The Stangrove Pond Survey - 2006

Stangrove Pond Slide Show

Key species

Newts

All of our native newts belong to the genus 'triturus', of which there are just twelve representatives in Europe. Seven large bodied like our great crested variety and five small bodied, as are our common and palmate newts, these being the extent of newts to be found in Britain today, other than a few isolated populations of introduced exotics. Here at Stangrove Park we are well blessed, having both the great crested, or warty, newt and the common, or smooth, newt in residence, albeit in low numbers (we conceivably also have the palmate newt: according to KMBRC records, two specimens were recorded in the pond on 21/05/85 by G. A. N. Davies). Both were clearly present in good numbers during the years following the renovations and could be seen easily, by casual observation, as they went about their business during spring and early summer. They are still present in reduced numbers but seem much harder to observe than during the previous survey (presence was confirmed by both egg counts and direct observation, by torching after dark), with great crested's seemingly having fared better than their common cousins. All sightings were located along the full length of the northern bank which is not surprising as it has a shallow edge and a reasonable emergent flora, primarily as it is better lit than the rest of the pond.

Following the revelations of my visit on 3rd June (see 'Diary of visits'). It is possible that what we consider here to be the main breeding pond (an assumption based on size rather than any other evidence) may only be a 'sink' pond, where a few newts manage to hang on without successfully breeding in large numbers. While the 'source' pond/ponds, where newts breed in good numbers and disperse, lay close at hand, in the gardens of certain houses in the direct vicinity of the park. Or to the west of Crouch House Road, where a fair number of potential ponds can be seen on the map (the KMBRC report seems to corroborate this), well within striking distance. Especially if the garden ponds form a sort of stepping stone, with a few adventurous stragglers occasionally making it as far as Stangrove Pond to reinforce the numbers present there.

The interrelationship of the local newt populations would provide a fascinating avenue of research but, sadly, lies beyond the scope of this report and we must content ourselves with trying to improve that which lies before us.

The common newt is, along with frog tadpoles (literally tail-head), the quarry par excellence of every schoolboy with access to a net and some open water. Until the seventies they seemed to be everywhere. Ponds, ditches, even the flooded depressions left by a passing tractor wheel, held at least a few of these fascinating creatures. To be observed feeding on small aquatic invertebrates or conducting their courtship dance: the male lashing a current of water towards the female with frantic movements of his tail as he stimulated her to mate with him. After mating the female lays her eggs singly (not in a single ball shaped mass, or strand, as with frogs and toads), wrapping each in the leaf of a submerged plant or blade of grass using her hind legs (this behaviour is common to all of our newt species).

Although the perception of newts is of an aquatic animal, perhaps leaving the water in autumn to hibernate, in the case of the common newt the period during which they are active in the water is limited to a few months between spring and mid-summer, during which time the male develops a crest and both sexes have what is best described as a 'wet skin' texture and enhanced markings. The male is blue/grey with black spots and the female a light brown, while the under parts give way to an orange belly with black spots in both sexes, the spotting being significantly finer in the female. Both colouration and the period of immersion are quite variable between populations. During this phase the newts become somewhat crepuscular (active mainly at dawn and dusk) in their activities while great crested's are rather more nocturnal in their behaviour, hence the need to carry out observations at night for the best results when surveying.

After breeding the newts leave the water and seek refuge ashore, this may be at some considerable distance from the pond, which underlines the need to take care of and preserve any nearby habitats such as the southern shaw. At this time the skin loses its wet aspect, becomes velvety to the touch, and the animals become quite sedentary, choosing to take cover beneath logs or other objects providing a sheltered, damp, environment. All of our newt species seek deeper shelter and hibernate throughout the winter months.

There is no excuse for even a novice to confuse common and great crested newts. While common newts average around four inches in length the great crested measures around six to seven inches (the male is actually slightly shorter than the female). Sexual dimorphism is not so marked in this species, with both giving the overall impression of a black animal, although in bright light they can be seen to be a dark, chocolate, brown colour with even darker spots. The skin has a warty texture, each wart being tipped with a white spot, hence the alternative name of warty newt. The male has a silver flash running down the centre of the tail during the breeding season, while the female has an orange line running along the lower edge of hers, which is absent in the male. Both sexes have an orange underbelly with black spots and, of course, the male develops a ragged crest during the breeding season, which gives the species its common name.

