2023-05-14 10:35:00
Het Zeeuwse Landschap wanted to please skylarks with special crops, but research has now shown that a good crop alone is not enough. The mower also has to stay away long enough.
“This is what Valhalla should look like for a skylark!” Researcher Raymond Klaassen of Montagu’s Harrier – Knowledge Center Akkervogels can still remember as if it were yesterday how he first got out of his car at the start of his research near Burghsluis, on Schouwen-Duiveland.
“I saw a nice variety of grains and protein crops in the fields. Herb-rich field margins had been laid out around the plots, cultivation in alternating strips with also beautiful wood belts around the area. And then that sound of all those jubilant larks above your head. All I could think was: wow!”
Klaassen also knew that a large number of singing larks is not necessarily an indication of success for the species. “People often only look at the numbers of breeding birds, but in the end, of course, everything revolves around the number of young that manage to grow up per nest,” he says. The researcher therefore only became really enthusiastic when the knowledge center was asked by site manager Het Zeeuwse Landschap to find out exactly that: how are our larks really doing?
Likely breeding territories
The apparently simple question involved an unimaginable amount of painstaking work, Klaassen laughs: “To start with, we mapped out the singing males during two breeding seasons, in 2021 and 2022. On average, we found over 18 singing males – so probable breeding territories – per hundred hectares. Mind you: that is more than twice as much as in comparable arable farming areas in the Northern Netherlands and even more than ten times as much as in the arable farming areas on the South Holland islands.”
Klaassen and colleagues then went to those territories from the car to see exactly where the birds dived into the crop after their minutes-long song flight. “Sometimes you just spend 45 minutes or more staring at a lucerne plot to see if you see a bird flying in or out. And then you have to look for a very small nest on the ground among all those plants.”
Grow into a ‘flying’ lark
In the end, the researchers found no less than 55 nests of skylarks during a two-year study. They counted the eggs, measured the chicks to determine their condition and followed the families over the two weeks or so it would take them to grow from hatched chick to ‘fleeting’ lark. But just a little too often it didn’t come to that. Mowing turned out to be an important cause of loss; the deadly reaper then came just before the moment the chicks were to fledge.
At the end of two years of observation, the researchers saw just under three in ten litters successfully producing young. In total, all nests found yielded an average of less than two fledged young. “That is just not enough to compensate for the natural annual mortality of the parent birds, in other words to maintain the population,” says Klaassen.
The sobering conclusion of two years of research is therefore that the carefully arranged lark landscape was not Valhalla. It may even have been counterproductive, because the larks are attracted to the protein crops, but are then unable to successfully breed there, Klaassen assumes. Although the researcher certainly does not dare to claim that they would have done better elsewhere, in regular crops.
Decimated population
Despite that damper, Klaassen thinks that the research has indeed provided tools to mean something for the plagued birds. And a look at the statistics shows that they can make good use of that. In the 1980s, the collected bird counters of Sovon Bird Research easily counted 100,000 pairs of skylarks, but now less than half of these have survived.
“The protein crops, such as those grown in Zeeland, are probably the key,” thinks Klaasssen. “A crop such as alfalfa on the clay or a grass-clover mixture on the sandy soils gives an open structure in which the birds can nest well. In principle, it also needs to be fertilized much less often, because these types of crops can fix nitrogen from the air with their special root nodules.”
“No pesticides need to be used either; all conditions that should in principle give a lark enough time and food to raise the young. We also see that the larks hardly have to leave such an alfalfa field. Apparently they easily scrape together the food for their young there.”
A second or third attempt to breed
Things go wrong when a farmer starts fertilizing between mowing sessions to increase production. Then the crop grows so fast that it has to be mowed again within six weeks; too fast for the lark to complete the whole cycle from oviposition to fledging of the young. After mowing, a lark will usually make a second or third attempt to breed, but if the mowing machine comes by again within six weeks, it won’t help the bird.
Klaassen draws hope from the changing European agricultural policy. “There has recently been an important place for protein crops such as alfalfa. It fits in with the pursuit of a more circular agriculture. If we start growing more protein in Europe, we will also have to import less soy from Brazil, for example.”
However, cultivation will then have to take place less intensively than is currently the case. “And that also fits in well with European agricultural policy,” says Klaassen. “With the nitrogen problem and also the problems with water quality, less fertilization is a good idea anyway.”
Crops get lazy
“You also make better use of the capacities of the plants themselves. It has been shown that nitrogen-fixing plants such as alfalfa and clover become ‘lazy’ if you give them too much fertilizer. The root nodules with the bacteria that can fix nitrogen from the air then work less efficiently, so that you lose most of the benefit.”
All in all, according to Klaassen, not much is needed to really solve the problems for the Zeeland larks. “Working just a little less intensively and therefore just a little more rest between mowing sessions would have meant the difference between flying out or being mown to pieces for most of the nests we followed.”
Tenancy construction
Despite the somewhat gloomy conclusion, client Het Zeeuwse Landschap is pleased with the results of the study. That is what ecologist Wannes Castelijns says on behalf of the site manager. “We have been working with a special lease construction for ten years. With the support of the Postcode Lottery, we were able to buy 50 hectares of fields. We lease them out at a relatively low rate.”
But, he emphasizes, “on the condition that the tenants also take measures for the farmland birds on the rest of their land. The ‘hunger’ for agricultural land is big enough here, so that several farmers are willing to cooperate. In this way we can now stimulate a nature-inclusive way of working on more than 500 hectares of fields.”
With the report in hand, Castelijns now wants to work with the farmers to see how they can further adjust the way of working. “Of course it has to fit the farmers. It is of no use to them if a crop stays on the field for too long and flattens out. But it must also suit nature. So we will now have to look at cultivation with less fertilizer or perhaps even at other crops that do better suit the timing of the skylarks.”
Read also:
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