Millions of birds take to the air in our country as soon as the fireworks start on December 31. Not only geese and ducks, but also other birds take to the airspace en masse. And they stay on the blades for a long time. On New Year’s night there are on average a thousand times as many birds in the sky as normal, with peaks of up to 100,000 times the normal number of birds. Even ten kilometers away from the fireworks, the impact is great. This is evident from new Dutch research published this month in Frontiers in Ecology and the Environment.
The biologists who led the research, from the University of Amsterdam (UvA), have been raising the alarm for years. They are one of the few groups in the world to use weather radar – such as that of the KNMI – to investigate large-scale disturbance of birds. In Behavioral Ecology they reported in 2011 that birds are still in the air en masse for at least 45 minutes after New Year’s Eve, with peak densities at an altitude of 500 meters.
Last year, researchers from Wageningen and Texel, partly also affiliated with the UvA, published another notable study. Together with colleagues from Germany and Denmark, they analyzed data from hundreds of geese with a GPS transmitter. It showed that on New Year’s night geese fly an average of five to sixteen kilometers further than normal, depending on the species – with outliers of hundreds of kilometers. During the first eleven days of January, the geese spend an average of 10 percent more time looking for food to compensate for their loss of energy. The magazine Nature picked up this article and released it late last year as ‘research highlight’.
And now the new research, which takes things even further. “Weather radar technology is improving rapidly,” says first author Bart Hoekstra of the UvA. “As a result, you can now see much more detail – and thanks to better software, we can now also interpret that data better. You can now say much more accurately: this is a rain shower, and these are birds. And that is important, because it often rains during New Year’s Eve.”
The new technology also provides a lot of new information spatially. “This allowed us to compare these weather radar data on the map with the results of bird counts, which are carried out in a very detailed and systematic manner in the Netherlands,” says Hoekstra. As an example, he mentions the large-scale winter counts of water birds, coordinated by Sovon Bird Research Netherlands and carried out by thousands of volunteers. But also counts of birds in other areas, such as forests, heaths and cities. “And that’s great,” says Hoekstra, “because until now we have been very focused on waterfowl. We didn’t yet know how other birds react to fireworks. It now appears that they also take to the air on a large scale – although less than water birds.”
He also finds the large scope of the impact of the fireworks worrying. “That influence is greatest within the first five kilometers, but even at ten kilometers there are still ten times as many birds in the air on New Year’s night as normal. That is really huge. Flying is one of the most energy-consuming activities for a bird. So this is a very costly form of disruption.” The previous research into the extra eating time in geese was limited to the first eleven days of January, but it may then take several days before the energy balance returns to normal, Hoekstra emphasizes.
Is all this sufficient reason to ban fireworks? “That is a political and social choice,” says Hoekstra diplomatically. “We can only say: the impact is great and widespread. And it is not just limited to the hour when we light fireworks.”
The Nature Conservation Act states that you may not disturb wild animals, Hoekstra notes. “At least, not intentionally. So if you know that something causes such a large-scale disruption, you could draw your conclusions from that.”
According to the researchers, a complete ban is not necessarily necessary; In their article they argue for limiting fireworks to urban centers, or for establishing large fireworks-free zones around waterfowl areas. Hoekstra: “Think of the floodplains of the major rivers. But also, for example, Waterland, the Biesbosch and the Vechtplassen area.”