Tag Archives: grey heron

Diapause and Diminishing Diversity

Capreolus capreolus, aka the roe deer, is native to the UK and can be seen in good numbers in the Fens. During an evening stroll there in July I encountered several. As well as being delightful to look at they have some interesting reproductive biochemistry. The roe deer rut takes place in July and August but the fawns are not born until the following May or June, nearly a year after the rut. The length of roe deer gestation had puzzled zoologists for a very long time and then they discovered that the roe undergoes delayed implantation, or ’embryonic diapause‘.

A roe deer peering at me as I meandered around Wicken Fen

But that wasn’t the end of the story. It was assumed that hormonal messages from the mother would tell the dormant fertilised egg, or ‘blastocyst‘ when it should implant into the endometrial layer of the uterus, but the search for the maternal hormonal trigger which has been observed in other mammals drew a blank. It transpires the trigger is a novel mechanism whereby the embryo, which at that stage consists of around 30 cells and has its own internal timer mechanism, secretes a messenger molecule called ‘rdPAG’ (roe deer Pregnancy Associated Glycoprotein) which precipitates a maternal hormone cascade of oestrogens that initiates the second stage of the pregnancy with implantation of the embryo. This is a remarkable piece of biology because it is orchestrated by the embryo, not the mother, and ensures the fawn is born during the favourable weather conditions of the summer thereby guaranteeing it sufficient time to prepare for the winter.

A visit to Wicken Fen always provides multiple unique photographic opportunities such as this pair of grey herons whose paths crossed, almost on a collision course:

Wicken Fen was mentioned in a BBC News article a couple of days ago about the importance of the Fens as a wildlife haven. The article is about a study into the biodiversity of fenland since 1670. Apparently, since the start of the study period 100 species of birds, bees and butterflies have been lost from the Fens and in total 504(!) rare species have not been recorded there in the last 25 years. A moments comtemplation on that rate of biodiversity loss is terrifying, and the implications of it even more so. It boggles my mind that the political decision makers, who are aware of all the environmental devastation, don’t appear to give a damn about it. Or at least not enough to want to do anything about it.

Despite that the Fens are still a very important refuge for endangered species, which I can vouch for based on my observations made whilst wandering around Wicken. The Fens are much maligned but are a unique and important haven for many species of all kinds of wildlife.

In order to manage and maintain the flora of the Fen which then provides shelter and sustenance for a multitude of other species, horses and cattle have been installed there, one of which is this magnificent chap:

This image doesn’t really do him justice, he is absolutely enormous – like a minibus on legs!

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Titchwell birds – the final episode

I’ve posted several times with pictures from my trip June to Titchwell on the north Norfolk coast but I’ve now exhausted my photo collection from that trip so this is the last one. There was a terrific number of bird species present the day I was there including ducks, waders, raptors, passerines and gulls, but the wildlife wasn’t confined to birds, a wall brown butterfly and a chinese water deer also putting in appearances.

Gulls are many and often not-so-varied and can be easy to overlook: “What’s that bird?”, “Oh it’s just a gull”. But I like gulls and and it’s always good to have a new species identified and on this trip it was the little gull (Hydrocoloeus minutus, Dansk: dværgmåge). At first glance the little gull looks like a black headed gull, but it is noticeably smaller:


Little gull in winter colours – the summer plumage includes a completely black head

The other obvious difference between the two species is the colour of the beak which is black on the little gull and red on the black headed. It may also be mistaken for a tern as it swoops down on the water in a similar way to a tern but it’s not fishing it’s picking food from the surface of the water. I haven’t seen other gulls feed in this way.


Black headed gull (Larus ridibundus, Dansk: hættemåge)

The black headed gull is common and I see large flocks of them feeding in the fields around Cambridge in the winter, unlike the little gull which is a rare breeder in the UK and a passage and winter visitor on it’s way to the Mediterranean.

Grey heron (Ardea cinerea, Dansk: fiskehejre)

Stalking the shallows were several grey herons searching for fish and amphibians. The heron is a very effective predator unlike the pied wagtail perched just a few metres away serenading the comings and goings of serried ranks of twitchers passing to and from one of the hides:


Pied wagtail (Motacilla alba, Dansk: hvid vipstjert)

This wagtail is an adult male, his colours are much darker and the black bib more extensive than the more delicately shaded female. The pied wagtail is a resident and migrant breeder and I regularly see them patrolling lawns, meadows and carparks with their characterisitic twitching tail.

