Saturday 27 December 2014

Week 49: Christmas Week Oak

Just a short post this week. I swapped the grey gloom of Hemel for the grey gloom of Warwick on Tuesday, heading off to feast with family over Christmas. However, I did explore Box Moor briefly on Monday in the mild (12 deg C) but overcast, dark and windy conditions.

I started at Lower Roughdown and then walked up and out onto Further Roughdown, where there were 14 Magpies, 8 Mistle Thrushes, 4 Redwing and both a Green and Great Spotted Woodpecker.

Late morning, I arrived at Dellfield where there were more thrushes feeding on the ground: 5 Redwing, 3 Mistle Thrushes and a single Fieldfare. There was little I could do about the lack of light so I went for a close up of the Oak this week, with its exposed winter branches.

I had a bit of a play in photoshop, with the aim of bringing out the textures and shapes… 

Next week we'll be into a new year…!

Saturday 20 December 2014

Week 48: Wintering Chiffchaff & Buntings in the Reed Bed

Buntings in the Reeds
Just five days until Christmas! I feel as though I should be in a state of Yuletide hysteria and sporting inadvertent smatterings of glitter accidentally acquired from cheap Christmas cards. Actually, I’m marvelling at how the year has flown by and that it won’t be long before the Oak and I part company. However, this isn’t the time for reflections. I shall save those for the new year, once the project has finished.

At the start of the week, when temperatures were only just above freezing, I walked both the Hemel moors and the Bovingdon Brickworks site. I was struck by the quiet, cold, stillness. The Brickworks in particular were largely devoid of bird song or movement, there was little breeze and no noticeable insect life. But, all around is potential and promise, with fresh new buds formed on otherwise bare, leafless trees.

On Monday, I wrapped up warm and went Bunting Hunting. Dan Forder had found a couple of Reed Buntings (Emberiza schoeniclus) flitting about near Old Fishery Lane and I was keen to include them in this year’s project. I got lucky and discovered the pair loitering in the tiny reed bed beside Fishery Moor.  Unfortunately, they were up and off to the Gadespring cress beds before I could say "my toes are cold and I have a hankering for a hot mince pie". One of the birds is obviously the ringed male, photographed by Dan last week. The other is either an unusually dark-headed female or is in fact another male. I didn’t get a good look. Anyway, they were lovely to see, especially in their typical habitat, a reed bed (not something we have a great deal of in Hemel Hempstead!)

Chiffchaff (Phylloscopus collybita), feeding on nettle seeds
The south-facing hedgerow, running along the south side of the Bulbourne (as it passes through Fishery Moor and Station Moor), is one place I can guarantee at least 12 species of common birds. It is something of a winter refuge and is particularly lively at the moment. There’s plenty of shelter from chilling winds and, when the sun is shining, birds push through to the outer-most branches and sit or preen in the available warmth.

One not so common species at this time of year, is the Chiffchaff (Phylloscopus collybita). Many (sensible) UK breeding birds migrate south to the Mediterranean and West Africa. Some Scandinavian, mainland European and even Siberian birds migrate from their breeding grounds to winter in Britain. And so, during the coldest months in the UK, there is this sparse population of multinational Chiffchaffs, of varying sub-species, and from a variety of breeding grounds. It made my morning this week when, along the Bulbourne hedgerow, I came across one of these little birds, intently feeding on Common Nettle seeds. I’m no expert in determining sub-species/race but, from the little I know, I think this bird is a fairly standard nominate form P. c. collybita rather than anything Eastern and exotic. Even so, they do make me smile and it was a cheery sight on a frosty winter’s day.

Further up, where the river bends and cuts across Station Moor, a male Kestrel was perched in a sapling, eyeing up the small birds. None appealed and he returned to the air and to patrolling the grass. Over on Harding’s Moor and beyond, I came across 3 Little Egrets and, of course, the Kingfishers were active along the river.

From the footbridge over the Bulbourne. Left (west) is Harding's Moor; right (east) is Bulbourne Meadow

Both the young male and the young female bird were fishing in their favoured areas. I heard at least a third bird and saw what I think was a fourth bird. It’s quite difficult to keep track of them, especially if all you experience is a jet propelled fly past.

