‘Birds are bothered by holidaymakers’

Every Friday – officially her day off – she worked on it. And now, after more than a year, there is a report of 456 pages, divided into two parts: Disturbance of birds through recreation† “I did my best on the summary,” says behavioral biologist Karen Krijgsveld in the Wageningen spring sun. “Because I also know that not everyone will read that entire report. But it is a subject that concerns everyone. Precisely because we are all making increasingly intensive use of nature.”

Krijgsveld wrote the report on behalf of Vogelbescherming Nederland, with the cooperation of Britt Klaassen and Jan van der Winden. “In fact it is an extension of two earlier versions, which I wrote in 2004 and 2008. But since then, both nature recreation and research into it have increased enormously. Nature is being opened up in more and more areas.” There are about 500 people per square kilometer in the Netherlands, so the pressure on nature is great. The Dutch nature reserves were visited en masse, especially during the corona pandemic, the report says. As a result, visits to nature reserves were up to 40 percent higher than in previous years. “It also depended on where you looked. Some areas were closed off or difficult to access. There you saw that nature flourished. This also emerges from this research: when people disappear from an area, this often has positive consequences for birds. Conversely, you see that disturbances occur in areas that were previously closed to people and opened up later.”

How do you recognize a disturbed bird? Because he flies away?

“It’s not that simple. Until recently, disturbance was mainly measured by flight distances, i.e. the distance at which you can approach a bird before it takes off. But nowadays we know that disturbance also occurs less visibly. With a bird of prey that stays on its nest when you approach it, the conclusion is not: nothing is wrong. But heart rate and stress hormones increase, and breeding success—that is, the number of young successfully reared—may fall. Birds constantly have to make trade-offs: if I sit still while a potential enemy approaches, it could kill me. But if I fly up, I’ll drop my eggs. Or: when I fly up, it costs me energy, and I don’t know if I can find enough food elsewhere to fatten up. This set of risk factors and interests is also called the landscape of fear† Birds are surrounded by potential danger. Of course, that threat doesn’t just come from humans. But recreation does contribute to it.”

Are some bird species more sensitive than others?

“Broadly speaking, the flight distance for small birds is shorter than that of large birds. In practice, however, that distance also depends on the context. In an open living environment – ​​for example on the water – a bird will take off faster than in the forest. If there are dogs, especially running loose, the distance will also be greater. And not every form of recreation has an equally strong effect.”

Who is the most disruptive? A hiker, a sailor or a kite surfer?

“The latter. In general, disturbances on land have less impact than on water – with walking and cycling, the impact is mainly large due to the large numbers of people. On the water, the open environment and the large numbers of waterfowl play a role – during bird migration periods you can easily have hundreds of sandpipers or ducks together. And with kitesurfing, the kite has an even more disruptive effect: it swings erratically and unpredictably through the air. Now I’m not saying this to blackmail kite surfers. On the contrary, there are collaborations with surf clubs to set up kite surfing zones along beaches. With buoys it is then indicated where the recreation area ends and the bird rest area begins.”

What other measures are possible?

“It is important that site managers take their responsibility. They must ensure that the carrying capacity of an area is maintained and that the numbers of birds do not decline. For this it is important to zoning, both in time – so for example closing an area during the migration period – and in space. On a lake where there is no quiet escape option, birds will experience stress and disappear. So choose which zones are for birdlife and which for recreation, and design your area accordingly – with surf zones, walking and cycling paths, picnic benches, lookout towers, parking lots, you name it. We know from research that habituation can occur among birds if holidaymakers stick to paths and waterways. But only one person has to deviate from the fairway and hop, then all the birds will take to the air.”

However, not all places with water sports enthusiasts also have water birds.

“No, but that doesn’t mean they weren’t there. That’s the tricky part: many birds leave at the first disturbance in the morning, and then don’t dare to come back because new holidaymakers keep coming. It is also a matter of informing people. If people only see a row of wooden posts with a no-entry sign, they may ignore it. So place an information board next to it, so that people also know why it is important.”

Have you started to adjust your recreational behavior yourself?

“Partly. While walking I walk around groups of birds in an arc, and when I go birdwatching by car I make sure I drive slowly and don’t stop too abruptly. I can watch endlessly, but keep my distance, because such a direct focus feels very threatening to birds. But I like sailing, although I stick to the fairways, sometimes the birds are so close to those channels that they still get disturbed. Some of the disturbance photos in the report were taken by myself… But I wouldn’t mind at all if my favorite boating spots were closed to water sports enthusiasts for part of the year, for example during the autumn migration.”

Shouldn’t nature lovers just sit inside, so as not to disturb anyone?

“No, that doesn’t work. Contact with nature is important for all of us. And who will then see the value of nature, and who will then work to protect it? Nobody. If we do our best, recreation and nature can really go hand in hand.”