Can Birds and Bugs Look Like UFOs on Radar?

Introduction

Yes. Birds, insects, rain, snow and ice can all produce genuine radar echoes that may be mistaken for aircraft when operators lack supporting information. Radar does not identify objects directly; it detects reflected radio energy. Anything that reflects enough energy back to the antenna can appear as a target. In aviation and military surveillance, these unwanted or ambiguous returns are known as biological or weather clutter. In some UFO reports, a radar contact may therefore represent a real phenomenon in the atmosphere without representing a conventional aircraft or an unknown craft. Understanding how bio-clutter appears is essential when evaluating radar-based UFO claims.[Weather.gov]weather.govUsing and Understanding Doppler RadarThe radar emits a burst of energy (green in the animated image). If the energy strikes an object (ra…

Can Birds and Bugs Look Like UFOs on Radar?

Birds and insects are not merely theoretical sources of radar interference. Modern weather-radar networks routinely detect them so clearly that entire scientific fields have developed around analysing these signals. Researchers use weather radar to track bird migration, bat movements and large-scale insect activity because the echoes are strong enough to be measured across vast areas.[BirdCast]birdcast.orgRadar OrnithologyWe turn weather radar data into information describing the numbers and flight directions, speeds and altitudes o… BirdCast The reason is simple: radar measures reflected energy[birdcast.org]birdcast.orgRadar OrnithologyWe turn weather radar data into information describing the numbers and flight directions, speeds and altitudes o…, not biological identity. A single bird usually creates only a small return, but thousands of birds flying together can generate a radar signature comparable to a much larger object. Large insect swarms can do the same, especially when concentrated in dense layers of warm air. Weather radars are sensitive enough that even individual bugs, birds and bats can contribute to detectable returns.[NOAA Institutional Repository]repository.library.noaa.govInstitutional RepositoryA Machine Learning Approach for Classifying Bird and…by P Jatau · 2021 · Cited by 44 — A machine learning appr…

Historically, radar operators encountered this problem almost immediately after radar entered widespread use. During the Second World War, unexplained radar echoes produced by birds and insects were sometimes called “angels” before their biological origin became better understood. Modern meteorological systems still devote significant effort to separating biological targets from weather and aircraft returns.[The Guardian]theguardian.comConducted between 2014 and 2021, the research repurposed data from 15 weather surveillance radars to monitor aerial insect activity, with…

Why biological targets appear on radar

Several characteristics make biological targets visible:

• Large numbers compensate for small size. A flock containing thousands of birds can create a substantial radar echo.[Lincoln Laboratory]ll.mit.eduLincoln Laboratory Radar Clutter and ChaffLincoln LaboratoryRadar Clutter and ChaffAugust 1, 2008 — Since birds move at relatively low velocities, their speed, if measured, can be…Published: August 1, 2008
• Migration occurs at aircraft-relevant altitudes. Migrating birds may travel hundreds or thousands of metres above the ground, placing them in the same volume of air monitored by surveillance radars.[BirdCast]birdcast.orgRadar OrnithologyWe turn weather radar data into information describing the numbers and flight directions, speeds and altitudes o…
• Insects can form dense aerial layers. Weather radars regularly observe huge concentrations of insects carried by winds.[The Weather Channel]weather.comSuch was the case Wednesday morning in the Midwest.Read moreThe Weather ChannelBugs Show Up on Radar in the MidwestMay 16, 2019 — Although radar is typically used for tracking rain and snow, it can…Published: May 16, 2019[FOX Weather]foxweather.comFOX WeatherProject tracks bird migration using NWS Doppler RadarMay 14, 2022 — Using algorithms over years of research, scientists can de…Published: May 14, 2022
• Biological movement creates coherent tracks. A flock moving steadily can appear as a legitimate moving target rather than random noise.[KNMI]cdn.knmi.nlBird detection by operational weather radarThe bird radar allows to verify the targets as birds by analyzing the wing beat pattern or…

These factors mean that a radar operator observing an isolated return without visual confirmation may initially see something that resembles an aircraft track.

