Winter flocks of Yellowhammer

YellowhammerIn the winter, flocks of yellowhammer (latin name Emberiza citrinella) form and right now, we’re lucky enough to have one such flock up at the hills and hollows overlooking the town. They gather into these flocks to feed on seeds in cereals and grassland fields. You can see them gathered in the shrubs and trees before descending down to the ground to feed in the relative safety that fifty pairs of eyes affords. The kestrel is seen hovering not so very far away but this doesn’t seem to concern them much. They are sometimes joined by other small species – I have seen chaffinches in with this small flock which numbers around 60 birds.

The yellowhammer is one of the ‘red list’ bird species in the UK – this classification is given to species which are of the highest conservation priority. This doesn’t necessarily mean that they are on the brink of extinction but may mean that their population is experiencing worrying trends. The recent population decline in yellowhammer is the reason for this designation.

Starlings are a good example of why populations can appear fine whilst still being of high conservation concern. Their UK population is estimated to be around 800,000 breeding pairs but this is only around a third of their population peak in the mid 1970’s. If this trend continued, we would be down to only 270,000 by 2050. The RSPB’s website has more detail on the starling decline.

Yellowhammer flock
Yellowhammer flock
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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.

Jubilee Tree – Copper beech in Harlaxton churchyard

The Woodland Trust has digitised a book recording all of the trees planted across the UK in 1936/7 to commemorate the coronation of King George VI.

According to the record, there were no trees planted in Grantham. The closest record however is from Harlaxton, a small village a mile or so to the west of the town. Here, two copper beech (Fagus sylvatica cuprea) were planted, one in the churchyard and one in the rectory garden.

I wasn’t able to find the tree in the rectory garden (at least without trespassing) but the tree in the churchyard has grown into a fantastic specimen, 75 years on. It stands close to the boundary wall on the right hand side as you enter the churchyard from the road.

Copper beech in Harlaxton churchyard

The tree has a diameter at breast height (dbh) of 2.62m.  There are a number of old well-healed scars where branches have been removed from the trunk, and a couple of scars it has made itself where the branches have twisted and grown around one another over the years.

Copper beech in Harlaxton Churchyard

In the winter it doesn’t look so very different from its native relative, the common beech, although you can clearly make out the tinge of purple. Copper beeches arose as mutants in the wild populations where they were first recorded in Germany around the 15th century*. The purple colouration to the leaves is caused by a buildup of the pigment anthocyanin which is sufficient to mask the chlorophyll which usually colours the leaves green. Scientists have identified a single gene mutation for copper colouration which is dominant*. Crossing the copper beech can even create trees with variagated or semi-purple colouring.Birch is another species where natural mutation has led to copper varieties being identified and bred for ornamental use.

Copper beeches are now found growing extensively throughout Europe now as ornamental trees in towns and gardens – there is another fine specimen in the centre of Grantham, in front of the council building. I will be back in the summer and take a photograph of the tree in all is copper glory!

Why does gorse flower in the winter?

At this time of year, the world in general (and Grantham in particular) can seem a rather bleak place. Trees are nothing but bare boughs, the grass is wet and sodden underfoot and the only flowers to be seen are those in the supermarket containers or the florists’ window. But there is a notable exception to this general rule.

On the south-eastern edge of the town, the fields rise up above the estates at the end of Gorse Road. This area is described as ‘Gorse Lawn’ on the OS map and rises up Hall Hill, on the edge of the Hills and Hollows. Walking over a small stile and scattering rabbits which are nibbling the tips off grass poking above the frost, you are soon surrounded by gorse – latin name Ulex europaeus. Even now, in the middle of January when the bulbs are only beginning to push up through the earth, the gorse growing on this hillside present yellow flowers in abundance.

You will almost certainly know gorse, if not by name then by sight. It is one of our prickliest shrubs and grows not only on heaths, where it compliments the purple heather beautifully, but on all kinds of waste ground, flourishing where the soil is shallow and nutrients are scarce. It loves sunny spots and often grows on sandy soils. It is a member of the pea family along with garden peas and beans, garden flowers such as lupins and even trees such as laburnum. The clue is in the lipped, irregular flowers.

Perhaps the most interesting question is quite why the gorse is flowering so profusely in the dead of winter. Flowers are clearly designed for greater things than simply decorating our houses, and butterflies and bees aren’t just taking a rest when the alight. The flowers attract insects through the offer of nectar and use the insects to pass the pollen, from one plant to the next and, so, fertilise them. The flowering season then is designed to coincide with the warmer weather, when most of the insects take to the air. Some plants flower early, some late, some in the middle, but almost none choose to bloom at the one time when insects are in such short supply as mid-winter. So why is the gorse such an exception?

Gorse flowers

A wonderful paper from the Linnean Society journal in November 1869 looked at a number of species which flowered at this most unusual time and concluded that the flowers are all arranged so that they can fertilise themselves without even opening the flowers, thereby ensuring that fertile seeds can be made even if the snow arrives and remains, and if no insects come to call. This ability of gorse to produce lots of clones of itself is part of the reason why it is such an invasive species in countries such as the United States.

This ability to reproduce without insects allows the winter flowering strategy without risk of a barren year, and on warm winter’s days when insects emerge, the gorse has very little competition for their attentions as it is one of the very few options on the menu.

That goes some way to answering the question of how, but it does still leave the why. Why not? isn’t really a good enough answer. This seems to have received attention from researchers only relatively recently. A group of French Researchers identified two main flowering strategies in gorse populations (as there are of course plenty of flowers to be seen in the spring and through the summer too) which seem to reflect two different ways of avoiding losing their seeds to little seed-eating weevils of the Exapion genus. One strategy is to avoid the weevil and, by flowering in the dead of winter in conditions that are too harsh for the weevil, they do just this. Winter flowering specimens tend to produce a smaller number of flowers through a long winter season, so maximising their chances of flowering through a warm spell when pollinators emerge. The other strategy is to produce so many seeds that there are many more than the weevils can consume and this is what the spring flowering shrubs do, producing very large numbers of flowers over a much shorter period. A later paper identified a genetic basis for this – that gorse seeds from a winter flowering specimen tend to produce offspring which do the same.

On a more practical note, gorse flowers can be used to make wine and winter may well be the best time to pick them if you want to do this – for the very reasons outlined above, you will spend much less time picking little black insects out of your harvest, although the flavour is less intense than spring and summer flowers! You’ll appreciate the slight reduction in workload though as gathering enough is rather a laborious process and don’t forget the gloves as being prickled by the sharp spines soon gets old. And if wine isn’t to your taste, there are lots of recipe’s for gorse cordial out there too.

As well as admiring the gorse, a wander up the hill gives you a wonderful opportunity to look down on Grantham, the skyline dominated by St Wulfrums. As the weather warms, you’ll be joined by a range of songbirds as the gorse provides a fantastic nesting site with its tangled mass of trunks and branches. And look out for a black rabbit amongst those grazing as you approach!