The one bird which I knew could be seen at Titchwell, but which I also knew was very elusive, so I didn’t really expect to catch a glimpse of it, was the bearded tit (Panurus biarmicus, Dansk: skægmejse). It’s one of those birds that I’ve seen pictures of and thought it almost looks unreal, like a childs drawing of an imaginary colourful songbird. A notion which seemed to be corroborated when I looked in my Collins field guide and it wasn’t listed! It transpires that it was listed, but as the ‘bearded reedling‘ instead of the ‘bearded tit‘, and it’s actually more closely related to the larks than the tits, to which it’s resemblance is only superficial. Despite the alternative name in my field guide it is listed on the British Trust for Ornithology ‘BirdFacts‘ website as the ‘bearded tit


Bearded tit juvenile

The bearded tit is resident in the UK but confined to the southern and eastern extremities. However, I did see some and even managed to get a photograph, albeit a not very good one(!). This one is a youngster, identified by the black eyestripe which differentiates it from the female, and the black patch on the nape which is absent in both adult genders. Of all the birds I saw on this visit the bearded tit (or reedling) was probably the highlight.

Returning migrants and lots more besides

Occasionally, but fairly infrequently, it’s a struggle to find enough interesting nature to put together a post, and then every now and again so much happens that it’s difficult to fit it all in. Last weekend was one of the latter.

It started to get interesting as I was cycling to work on Friday morning, a bird caught my eye in a hedge outside work and first off I thought it was a bullfinch, which I’ve never seen on Cambridge Science Park before. But then I got a better look at it and it was immediately apparent it wasn’t a bullfinch, it had similar colours but in a different pattern, so I did a quick U-turn to get a better look. It turned out to be a black redstart male in full breeding regalia (Phoenicurus ochruros, Dansk: husrødstjert). He was magnificent but alas, because I was heading to work I was camera-less, so if you’ve never seen one, dig out a bird reference book and check him out, it’s worth the effort.

I went back to work on Saturday morning with my camera to see if he was still there but there was no sign of him so I carried on to Milton Country Park, on the northern edge of Cambridge. It was a bright sunny morning and I arrived there just after 8.30 and it was already warm. And it augured well because it turned into a real bird fest. I was hoping to see some returning migrants and as I got out the car I could hear chiffchaff (Phylloscopus collybita, Dansk: gransanger) calling in the trees around the carpark. The first migrant I actually saw was completely unexpected and turned out to be a pair of sand martins (Riparia riparia, Dansk: digesvale) which I haven’t seen for years. There were also swallows (Hirundo rustica, Dansk:  land svale) flying low over a lake and this is roughly the same time I saw the first swallow last year. Like swallows, sand martins also over winter in South Africa, but unlike swallows they nest in burrows which they excavate in sandy banks. There are some man made burrows for the sand martins at the country park but so far they’ve been ignored by the martins, but the occassional kingfisher pair have availed themselves of the opportunity.

Close to where the swallow was hunting is a small island with a tree on it where cormorants (Phalacrocorax carbo, Dansk: skarv) can often be seen perched. This time there was a carrion crow (Corvus corone, Dansk: sortkrage) sat on top and a pair of common terns (Sterna hirundo, Dansk: fjordterne) were taking exception to its presence and were working as a team to dive bomb it:

A singleton…


… and in tandem

I almost felt a little sorry for the crow, but I’ve watched them terrorise so many birds, especially buzzards and other birds of prey, in a similar fashion that the sympathy was a tad less enthusiastic than it may otherwise have been.

A migrant which was present all over the country park was the blackcap (Sylvia atricapilla, Dansk: munk), in one bush there were a minimum of four and possibly six or even more. They were squabbling away in the  bush presumably in the midst of a territorial dispute. I saw the first blackcap of 2012 a few weeks ago at Danbury Common in Essex during my unsuccessful mission to look for adders.


Blackcap male, the female is similar but easily distinguished because her cap is a rusty brown colour.

