Biodiversity
Over the many years I have been wandering on the Common I have compiled a list of animals and plant species I have seen. In all I have recorded 437 different species which is 20% of the total I have recorded for the whole county; in other words, Wareham Common has a rich biodiversity.
The main body of these species are flowering plants with 183 species in all. Add to this 12 species of trees and shrubs, 24 types of grass, 10 sedges, 8 rushes and 7 ferns (and related species) and you can see just how important the Common should be as a natural habitat. I have not kept detailed counts and I have not done consistent annual reviews but my impression is that overall the plant populations on the Common are stable with some thriving and a few a little precarious.
As far as vertebrates are concerned the figures are a little misleading as although the list of birds stands at 58 many of these have not been seen actually on the Common but over it during one of my visits. The diversity of birdlife on the Common is poor with very few regular over wintering species and very few nesting species. I have recorded just 5 mammal species and one reptile and one amphibian. The reality is that the wet environment really does not suit these creatures.
Invertebrate life was once much more diverse than it is now. There have been 19 different species of butterfly and just 10 species of mainly day flying moths; I have never put a moth trap on the Common. Odonata (damsels and dragons) amount to 11 species which is poor but I believe that there are a couple of quite scarce species I have never found. The remaining invertebrate species amount to 82 with 28 of those being fly species.
The total variety of species will of course be far greater than my numbers for various reasons. Firstly, there are many I have not been able to identify as I am not an expert, just an enthusiast. Secondly, I have never used any trapping equipment to catch samples which is the only way to track some species, small mammals for example. Finally, I have not carried out systematic recording, just ad hoc records from the various visits I have made.
Vertebrates
I have only ever seen five species of mammal on the Common and three of these, rabbit, its nemesis the stoat and moles were on the grassy dry slopes of unit 3 (West Mill). A couple of roe deer used to be frequent on unit 1 (Carey) but I have not seen them now for several years. The other species seen was a water vole, again some time ago now but there is anecdotal evidence that they are present further up-river and maybe they are staging a small revival having seen their populations everywhere plummet since the 1980s. There is trail camera evidence that otters are back along this stretch of the river too.
Small mammals are difficult to record without a license to set human Longworth traps but my impression is that the Common has few small mammals apart, perhaps, from around the drier fringes. I think if there are small mammals present there would be a greater presence of prey species, notably kestrels. The annual flooding would make the Common unsuitable for small mice, voles and shrews although water shrews are probably present along the ditches.
The flooding also means reptiles are not present either, apart from grass snakes which are quite at home in freshwater and feed on frogs and toads. I have seen toads on the Common but never any sign of frogs but as frogs spawn in February and that is when the common is most likely to be flooded it is not likely to be good territory for frogs.
Of the 58 bird species seen four have been recorded flying over and not using the Common and another fifteen species are winter ‘vagrants’; that is species you would not generally expect but have made the odd appearance from time to time, some when the flooding is receding and so making it suitable for waders. That leaves just thirty-nine species that are using the common either for feeding or possibly nesting. Sixteen of these are what one might term ‘ubiquitous’ in that they are fairly common and can be found almost anywhere; found all year round these species may be using the neighbouring areas for nesting and just using the common for feeding (house sparrow, blackbird, wood pigeon, etc.).
My estimate is that only eight or so species are actually nesting on the Common (mute swan, mallard, possibly reed bunting) or immediate fringes, especially the railway embankment. A further eight species of summer migrants might be using the Common for feeding and seven using the Common for feeding in the winter although the black-headed gull and herring gull visit during high tide in Poole Harbour for much of the year.
Invertebrates
Insect varieties and numbers have fallen somewhat in recent years and I will give some personal thoughts on that later in my observations. Of the 82 invertebrate species I have seen on the Common since 2006 I am sure I would be hard pressed to find some of them now.