The great crested newt is the rarest of our native newts, mostly due to loss of habitat, but it is also handicapped by the fact that genetic differences affecting them mean that each mating has only a fifty-fifty chance of success. The two genetic varieties (roughly equal in number) are able to mate successfully and produce fertile eggs but those produced by incompatible individuals always abort before hatching. Being a long lived species (7-15 years) one or two failed breeding seasons, for whatever reason, need not necessarily spell the kiss of death, even to an isolated population such as this one.

It should be mentioned that newt tadpoles are totally different in appearance from frog and toad tadpoles. Newts appear as small legless versions of the adult with large feathery gills situated behind the head, and whereas in the case of frogs and toads the hind limbs appear first, with newts it is the forelimbs, which are first to be seen. Apart form being much larger than those of the common newt, great crested tadpoles are far more free swimming and, therefore, more easily observed as they appear to hang in mid-water for long periods, particularly on sunny days.

Again the aquatic phase varies but starts somewhat earlier than with our other two species, sometimes as early as February, and varies in duration from about ten days to the other extreme of full time, year round, occupancy at a few steep sided sites. The best time to observe them, however, as with the common newt, is throughout the early spring and summer, with the adults leaving to seek hibernation sites, on average, between August and September, preferably close to the pond but up to several hundred yards distant. They are even more sensitive to the correct type of terrestrial habitat, preferring ponds bordered by long grass with a scrubby aspect and plenty of hiding places, which underlines the need to revue the way in which the grassland around this pond is managed. They are the most aquatic of our three newt species and, unlike the other two, retain a moist skin throughout, having no velvety phase.

According to records submitted by G. A. N Davies, our third British species, the palmate newt, was also present until at least 1985 when two specimens were discovered. Without capture and close examination these are virtually impossible to distinguish from female common newts and may still be present. Apart from the webbed hind feet, which give the species it's name, the main diagnostic feature is that the tail appears as if it had been cut off obliquely about half an inch from the tip and ends in a filamentous black thread.

Frogs

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The common frog - is probably the most instantly recognisable of all our native amphibians and, with the possible exception of the common toad, the most far ranging...
The common frog...

The common frog is probably the most instantly recognisable of all our native amphibians and, with the possible exception of the common toad, the most far ranging. Of the amphibians using Stangrove Park pond this, should it become extinct from the site, is the most likely to repopulate, should conditions improve. Local populations have crashed dramatically over the past ten years, possibly due to the viral disease known as red legs. My own garden pond, barely four feet across at any point, once held over twenty individuals at spawning time but it is now rare to see a single individual. Globally too, frog numbers of all species, have fallen dramatically, with intensified ultraviolet light, caused by reduced ozone cover, being cited as one potential cause.

It should be mentioned that the common frog is the most likely species to suffer adverse effects from any dredging work, unless particularly well timed. This is because a good proportion of the mature males hibernate in the mud at the bottom of the pond, breathing through their skin, which, as in most amphibians, also acts as an organ of respiration (the crest which develops on male newts is thought to serve two purposes, being both an organ of display and also increasing the oxygen available, by maximising the area of absorption, during the energetic courtship). The females and immature specimens seek refuge ashore. There is little that can be done to avoid this problem other than cautious timing (not after early December) and carrying out the work in sections involving no more than half the pond in any given year.

Back in the mid nineties Stangrove pond had a strong presence of this species with masses of spawn to be found in early spring, usually in the shallows of the north-western corner. This year, especially given the species local history, I began to get concerned when no spawn was to be found by mid March. Happily, on the twenty-eighth, my fears were allayed when twenty seven clumps of spawn and a dozen or so individuals were to be observed in exactly the same spot as before, giving rise to large numbers of well developed tadpoles (at least to the hind limb stage-by mid-June). It is impossible to estimate exact numbers of metamorphosed individuals attending in spring from spawn alone as non breeding specimens may be present and each female produces eggs from two ovaries, which may or may not mould into a single mass. Suffice it to say that this species, at least, is present in numbers comparable with previous observations and appears to be holding its own.

