23 | May | 2011 | The Naturephile

Daily Archives: May 23, 2011

Dragon hunt

Posted on May 23, 2011 | 3 comments

Not the fire-breathing type but Anisoptera. I spotted the first dragon this year over Easter during a picnic at Grantchester Meadows, south of Cambridge. It wasn’t, technically speaking a dragonfly, but a damselfly, specifically, a large red damselfly (Pyrrhosoma nymphula), which is one of the first to emerge after the Winter. Due to the weather this year many things have happened earlier than usual and the large red was out and about in late April. And they are magnificently red:

Large red damselfly male. There are three colour forms of the female all of which have more dark banding on the abdomen than the male

Milton Country Park on the northern edge of Cambridge is a great place to see numerous species of dragonfly and damselfly, and on a foray there on Saturday with my friend, David, we counted 10 species. Dragonflies – I’m using this generic term interchangeably to cover dragonflies (Anisoptera) and damselflies (Zygoptera) – are remarkable creatures, there are few more accomplished aeronauts in the animal kingdom, and the various life cycles are amazing.

The life cycles involve an aqautic larval stage, the larvae hatching from eggs laid either underwater or inside plant material close to the waters surface. The duration of the larval stage is affected by various factors including temperature, and for species such as the blue tailed damselfly (Ischnura elegans), this results in the difference in duration of the larval stadium (developmental stage) of 1 year in warmer parts and 2 years where it’s colder.

Blue tailed damselfly, immature male

After the larval stage, metamorphosis, switched on by warmer temperatures and extended day length, occurs over a few weeks and concludes with the emergence of the adult from the larval cuticle when it will dry out and take to the air. The drying out process is hazardous as it renders the new adults susceptible to predation by birds, consequently they time their emergence to occur at night or in the early morning. New adult dragonflies then disperse from water for approximately a few days to a few weeks, until they are sexually mature, when they return to the water for the serious business of finding a mate and starting the whole process over again.

This is a very incomplete and generic description of the dragonfly lifecycle, but if you want to discover more I recommend a book called ‘Field guide to the dragonflies and damselflies of Great Britain and Ireland’ written by Steve Brooks and illustrated by Richard Lewington (ISBN 978 0 9531399 0 3). It’s a very well written book with lots of easy to read information and high quality illustrations. And because there are only around 40 or so species of dragon and damselfy in GB and Ireland it won’t take you all year to read!

On our walk we saw hairy and emperor dragonflies (Brachytron pratense and Anax imperator respectively), both species of hawker, which I couldn’t get good photographs of as they were whizzing around over the water at high speed and never seemed to settle within range. Similarly with the four-spotted chaser (Libellula quadrimaculata), but then as we positioned ourselves in a very good viewing location on one of the smaller lakes a scarce chaser (Libellula fulva) appeared on a nearby seedhead and with occasional forays stayed there all the time we were there, giving some great photo opportunities:

Scarce chaser male, the female has a yellow abdomen with a thin black spine and doesn’t have the three black end segments

There were lots of damselflies too, apart from the large red and blue tailed already mentioned. Variable damselfly (Coenagrion pulchellum):

Azure damselfly (Coenagrion puella):

And common blue damselfly (Enallagma cyathigerum)

This pair of common blues are in ‘tandem’ with the green eyed female underneath. This position is adopted by non-territorial damselflies where the male grips the female behind the head and in this way ensures that no other male can mate with her before his eggs have been laid – a process called ‘ovipositing’. The eggs hatch out after 2-5 weeks and the larvae begin their development underwater where they are ambush predators, feeding on a variety of prey from other insect larvae to tadpoles and even small fish!

They are amazing creatures, and more species will be emerging over the next weeks and month so hopefully I can gather some more images of other species for subsequent posts before the Summer ends.

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Posted in Anisoptera, Chaser dragonflies, Countryside walks, Damselflies, Dragonflies, Hawker dragonflies, Insects, Milton Country Park, Walks around Cambridge and Histon, Zygoptera

Tagged Anax imperator, Anisoptera, azure damselfly, blue tailed damselfly, Brachytron pratense, Cambridge, Coenagrion puella, Coenagrion pulchellum, common blue damselfly, damselflies, developmental biology, dragonflies, emperor dragonfly, Enallagma cyathigerum, four-spotted chaser, Grantchester Meadows, hairy dragonfly, Ischnura elegans, large red damselfly, Libellula fulva, Libellula quadrimaculata, milton country park, Pyrrhosoma nymphula, scarce chaser, variable damselfly, Zygoptera

The birds and the bees (and the flowers)

Posted on May 23, 2011 | Leave a comment

As our warmest and driest Spring on record turns into what is shaping up to be a warm and dry Summer, nature’s great events are occurring apace to exploit the prevailing climatic conditions.

