Zebra Finch Taeniopygia guttata clutch in nestbox and © thermal survey of Feral Pigeons Columba livia (FLIR E300). (borrowed from:, Accessed on: 10:55 PM (EST), December 4, 2018)

Citizen Science

Today, there are multiple citizen science (also known as crowdsourcing or human-computation tools) mobile and web apps that allow people to log bird sightings in their neighborhoods or surroundings of interest. These can be logged with their phones along with the species, count and pictures at a given geo-location.

Fig 5. [Left] Animated visualization of 118 bird species for cyclic seasons in a year. [Right] Species Index (borrowed from: ( Accessed on: 2:49 PM (EST), December 2, 2018)
Fig 6. Map showing hot spots for a selected bird species in a given time and location. (borrowed from: Accessed on: 2:52 PM (EST), December 2, 2018)
Fig 7. Map species observed hotspots across the world (borrowed from: Accessed on: 2:59 PM (EST), December 2, 2018)
Fig 8. Map showing species data card for Assateague State Park(borrowed from: Accessed on: 2:59 PM (EST), December 2, 2018)
Fig 9. Dashboard showing the various species sighted at a given location along with metadata like comments and pictures for birders. It also contains recent sightings and a leaderboard for top eBirders. (borrowed from: Accessed on: 2:59 PM (EST), December 2, 2018)
Fig 10. Dashboard showing the frequency of bird sightings in each month over a given time period for a given location. (borrowed from: Accessed on: 2:59 PM (EST), December 2, 2018)
Fig 11. Journey north map showing hummingbird sightings over a period of time. (borrowed from: Accessed on: 3:21 PM (EST), December 2, 2018)
Fig 12. Birders are encouraged to keep food and water in their backyards for birds at popular resting stopovers. (borrowed from: Accessed on: 3:30 PM (EST), December 2, 2018)

Radio Telemetry

Radio transmission, developed after the world war II, allows remote monitoring by attaching a transmitter to its tail feathers (for a large bird) or as a bag pack (for smaller birds). This allows measuring parameters including altitude, length of individual flights, flight speeds, stopover duration and other behaviors that cannot be individually be observed (like behavior or partial migrants, individual birds at communal roosts and disposal of juveniles from breeding grounds).

zFig 13. GPS unit with a mini solar panel on a Swainson’s Hawk at Raptor Recovery Nebraska.(borrowed from:, Accessed on: 3:45 PM (EST), December 2, 2018)

Satellite Tracking

If the radio has enough power, signals can be caught by a satellite which is much better than keeping track from the ground because of complete coverage. Satellite tracking is done by the ARGOS system of satellite receivers. These systems are aboard five satellites belonging to National Oceanic and Atmospheric Administration or European Organization for the exploitation of Meteorological Satellites. These are in a polar orbit which means they pass over the poles on every orbit.

Fig 14. Birds migrating towards Africa. Green moving points are the birds with PTTs. Many birds die after getting trapped in bird nets on the coasts of Libya and Egypt (shown in red). (borrowed from: Migrating Birds: Scouts of Distant Worlds by Petra Höfer, Freddie Röckenhaus on Amazon Prime)
Fig 15. Screenshot mapping the bird's movements as it moves in the lift of hot air currents. (borrowed from: Migrating Birds: Scouts of Distant Worlds by Petra Höfer, Freddie Röckenhaus on Amazon Prime)


Geologgers (fig 16) are smaller and lighter than PTT and can be installed easily on small birds. They work by capturing the light levels between the sunrise and sunset. Using this data a calculation can be made within 40 miles of the latitude and 100–200 miles of longitude.

Fig 16. Geologger attached to a common swift. (borrowed from:, Accessed on: 3:430 PM (EST), December 2, 2018))


Bird observation using the radar occurred for the first time in 1940 during World War II when a British radar detected a flock of geese instead of German planes.

Fig 17. Animated map showing flock of birds appearing on the radar. They suddenly bloom and then disappear. (borrowed from: Weather Radar Captures Flocks of Birds Taking Off by Hannah Waters(, Accessed on: 5:05 PM (EST), December 2, 2018)

Significance of Bird Migration Visualization

Bird Migration visualizations are of importance to the scientific community as well as for general public consumption. They help to visualize complex patterns of bird movements across the world which can have an impact on various fields such as conservation, climate change studies.