Finally, before I get to this week’s Oak photograph, I’d like to wish you all a very happy Christmas. Roll on the Turkey and the ill-advised but irresistibly large quantities of chocolate!

Saturday 13 December 2014

Week 47: Birds along the Bulbourne

I fancied a spot of pre-Christmas birding this week, concentrating on the River Bulbourne between Two Waters Road and where it meets the canal on Station Moor. I’m a sucker for our feathered friends. They have a unique effect on me. I spy a bird and I’m transported to a state of simple, primitive happiness. As my brain catches up: what’s not to like about a creature that is covered in thousands of perfectly formed, downy quills, arranged in patterns subtle or pronounced and which require tending to, with delicate care, through a fascinating life cycle of moult and wear? No other organism can look you in the eye, spread its wings and then rise into the skies come rain or shine. Each species, and each individual within that species, has a unique character or pattern of behaviour which, when observed over time, gives a sense of one connecting with, and relating to, that which is fundamentally wild and free. There’s nothing like it!

Grey Wagtail (Motacilla cinerea), preening
And so, on a bright Monday morning, I set off for the river. At one point, I was crouching down on the bank, photographing the immature female Kingfisher, when a Grey Wagtail flew in. It landed close to me, perching over the water, and began to preen in the sunshine. S/he wasn’t concerned by my watching and spent a good five minutes poking its bill into its feathers, smoothing them out, fluffing them up and doing a very good impression of a contortionist. It’s at moments like this that observing with a camera really comes into its own. Movements which are complete in the blink of an eye are frozen in time and you give yourself the opportunity to see exactly what’s going on. The photographs opposite show the bird grasping a single feather and then running its bill along the length of the shaft to bring each vane into line. Such care and precision. Beautiful.

Just fifteen minutes earlier, the young female Kingfisher had made a similar approach. She’d been perched across the river from where I was sitting but suddenly decided to fly towards me. She touched down only a few metres away and just sat there. I felt as though I should hold my breath, concerned that even the slightest movement would scare her off. Magical.

Other birds along the length of the river included the bobbing, diving Little Grebe; a handful of Mallards; at least 7 Moorhens; a Little Egret; one adult and one immature Grey Heron; flocks of Chaffinches, Goldfinches, Great Tits, Blue Tits and Blackbirds; 4+ Wrens; 15+ House Sparrows and 40+ Starlings; c12 Black-headed Gulls; 7+ Magpies; a handful of Jays, Crows, Jackdaws and Woodpigeons; a few Mistle Thrushes and a number of territorial Robins. Green and Great-spotted Woodpeckers, Nuthatch and Greenfinch are regularly around but I didn’t see/hear them on Monday. Sparrowhawk and Kestrel frequently patrol the area but, again, neither came through whilst I was there at the beginning of the week.

Black-headed Gull

I willed this little Robin to look up before taking flight but telepathy failed

It’s The Box Moor Trust’s volunteers’ Christmas lunch next week so if you’re involved in that, I shall look forward to seeing you there. In the meantime, I’ll finish off with this week’s Oak photograph, taken on Wednesday, just before midday.

Saturday 6 December 2014

Week 46: Winter Sun & Ravens Over Dellfield

Unlike this morning, a number of days this week really have been the epitome of Dickensian, winter gloom. Headlight days, I call them, where, even at midday, cars run on dipped beams. On Monday, in the dusk-like milieu, I walked the length of the moors (from Bulbourne Moor, west, all the way to Dellfield). It was not a day for nice photographs unfortunately, but the bird life was cheerful and absorbing. One of the two regular Little Egrets was in the river on Harding’s Moor; 3 Jays were squabbling with Magpies; Crows fought over some bread one of them had found, and the two young Kingfishers were perched over the river on Bulbourne Meadow, eyes trained on the shallows. Close to the Two Waters Road bridge, a Little Grebe bobbed and dived in the company of a pair of Mallards; flocks of Blackbirds stripped berries from Hawthorns along the canal, and a charm of at least 30 Goldfinches was feeding in Alder trees. The two young Herons were doing their best to look like statues at odd locations on the moors; Robins flitted in and out of bushes, and a Grey Wagtail chirped and flew overhead.

