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Background image, geese on the water in winter

Monitoring the reaction of birds to fireworks

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Birds flee en mass from fireworks on New Year's Eve

Every year thousands of waterfowl take flight right after midnight as citizens shoot their fireworks. Researchers from the University of Amsterdam, the Dutch and Belgian weather services and the Royal Netherlands Air Force conclude this based on measurements with weather radars in the Netherlands and Belgium. While normally used to observe rain, these radars can also detect flying birds.

On New Year’s Eve the radars detected thousands of birds in the air up to altitudes of 500 m. High densities of birds are measured in the radar air space for 45 minutes after fireworks are first lit. The highest densities were observed over grasslands and wetlands, including nature conservation sites, where thousands of waterfowl rest and feed in the winter.

The animations show images of radar reflectivity within a 40 km radius from the radar in De Bilt. Reflectivity abruptly increases every year at midnight as birds take off in great numbers. Dark red represents a high radar reflectivity, which is correlated with a large density of flying birds. The highest density of birds in the air at one time may reach 1000 birds/km2. If it rains, birds can be invisible because the reflectivity is dominated by the rain.

Researchers from the University of Amsterdam, KNMI and the Royal Netherlands Air Force have been studying the response of birds to fireworks on New Year’s Eve using weather radar for several years. In 2012/2013 the Belgian Meteorological Institute joined this effort. More information can be found in the scientific article "Birds Flee en mass from New Year's Eve fireworks" and the blog-post "New Year’s Eve fireworks cause a mass exodus of birds".

Overview of the area, bordered by Amsterdam, Harderwijk, Oss and Rotterdam

The images (center panel) are centered around the KNMI weather radars in the Netherlands, Herwijnen (upper image) and Den Helder (lower image). Important areas for waterfowl around the Herwijnen radar are: The Biesbosch (SW), the river area around the radar and the Nieuwkoopse- and Reeuwijkse plassen in the NW part of the image. The weather radar from Den Helder is surrounded by important Natura-2000 areas for waterfowl including tens-of-thousands of waders and ducks (Waddensea, Texel and North Sea coastal area).

Monthly waterfowl counts

Hans van Gas­te­ren, one of the re­search­ers, con­ducts month­ly wa­ter­fowl counts for SOVON in the lakes and sur­round­ing grass­land areas around Reeu­wijk (blue area in the map on the left). This pro­vides in­for­ma­tion on spe­cies and num­bers of birds that are po­ten­tial­ly dis­tur­bed by fire­works, and may there­fore be seen on ra­dar.

Large num­bers of ducks spend the day res­ting on the lakes, and for­age in the sur­roun­ding grass­land areas du­ring the night. Geese and gulls show the op­po­site pat­tern. They roost on the la­kes, and are there­fore prime can­di­da­tes to be dis­tur­bed on New Year's Eve.

Geese num­bers have been in­creas­ing over the last five years, while ot­her spe­cies' num­bers have been sta­ble. On ave­rage, there are ap­prox­i­mate­ly 8,000 White-fron­ted geese, 2,500 Grey­lag geese (with a peak of 6,000 birds in De­cem­ber 2013), 30,000 Eur­asian Wigeons and 1,500 Gad­walls. Roost counts in­di­cate that 15,000 - 25,000 Black-head­ed Gulls and Com­mon Gulls sleep on the la­kes.