Saturday, 10 January 2015

Week 51: Mistletoe & Lime

Hay Wood
My head this week has been full of Mabel the Goshawk and the last of lingering flu bugs. However, I have crawled out from under the duvet and I did manage to put down “H is for Hawk” by Helen Macdonald long enough to explore a little of Box Moor. I made it to Lower and Further Roughdown, walked the Brickworks circuit and, of course, visited Dellfield and Hay Wood. Treecreepers seemed to pop up at various points on dull, dark days and transformed hapless wandering into joyful discovery. In the woods at Lower Roughdown, I was following a scurrying little mouse-bird up at nearby tree trunk when I heard the whistling of Redwing. Through the trees, flinging fallen oak leaves this way and that, was a flock of c35 thrushes searching for food on the woodland floor. Amongst them were c12 Chaffinches. Unfortunately, they did a stirling job of disappearing into thin air the moment I moved and I didn’t really get a chance to check for Brambling or other winter finches amongst them.

Over on Dellfield, there were another 67 Redwing and a few Mistle Thrushes probing the sodden earth for worms. Into Hay Wood, I came across another couple of singing Treecreepers along with Goldcrests, Nuthatch and a mixed Tit flock. Already, the shoots of Bluebells have broken through and I can’t help feeling like Spring is just around the corner! This sense of new beginnings was reinforced at the Brickworks, where a number of male Great Tits were in full song, chiming loudly to assert territory and lure a lady. I had hoped that the abundance of Teasels on site there might be too much for any self-respecting finch to resist, particularly Lesser Redpolls. Sadly, no luck. Bullfinches and Goldfinches, along with another small flock of Chaffinches had to suffice.

So, what of the title “Mistletoe & Lime”? Well, hopefully, with more inane rambling, all will become clear. There’s no point to be made, just observations to share. Back at Westbrook Hay, I wandered over to admire the handiwork of the Conservation Volunteers in laying the hedge along the south-west boundary of Barnfield meadow. In doing so, I stumbled upon a rotting tree trunk, complete with its own miniature terrain and curious trumpet-like formations. In fact, they are the podetia (stalk-like growths) of the thallus (the body) of the lichen Cladonia fimbriata, commonly known as Trumpet Lichen. This got me thinking about the relationship between organisms. In the case of lichen, this is a mutualistic symbiotic partnership of a fungus with an algae and/or cyanobacteria. The mycrobiont (the fungus) provides a robust structure and an anchor to a surface, whilst the photobiont (the algea or cyanobacteria) supplies energy (glucose) via photosynthesis. The combination of the two creates a unique form and structure, a composite organism, which is totally unlike either of its constituent parts. Ultimately, both benefit from the marriage, combined they take on a new form and they thrive. This is, of course, a powerful contrast to a parasitic relationship and the one which I had been meaning to briefly include in a blog post all year!

Trumpet Lichen (Cladonia fimbriata): approx height 15-20mm; approx diameter of cup 3-7mm

Trumpet Lichen (Cladonia fimbriata)

During the last 12 months, it has been impossible not to notice the numerous infestations of Mistletoe (Viscum album) on the Lime trees in Ryders meadow. I couldn’t leave this project without mentioning them and, as it happens, Lichen symbiosis seemed a fitting context. From what I understand, Mistletoe is predominantly a parasitic plant, although there is some argument that it does make a photosynthetic contribution, albeit minimal.

According to the RHS, Mistletoe is “a parasitic plant that lives off the nutrients and water from a host tree. Although it is parasitic, it will not kill the host tree but can weaken it. The berries are often spread by birds from one tree to another, and this is how the large rounded clumps of mistletoe form in tree branches. The most common host tree in the UK is apple, but poplar and lime are also frequent hosts.”

It is no coincidence that the Limes on Ryders are frequently rattling with the alarm calls of Mistle Thrushes (Turdus viscivorus). The bird’s scientific name means “Mistletoe eating thrush” [Turdus is the Latin for "thrush", and viscivorus, "mistletoe eater", comes from viscum "mistletoe" and vorare, "to devour"]. The bird loves Mistletoe berries, it’s just a shame the Lime trees have to suffer.


Finally I’ve also included a photograph of some Ivy (Hedera helix) growing up the trunk of a tree in Lower Roughdown. Ivy isn’t parasitic and doesn’t penetrate the tree’s bark or roots. I just liked the way it looked and the sense that the tree leant form and strength to an otherwise flimsy organism. The RHS discuss its relative merits and pitfalls here if you’re interested.

    Mistletoe (Viscum album) in Lime tree
    Ivy (Hedera helix)

This week’s Oak photograph was taken on Monday, in the misty gloom.

3 comments:

Martin Parr said...

Inspirational as ever Lucy, I haven't had flu but have still hardly stepped outside! Love the pics of the Lichen, I really must do some macros of them this year, they really are beautiful up close!

Anonymous said...

The wood shot and lichen shots are amazing and your description of your walk is lovely. What a fantastic record and a testament to your skill as photographer, birder and lover of nature.

Boxmoor, naturally... said...

Thank you Martin and Anon. Martin, I don't blame you for taking cover last week - most days were gloomy and grey, lol. Next week looks very unsettled too, unfortunately.