On Wednesday, with clear skies forecast, I rose early, hoping to catch the Oak in the first light of day. With dawning realisation (pun intended), it became apparent that at this time of the year, the Oak doesn’t even glimpse sunlight until at least 11am and, in fact, stands cold, mostly in the shade, until, I’d guess, around 1pm. By 3pm, it is back in full shade. The sun skirts its way around, behind Hay Wood, and then dips behind Westbrook Hay school. So, this week’s Oak photographs are a little different. The first was taken at 10:30am, when the Oak was in full shade but the sun was breaking through the tree tops of Hay Wood, casting long shadows across Dellfield. With some tinkering in photoshop, I came up with this (the original is here)...

Photo-art. Into the Sun. The Oak and Scots Pine with the low Winter sun blazing through from behind Hay Wood

Up on Preston Hill, a Mistle Thrush was bathing in the pond and 2 pairs of Bullfinches and a handful of Redwing darted through the scrub. Into Hay Wood and I found some lovely fungi. New ones to add to the list were a coral-like growth. I think the genus is Ramaria, the species is likely Ramaria Stricta (Upright Coral)? The other was a tiny, delicate but beautiful sessile “cap” of the genus Crepidotus. Both species were growing on dead wood and likely saprobic.

Coral-like fungus (Ramaria Stricta) growing on rotting wood. Max height approx 11cm.

Tiny "caps" growing on dead wood. Approx diameter 7mm
Genus: Crepidotus

As I walked onto Bovingdon Reach, a Red Kite flew up from the grass and lazily rose into the blue skies. By midday, I was walking down through Barnfield meadow and on into Ryders. As I was standing amongst the Limes and furtive bunnies, photographing the view across Dellfield, a pair of large birds caught my eye. I then heard the distinctive “kronk, kronk, kronk” of Ravens (Corvus corax). Through binoculars, it was easy to see the diamond-shaped tail and their sizeable wing-span (similar to a Buzzard’s). Unfortunately, by the time I’d changed lenses, both birds had flown behind the Limes and I failed to get even a decent record shot, much to my annoyance. Still, a great way to end the morning and my first sighting of this species in Hemel or over Trust land.

From Ryders, looking north-east across Dellfield at 12:10pm. Off to my right, a pair of Ravens kronk'ed and drifted west.

On Tuesday 18th November, I'd collected a fresh Barn Owl pellet from Trust land. It was a lot smaller than previous pellets, just 3cm long and about 1.5-2cm wide, which made it ideal for dissection one dark, dank afternoon this week. Interestingly, it contained the fur and bones of just one mammal. A Field Vole (typically 13cm long + tail of 4cm). It provided the perfect opportunity to get an idea of exactly what one of these little fellas consists of...

Frankenstein's Field Vole

From one small Barn Owl pellet (3cm long): the remains of a single Field Vole, crudely and likely inaccurately(!) reconstructed. Scale in mm 

I have no idea how many ribs or vertebrae a Field Vole (Microtus agrestis) is meant to have. Nor do I know which way around the various bones go (i.e. which is left and which is right) but above is my “artisitic impression” of a Field Vole skeleton. It’s not a good sign when you have bones left over (top right hand corner) but my excuse is that you can’t really place damaged and crushed bones very easily (especially when you barely know what you’re doing to begin with!). I'm missing a humerus and the bones of the feet/toes are “absent” or unidentifiable. Anyway, it was an interesting exercise and well worth the time and patience required. (For more detailed info on pellet dissection and bone identification see my previous post).

Field Vole (Microtus agrestis): Jaws & Teeth


If you’d like to see photographs of these little mammals before they get snaffled by Barn Owls, Biodiversity Gatwick were involved in a small mammal survey recently. The relevant post is here and I thoroughly enjoyed reading it and browsing their images.

I'll finish off with a photo from my Monday walk and Wednesday's Oak in the shade.

Black-headed Gull on Station Moor footbridge

The Oak in shade at 11:20am

Saturday 29 November 2014

Week 45: Of Beetles, Digested & Rare

A beautiful Oak at the Brickworks

Monday dawned crisp and bright, following the first real frost of the season. Mid-morning, over at the Brickworks, there were still areas untouched by the warmth of the sun, covered in frost and ice.

