Tag Archives: Butterfly

Plantlife’s road verge advice could negatively affect pollinators

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Did anyone else hear the item on Radio 4 this morning about Plantlife’s road verge campaign and associated petition?  I listened carefully to the discussion and am broadly supportive of what they are trying to achieve.  But I was immediately struck by a comment that local councils should cut the verges “from mid July onwards” because most plants will have set seed by then.  I’ve seen this advice given before and whilst it might be an appropriate option for plants, it could severely impact local pollinator populations.

The printed advice that Plantlife is offering (which can be found here) states that if it’s only possible to cut a verge once a year:

“Cut the full width of the verge….between mid July and September. This allows plants to flower and, importantly, gives time for seed to be set.”

This misses a vital point: between mid-July and September there is still an abundance of flower-visiting insects that require these flowers to provide resources for their nesting and egg laying activities, or to build up reserves of energy to allow them to hibernate, particularly newly-mated queen bumblebees.

Where’s the evidence to support my assertion?  It’s been demonstrated by a number of studies, but I’ll point you in the direction of a paper that came out of the PhD work of one of my former students, Dr Sam Tarrant, who now works with RSPB.  If you look at Figure 4 of this paper, you’ll see that on restored landfill sites the abundance of pollinators in autumn surveys (conducted September-October) was just as high as for summer surveys.  On nature reserves, which are routinely cut from mid-July onwards (see Figure 2), this was not the case.

Climate change means that flower-visiting insects are now active in the UK for a much longer period of time than was previously the case, up to at least November in the south of the country.  I agree with Plantlife that road verges are important habitats for plants and other wildlife.  But advice that suggests cutting floral resources at a key time of the year for these insects is simply misguided.  A cut between October and December would be much more appropriate.

I don’t use Twitter so if anyone could point this at Plantlife’s account I’d be interested to see what their reaction is.

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Filed under Bees, Biodiversity, Butterflies, Hoverflies

Gatekeeper in the garden

Gatekeeper 1 - summer 2014

Since moving into our house in January 2012 I’ve been keeping a list of butterflies and day-flying moths seen in the garden (as well as birds and bees, of course). That list currently contains 14 species*, one of the most interesting of which is the Gatekeeper (Pyronia tithonus).

Gatekeeper 3 - summer 2014

According to the account of this species on the UK Butterflies web site, the Gatekeeper:

“can be found wherever shrubs grow close to rough grassland. ……some of the largest colonies can be found at field edges and along hedgerows and we can expect to find this butterfly in scrubby grassland, woodland rides, country lanes, hedgerows and the like anywhere within its range”.

So what is it doing in an urban garden?  The BTO’s summary of the species mentions that:

“It is rare for Gatekeepers to appear in city-centre gardens. However, in recent years this species has been recorded at some urban sites across north-east London and Hampstead Heath and, more recently, on Wimbledon and Mitcham Commons. Such range expansion into urban areas may be due in part to changes in the management of urban parks and cemeteries”.

Clearly, in order to exist in an urban setting the Gatekeeper must have its basic requirements met by the habitat in which it finds itself.  As I’ve mentioned before, the lawn in our garden is quite diverse and contains a number of native species, including a range of grasses that could be used as food plants by the caterpillars, though we do keep it quite short.  It’s more likely that the caterpillars are feeding in some of our neighbouring gardens, which are rarely troubled by a mower (do neglected gardens host more biodiversity than highly managed gardens?  I suppose it depends on the type of management; would be an interesting question to research).

Gatekeeper 4 - summer 2014

As well as the larval food plants required by Gatekeepers, there’s a range of nectar sources available in a mixed native/introduced hedge along the northwest boundary, including the bramble I recently discussed, oval-leafed privet (Ligustrum ovalifolium), and the buddleia (Buddleja davidii var.) seen in these photographs.

It will be interesting to see if this colony persists over time (I also recorded the species in 2013 but not in 2012).  I get the impression that there’s only a small number of individuals, though it’s difficult to assess the population size of butterflies without catching and marking individuals, which I plan to do next year. It’s a lovely species and we’re fortunate that it likes our garden.  I’d be very interested to hear from any other urban gardeners who have seen it in their patch.

 

*Large White, Speckled Wood, Small White, Holly Blue, Red Admiral, Cinnabar, Large Skipper, Meadow Brown, Peacock, Gatekeeper, Comma, Brimstone, Orange Tip, Small Tortoiseshell.

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Filed under Biodiversity, Butterflies, Gardens, Hedgerows, Urban biodiversity