Monthly Archives: October 2010

Larus ridibundus – 23rd October 2010

There were several ornithological highlights to be enjoyed in the Histon fields this weekend. It looks as though autumn is here properly as the weather has turned more chilly, so for the last week or two I’ve been hoping to see some of our winter visitors arriving from the north and the east. It was an exciting day today because the first flock of the year of several hundred fieldfare (Turdus pilaris) duly appeared, flying low and fast from east to west. Alas, they didn’t stop, but it was great to see them arriving safely in numbers. I’m anxious to get some photographs of fieldfare so now I have my new 300mm zoom lens I’m hoping this winter will provide some opportunities to capture them on pixels. If I manage to get some good shots I’ll post them here as and when.

For the record, I’m an amateur wildlife photographer and I use all my own pictures to illustrate my posts. I use a Nikon D40x and a combination of lenses: Nikkor 18-55mm kit lens that came with my camera which I use for flowers, insects and landscapes, Nikkor 55-200mm zoom which I used as my default general purpose lens until a month ago when I acquired a Nikkor 70-300mm zoom lens which gives me that extra bit of reach. I don’t often sit in hides or wait for wildlife to come to me, I walk around and photograph anything I encounter which I think is interesting and photogenic. Which covers just about everything!

Back to ornithology, other good sightings this weekend have included corn bunting (Emberiza calandra) which is a real favourite of mine as they have a wonderfully distinctive call and they often sit proud  on top of hedges and let me take photographs from a distance of less than around 20 feet, and they’ll sit tight as long as I don’t make any sharp movements – even the dog running past doesn’t faze them.


Corn bunting

Other regulars this week have included yellowhammer (Emberiza citrinella), reed bunting (Emberiza schoeniclus), long tailed tit (Aegithalos caudatus), goldfinch (Carduelis carduelis), and skylark (Alauda arvensis). The latter are great to watch at the moment, on a sunny day they whizz around low and high chasing each other at incredibly high speed in groups of up to 5 or 6. Lone larks sing the characteristic skylark song up high, and plenty more can be seen on the ground feeding in ploughed fields, and disappearing into the scrub of unploughed fields where they don’t seem to stay for long before joining in another game of aerial tag.


Skylark

However, I’m digressing from my main theme of this weekend which is ‘Larus ridibundus’, or the black headed gull. Both yesterday and today (23rd and 24th October 2010) there have been a flock of 35-50 black headed gulls on the ground in two different, but adjacent, ploughed fields. I think it’s easy to dismiss gulls as not being very interesting but a closer inspection of a flock of gulls is a real treat. They are consummate aeronauts with beautiful plumage and are highly gregarious in winter. Consequently I’ve spent a sizeable chunk of this weekend enjoying watching them and trying to photograph them:


Adult black headed gull with brown face (this one was taken last summer at Seahouses in Northumberland – not Histon)

Adult black head in winter plumage – note the dark spot behind the eye and the red beak and legs (this and the rest of the gull pictures in this post were taken in Histon)


Note the white tail and forewing and the black tips of the first five primaries

Black headed gulls are fairly small as gulls go, around 35cm long and 100-110cm wingspan. They build nests on the ground on coastal and inland reedbeds and marshes, lay one clutch of 2-3 eggs per year and live on average for around 10-15 years. It is not an endangered species with approximately 1.5million pairs in Europe. (For a full set of facts and figures check out the BTO BirdFacts website (http://www.bto.org/birdfacts/), this site is excellent for comprehensive metrics datasets on all common UK birds). Black headed gulls are rather inaccurately named as they don’t have a black head at all. It is dark brown and only covers the front part of the face and is only present in summer when it serves as a form of aggression between rival males. They stand face to face to maximise the visible area of the dark mask to each other, but within a breeding pair aggression is minimised by displays involving turning the head to show the white nape to the partner. The dark hood recedes in winter to a small dark spot just behind the eye. Adults have a deep red bill and legs and pale grey back with a white tail and white outer edge of upper and lower wings formed by 4-5 primaries with black tips.