How Weather Creates Aircraft-Like Returns

Weather is among the most common sources of radar echoes because precipitation is specifically designed to be detected by radar. Rain, snow, hail and ice crystals all scatter radio energy back toward the receiver.[Weather.gov]weather.govOpen source on weather.gov.

In favourable conditions, weather returns can create patterns that appear surprisingly structured. Radar displays may show compact cells, elongated bands, expanding rings or moving patches. If an observer focuses only on motion rather than meteorological context, these returns can appear to represent discrete airborne objects.[Radartutorial]radartutorial.euWeather Radar ClutterThis page provides an overview of some of the techniques that are commonly used to eliminate clutter an…

Weather-related ambiguity increases when:

Modern weather radars are highly sensitive and frequently detect phenomena beyond ordinary rain and snow. Radar systems have recorded butterflies, birds trapped within storms, meteor fragments and aircraft-generated atmospheric effects. Such examples demonstrate how diverse radar targets can be.[The Washington Post]washingtonpost.comThe Washington Post Is that a meteor or a flock of birds?Things you can catch on radar.February 23, 2025 — Weather radar systems operated by the National Weather Service are primarily designed t…Published: February 23, 2025

A memorable example: roost rings

One of the clearest demonstrations of biological radar clutter is the “roost ring”. Shortly before sunrise, thousands of birds leaving a communal roost create an expanding circular pattern on Doppler weather radar. To an untrained observer, the expanding ring could appear highly unusual. To radar ornithologists, however, it is a recognised biological signature produced by birds dispersing from a central location.[Weather.gov]weather.comSuch was the case Wednesday morning in the Midwest.Read moreThe Weather ChannelBugs Show Up on Radar in the MidwestMay 16, 2019 — Although radar is typically used for tracking rain and snow, it can…Published: May 16, 2019

The existence of such distinctive patterns shows that radar can display dramatic moving targets generated entirely by wildlife rather than aircraft.[Weather.gov]weather.govWIND FARM INTERACTION WITH NEXRAD RADARIn fact, wind turbine clutter appears on the radar much like numerous other non-meteorological obj…

Why Clutter Sometimes Produces UFO Reports

A radar contact can appear impressive because it seems objective and instrument-based. Yet radar operators often work with incomplete information. A brief return may appear before weather data, visual observations or identification algorithms are consulted.

Several factors can make clutter appear more mysterious than it is:

Bird flocks can be particularly confusing because they sometimes move cohesively and generate trackable radar signatures. Modern studies of airport surveillance and drone detection continue to identify bird-versus-aircraft or bird-versus-drone discrimination as a significant technical challenge.[MDPI]mdpi.com2504 446XAirport Ground-Based Aerial Object Surveillance…by J Samu · 2025 — A recurring difficulty is distinguishing between birds and UAS…

Clues That Separate Aircraft from Clutter

Radar operators and researchers have developed many techniques for distinguishing aircraft from biological and weather targets.

Movement relative to the wind

One of the strongest clues is whether the target follows atmospheric motion.

Large insect concentrations often drift with prevailing winds. Birds, by contrast, can maintain headings independent of the wind. Aircraft usually exhibit even more deliberate and consistent navigation behaviour. Comparing target motion with weather and wind data often helps identify the source.[FOX Weather]foxweather.comFOX WeatherProject tracks bird migration using NWS Doppler RadarMay 14, 2022 — Using algorithms over years of research, scientists can de…Published: May 14, 2022

Shape and distribution

Biological targets often appear as diffuse clouds, rings or broad regions rather than isolated point targets. Weather returns likewise tend to form larger structures. Aircraft generally generate more compact and persistent tracks.[Weather.gov]weather.govNational Weather ServiceIsolated Severe Thunderstorms and Critical Fire Weather Tuesday · Freeze Warning · Red Flag Warning · Heat Adviso…

Time of day and season

Many biological echoes follow predictable patterns:

• Bird migration peaks during specific seasons.
• Roost departures occur around dawn.[weather.gov]weather.govSource details in endnotes.
• Insect activity increases under favourable temperature conditions.
• Bat emergence occurs at characteristic evening periods. Weather.gov+2Inside NSSL[inside.nssl.noaa.gov]inside.nssl.noaa.govnssl uses weather radar clutter to help biologistsInside NSSLNSSL uses weather radar clutter to help biologistsMar 2, 2011 — The radar images of bats appear as distinct “blooms.” Usually…

A radar contact that coincides with these patterns is less likely to represent an unidentified craft.