Community and Scientific Outreach

Bird migration charts capture the attention of expert ornithologists and common citizens alike. They have been a great source of knowledge on various applied fields like climate change, habitat conservations, bird conservation to name a few. There are efforts to combine the power of technology and the manpower of citizens to work towards providing a conducive environment for counting birds as they take up perilous migrations. Audubon and Bird Cast, by the Cornell Lab are two such communities. Bird Cast is a project which combines the might of the Next Generation Radar (NEXRAD) along with volunteering bird watchers to keep a track of a database of bird data (fig 18).

Fig 18. Real-time analysis maps showing the intensity of bird migration as detected by the US weather radar network. (borrowed from: Accessed on: 5:53 PM (EST), December 2, 2018)

Education and awareness

It is observed in most bird watching experts, there is an enthusiasm to educate younger generations and school children about birds and bird watching practices. They want to inculcate a sense of responsibility in the children so that they grow up to be sensitive adults and treat the environment and everything it contains as their own. Needless to say, there are a lot of examples of bird migration visualizations in the print medium like posters, bird migration encyclopedias and birding handbooks. National Geographic has a collectible poster that can be used for educational purposes or as a birder’s collection (fig 19). Another book is the Atlas of Bird Migration: Tracing the Great Journeys of the Worlds by Jonathan Elphick. It contains illustrated maps of migration for various bird species (fig 20). The book, The Art of Migration by John Bates, James H. Boone and Peggy Macnamara uses artist Peggy Macnamara’s watercolor art to tell visual stories of bird migration (fig 21).

Fig 19. National Geographic’s migration poster (available as an art collectible). (borrowed from: (, Accessed on: 6:53 PM (EST), December 2, 2018)
Fig 20. Illustrative representations of migration paths for [Left] Storks [Right] pigeons. (borrowed from: Atlas of Bird Migration: Tracing the Great Journeys of the Worlds (2011)-Jonathan Elphick )
Fig 21. Peggy uses her unique watercolor style to visualize some common birds and butterflies as they take on the perilous journeys of migration. (borrowed from: The Art of Migration by John Bates , James H. Boone and Peggy Macnamara (Illustrator))
Fig 22. Screenshots from their interactive article showing migration patterns for a[left]Wood Thrust and [right] Western Tanager . The article is titled ‘Billions of Birds Migrate-Where do they go?’. (borrowed from: ( Accessed on: 6:00 PM (EST), December 2, 2018)
Fig 23. Motion map showing the movement of birds, mammals and amphibians as climate changes. (borrowed from:, Accessed on: 6:08 PM (EST), December 2, 2018)


One of the primary reasons why bird migration is important is because of its impact on many related fields like climate change, bird conservation, habitat studies, and policymaking to name a few. Interestingly this rather interesting and important phenomenon was not visualized for a long time in history. This was because collecting bird data is a rather difficult task and scientific methods are only a century old. There are multiple methods but they all come with their limitations. There is a need to coordinate internationally with various agencies. It is thus also important to have enough bird literate citizens who can lend a helping hand in various bird census efforts.


I would thank Ms. Bahare Sanaie-Movahed, GIS specialist at Northeastern University for helping me understand the concepts of GIS mapping.


  1. Walters, M.(2003), A Concise History of Ornithology
  2. Danny, M.(2016), Long hops: Making sense of Bird Migration
  3. Mayr, E. (1984). Commentary: The Contributions of Ornithology to Biology. BioScience, 34(4), 250–255.
  4. Bibby, C.J. (2003). “Fifty years of Bird Study: Capsule Field ornithology is alive and well, and in the future can contribute much more in Britain and elsewhere”. Bird Study. 50 (3): 194–210. doi:10.1080/00063650309461314.
  5., Accessed on: 7:45 PM (EST), December 2, 2018
  6., Accessed on: 7:45 PM (EST), December 2, 2018
  7., Accessed on: 10:17 PM (EST), December 4, 2018
  8. Migrating Birds: Scouts of Distant Worlds by Petra Höfer, Freddie Röckenhaus on Amazon Prime, Accessed on: 8:00 PM (EST), December 4, 2018

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