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Monday, 29 June 2015

Things which really work 1

Improvised birdbaths, from old small plastic tubs, have proven immensely popular with the sparrows, blackbirds and the odd passing squirrel.

The sparrows regularly drink or dunk. If the blackbird gets there first, it sits in the tub shaking its wings, fluffing up its feathers, and splashing about. Presumably this is a way of getting rid of parasites.

Hence make sure to clean and re-fill regularly....

"Things which really work"?

Or, if you build it, will they come....?

This is the new swift nesting tower on Paris St roundabout, installed over weekend of 27-28 June.

Swifts are believed to be suffering a national decline, partly due, it is thought, to lack of nesting sites. These are urban birds, which presumably find our tall urban buildings to be similar to vertical cliffs, and feed on the aerial plankton of invertebrates in updrafts and thermals. Their swooping free-flying around the rooftops on a summer's day is exhilarating to watch. This year I've not seen or heard so many swift screaming parties around St David's, but colleagues report plenty zooming around around Newtown and Heavitree. As they have come, Exeter has built it.


The final tower design, by architect Rafał Pieszko, is different from original sketch visualisations (see www.exeter.gov.uk/index.aspx?articleid=13960); the tower is similar to one already tried in Poland (www.menthol.pl/eng_swift_tower.php). Each of the 'arms' of the 'Y' is packed with swift boxes, which, because of the upward angle, should remain shaded from direct sun. The shape echoes that of the birds in flight. Playing recorded swift calls is said to encourage adoption of new swift boxes considerably, hence the intermittent bursts, which seem to be powered by solar panels.

Around the base of the tower is wildflower planting. Will it all work? At ~8.5m high, is the structure a bit low? Though it is known swifts can nest at 5m height. One of the advantages of swift boxes is that, even if swifts themselves don't use them, many other species can, including house sparrows, populations of which have their own recent and drastic decline to deal with. Yesterday there were several sparrows enjoying bashing about among the poppies and cornflowers at least.

A number of urban swift conservation projects are running in the UK, which on a national scale this would help contribute towards. Some more information about these, and about the decline of swifts, is below.

Exeter Wild City  www.devonwildlifetrust.org/swifts/
Bristol   http://www.bristolswifts.co.uk/
Cambridge, a similar art/ecology project
http://actionforswifts.blogspot.co.uk/2011/03/cambridge-city-council-swift-tower.html

Swift conservation news www.swift-conservation.org/
Examples of building projects www.swift-conservation.org/OurProjects.htm

I understand the funding was planning gain money dedicated to art/ecological projects, and wouldn't otherwise have been available.
An earlier design, from Exeter City Council website

Thursday, 18 June 2015

Staring at the walls

'Life after concrete' urban botany walk, Tues 2 June

In two hours we recorded over 100 plant species in the overlooked gaps, cracks, pavements and walls around the very central parts of Exeter, around the quay and Catacombs park. Or as Jeremy, BSBI recorder and our walk leader, pointed out, these urban survivors more accurately live 'with concrete' than after it.
City wall behind Cricklepit St
Spray-dodging weeds might be another view of them, but all have interesting tales to tell - how they can support other biodiversity, or reveal insights into Exeter's history.

Within a few steps, we found common mallow, shining crane's-bill, lesser trefoil, spotted medick, wall speedwell and common sow thistle, mixed with cosmopolitan Mexican fleabane, purple toadflax and wall bellflower. Some species are more accepted and tolerated as wall plants than others. For example, Jeremy reported that Ivy-leaved toadflax Cymbalaria muralis is Exeter's most widespread urban wall plant, found in every one of the city's survey squares. Exeter's city wall would have been suitably ready and prepared, having been standing for over a millennium and a half, for the arrival of this plant to Britain in 1640.

The building material itself, 290-208 million year old Permian sandstone, is slightly older. Romans laid down the purply red, often pock-marked, basalt blocks of 'trap'; later Saxon and Mediaeval builders made use of the orange-red Heavitree breccia stone.The type of mortar is the key, according to a favourite book for the occasion, Arnold Darlington's 1981 Ecology of Walls (among Amazon's top 625,020). High pH suits certain plants, but once Portland cement became standard in the 1850s, there was no longer a substrate which allowed access to the gradual slow flow of moisture and nutrients. The result is Ivy-leaved toadflax can be a handy indicator that a wall is probably well over 50 years old. 
Ivy-leaved toadflax
Ivy-leaved toadflax is a valued bee plant: I've seen Red mason bee Osmia bicornis following the honey guides on the pale and purple petals to enter the flower tube. After fertilisation, the stalks turn inward and wedge the ridged seeds into gaps in the wall. Sometimes one can trace back the pattern of historical plant colonisation; sometimes ants carry the seeds away first. Lying in wait for the ants might be the common jumping spider Salticus scenicus, which we saw on the walk.
Jumping spider seen on the wall

Pellitory-of-the-wall Parietina judaica is another plant species particularly prevalent in the south west. A non-stinging relative of the common stinging nettle, it can support caterpillars of the Red admiral butterfly, and the Nettle tap moth Anthophila fabriciana.  A rare, but possibly colonising and spreading moth species Cosmopterix pulchrimella is also worth looking out for: the leaf-mining caterpillars feed within the Pellitory-of-the-wall leaves. This moth was first discovered in the UK in Dorset in 2001, and has since been found in Cornwall in 2004, and in the Channel Islands.
Pellitory-of-the-wall
A final example is Red valerian Centranthus ruber, a long-flowering, nectar-rich wall specialist.