The most visible order of insects are the butterflies and I have recorded nineteen species so far. Of these sixteen are amongst the most common and widespread species that you might encounter anywhere and two, the painted lady and the clouded yellow, are immigrant species that occur in varying numbers each year. Only the wall brown of the species recorded is notable. The damp meadows are important for the spring emergence of the orange-tip because the food plant for its larvae is the cuckooflower (or Lady’s smock) which grows quite readily here.
Alongside the butterflies some day flying members of the other order of lepidoptera, moths, can occasionally be found including the increasingly scarce scarlet tiger moth which can sometimes be seen near the well vegetated ditches. Another scarcity is the antler moth which can be found gorging on common ragwort.
There have so far been eleven species of odonata, five damselflies and six dragonflies. The beautiful metallic green banded agrion is particularly numerous in summer along the lush vegetation by the river to the west of the railway. Large red damselfly, blue-tailed damselfly, azure damselfly and common blue damselfly are more likely to be seen around the ditches. Dragonfly species are now seen less frequently with emperor dragonfly, southern hawker, broad-bodied chaser and common darter all nationally common species but the keeled skimmer is only found in areas with acidic water. The main interest is the sky blue scarce chaser, a species spreading its range in Britain which can now be seen along the river.
The most diverse order present with twenty nine species recorded are the diptera or flies. Unpopular with most people but a range of insects that fulfill vital functions within ecosystems. The larvae of many flies feed on cow excrement and so break it down and dispose of it; it is a dirty job but someone has to do it! The number of diptera species includes thirteen varieties of hoverfly; the larvae of several species feed in drains and ditches which accounts for their presence on the Common.
The order of bees, wasps and ants, hymenoptera, has thirteen species on my Common list. These tend to be pollen collecting insects heavily dependent on bramble flowers for survival. None of the species I have found are particularly noteworthy.
There are at least eighteen species of coleoptera, beetles, on the Common. These, too, are heavily dependent on one either cow dung, bramble flowers or the flowers of the carrot family such as hogweed and hemlock water-dropwort.
There are a number of other insect species present including some caddis flies that live as larvae in the river and they can be quite numerous at times during the year.
My efforts have also yielded nine species of arachnid, spiders and harvestmen, but I am sure there are many more species present but they can be hard to find and even harder to identify without taking samples for microscopic examination and that is something I am not prepared to do.
Plants
Having already mentioned the most interesting plants on the Common when describing the various SSSI units I would now like to look at the diversity of plants from a different angle. Most plants require a specific set of conditions to be present to suit their needs and to enable them to grow; this leads to each growing in its preferred range of habitats. If we attach the preferred habitats to each of the plant species found on the Common it reveals the range of natural habitats present and a guide to their value to plant life.
The chart above shows the number of species per habitat type on Wareham Common; only habitats with ten or more species are included. It should be borne in mind that some plants grow in more than one habitat type.
The drainage ditches that cross the common and the surrounding areas that are very wet not surprisingly produce the most species and this is why parts of the Common are designated SSSI. Likewise, there are 16 species associated with fen and carr, and 15 with flush and spring; all wet habitats.
The presence of Dwarf Shrub Heath may seem a surprise but the Common, as I said at the outset, is bordered by dry acid conditions and that is where these species can be found. Given the heavy cattle grazing 17 species linked to cultivated or disturbed land is to be expected.
There is no broadleaf woodland as such on the Common but a number of wooded areas border it, especially along the railway embankment. Many of these species are also found in mixed woodland which also appears on the list.The 12 shrub species are to be expected from the area.
The presence of 14 species of calcareous grassland is a little surprising but the river does rise in the chalk hills of Dorset and so one assumes seeds from further up steam have arrived here via the flow of the river.
There are, of course, no sand dunes but there is overlap here with species that occur both on dunes and on dwarf shrub heath.
On a primary habitat of coastal flood grazing one expects lush grass, diverse damp tolerant flora and fresh water plants that favour ditches and river banks. That is what this chart confirms.
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