SE of Baker's Wood, looking north

Frosty Nettles

Shards of ice over the grass

I squelched my way around the site, coming across a few more species of fungi (including Parrot Waxcap (Hygrocybe psittacina) and Golden Waxcap (Hygrocybe chlorophana)). Green Woodpeckers (Picus viridis) were conspicuous and, as on my last visit, a group of Jays were having a hum-dinger of a fight near the entrance track. On my way round, I could hear a small gathering of Fieldfare “chacking” to one another, which I eventually spotted. Bullfinches called softly and it was lovely when a bright, red male, brilliant in the autumn sunshine, flew over my head.

Golden Waxcap (Hygrocybe chlorophana), cap diameter approx 25mm

Having had owl pellets in my freezer for months, it will probably come as no surprise that this week I had Green Woodpecker poo drying on the radiator. It wasn’t planned, honestly. I spotted a very distinctive dropping whilst walking over Dellfield and, after a little research, discovered it was Green Woodpecker poo and that if I found a dry specimen, I’d be able to see that it was packed full of the remains of ants. Well, not one to be put off by the fact that everything was sopping wet from a day’s rain on Sunday, I returned prepared: I bagged up some prime ‘pecker poo and brought it home to dry out.

Wet ‘pecker poo in situ: 35mm long, 6mm diameter

I am mildly reassured that Chris Packham is a fan of Green Woodpecker poo and wrote, “[p]erhaps my favourite bird poo (and I'm sure many other people's too) is produced by the green woodpecker. Again cylindrical, it can be found on short grassy areas where the birds have been foraging. It is about 6-8mm in diameter and somewhere between 25-35mm in length. Its outer skin is white and the interior, visible at either end, is tan brown and roughly textured, so it can look a bit like a crumpled length of a cigarette.

The real joy of woodpecker poo, however, is picking up a dry length and squashing it in the palm of your hand as this reveals the contents as the bodies of countless ants which the bird had eaten, lots of tiny legs and heads and abdomens. Superb.”

Obviously, once the poo had dried out, I was expecting it to crumble into a mass of minute ant bodies and limbs. In fact, it appeared that this particular ‘pecker had been feasting on a smorgasbord of tiny beetles! If I had more time and patience, it is probably possible to identify a few of them from their remains. There are definitely a variety of Weevil carcasses and I did spy the elytra (outer casing) of a 14-spot Ladybird, which was surprising, given how distasteful they are meant to be to birds. Anyway, feel free to let me know in the comments if you can ID any more of them - I’d be interested to hear.

Dried Green Woodpecker poo, split in two. Diameter 6mm

Closer views of crumbled Green Woodpecker poo (scale in mm)

Whilst we’re on the subject of Beetles, the Trust had some very encouraging news last week from Martin Parr (Conservation Manager at Maple Lodge). Earlier this year, Martin had done some informal survey work at the Trust’s Brickworks and Gadespring Cress Beds sites. At the latter, he'd photographed some Bloody-nosed Beetle larvae but didn’t think too much of it until he read Trevor James’ beetle report in the Hertfordshire Naturalist 2014, which contained the following entry:-

"Timarcha tenebricosa Bloody-nosed Beetle. This conspicuous beetle was found on the towpath at Boxmoor, 12th August 2011 D.Hodges. A welcome record of a species that is strangely rare in our county, although its food plant, Cleavers Galium aparine, could not be more common."

Martin got in touch with Trevor and it transpires that the Box Moor Trust’s Gadespring Cress Beds site has the only known colony of this beetle in Hertfordshire! It’s a fantastic record and, thanks to Martin, the site can now be managed in such a way as to enable this rare Hertfordshire Beetle to continue to thrive. If, like me, you're wondering why it's called Bloody-nosed, the answer is that its defence mechanism is to secrete a blood-red liquid from its mouth which irritates the mouth of mammal predators. So, there we go!

Thank you Martin for sharing your time and expertise with the Trust (and me!) and thanks too for providing the information and photographs.

