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Monday, 26 September 2016

Ivy bee event goes ahead smoothly shock

Ivy League event 25 Sept 2016

Sometimes organising a wildlife-spotting event is a tense matter of hope and prayer that the featured species will actually turn up.

No such problems yesterday, luckily dodging the showers, for a warm blue-skied autumn afternoon looking for the Ivy bee Colletes hederae, with colleagues from Exmouth Local Group.  

This handsome solitary bee was busy in numbers, swarming at ankle height round the coastal grasslands of the Maer, and the mini-quarries of bare earth where it excavates its nests. Faster than the eye can follow, only when stopped for some digging were there chances for a good view, and non-blurred photos.
Head in the sand - busy burrowing out a nest site

Not recognised as a separate species until 1993 (from the similar C. halophilus and C. succinctus), and first sighted in the UK in Dorset and at a single location in Devon in 2001, it has gradually been spreading its range since. Ivy Hedera helix , which flowers late in the year, is its predominant, and often sole, pollen and nectar source of choice; hence, in sync, the Ivy bee is also late flying; in more sense than one, it's our latest solitary bee.

Although solitary, where the habitat is suitable, as it definitely is at the Maer, large numbers can nest in aggregations, a fascinating, often overlooked, spectacle, right under one's feet.

Potted (natural) history: Ivy bee reveals itself to budding naturalist

From the nesting site on to the other main component of the life cycle, stopping off to check out a dense clump of ivy. Ivy bees were conspicuous foraging here, alongside numerous other bees, wasps, hoverflies and other insects, at this important late food source. A successful event, which the wildlife also turned up to.

Eristalis hoverfly (note looped vein in wing)

Some further information about the Ivy bee:

Monday, 5 September 2016

Knotgrass in my backyard

Life after concrete (reprise)

Knotgrass Polygonum aviculare 
The sort of plant which catches the attention of herbicides, in the name of botanical cleanliness. But Wait! Stop before you spray!   

Not just a weed, this is a bare ground coloniser, taking nature's first steps to fill a vacuum. It has noted wildlife value: as the 'aviculare' part of the name suggests, birds such as finches and sparrows feed avidly on the seeds
Knot overlooked ... supporting wildlife on Cathedral Green

Added to which, the long flowering period can support insects from May - NovemberRight now Knotgrass clumps are flowering in profusion around Cathedral Green and St David's church, in the worn bare areas among the grass

The tiny clusters of 1-6 flowers emerge at the bases of the upper leaf stalks. The three inner stamens are bent over so that pollen falls directly on the styles; the others point outwards for any passing insects. But this isn't all: there are also concealed flowers under the membraneous sheaths (the ochreae) around the stem 'joints' (the joints give the plant the other part of its scientific name: Polygonum 'many - kneed'). These hermetically sealed flowers do not open (or in technical terminology, are cleistogamic), which, along with the arrangement of inner stamens, ensures some self-pollination at least. It is said Knotgrass may produce similar cleistogamic subterranean flowers underground as well, among its roots and runners, alongside which the tap root can penetrate up to 45cm deep into the ground. 

As a multi-pronged pollination and propagation strategy, these would be useful adaptations for an annual plant, which dies off every year, but for which the seed bank must persist biding its time in the soil for years, until the next unpredictable opportunity brings seeds to the surface where they can expeditiously germinate.

As well as a pioneer species to kickstart vegetation recovery on bare ground, Knotgrass is a host plant for over a hundred different invertebrates: some 9 beetle species, 2 flies, 8 bugs, and 93 moths, especially among the the Geometer moths.  

Tolerating a bit of Knotgrass in the bare patches and nooks and crannies among the concrete would be small, simple and effective action to help our urban wildlife.    



Sunday, 4 September 2016

Have we got newts for you?

Monday 29 August dipping at the new flood relief channels, Riverside Valley Park
The quick answer would be nope, we didn't find any newts.
Net gain: pondlife enthusiasts dip in 

Possibly the new channels are just too new for any newt population to have re-established itself yet. We used to run this event annually over several years, recording numbers of palmate newts, water scorpions, sticklebacks, dragonfly, damselfy and mayfly nymphs, and the occasional water measurer and eel.

In addition to being still quite bare, yet to develop more mature bankside and floating- leaved vegetation, the newly re-formed channels (see post 'Joy of Exe' Mon 26 October 2015 about the larger flood relief scheme) flow much more quickly, shallowly and clearly, as opposed to being deeper, standing water. It might suggest we were in for a long afternoon. 

But the first nettings proved otherwise, with abundant water boatmen and water snails. These seemed both numerous and quite small sized, new colonisers moving in to the new habitat.  
Spot the freshwater minibeasts ... they are in there somewhere

As the tray contents settled, more species were found with successive dips: Daphnia water fleas, water slaters, midge larvae, freshwater shrimp Gammerus, a gelatinous glob of snail eggs. A stick turned out to contain a Caddis fly larvae. Most of these feed on vegetation or detritus, quite sparse in the new and constantly flowing channels. We also found several freshwater leeches (probably Erpobdella octoculata, with its 8 eyes and mottled coloration), a minnow, and a planarian flatworm, from the different ventral and dorsal colouring Dugesia polychroa, with its amazing orange eye slits and partial shapeshifting. Despite the flow, there were also a few pond skaters skimming over the surface.
Brown and sticky. With a caddis fly inside
As to what could be supporting such proportions of predatory species ... a pond, or a freshwater channel, is a bug eat bug world, where survival is of the biggest, the fastest growing, or the best at hiding. 

Interestingly while most of minibeasts in the newest channel were early stage, mobile or fast-developing species, some of the other deeper, more established and weedier channels with still water contained other species, such as sticklebacks, damselfly nymphs, and a dragonfly nymph (likely one of this year's Broad-bodied-chasers Libellula depressa), in the early stages of accumulating its cladding of algae.

Around the watercourses themselves were a few other terrestrial species to spot amongst the emerging vegetation: a Common darter dragonfly basking on the open ground, a Rusty dot pearl moth Udea ferrugalis, and the telltale woven together leaf blade of a Clubionid spider.
Ruddy for action: Common darter dragonfly (photo: D Ireland)

Who lives in a web like this? Probably a Clubionid spider

Rusty dot pearl moth dropped by

By the end of our allotted two hour survey event slot, we had gathered a useful species list. The value is in regular monitoring, to build up a picture of the species assemblage and any changes over time. We'll be back; no newts today; but next time....

With many thanks to Matt, Nicky and Dave for help on the day.