Advanced radar classification

Modern Doppler and dual-polarisation radars analyse more than simple position. Researchers now use machine-learning systems and polarimetric measurements to distinguish birds, insects and precipitation from one another. These techniques exist precisely because biological and weather clutter are common and significant radar targets.[NOAA Institutional Repository]repository.library.noaa.govInstitutional RepositoryA Machine Learning Approach for Classifying Bird and…by P Jatau · 2021 · Cited by 44 — A machine learning appr…

What This Means for Radar-Based UFO Reports

Radar clutter from birds, insects and weather does not mean every radar-associated UFO report is explained. It does mean that a radar return alone is not sufficient evidence that an unknown craft was present. Biological scatter and weather echoes are well-documented, routinely observed and sometimes dramatic enough to resemble meaningful targets on radar displays. Investigators therefore treat weather records, migration data, wind conditions and radar-processing details as essential context before concluding that a radar contact represents anything unusual.[SkyRadar]skyradar.comATSEP Use Cases: Impact of False Targets on Air Traffic Control21 Sept 2023 — Clutter refers to false targets generated by radar…[BirdCast]birdcast.orgRadar OrnithologyWe turn weather radar data into information describing the numbers and flight directions, speeds and altitudes o…

Amazon book picks

Further Reading

Books and field guides related to Can Birds and Bugs Look Like UFOs on Radar?. Use these as the next step if you want deeper reading beyond the article.

Book

The UFO Enigma

By Peter A. Sturrock

Provides context for evaluating unusual radar-associated reports.

See on Amazon

Book

Introduction to Radar Systems

By Merrill Ivan Skolnik

Provides the foundation for understanding biological and weather clutter.

See on Amazon

Book

Weather radar technology beyond NEXRAD

By National Research Council (U.S.). Committee on Weather Radar Technology Beyond NEXRAD.

First published 2002. Subjects: Evaluation, Meteorological services, Radar meteorology, Technological innovations, Weather forcasting.

See on Amazon

Book

Living on the Wind

By Scott Weidensaul

First published 1999. Subjects: Birds, Migration, Birds, migration, Migratory birds.

See on Amazon

Browse more on Amazon:The UFO Enigmato Radar Systems booksWeather radar technology beyond NEXRAD

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Endnotes

1. Source: weather.gov
Link:https://www.weather.gov/mkx/using-radar

2. Source: skyradar.com
Link:https://www.skyradar.com/blog/atsep-use-cases-impact-of-false-targets-on-air-traffic-control

3. Source: birdcast.org
Link:https://birdcast.org/radar-technology/

4. Source: birdcast.org
Link:https://birdcast.org/a-primer-for-using-weather-surveillance-radar-to-study-bird-migration/

5. Source: inside.nssl.noaa.gov
Title: nssl uses weather radar clutter to help biologists
Link:https://inside.nssl.noaa.gov/nsslnews/2011/03/nssl-uses-weather-radar-clutter-to-help-biologists/

6. Source: repository.library.noaa.gov
Link:https://repository.library.noaa.gov/view/noaa/34122

7. Source: repository.library.noaa.gov
Title: noaa 61003 DS1
Link:https://repository.library.noaa.gov/view/noaa/61003/noaa_61003_DS1.pdf

8. Source: weather.gov
Link:https://www.weather.gov/iln/birds

9. Source: weather.com
Title: Such was the case Wednesday morning in the Midwest.Read more
Link:https://weather.com/science/weather-explainers/news/2019-05-16-radar-bugs-bats-sunrise