Introduced to Britain in the 16th Century, it is a food plant of two moth species, Large ranunculus and Angle shades, though the nectar is attractive to a wide range of species. I've seen Hummingbird hawk-moth feeding at Red valerian alongside Exeter walls this year; at night the plant can be smothered in moths and other insects.

That's enough individual examples. The wider point was that there are numerous such small and random patches of wildness, trying to bloom across the cityscape: footpath verges, triangles of roadside visibility splay, small greens with a tree in the middle. If someone were to repeat our walk along Cricklepit St now in late July, they'd find many of these plants have been chopped down and strimmed away: no more bees, spiders or Hummingbird hawk-moths. It would need only a small adjustment in attitude and management - and it should be a cost saving - to cut less often, and allow a few clovers and trefoils to flower in the lawn for the bees and butterflies, instead of everything everywhere having to be mown flat to a green desert.  



Monday, 1 June 2015

Terror in the skies

Is it a bird? Well yes it is, the Exeter peregrines being very vocal, as fledging time approaches. This year there are two chicks, a male and a female, expected to launch next week sometime between Tuesday and Saturday (live nestcam: www.stmichaelsmountdinham.org.uk/peregrine-falcons/).

St Michael and All Angels Church in Mount Dinham was one of the first churches in the UK to host urban peregrines in 1988, making the church possibly the biggest birdbox in Exeter. Since then almost 50 young have hatched and been reared to maturity. 

Often the fledglings, instead of flying, 'parachute' in a fairly uncontrolled descent down on to pavements and roofs around St David's Hill and Iron Bridge. A group of us is on call again this year to retrieve any chicks from such abortive maiden flights, to return them to the nest. If over the next few days the phone call never comes, I'd be both relieved and disappointed.

The adults are especially protective around this time and don't tolerate any large birds, such as ravens or buzzards, coming anywhere near the church. Nick Dixon, main monitor of the Exeter peregrines for well over a decade, has been recording interactions with buzzards for the last few years, and recently published a paper on this topic with Andrew Gibbs in the May 2015 edition of British Birds.
www.britishbirds.co.uk/article/cooperative-attacks-by-urban-peregrines-on-common-buzzards/ 
www.bbc.co.uk/news/uk-england-23519183  

The Exeter peregrines seem particularly belligerent, or diligent, in clearing the local sky of potential threats to the fledglings. Nick says: "we have recorded over 100 attacks this year alone with 9 downed buzzards recorded up to the end of May. We have seen a real increase in buzzards over the city in good weather conditions and this year’s tally to date exceeds the total recorded over the previous 6 years.

I've seen this 2-3 times this year through April-May: one peregrine stopping fast and from high at a buzzard repeatedly, while the other sometimes circles round at buzzard height. Each time the buzzard flipped upside down to present its talons at the onrushing peregrine, which would divert away at the last moment, in the last heart beat before impact. On those occasions the buzzard was gradually driven away. 

Nick is interested in any further sightings, and asks for the following information for each attack: 
  • date and time,
  • whether just one or both peregrines involved, and
  • the outcome (buzzard driven off/direction, downed or unseen)

Please forward records of buzzard-peregrine encounters to Emily at Devon Wildlife Trust, who will send them on to Nick (e-mail estallworthy@devonwildlifetrust.org). Nick and Andrew record more detailed information if anyone is interested in making more systematic observations.  

Watch the skies! Especially on warm days with rising thermals, if you see a buzzard over Exeter, look up even further to see if the dark arrow of a peregrine is there above.


STOP PRESS: Nick reports "The male fledged on Thurs 11th, exactly 42 days from hatching, and the female finally left the nest today, 45 days after hatch. There have been some fears that she wasnt feeding properly and seemed to lack the frantic wing flapping of the male to build up the wing muscles prior to her first flight, but she left the nest at 08.10, flew to a stone cross and has spent most of the day on the eastern roof ridge."

Nick is still interested to receive details of any peregrine-buzzard encounters.

Spp that pass in the night

Who could live in a garden like this? A tiny lawned space facing the road, right in the city centre near Iron Bridge, though there is a large old garden hedge. In that hedge has been a growingly prominent small gap and suggestion of a track, leading to next door; and in that lawn some odd scrapes and holes.

The neighbouring flat's trail camera revealed all.
 
                                                                                                    Pics: G. Slack

I've seen badgers twice before either in the front garden or nearby grassed areas, and many times near the University campus. Even with a large home range (for which the average is reported to be 50 hectares, up to 300ha in low quality foraging habitat), one wonders where the nearest sett might be. There aren't too many obvious places within 500m, a typical roaming distance.