Juvenile diving in on an insect or worm. It has the dark tip to the tail, pale brown mottled upper wings and pale buff legs characteristic of an immature individual

Juveniles have mottled brown plumage with a dark tail tip and orangey-buff legs. They feed on worms, insects, seeds, waste and carrion, and can be seen on inland water, grassland and farmland aswell as on the coast during the winter.

I think they’re amazing to watch so next time you see a flock of gulls have a good look and appreciate the beauty of these creatures – you wont be disappointed!

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Dragonfly discoveries

Dragonflies are amazing insects which it seems can be seen just about anywhere. In 2010 I’ve even spotted them over my garden in Histon. It occurred to me I should put some effort into photographing and learning about them as I sat with my family eating a picnic on a bench overlooking the fountain in the Cambridge University Botanical Gardens. Numerous small, magnificently bright red, individuals were whizzing around the pond, and a few big blue ones a short distance away from the pond (the small red ones were a species of darter, and the big blue ones were hawkers – probably migrant hawkers). I attempted to photograph these for subsequent identification but alas my photographic skills were’t up to the job on that occasion. Despite that I looked up some information and lots of great pictures at http://www.dragonflysoc.org.uk/home.html. This is a great website and started me off on a journey of discovery which is now pretty much finished this year but which I plan to resume as soon as possible next year.

Subsequent walks around Milton Country Park and the fields north of Histon provided lots of opportunities to see many species of dragonflies and damselflies:


Female brown hawker sunbathing on a birdbox at Milton Country Park

Migrant hawker male. The yellow ‘golf tee’ on segment S2 is diagnostic 

Dragonflies originate from species which fossil records date to the Carboniferous period, around 300 million years ago, and could have a wingspan up to 70cm! They comprise the taxonomic sub-order known as ‘Anisoptera‘ and are part of the order ‘Odonata‘ which also includes damselflies (Zygoptera) and another group which is virtually extinct called ‘Anisozygoptera‘. There are now around 5300 species of dragonflies of which approximately 40 reside in the UK.

Dragonflies lay eggs underwater either loose, protected by a hygroscopic gel, or inside plants. The eggs of some species can lie dormant over winter and resume development when temperatures rise in springtime. Time to hatching is temperature dependent but is usually around 2-5 weeks and the larvae develop in water, all British species overwinter once as larvae but time to adulthood can be up to 5 years. Metamorphosis from larva to adult is triggered by increasing day length and temperature in spring, and includes the transition to breathing air and growth of their incredible compound eyes. Each eye is made up of around 29000 individual elements called ‘ommatidia‘. They also possess three addtional ‘simple eyes’ call ‘ocelli‘ which are sensitive to light intensity and assist in controlling flight via direct nerve connections to the flight muscles. Dragonflies have excellent colour vision and can also see ultra violet light. It makes me wonder what the neural activity behind all that optical prowess is capable of: are dragonflies merely responding directly to visual stimuli via reflex arcs, or is there more sophisticated image processing going on?


Common darter, immature male

Common darter, female. Note the compound eye.

Dragonfly larvae are ambush predators feeding on moving prey including other insect larvae, snails, small fish and tadpoles. Adults catch other insects in flight, holding their legs out in front like a bread basket to scoop prey from the air such as flies, flying ants, mosquitoes and even other, smaller, dragon flies.

Newly emergent dragonflies are powerful fliers and disperse widely. They are often seen a long way from water and can even cross seas. They reach maturity after a few days to a few weeks, a process also controlled by temperature, when the males will congregate at vantage points near water where females come to oviposit. The male will grasp the female around the head with his anal appendages and attempt to mate with the female by swinging her round to form the ‘copulatory wheel’ enabling him to pass a packet of sperm from the secondary male sexual organs located on his second abdominal segment to the female sex organs located on her eighth abdominal segment. After mating, sometimes under the guard of the male, to ensure his sperm is not displaced by another male, the female will oviposit underwater. And so the cycle begins again.


