The black-tailed godwit is one of the most typical waders in the Netherlands. But for how much longer? The godwit’s breeding success rates have fallen significantly in recent decades. Research by Hans Schekkerman has revealed that this is caused mainly by a strong increase in chick mortality. Simple protective measures such as nest protection and postponing mowing dates no longer appear sufficient to increase the birds' chances of survival. Measures for wader management must be made more intensive and comprehensive, Schekkerman concludes. He will be awarded a PhD by the University of Groningen on 26 May 2008.
The godwit is a so-called precocial bird: its newborn chicks immediately start finding their own food. This active way of growing up means that the chicks need about 40% more food than young birds who are fed in the nest by their parents. On the other hand, precocial chicks are able to eat small prey that altricial chicks have no access to because their parents have no profitable way of transporting it to the nest.
Decline in food supply
Godwit chicks mainly eat insects found in the vegetation, such as small flies, spiders, crane flies and beetles. However, this has become increasingly difficult in recent years, mainly due to a combination of more intensive agricultural use of grassland and climatological changes. For example, earlier mowing dates and higher amounts of fertilizer used on grasslands has resulted in a decline in the number of insects and thus in the chicks’ food supply.
First cutting
Climatological changes make the problem even more serious. Schekkerman: ‘Since the 1980s, the winters and springs have been noticeably warmer, and the agricultural industry has adapted to this climatological change. Farmers can harvest their first grass two to three weeks earlier in the spring than in the past. Nowadays, the first cutting thus often coincides with the moment when godwit eggs hatch, in mid-May. And it’s a simple fact that there are two or three times as many insects in unmown grassland’, says Schekkerman. Chicks will therefore immediately move to unmown land, if there is any.’ Interestingly, the godwits have not adapted their breeding time to the climatological change in the past twenty years. As a result the unmown grass will often have grown too high and thick to forage in by the time the eggs hatch.
Increase in losses to predation
Another major cause of chick mortality are predators such as buzzards, stoats and grey herons. Some of these predators, in particular the buzzard, have increased in numbers in recent decades. In addition, the increasingly early mowing dates play a role here too: chicks are much more visible to predators in mown grassland.
More intensive wader management
A more intensive form of wader management is therefore needed to protect the godwit. Combined measures such as later mowing dates for more plots, limiting the amount of fertilizer used so that the grass does not grow too thick and a higher ground water level which prevents the grass from growing too early in the year may increase the foraging chicks’ chances of survival. However, Schekkerman realizes that these measures will be difficult to integrate in modern dairy farming. His recommendation therefore is as follows: ‘Wader management should focus on open environments that are suitable for the birds in other landscape-related aspects as well. There is not enough money to practise wader management everywhere anyway. Reality has shown that doing a little bit of management everywhere is useless. We should thus take smaller areas and manage these more intensively.’
Curriculum Vitae
Hans Schekkerman (Alkmaar, 1963) studied Biology at the UvA and will be awarded a PhD in Mathematics and Natural Sciences at the University of Groningen. He conducted his research at the Department of Animal Ecology, Centre for Ecological and Evolutionary Studies (CEES), of the University of Groningen and at the Centre for Ecosystem Studies (Alterra) of Wageningen University. His thesis is entitled ‘Nestvliederperikelen – steltloperkuikens in de ban van weer, landbouw en predatie.’ [Precocial bird matters – wader chicks at the mercy of the weather, agriculture and predation]. Schekkerman works as a researcher for the Vogeltrekstation [migratory birds station], part of the Netherlands Institute of Ecology (NIOO-KNAW) in Heteren.
Note for the press
More information: H. Schekkerman, tel. 06 – 128 219 85, e-mail: h.schekkerman@nioo.knaw.nl
