Green hairstreaks at Barnack Hills and Holes

On the way back from a site survey in Cambridgeshire, I had the opportunity to call by and take my lunch break in Barnack Hills and Holes in the sunshine. Having seen a photograph posted by Nottinghamshire Wildlife Trust the previous day, I knew that green hairstreaks were on the wing so I went off in hunt of these iridescent little jewels!

Green hairstreak (Callophrys rubi) can be hard to track down for a few reasons; firstly, they are wonderfully camouflaged against the leaves – seeing one at a flower can be almost like noticing that one of the leaves is drinking! Secondly, their populations can be small – some colonies are only a few individuals strong and so tracking them down on a large site could be time consuming.

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Spot the hairstreak drinking from the hawthorn flower!
Luckily, after a pleasant half an hour wandering through the cowslips and orchids, I came across several on a hawthorn shrub. It was a windy but sunny afternoon and this hawthorn bush was more sheltered than many others. When in flight, the butterflies reveal the brown uppers of their wings making them easy to spot on the wing – but they always rest with their wings held together and blend beautifully into the greenery.

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Green hairstreak amongst the hawthorn leaves
I watched two males take up sentry posts, settling on hawthorn buds or leaves, poised to leap into action and defend their territory against intruders. Other males were the most targets likely to be chased, along with other insects and butterflies of other species, but they also use this vantage point to spot females on the wing. When resting and waiting, these males tilted their wings towards or away from the sun, micro-managing their temperature with these movements.

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Male green hairstreak poised on a hawthorn bud ready to intercept intruders
Green hairstreaks are widely but locally distributed in the UK – this means there is likely to be a colony somewhere near you but they have particular habitat requirements so you might need to go to just the right place to find them. They occur in a range of habitat types including dry heathlands, grasslands, old railway embankments, woodland and quarries. The key habitat requirement seems to be open grassland with a good scrub component. Adult food plants include trefoils, vetches, hawthorn, gorse and spring flowers such as cowslip and bluebell. The larval food plants are similarly diverse including trefoils, dogwood, vetches, gorse and broom.

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Green hairstreak on a hawthorn flower – one of the favoured food sources for the imago (adult butterfly)
These butterflies are on the wing early in the year – often in April and early May through to early-June or perhaps later in the north. Barnack is a great place to spot them but this site can help you find a location near you!

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Green hairstreak standing guard over his territory on a hawthorn flower

Winter Buds ID Part 1 – Londonthorpe Woods

Tree identification in the winter isn’t so difficult as you might think! Broadleaf trees lose their leaves in the autumn and develop buds which remain throughout the winter and these make it very easy to work out which species is which. The Woodland Trust have produced a very handy guide to some of the most common species which shows photographs side-by-side for comparison. If you want to identify them in a little more detail, this little booklet is invaluable and provides a few more diagnostic characteristics such as the architecture and bark types. It even has a handy key which takes you step by step towards the correct identification!

Of course, one drawback of relying on the buds to identify the tree is getting to the buds in the first place, which can be a long way off the ground depending upon the tree in question. So Londonthorpe Woods seemed like an ideal place to begin.

Londonthorpe Woods is located just off Londonthorpe Lane as you leave Grantham to the north-east. The wood was created by the Woodland Trust who planted thousands of trees on the 56ha arable site between 1993-1995. The Woodland Trust continue to own and manage the site.

As the site is so large, I concentrated on the first area you arrive at if you step through the gate from the car park. This area has been planted with a number of our native species which will one day develop into a woodland much more natural in character than it may appear at present. Alder (Alnus glutinosa) and willow (Salix spp.) will grow quickly but remain smaller, as will the silver birch (Betula pendula) and cherry (Prunus spp.). The English oak (Quercus robur) on the other hand will grow slowly and steadily to rise to prominance above the canopy one day, with ash (Fraxinus excelsior) close behind. Finally there are hazel (Corylus avellana), hawthorn (Crataegus monogyna) and blackthorn (Prunus spinosa) shrubs which will form an understorey, along with dog rose (Rosa canina).