Broad bodied chaser – female

Weekend field walks 9th and 10th October 2010

This Saturday (9th October,2010) I was lucky enough to be accompanied by my friend David on a long walk around the Histon countryside. David is a zoologist and knows considerably more about the wildlife than myself, consequently it was a terrific walk and something of an education.

We set off around 8.15am and the weather was mild but very grey with 100% low cloud cover. Very soon after entering the fields we heard a jay making alot of noise in some trees bordering gardens at the back of the main road.  As we passed a small sycamore tree a possible meadow pipit passed overhead and we heard a second flying past later on in our walk. Shortly after that a large flock of golden plover flew over at high speed and several groups varying in size from approximately 5-10 up to 70-80 were spotted in the air and on the ground in several other fields. Many evenings whilst walking at night last winter I heard birds on the ground making a short whistle consisting of a single  note and had no idea which species was responsible. Our golden plovers in the air were making exactly the same noise so the mystery of the night time whistlers was solved too. A kestrel and a sparrowhawk made solitary appearances and a peer into an old tumbledown barn revealed a little owl – a good day for birds of prey.

The mild damp conditions of late have been ideal for fungi. Gorgeous bright yellow heads of the yellow fieldcap mushroom (Bolbitius vitellinus) lined the walk, all at various stages of growth from recently sprouted, just a couple of centimeteres tall with very rounded unopened caps, to old and nibbled specimens around 10cm tall and the caps more dull in colour and 4-5cm in diameter:


Recently emerged yellow fieldcap mushrooms


Older yellow fieldcap


A cluster of four mature yellow fieldcaps

We also found a ‘substance’ which preliminary inspection suggested the most likely identity was dog vomit! It occurred every few paces for several hundered metres wrapped around grass stems – suggesting a very poorly dog. When it was gently disturbed at the edge it had a powdery consistency and blew away in the breeze like dry Ready Brek. It varied in colour from grey/white to pale buttery yellow, so we concluded it must have been some kind of mould:


Mucilago crustacea – a slime mould. This stuff can move slowly to new food. Only at a snails pace, but don’t stand still for too long!

Toward the end of our outing as we headed back to the village a small flock of gulls consisting of a lone herring gull, a black headed gull and around 30 lesser black backed gull were beautifully contrasted against the dark ground in a ploughed field. Despite the grey weather it was a great day for wildlife.

After the nature fest on Saturday followed by just one or two small drinks with some good friends in the evening, I contemplated a shorter stroll this morning to blow away the cobwebs. But the weather was absolutely glorious and the profusion of birdlife resulted in another whole morning spent in the countryside. I heard six green woodpecker, one of which was exiting an old oak tree at high speed having been flushed out by a buzzard. A second buzzard appeared over the farmhouse with a sparrowhawk shadowing it right overhead but at much greater height. The buzzard quartered the fields and then headed off south west over Histon:


The unmistakeable shape of a buzzard. I love watching
big birds of prey so seeing two buzzards in one walk
was very special

Despite the weather no swallows were around today, I saw small numbers (less than 10) on Saturday and Sunday last weekend but we’re now heading towards mid-October so the last stragglers must be heading for Africa.

Many songbirds put in an appearance today which has been an unusual event since the harvest got underway at the beginning of August. Two yellowhammer, two corn bunting, numerous reed bunting, dunnock, blue tit, robin and a pied wagtail were all spotted today.


A corn bunting on the right and a male reed bunting sitting together and as I watched a female reed bunting arrived. Marvellous!

Yellowhammer

I was particularly pleased to see the wagtail, it’s the first one I’ve seen in the fields this year, whereas last year they were on display almost every day. I hope that’s not a nationwide phenomenon.