    Bloody-nosed Beetle larva (Timarcha tenebricosa)
    Bloody-nosed Beetle larva (Timarcha tenebricosa)

I'll finish with a couple of shots of the Dellfield Oak.

Taken at 14:40 on Monday, just before Dellfield went into complete shadow, as the sun disappeared behind the ridge of Westbrook Hay

Saturday 22 November 2014

Week 44: Barn Owl Pellet Dissection & Analysis

With just 8 weeks left of this year-long Project, I thought it was about time I tackled the Barn Owl (Tyto alba) pellets I’d retrieved from Box Moor Trust land over the summer. These black, shiny regurgitated nuggets are the Rolls Royce of The-Stuff-That-Animals-Leave-Behind. Just one of these little gems can contain the tell-tale remains of a whole night’s feeding.

Photo: Barn Owl at a rescue centre in Yorkshire, 2009
Like a lot of birds, Barn Owls swallow the majority of their prey items whole: fur, bones, teeth and all. Unsuspecting Field Voles go down the hatch and, initially, into the glandular stomach (proventriculus) where digestive juices get to work. After this, it’s the muscular stomach or gizzard (ventriculus) which acts as a kind of sieve or filter. All the insoluble stuff like fur, feathers, bones etc are retained in here whilst muscular contractions enable the soluble contents to pass through into the rest of the digestive system (small and large intestines and so on). Once the evening’s feed is done, and before further feeding can take place, the gizzard has to be cleared out. It could be up to 10 hours after feeding has finished that the gizzard-shaped pellet is pushed back up through the glandular stomach and coughed up out through the bill. Pellets can be found on the ground at favoured roost sites and, when nesting, the female uses these as her nesting material. There’s nothing like laying your precious eggs in the fetid remains of partially digested rodents! Having said that, I'm the one who systematically collected more than a dozen of these things and lovingly placed them in her freezer next to the sausages. I’ll press on...

Small mammals, most notably Field Voles (Microtus agrestis), make up a large proportion of a Barn Owl’s diet. Reading suggested that one pellet, following a night’s feeding, could hold 4 full skeletons. I was keen to see if this really was the case and what exactly the Barn Owls had found to eat on/around Box Moor Trust land. I got hold of a copy of D. W. Yalden’s “Analysis of Owl Pellets” and downloaded the Pellet Analysis leaflet from the Barn Owl Trust (the images left/right are linked to the info), and set about dissecting a couple of pellets. The results were really very interesting. A special thanks to Martin Parr, Conservation Manager at Maple Lodge nature reserve, for his patience and help in identifying the prey items from the bones. Neither of us had any experience but we gave it a good go (tweezers and magnifying glass essential!).

Barn Owl pellet, approx 5cm long

Ok, so, this (below) is what came out of the (above) thoroughly dissected Barn Owl pellet (I abandoned the second pellet when I realised what a time consuming and painstaking task it was going to be). The bone fragments I couldn't identify are still in the plastic container. Essentially, within a fur matrix and amongst the 500 bones and bone fragments, the pellet very obviously contained at least 4 similarly sized rodents, identified as 1 Bank Vole (Myodes glareolus) (typically 9-11cm long) and 3 Wood Mice (Apodemus sylvaticus) (typically 8-11cm long). Thankfully, this is consistent with published research. Wood Mice are generally one of the main prey items of Barn Owls whilst Bank Voles also feature but to a much lesser extent (see National Owl Pellet Survey Report 2009 for further details). The most notable skeleton bones were 1 upper jaw set/skull, 4 sets of: lower jaw bones, pelvises, shins, thighs, upper arms and skull fragments. There were 3 sets of shoulder blades and forearms and a good selection of ribs, vertebrae, teeth and other likely limb bones. Ultimately, just as the literature suggested, the pellet contained at least 4 small mammals and was likely the sum of a night’s feeding in the wilds of Hemel Hempstead. It's incredible what you can dig out of something created within the digestive system of an Owl!

Approx 500 bones & bone fragments from 1 dissected Barn Owl pellet

I was lucky that the second pellet I half-heartedly dissected contained a Field Vole (Microtus agrestis), the main prey species for Barn Owls. So, I have a set of upper and lower jaws for Field Vole and Bank Vole, and a set of lower jaws for Wood Mouse.

