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Monday, 26 October 2015

The Joy of Exe

Sunday 11 October 2015

A slightly murky Sunday, fitting for an elucidation and verbal preview of the Exeter flood relief works in Riverside Valley Park, with thanks to officers from the Environment Agency and Exeter Growth Point, who have been advising on wildlife measures for the scheme, and who kindly led our walk.

Tons of earth have and will be moved during phase 1, and there has been very conspicuous clearance of trees and scrub. If it looks like a building site, it's because it is. At a cost of £30 million, running from upstream of Station Rd in Exwick to downstream of the Bridge Rd A379 swing bridge, and from 2015-2019, this is a big project. Most of the funding has been provided by central government, and calculated to be much less expensive, risky, and damaging than another 1960s level flood inundating the Quay, St Thomas and Marsh Barton. While this was being explained, we could hear, and then glimpse, a skylark singing high overhead.

Future days - looking ahead towards and back from Trews Weir footbridge, comparing with aerial photo

The original 1970s channels were straight-sided and in places hard-engineered to be purely functional, funnelling water as speedily as possible out to the Exe Estuary; the new scheme plans for future function and maintenance to be more sympathetic to biodiversity. Some siltation, and taller growth of wetland vegetation, will be allowed for. Near the quay, the 'cormorant wall' with the main river has been lowered so that the flood channel will routinely receive water more often. This open water area below the Trews Weir footbridge is a regular spot for waders and other water birds. A new fish ladder has been constructed in the corner for high flow situations when fish could get drawn into this side channel. Sure enough, cormorants, in their 'wings out to dry' posture, were stood along the wall, alongside black-headed and black-backed gulls. Below them grey and pied wagtail investigated the flood channel.

Fish ladder, to left, ascending the lowered 'cormorant wall'

The former grassed area to the south of the footbridge has now been dug out, deepened to increase water storage capacity. The two steep and straight drainage ditches have been replaced by a more naturalistic, gentler sloping and meandering channel, while the surrounding banks, between the cyclepath on one side and the allotments on the other, are to become wetland wildflower meadows, part re-seeded, part naturally regenerating. Not waiting for any of that, a fox has already contributed some of its own bankside digging.

Fox & sons new residence

For some 5-6 consecutive years, we ran summer pond - or rather, ditch - dipping here to coincide with Exeter Cycle Sundays. Over that time we recorded sticklebacks, dragonfly larvae, water scorpions, water fleas, palmate newts, water stick insect, eels, water fleas, flatworms, pond snails, among other freshwater species. The new scheme is to include paths, and a boardwalk which can double up as a dipping platform (look out for a pond dipping event in 2019). Taking in the scene, a wedge - Google tells me - of swans, overflew us, whirring by in formation.

Views from a bridge, looking towards (earlier and sunnier in the year), and back from, the footbridge by Bromhams field

Viewing from the Bromhams field footbridge, I can remember when all this used to be trees. The change looks drastic, though with more light reaching the open banks, there should be greater growth and flowering of shrubs and herbaceous plants. Some of which, such as invading Himalyan balsam, will be controlled as part of aftercare maintenance. In strategic locations, such as on Bromhams field itself, lines of trees are to retained, with standing and fallen dead wood left in situ to rot down in their own time. While we were on the bridge, there was the piping of a kingfisher, then a flash of azure. We watched the kingfisher at the water's new edge for a few minutes. A magpie emerged from the row of poplars, followed by a sparrowhawk pair, with their characteristic flap-flap-flap glide.

Works so far have been necessarily destructive, and the restored areas will need 3-4 years to become established. But even from the current bank re-profiling and initial vegetation growth, one can imagine perhaps how it might eventually look: a wetland wildflower meadow, with open water ponds and flushes, dotted with wading birds. This is just Phase 1, with much more to follow. Land next to Station Rd in Exwick is to be set aside as a further flood storage area and nature reserve, while additional sand martin nesting sites are to be excavated into the existing tall concrete sidings there; new orchard planting is to take place next to the allotments by the canal at Trews Weir; and a further grazing marsh area is to be set aside at Countess Wear near Bridge Rd. This is because the city borne sections of the River Exe cannot be considered in isolation: upstream, the Rivers Creedy, Culm and Clyst feed the Exe at a crucial confluence, all the way up to Exmoor, where a mire restoration project will have the beneficial effect of absorbing, and releasing more slowly, high rainfall in head waters.