As well as the migrants the trees and bushes were full of the song of more familiar resident species such as the robin, blue tit, great tit, blackbird and wren. All were energetically vociferous, filling the air with a wonderful cacophany. And amongst these I caught a tantalising glimpse of a much less common species, the treecreeper (Certhia familiaris, Dansk:  træløber). Treecreepers are very aptly named and are fun to watch as they hunt insects in the crevices of tree trunks, spiralling upwards in a corkscrew pattern. A pair of sparrowhawk and a pair of buzzard were also busy performing their aerial courtship routines.

There were none of the winter ducks such as tufted duck (Aythya fuligula, Dansk: troldand), pochard (Aythya ferina, Dansk: taffeland), gadwall (Anas strepera, Dansk: knarand), teal (Anas crecca, Dansk: krikand) or widgeon (Anas penelope, Dansk: pibeand) on the water, they had all headed off north to their breeding grounds. But several birds including coot (Fulica atra, Dansk: blishøne) and greylag geese (Anser anser, Dansk: grågås) had chicks on the water:


Greylag geese with six chicks

I paused to try to get a shot of a great crested grebe (Podiceps cristatus, Dansk: toppet lappedykker), all now in full brown breeding plumage:

And as I stretched over the water, trying hard to get a clean shot of the grebe, and even harder not to pitch headlong into the lake, a grey heron (Ardea cinerea, Dansk: fiskehejre) flew low overhead:

It was so low I thought it must have pitched up very close to where I was but on an adjacent lake, and a quick scan revealed it sat in the top of a tree being pestered by the common tern that had earlier been harrassing the carrion crow:

The terns were deeply unhappy with any potential predator, although they were less keen to buzz a pair of sparrowhawks which were in the air above the same stretch of water!

Hungry Heron

The current beautiful but brutally cold weather we are experiencing is lethal for many tiny creatures but also larger birds including our grey heron (Ardea cinerea). Cold spells such as the current one can result in the death of a large proportion of our heron population as they are unable to fish for their normal food supply when water courses freeze over.

Statuesque grey heron on Cambridge Science Park

The grey heron is a member of the family containing  bitterns and egrets and aswell as being the largest European heron is one of the largest UK birds.  They stand almost a metre tall with an average wingspan approximately 185cm and feed predominantly on fish and other creatures, in or close to water, such as frogs and other amphibians, but have been known to take small mammals, reptiles and insects.

Herons are considered to be among the more intelligent birds due to their ability to hunt and catch such a wide range of prey. One individual in Histon has recently exemplified this intelligence in an unusual and amusing way. It arrived in my friends garden looking very sorry for itself a few weeks ago at the start of the winter weather. My friend, being a thoroughly decent sort, gave it some fish from his freezer after which the heron decided to loiter. After several free and very easy meals of frozen pollock it took up residence in the garden and when the stipulated mealtime was not observed to its full satisfaction would sidle along to the door and tap on the glass with it’s bill to summon the next course.


The Histon heron
Waiting for a snack…

…and tucking in to a pollock fillet…
…then retired to a nearby vantage point for some post-prandial relaxation

As well as being sizeable birds heron can be stealthy and are extremely efficient fishermen. They catch smaller fish and eels in their bill but as you can see from the photographs the bill is a fearsome weapon and is used to spear larger prey. I once encountered a heron pecking at a prey item on the bank of the Lode at Wicken Fen, as I approached the heron flew away and I found an enormous pike on the riverbank, approximately 2 feet long (I don’t know if a heron would be capable of catching and killing such a big fish) and it had made a surgical incision running from top to bottom immediately behind the gill and had been busy extracting the entrails.

Heron are not migrants to or from the UK but they have been known to cross the English Channel and turn up in France and the Iberian peninsula. They have various common names including the ‘hernshaw’ in Lincolnshire, the ‘marshmens harnser’ in Norfolk and a ‘shiterow’ or ‘shiteheron’ thought to originate from the herons habit of defecating when disturbed prior to take off!

So if your pond is overstocked with fish in the freezing cold weather and could use  some thinning out why not spare a thought for the struggling heron and break the ice so he can refuel and stave off the cold.