On average, Dutch breeding birds increased in number over the period 1980-2010. Common species even did better than birds in other European countries. Field birds are an exception: they have declined sharply both in the Netherlands and elsewhere in Europe.
Dat blijkt uit onderzoek van de stichting Centrum voor Landbouw en Milieu (CLM) en het Centrum voor Milieuwetenschappen van de Universiteit Leiden (CML), online open access gepubliceerd in het Britse tijdschrift Bird Study.
In Europe, scarcity has played a key role
The authors looked for factors that could explain the increase and decrease in bird species in the Netherlands. They suggested that the type of habitat was the most important factor: for example, the intensification of agriculture could explain the decline of birds of farmland.
But in 2015, a British study of bird trends in Europe from 1980 to 2010 came to a startling conclusion: it was not habitat type but bird scarcity that was most closely linked to evolution. bird populations: common species have become rarer and rare species have become less rare. Wil Tamis of the CML offers a possible explanation for this population growth: “It could be, for example, that in conservation policy, there is more attention for these rare species, which made them increase in number. .
Species of all rarity classes in the Netherlands are doing better
Helias Udo de Haes from CML explains that they predicted a different trend in the Netherlands: “We suspected that in the Netherlands it was exactly the opposite. But none of the hypotheses proved to be tenable: in the Netherlands, species of all rarity classes have increased, which is good news for nature. We have confirmed our hypothesis that in the Netherlands habitat is more important than scarcity. ‘
Nature policy is bearing fruit
According to the researchers, the fact that the habitat factor was not dominant in the European study was probably due to differences between European regions: intensification of agriculture occurred in most regions, but not in others. On average, the effect of habitats is therefore less important at European level.
In the Netherlands it is mainly waterfowl, marsh and forest birds that have improved considerably. The main causes are probably the expansion of water, marsh and forest areas, improved water quality and aging forests. In addition, dead trees more often remained in the forest. Thus, the nature policy seems to be effective for these areas.
Large bird species do better
Based on impressions from the field, the authors also expected larger bird species to do better than smaller ones. For example, they saw an increasing number of storks, herons, buzzards and geese. They did find a difference, but it was not found to be statistically significant: “The explanation is probably that the British had excluded geese from their study,” says Wouter van der Weijden of the Center for Agriculture and Agriculture. environment. “To keep the comparison pure, we had to do the same, even though the geese in the Netherlands actually became more numerous. Overall, we dare to conclude that the larger species do actually fare better than the smaller ones. ‘
Impact of insect decline not yet visible
Finally, the authors also expected that bird food choice would have an effect on the increase and decrease of different species. Researchers based their suspicions, for example, on alarming reports of declining insects. But the group of insectivorous birds did not do any worse in the Netherlands than the other groups. effect.
Both regional and European analysis for a targeted nature policy
According to Udo de Haes, rhw research illustrates the importance of regional and European trend analyzes. “It reveals various trends and factors. It is important to combine the two levels of scale for a targeted nature policy. It has also become clear once again that we need to pay much more attention to farmland birds. In addition, research is needed on the differences in trends in a wider range of habitats (such as urban, coastal, heathland and dunes) and a wider range of species groups. Think of subgroups of insectivores, generalists versus specialists, migratory birds versus resident birds, and protected versus unprotected species. It could be very informative.
Communication: Helias A. Udo de Haes, Wil LM Tamis, Ellen Cieraad & Wouter J. van der Weijden. Comparison of breeding bird trends between the Netherlands and Europe. Bird Study, DOI: 10.1080 / 00063657.2021.1939652
To the Dutch press release of CLM – Broedvogels doen het in Nederland beter dan in Europa