The first swifts were seen over Histon 3 weeks ago (by me at least) after their heroic journey back to their breeding sites from overwintering in Africa. To celebrate this event I’ve spent several hours sitting in the garden of the Castle pub on Castle Hill in Cambridge enjoying a few convivial sharpeners and watching the swifts shrieking through the sky like an avian aerobatic team. I can heartily recommend both activities!

Wild flowers, including one of my favourites, white campion, are now in bloom:

White campion, Silene latifolia, decorating ditches and hedgerows

White campion is a dioecious plant which means the male and female reproductive machinery are on separate flowers. It grows in well drained earth and flowers from Spring to Autumn and is now delineating my walks across the open countryside. Another one of my favourite wild flowers is red clover (Trifolium pratense) which is a gorgeous colour and provides nourishment for bumble bees:

Red clover flower being harvested for pollen and nectar by a common carder bee (Bombus pascuorum). This is the national flower of Denmark.

And of course the local birdlife has been very busy breeding and raising chicks. Alot of species started this process earlier this year due to the unusually warm weather in Spring. I have a pair of blue tits raising a brood in the nestbox in my crab apple tree and my friend told me of a family of song thrushes which fledged from his garden a month ago. Which is very early.

A pair of great tit have been feeding their chicks on crushed peanuts which I put out on my bird feeder over the last month and last week they fledged and the whole family were feeding in my garden for just a day or two before they ventured further afield. (If you put nuts out for the birds during the breeding season please make sure you use crushed nuts as inexperienced parents can try to feed whole nuts to chicks and this can have fatal consequences). Great tits have over 70 different vocalisations which I think is remarkable, almost simple language! And on my explorations along the fields and hedgerows around Histon last weekend (21st May, 2011) I saw more great tit, blackcap and whitethroat all feeding gangs of fledglings:

Common whitethroat male, Sylvia communis

There are two species of whitethroat to be found locally, the common and the lesser (Sylvia curruca). They are distinguished by their song, which I won’t try to describe because I’ve never yet read a book which gives the remotest idea of what birdsong actually sounds like by a written description! But if you want to compare them try here for the common whitethroat, and here for the lesser whitethroat.

And another male whitethroat, this chap was singing long and loud, punctuated with characteristic jerky flights straight up in the air and back to the same spot

There are a good number of common whitethroat in the hedgerows north of Cambridge, lesser whitethroat are also here but are not so numerous. There are other distinguishing features between the two species, the lesser, as the name suggests is smaller (~11cm long compared to ~13 for the common), and is generally more grey with a pale grey head and noticeably darker grey ‘ear’ patches. It also has dark grey legs. Both species overwinter in sub-Saharan Africa, the common in central Africa and the lesser in eastern Africa.

Linnet can be regularly seen flying around the bramble thickets on the edges of the village and perching and singing on top of them. On Saturday early in the morning a fracas was going on in an elderbery tree in Rowleys Meadow in Histon which ended when a jay was chased out of the tree by a family of linnet and a family of whitethroat. The jay alighted on an adjacent shed to suss out the lie of the land and contemplate another raid whilst the indignant songbirds dispersed into some scrub to hide. Eventually the jay decided to keep his powder dry and disappeared into a nearby wood. Jays, like other members of the crow family, will raid nests of smaller birds for eggs and chicks, so it’s a perilous business being a small bird with a family to rear.

A linnet male perching on a bramble. When they’re not protecting a nest I’ve managed to sneak within 15 feet of linnet perched like this.

Linnet, Carduelis cannabina, are abundant resident and migrant breeders, although their numbers, as with many of our songbirds, are declining, and they are also passage and winter visitors. Due to their declining numbers over the past 40 years or so their conservation status is red, indicating they are globally threatened. They are finches which live in open country and farmland and feed on seeds.

Many species of moths, butterflies, bees, flowers and a plethora of other creatures are all appearing as trhe seasons are progressing and there’s something new to see every week!