Waterfowl

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The main representatives are mallard and moorhen - with numbers of around sixteen and five adult individuals respectively comprising the maximum resident population by the end of winter...
The main representatives are mallard and moorhen...

The main representatives are mallard and moorhen, with numbers of around sixteen and five adult individuals respectively comprising the maximum resident population by the end of winter. This is, of course, variable as they are both capable of flying in and out as conditions favour and produce their young from early spring onwards, more than doubling the population present. Adult numbers are more stable throughout the summer, when moulting occurs and they become grounded for a period, but the rapidly growing young meant that, this year, over thirty large ducks were present throughout the summer months.

Moorhens are members of the rail family, characterised by the coloured shields on the front of their heads and disproportionately large feet for walking over water plants and soft mud. The moorhen is easily recognised by its red bill and shield and it's affinity to smaller ponds with scrubby margins, while it's cousin, the coot, has a white beak and shield and prefers larger, more open, waters. The moorhen is also more likely to build its nest ashore, with the coot preferring to build raft-like nests in shallow open water. The moorhen is omnivorous in its diet feeding freely on plants, invertebrates and tadpoles, etc.

The mallard is, without doubt, our best known duck, making itself at home on almost any expanse of water where it may find a living. At Stangrove Park pond it's numbers have increased dramatically since the site was renovated in the early nineties, from around half a dozen individuals to the present level. It is encouraged here by substantial feeding (I saw one person throw five whole loaves into the pond in one go and would estimate that a minimum of at least half a dozen loaves enter the pond every day in summer!) and the provision of a duck house on the island, for shelter. This brings its own problems in that the food and droppings add to the overall enrichment problems, while its feeding habits denude the oxygenating plants and continually disturb the bottom silt, which makes the reestablishment of such flora difficult, if not impossible. They are, like the moorhens, omnivorous and will happily predate on both frogs and newts, although they may find great crested newts more unpalatable than the other species.

I realise that, like trees, ducks are an emotive issue but, if other wildlife is to thrive, some uncomfortable decisions may need to be taken in order to restrict their numbers, or we must content ourselves with a duck-pond, which may, ultimately, prove to be the more acceptable objective to the general public.

Dragonflies and Damselflies

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Sympetrum Sanguineum - the Ruddy Darter...
The Ruddy Darter...

Dragonflies and damselflies together make up the order odonata, they are very similar but damselflies are generally more frail and perch with their wings folded behind their backs, while dragonflies hold their wings outstretched.

Variety was poor when I first became involved with the pond but improved rapidly after renovation to include: large red damselfly, azure damselfly, southern hawker, emperor, broad-bodied chaser, black-tailed skimmer, common darter and ruddy darter. This year we were reduced to only two species (discounting the very brief visit by a common blue damselfly on 19/7): the banded agrion, which although a new recording were doubtless only visitors from The River Eden, as they are predominantly a species of slow-moving waterways rather than ponds or lakes, and the large red damselfly. The latter, observed in pairs on one occasion, was the only species attempting to breed.

Dragonflies and damselflies are a good guide as to the health of a body of water. Very few were present during 2006 neither were any nymphs discovered during my dipping forays, which is further evidence as to the poor condition of the pond. It is the decline in aquatic flora and water quality, which is, in my view, responsible for the loss of all but one of the species previously present. The black-tailed skimmer was expected to disappear as the pond matured, generally being a pioneer of newly created bare bottomed ponds.

Vascular Plants

Flora is poor overall but the aquatics and emergents are particularly bad, there being no oxygenating plants to be found at all. Perhaps saddest of all is the loss of curled pond weed which was present in good quantities, even prior to restoration, and which served as an excellent spawning media for newts of all species.

Branched bur-reed and reedmace were once present in sufficient quantity as to present a nuisance, in choking the open water to an unacceptable degree. Reduction was desirable, but reedmace has been eradicated all together (and with it the ruddy darter which has an involved relationship with the plant) and bur-reed, which supports one of the few beetles to be found (Donacia vulgaris), could usefully be allowed to re-establish to a moderate level.