A lone kestrel and two sparrowhawks were up and about today so another good day for birds of prey. Also as yesterday, many skylark were extremely active playing tag and because of the lovely weather they were singing up high. I managed to go one better with the pipits of yesterday as I watched one fly up out of a small bush when disturbed by me landing in another one about 30m away in full view. The local churchyard rooks were omnipresent, digging out invertebrates in most of the fields accompanied by countless wood pigeon and carrion crows.

It was difficult to choose a highlight from this weekend, but as I sat on a tractor trailer in the sunshine making some notes a common darter dragonfly buzzed past and settled on an old plough to sun itself. It’s late in the year for dragonflies so that was good to see.


Mature male common darter warming up in the morning sunshine sat on an old plough

I shall post again soon about our local birds and hopefully next time I shall have seen the first winter immigrants such as fieldfare and redwing. Fingers crossed.

Araneus diadematus

Araneus diadematus” is the Latin name for the garden spider, which is ubiquitous in my garden just now. Every piece of garden furniture is being used as a support for webs, and some of them are huge, up to 12 inches in diameter with anchor lines up to 3m long holding them in place. I’ve never seen such long anchors which the spiders construct by spinning a fine sticky line from spinneret glands at the end of the abdomen which blows on the wind until it sticks to a suitable support. These are the ones which get stuck to your face when you walk in the garden at night! The spider reinforces the first line with thicker, stronger thread until it can support the weight of the whole web. Further support and radial lines are added until sufficient structure is in place to enable strengthening of the middle with a non-sticky spiral, followed by construction of a widely spaced non sticky spiral out to the edge of the web. The spider can walk on this and use it as a guide to build a sticky spiral inwards from the outside edge and this is used to catch prey.    


Garden spider adding the sticky spiral which will trap prey

Spiders have up to 8 spinnerets of different types to produce the various grades of silk required to construct a whole web. It’s a truly incredible biochemical process resulting in a material with strength per gram greater than steel, and so far, despite a huge amount of research, one that humans have been unable to replicate synthetically.    


Perfect web illuminated by the morning sun

Once the web is constructed, the garden spider waits under cover at the end of one of the radials monitoring vibration in the web with one or more of its foremost legs. When struggling prey causes the right frequency of vibration (they don’t react to vibration caused by the wind) the spider ambushes its prey and kills it with a venomous bite before wrapping it in silk and storing it until it’s eaten.    

In the last week or so, as well as finding some beautiful webs laden with early morning moisture and lit up by the sun, I’ve been lucky enough to see some fascinating behaviour by garden spiders. My son pointed one out to me that had built a web between my garden table and the french window and was behaving in an unusual way, alternately raising front and rear legs as though it was dancing. Closer inspection revealed that it was using all eight legs to gather broken web which it then rolled into a ball and ate before recycling it into more web to patch up the original. I found another one at the other end of my garden table – which is no place for an arachnophobe to sit and enjoy an evening beer – which was lurking under a clematis leaf with both of its front legs feeling for vibrations on an anchor line of its web:   


Lurking undercover waiting for breakfast

This morning I was looking for larger spiders to try to get some good photographs and there was a beauty putting the finishing touches to its web on the childrens climbing frame. While I was looking at this adult female, a second much smaller version, possibly an amorous suitor, was building a web from a plant pot joining onto the web of the adult. It occurred to me this was no way to ensure longer term survival for the small spider. As I watched, it approached the female, who was now in the middle of her web, waving its two front legs in the face of the much bigger female. The female reciprocated and for several minutes this game went on with no apparent aggression.   


Female garden spider  


Close Encounter 


Closer encounter 


Dangerous encounter 

I haven’t seen this before so I’m not sure what the small spider was doing, but after several minutes the inevitable consequence was the lady pounced on the smaller spider and killed it rapidly before wrapping it in a silken coffin and transporting it higher up into its own web.     


Lethal encounter 


Shrink wrapping her ready meal 


Carrying off the spoils 

All this within a few centimeters of my eyes. Exciting stuff… and right outside my back door!