Published: May 16, 2019

10. Source: cdn.knmi.nl
Link:https://cdn.knmi.nl/knmi/pdf/bibliotheek/knmipubWR/WR2009-06.pdf

11. Source: radartutorial.eu
Link:https://www.radartutorial.eu/15.weather/wr22.en.html

12. Source: mdpi.com
Title: 2504 446X
Link:https://www.mdpi.com/2504-446X/10/1/22

13. Source: nssl.noaa.gov
Link:https://www.nssl.noaa.gov/publications/wsr88d_reports/Bird_detection_algorithm_2019.pdf

14. Source: repository.library.noaa.gov
Title: noaa 32181 DS1
Link:https://repository.library.noaa.gov/view/noaa/32181/noaa_32181_DS1.pdf

15. Source: weather.gov
Link:https://www.weather.gov/roc/WindFarms

16. Source: weather.gov
Link:https://www.weather.gov/

17. Source: weather.gov
Link:https://www.weather.gov/mlb/Doppler_Dual_Pol_Weather_Radar

18. Source: weather.gov
Link:https://www.weather.gov/bgm/researchRadarandBirds1997

19. Source: wildlife.org
Link:https://wildlife.org/wsb-airports-avian-radar-spots-just-15-percent-of-birds/

20. Source: birdcast.org
Link:https://birdcast.org/weather-surveillance-radar-beyond-meteorology/

21. Source: mdpi.com
Link:https://www.mdpi.com/2673-4931/8/1/48

22. Source: radartutorial.eu
Title: Weather is not clutter in a weather detecting radar.Read more
Link:https://www.radartutorial.eu/11.coherent/co04.en.html

23. Source: theguardian.com
Link:https://www.theguardian.com/environment/2025/oct/27/night-flying-insects-over-uk-in-decline-weather-radar-study-reveals

24. Source: ll.mit.edu
Title: Lincoln Laboratory Radar Clutter and Chaff
Link:https://www.ll.mit.edu/sites/default/files/outreach/doc/2018-07/lecture%207.pdf

Published: August 1, 2008

25. Source: foxweather.com
Link:https://www.foxweather.com/learn/birds-project-tracks-bird-migration-using-nws-doppler-radar

Published: May 14, 2022

26. Source: washingtonpost.com
Title: The Washington Post Is that a meteor or a flock of birds?
Link:https://www.washingtonpost.com/weather/2025/02/23/weather-radar-butterflies-planes-doppler/

Published: February 23, 2025

27. Source: facebook.com
Link:https://www.facebook.com/NOAA/

28. Source: radarscope.zendesk.com
Link:https://radarscope.zendesk.com/hc/en-us/articles/4416722636946-Biological-Scatter-What-You-Can-See-On-Radar-Other-Than-Rain

Additional References

29. Source: facebook.com
Link:https://www.facebook.com/ericsnitilwx/posts/hey-whats-that-theres-all-sorts-of-stuff-showing-up-on-radar-tonight-yet-its-not/1313906850101710/

30. Source: researchgate.net
Link:https://www.researchgate.net/publication/282366086_Aviation_Bird_Hazard_in_NEXRAD_Dual_Polarization_Weather_Radar_Confirmed_by_Visual_Observations

31. Source: detect-inc.com
Link:https://detect-inc.com/aircraft-birdstrike-avoidance-radar/

32. Source: pmc.ncbi.nlm.nih.gov
Link:https://pmc.ncbi.nlm.nih.gov/articles/PMC2607429/

33. Source: youtube.com
Link:https://www.youtube.com/user/FAAnews

34. Source: youtube.com
Link:https://www.youtube.com/noaa

35. Source: animalmigration.org
Link:https://www.animalmigration.org/aeroecology/index.htm

36. Source: facebook.com
Title: Federal Aviation Administration | Washington D.C
Link:https://www.facebook.com/FAA/

37. Source: Wikipedia
Title: National Oceanic and Atmospheric Administration
Link:https://de.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administration

38. Source: Wikipedia
Title: National Oceanic and Atmospheric Administration
Link:https://en.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administration