Let there be leat: plan of St James leat, and the real thing

We finished at the 'pooh sticks bridge' over St James leat, near the weir by Duckes Meadow. Twittering through the foliage was an autumn flock of mixed blue, coal, and great tits, long-tailed tits and goldfinches. A nuthatch was calling from somewhere, followed by a great spotted woodpecker's dipping flight breaking from cover. A moorhen clucked in the channel below. There may be future opportunities to get involved in wildlife surveys, and practical events to enhance the stream and bankside habitats; watch this green space.


Many thanks to Mary-rose and Simon for kindly leading the walk.

Some more info about the scheme is at
Environment Agency / gov.uk webpage link 
Exe Catchment Flood Management Plan 2012 pdf 


Following on will be the Exeter Green Circle walks on 18 Oct and 1st Nov.
Also look out for George's popular Quay and Belle Isle Park bird walk in February 2016.

Monday, 12 October 2015

Pentatomids and pavements

On central Exeter pavements recently, for example on Queen St, I've crossed paths with a small green shieldbug ambling along, the Birch shieldbug Elasmostethus interstinctus.

Like many of the 32 UK species, these over-winter as adults. Also seen this month has been the larger Green shieldbug Palomena prasina, except in winter this turns brown. The coloration will green up next spring, as the shieldbugs start to feed on their host trees once again.

Birch shieldbug 8-11mm, looks a bit like a smaller version of the 13-15mm Hawthorn shieldbug, except the 'shoulders' on the pronotum are not so pointed and are duller red; the rear of the Hawthorn shieldbug's wing membrane is also more extensively red, whereas this is more translucently clear in the Birch shieldbug. 
 
These two species are commonly found in urban areas, in parks and gardens, sometimes seen on ivy blossom. Maybe they were in town shopping around for late nectar or winter accommodation.

Some more information is at:
http://www.britishbugs.org.uk/heteroptera/Acanthosomatidae/e_intersinctus.html
http://www.britishbugs.org.uk/heteroptera/Pentatomidae/palomena_prasina.html


Monday, 5 October 2015

Ivy League

Ivy is starting to come into flower. Unseasonably late flowering (and hence a source of berries later on in winter), it is ever so useful for wildlife, and for an autumn small-scale mini-wildlife spectacle.

Some flower morphologies are designed for particular pollinators; in ivy the nectaries are fully exposed and open to all generalist nectar and pollen feeders. A 2013 scientific paper suggested ivy is so important it should be considered a keystone species. Some 70 moth species, 20 bugs and 12 beetles are associated with ivy, according to the BRC food plant database (Hedera helix www.brc.ac.uk/dbif/hostsresults.aspx?hostid=2563), and this doesn't include Holly blue butterflies, and the many hoverflies, bees and wasps that visit.
Red admirals on 29 Sept 2015 ignoring Buddleia
One bee especially to look out for is the Ivy bee Colletes hederae, first recorded in Dorset in 2001, and only recognised as a separate species in 1993. It forages almost solely at ivy, so is late flying; in more sense than one, our latest solitary bee. First Devon records date from 2008 and all county records so far have been from coastal locations. This year, Ivy bee emergence started in earnest around the last week of September 2015. Hence a short train ride to Exmouth, to see what could be seen.... 
Foraging Ivy bees
Burrowing Ivy bee

This properly golden yellow and black stripey bee was conspicuous in large numbers on flowering ivy near the beach, and zooming at ankle height around areas with loose sandy soil, where they dig their burrows. One question is why they aren't found away from coastal areas in Devon (perhaps due to availability of nesting sites?) - any inland records for the county would be of great interest. Records can be submitted to DBRC and to the BWARS Ivy bee mapping scheme.

On the walk back to Exmouth station, a few Ivy bees could be seen on hedgerow ivy, but in much smaller numbers. They were joined by numerous butterflies and hoverflies, all mostly ignoring the Michaelmas daisies nearby. To emphasise the point about the range of species supported by ivy, popping up among the foliage were also some flowerheads of Ivy broomrape Orobanche hederae.