A few photos (scale in mm) and brief notes follow in case they are of interest or use to others. Hopefully, the IDs are correct but, if not, give me a shout.

Bank Vole Jaws

Field Vole Jaws

Comparing Bank and Field Vole jaws

3 cheek teeth in each jaw
Zig-zag chewing surfaces

(UJ = upper jaw; LJ = lower jaw)

Bank Vole Jaws
UJ: no extra loop on second molar (M2) on inner side.
LJ: M2 has loops opposite and
M3 has minor 3rd loop (not present in Field Vole)

Field Vole Jaws
UJ: M2 has extra loop on inner (tongue) side
LJ: M2 has loops alternate and
M3 only has 2 loops on outer edge

Wood Mouse (Apodemus sylvaticus) lower jaw

3 cheek teeth, each with rounded cusps
Lower molars have 6 roots (2 on each tooth) [House Mouse (Mus musculus) has 5 roots; Harvest Mouse (Micromys minutus) has 7 roots]
First molar (M1) has 3 cusps along the front edge
Length of lower jaw approx 15mm (incl. incisor tooth)

Wildlife Explorers (Junior RSPB)

Last Saturday, the children of Box Moor Trust’s Wildlife Explorers’ club dissected 5 of the Barn Owl pellets. It was wonderful to hear how enthusiastic the children had been and that their curiosity and fascination had kept them digging for skeleton treasures for more than an hour. I collected the sum of their findings but haven’t yet had time to examine them in any depth. A cursory glance at the upper and lower jaw bones suggest more Field Voles (Microtus agrestis) and Wood Mice (Apodemus sylvaticus). However, there is one lower jaw bone which is particularly interesting. It has all the features of a Harvest Mouse (Micromys minutus), an increasingly scarce and therefore significant species. It’s a similar length to the Wood Mouse jaw; has 3 rounded cusp molars; 7 roots on those molars (3 on M1), and 3 cusps on the leading edge of M1. My only reservation is that it’s actually 1mm longer than the Wood Mouse jaw bone, which is something of an anomaly. However, assuming the other features are diagnostic, I’ll stick with the initial ID of Harvest Mouse (Micromys minutus), until/unless anyone can persuade me otherwise.

Harvest Mouse (Micromys minutus) lower jaw

3 rounded cusp molars; 7 roots (3 on M1);
3 cusps on leading edge of M1

A = Wood Mouse
B = Harvest Mouse

Harvest Mouse lower jaw
Length = 16mm

This is an exciting record and great work from the Wildlife Explorers. If I uncover anything else of special interest, I’ll be sure to include it in a later post.

Finally, if anyone is planning to dissect an owl pellet, I did discover that although a basic magnifying glass was useful, it didn’t give me enough magnification to be able to pick out the defining tooth features. Photographing the jaw bones with my macro lens was the best way to really see the pertinent details. Also, when the number of roots is significant, I did find that, with care, it was possible to pull the relevant tooth out a short distance (not the whole way) and then photograph the gum line. This enabled me to count the roots accurately.

Box Moor This Week

Although I do seem to have spent most of the week hunched over minuscule bones, clutching tweezers, trying to decipher tooth anatomy, I did escape into the fresh air of Box Moor on Tuesday morning. As temperatures reached around 14 degrees Celsius I shouldn’t have been surprised that a Small Tortoiseshell butterfly was fooled into flight over Fishery Moor. The Oak’s leaves are turning a beautiful orangey, yellow now and, out on the river Bulbourne, the Kingfisher family continue to squabble over territory. The young male was systematically fishing the river on Station Moor, moving from perch to perch, before going back to start all over again. It was interesting to see that the tip of his malformed upper bill looks as though it is in the process of breaking off. A second Kingfisher put in a brief appearance, quarrelled and then flew off east along the canal. The young male resumed fishing, regularly hovering over the water like a humming bird before diving for prey. I never tire of watching Kingfishers…

P.S. If anyone is interested in seeing something of the pellet dissection process, I made a short video here