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Dr Vince Lea

Appropriately enough, Mayflies featured in the sightings this month.

Studying our invertebrates

The meander on the Bourn Brook which we restored four years ago was surveyed in the middle of the month, to see what species of aquatic invertebrates had colonised it. We used the same technique that we have applied to a section of the brook at Telegraph field, restored by the CRT in the mid 1990s. We found very encouraging results at the Westfield meander, with a similar array of invertebrate species and abundance to the Telegraph field surveys, but with a higher number of the large true Mayflies (most likely Ephemera danica) and a lower number of flat-bodied stone clingers (a smaller type of Mayfly). This probably reflects the natural clay stream bed at Westfield, compared with the large cobblestones which have been used to enhance the stream flow at the Telegraph field restoration site. The true Mayfly larvae burrow into soft substrate and filter out debris from the stream water, usually taking two years to grow to full size (up to 30mm/over an inch long), shedding their skin each time the nymph grows to the next size up. Eventually they emerge from the stream and hatch into flying adults, the mayflies which trout fisherman know so well. These large insects are initially fairly helpless as they emerge from their nymphal skins on the water surface, and struggle to get airborne – an ideal opportunity for a hungry fish. They fly to bankside vegetation and then, fairly soon, change their skin again to become a more brightly coloured, longer tailed version of themselves, the breeding stage of the insect. These two adult phases are known as the ‘dun’ and ‘spinner’ in fishing terms and this metamorphosis of two flying stages is unique to the mayfly order. The male spinners form swarms which dance in the air near the river, tempting females to come and mate with one of them. The mated females then lay eggs by dipping into the water surface in flight, and eventually when all the eggs are spent she floats on the water surface and becomes the trout’s second easy picking opportunity! By emerging en masse at the end of May, the mayflies try to outnumber the many fish, birds, bats and spiders etc. that feed on them, and enough manage to complete the lifecycle.

Barton Wildlife ‘Safari’

At the end of the month we had a wildlife safari with some of the Barton village families, and it was great to show these large and fascinating insects to the children. I was very impressed that one of the boys already knew about the unique lifecycle! Numbers of this insect seem to be quite good this year, but not enough to sustain a trout population yet perhaps. It is a long-term hope that wild trout will eventually recolonise the Bourn Brook but we have a lot more restoration work to do before that becomes possible I think.

We also saw plenty of Brown Hares on the safari, they have particularly appreciated the very short spring-sown barley which has not grown very well in the direct drilling experimental field, probably due to the very dry spring soil conditions. While the better-established crops are now too tall for easy feeding, this barley is still only a couple of inches high. In one small strip of it, I counted 10 hares together on one early morning bird survey visit. While the hares are loving this opportunity, it is not going down well for our farmer, Tim, who would like a lot more rain to come along and get the barley growing properly! It has been pretty dry all month.

Another star sighting on the wildlife safari was the Barn Owl, which we saw near the nestbox and bird hide in Warners Corner. We are fairly sure we could hear a female snoring in the box during the afternoon, and a male was disturbed from the old barn during the day, later to be seen hunting at dusk. A pair of Barn Owls also appeared to be occupying the Roman Hill nest box based on observations made during a dusk survey visit. Towards the end of June we will be checking the nest boxes and fingers crossed it looks like being a better year for them this year after last years lack of chicks.

Farmer and wildlife monitors have been going 'cuckoo' over the sightings and calls recorded in Barton and the surrounding areas.In the past week, wildlife monitor Roger Buisson spotted a Cuckoo flying over the farm yard, head of wildlife monitoring Dr Vince Lea has heard the calls on several occasions (including by his house half a mile away) and farmer Tim Scott's wife Libby managed to catch distant call on her phone!

Posted by Countryside Restoration Trust on Monday, April 29, 2019

Highlight of the month

At the end of April we had the very cold Mayfields open day, where one of the few signs of spring was hearing a Cuckoo – something that is becoming increasingly unusual in the countryside these days. During May, I’m pleased to report that a Cuckoo has been heard quite regularly around Lark Rise Farm all month, the first time we’ve had a long-stayer for a while. He probably travels a lot further afield as most male Cuckoos have very large territories (10 miles or so) so we don’t hear him every day, but he keeps coming back to Lark Rise where there are plenty of good caterpillars, they particularly like the hairy ones! I also heard a couple of Cuckoos at Green Farm on the bird survey there in the middle of May. It seems the last couple of springs have been slightly better all round for this much loved species, let’s hope this reversal of fortunes continues.

Dr Vince Lea
(Head of Wildlife Monitoring)