As the days get shorter, the Netherlands, a low lying waterlogged country, becomes a safe haven for approximately five million waders, gulls, ducks, and geese, which spend the winter here resting and foraging in fresh water lakes, wetlands, and along rivers. Many of these birds travel to the Netherlands from their breeding ranges in the Arctic. Many of these wetlands are part of the European Natura2000 network, which is an initiative that aims to assure the long-term survival of Europe’s most valuable and threatened species and habitats.
Every New Year’s Eve the people of the Netherlands, like many countries around the world, seem to be taken over by a fireworks frenzy. People are allowed to light their own fireworks on New Year’s Eve and they do it with great zeal. It has become anintegral part of New Year’s celebrations, with an estimated 10.8 million kg of fireworks ignited each year. While the negative impact of fireworks on public health is often discussed in the media, the potential negative impact on wildlife is rarely considered.
Over the last several years, ecologists at the Royal Netherlands Air Force have been registering unusual flights of thousands of birds on military surveillance radar on New Year’s Eve, with birds appearing to flee in response to New Year’s Eve fireworks. These bird movements are monitored by radar in order to develop forecast models of bird migration, and provide near real-time warnings to alter flight planning and reduce the risk of collisions between birds and military aircraft. In 2010 a multi-disciplinary team, with researchers from the University of Amsterdam, the Netherlands Meteorological Institute (KNMI) and the Royal Netherlands Air Force (RNLAF) got together to carefully document the reaction of free living birds to fireworks on New Year’s Eve for the first time, and try to quantify the number of birds involved.
This study found that each year on New Year’s Eve, birds alight from water bodies en mass just after midnight and climb to altitudes of 800 metres above the ground surface. These altitudes far exceed any these birds would usually reach during local flights, and are in fact comparable to flight altitudes measured during migration. Birds fleeing to these unusual heights appear to remain there for up to 45 minutes in dense flocks, and it is likely that these flights are energetically quite costly and stressful for the birds. It is an unexpected investment in flight and birds then the need to resettle somewhere safe in the middle of the night. It is estimated that hundreds of thousands of birds take flight, just within a 40 kilometre radius of where the radar was taking measurements. If we consider the entire country using this statistic, millions of birds could be affected. These figures are quite staggering, especially when considering that birds are disturbed from areas that are otherwise designated for conservation of the species, especially during the winter and migration season. This phenomenon has also been observed in Belgium, so this issue is clearly not isolated to the area where this particular study took place.
While the long term impact of these findings on birds is not yet clear, journalists and policy makers would like a decisive answer to the question, “what is the impact on the birds, and is this a serious problem?” However the answer to such a question is still elusive. Based on the flight behaviour that’s been measured, it is clear that there is an immediate energetic cost for the birds while sleep or foraging activities may be disrupted. While we do not expect that these evasive flights are generally life threatening, there may be other indirect effects. For example, immune capacity could be reduced, which might increase the risk of acquiring diseases or the ability to deal with harsh weather conditions. Furthermore, there could be physiological costs resulting from a stress response to fireworks.
Occasionally, the evasive response in combination with adverse weather conditions reducing visibility, or flight capacity, could have detrimental results ending in collisions with static objects in the landscape or with aerial vehicles, for example. This was observed in a recent report about red winged blackbirds seemingly falling out of the sky in Beebe, Arkansas, due perhaps to similar circumstances, and showing that occasionally such a response can be deadly. Direct and indirect impacts aside, we have seen that birds, just like dogs and cats and perhaps many other animals can have an acute response to fireworks and do their best to flee from this perceived threat. The observations in the Netherlands are perhaps extreme due to the high concentrations of birds found in waterbodies in the winter and the close proximity of human activity, and we can expect responses on such a grand scale in other parts of the world where conditions are similar. Initiatives such as the European Network for the Radar surveillance of Animal Movement, could help elucidate the scope of such problems in the future, while the use of radar remains an extremely powerful tool to reveal aerial behaviour that would otherwise remain invisible.
Featured image credit: “Fireworks” by jeff_golden. CC BY-SA 2.0 via Flickr.