Map of the plantation behind the main carpark of Londonthorpe Woods (courtesy of Google Maps).

Each of the species is described briefly below, along with a photograph of the buds to show you what to look for! Click on any of the photos for a larger image.


Alder

Alder buds are red and vaguely conical and remain quite close (appressed) to the stem. They are alternate – each bud is present as an individual rather than a pair and they alternate as you look along the twig, one to the left, then one to the right.

Alder is one of the more helpful tree species in that it often provides extra clues in the winter – the cones are generally present right through until spring time.


Willow

Willow’s are a variable bunch and as well as having several species native to the UK, they hybridise so there is even greater variety than you might expect. I think that this example might be goat willow (Salix caprea) – it will be easy to check when the buds break – goat willow produce fantastic flowers so watch this space! The buds are alternate again, lime green with redness towards the tip.

The presence of both the willow and the alder in this plantation suggests that the ground may be damp – both species are most commonly found along river banks or in other damp conditions. Like the hazel (see below for more details), the willows have been coppiced in this site.


Silver birch

Now this is a species which few will need the buds to identify – the distinct silver banded bark is visible behind the buds in this photograph!

The buds themselves are alternate and on small stems which protrude from the main twig.

Silver birch grow quickly but are relatively short lived – they are often one of the first pioneer species in a new woodland but soon become out-competed by larger, taller trees.


Cherry

Cherry is another difficult species as there are so many ornamental and hybrid varieties to choose from. The buds are alternate and dark brown with scales visible. Cherry is another species where the bark is very useful in the winter – the lines which look almost like horizontal cracks in their shiny bark are called lenticels and these are quite characteristic of cherries.

Although it is difficult to be sure of the exact species, it is likely that the Woodland Trust would have planted one of the native varieties – wild or bird cherry. Of the two, this one looks more like wild cherry (Prunus avium). Again, we can return to check this in the spring or summer!


English oak

The oak has tight clusters of buds especially at the tips. The buds are brown and have lots of scales.

One day this tree will probably tower above the others – think of the Major Oak in Sherwood Forest. For an example closer to home, there is a beautiful mature oak specimen along Belton Lane which you will probably pass on your way to Londonthorpe Woods – more on this magnificent tree in a later post!


Ash

The ash has one of the most distinctive buds – they form jet black pointed cones which really can’t be confused with much else. If you find buds of a similar shape but a different colour, such as grey, think of one of the other ashes which we sometimes encounter such as manna ash.


Hazel

Hazel buds are a greenish red in colour – a little like a red and green apple. They are alternate along the twig which itself is often hairy. Hazel provides a few extra clues in the winter time – the catkins (the male flowers) are often visible and if you look very carefully, you can see the tiny red female flowers on the same branch.

Another clue, depending on the management, is the growth form of hazel. It is often coppiced – that is cut down to the ground – and from here it sends up lots of new shoots which are often allowed to grow for several years before being cut back. The hazels in this plantation have been coppiced.


Hawthorn

The spiky shrubby hawthorn bush is fairly distinctive, even in the winter time. The spikes are generally quite visible and the buds compete with these along the twig. The buds are alternate and a similar dark reddish colour to the twigs.


Blackthorn

Blackthorn buds, by contrast with the hawthorn, are tiny little red dots which appear along the stem. The twigs are often long spikes and the buds appear along these. The colour of the bark of blackthorn is, as you might imagine quite dark, a blackish grey perhaps.


Dog Rose

Another species which you are unlikely to confuse with many others. Native roses grow lower to the ground than the other species in this plantation but can develop quite a shrubby form. The curved rose thorns, like a hawk’s talon, are quite distinctive and the rose hips, still present in January, are another key clue. The buds themselves are a slightly lurid red and grow  alternately up the twig, alongside the thorns.