Two Men went to Mow a Meadow = Fen.
I must state here that the following are my observations during the Adults flight period during July 2015 and report it here because it was remarked upon by other Dutch naturalists who I have the great pleasure of meeting in the field. Excuse, the above humour of the title of this article, that was a sentence in a rather boring and long repetitive song that we were encouraged to sing on long family trips in the old car we owned when I was a young boy. The other English members here may have had to sing that ditty too.
Lycaena dispar batavus occurs in medium Fen sward that is cut in the summer. This cutting is essential to keep out scrub and dense taller reeds. When I had met those two botanists mentioned in the previous article, I asked them " why they thought ' batavus ' was so rare ". They suggested that one of the problems was the cutting of the fens too early, while the butterfly were still on the wing.
A good site for batavus which I found early on in the Weerribben, was along the road running north from Ossenzijl . This roadside site was very similar to the Woldlakebos lagoon locality but the breeding colony was in a dyke by the fen. A few butterflies were again found to be visiting Creeping Thistle Cirsium arvense. One morning I arrived here and a Large female L. dispar batavus was feeding at the thistles. I had seen another male and a female the day before but none were in very good condition.
The female today was occasionally leaving the thistles to bask in the fen vegetation. Then a lorry stopped and a man started to unload a hand held cutter and proceeded to cut the edges of the small fen. The female flew off into the fen. It was still only 9 am and then a tractor came and went into the fen lowering its great scythe and gone were the thistles and when I came back later the entire fen was mown. I wondered if the female survived but any other less active resting batavus might have not.
Figure 1. The female encountered just before the fen was cut. Cleaning herself after feeding at the thistles.
I was astonished and rather dismayed by what I had seen. Why do not the Park authorites cut the fen say in Mid-late August when the flight period is over.
The same day as the cutting of the roadside fen, I went to another site in the Woldlakebos where the day before there was a gathering of people. A number of Dutch naturalists were photographing a nice batavus male feeding on Purple Loosestrife Lythrum salicaria. This seemed to be the most well known Weerribben site. It was there that I met the helpful Dutch entomologist who I have previously mentioned . He was standing there in amazement and he was quite angry, they had also mown the fen containing the butterflies food source.
Figure two. The male at the more well known Woldlakebos fen-dyke site. Basking after feeding at Lythrum salicaria. The very next day the fen and nectar source were mown.
The Dutch entomologist thought that the mowing of the fen was astonishing. When I met the Warden ( see the last post ) and asked him why they were cutting the fens with the nectar source he stated " they are cutting too early " and he said " but there is the well known site in Woldlakebos" when I told him that they have cut that too, he said " he was quite angry about that" and " was going to bring it up at a management meeting the next day". It seems almost unbelievable that those Park officials that hire the contractors to cut the fens, do not even bother to consult the warden!!
Considering how rare batavus is and, the Dutch class it as endangered, the act of cutting the fens with nectar sources during the height of the flight period during the butterflies centennial year when they are celebrating this special butterfly seems to be rather negative conservation.
Hopefully next year when two men come to mow the fen it will be later in the year!!
In writing this, I must say that there is probably a number of contributing factors, as to why batavus is a rare and declining species. The Dutch have been successful in maintaining a viable breeding population of L. dispar in a large area of fenland, while we Brits did not and drained them all as far back as the 1850s!! All because of a lot of greedy landowners. Shame on them!!
Next Meetings in the Weerribben.