This week's notes will delve into the intriguing life of the ragworm, followed by a brief run-down of wildlife activity on the basin.
Ragworms (nereis diversicolor) live in abundance in estuaries and muddy shores where they live in the substrate. Ragworms have long, flattened bodies, consisting of many segments each with a pair of parapods, (swimming legs). They an integral part of the basin and food for many a bird, like black tailed godwits.
They can live for 1-3 years and an adult may reach 6-12cm in length and consist of 90-120 segments. They are variable in color typically appearing reddish brown but turning more green when spawning. The head end has a toothed proboscis, four eyes and two pairs of antennae. Their U or J shaped burrows may reach around 20cm in depth.
A ragworm is both a scavenger and predator. It scavenges on mud, detritus (organic matter) and plankton (very small organisms). As a predator it rapidly shoots out its jaws to catch other soft-bodied invertebrates. They are known to spin a net at the top of its burrow, then by undulating its body within its burrow, causes a water current which carries phyto-plankton into the sticky net (which is then all consumed and another net made). Feeding behaviour depends on phytoplankton densities. When high it will tend to use the net method but when low it scavenges for its prey.
Spawning is triggered by a rise in temperature during spring. Females brood eggs within their bodies. As the eggs develop, the female's body becomes brittle and ultimately ruptures, releasing the eggs into the burrow. Males are drawn to the burrow by pheromones and discharge their sperm around the burrow entrance. The female draws this sperm down into the burrow using water currents where they fertilise the eggs. After spawning, both males and female ragworms die.
The strong mouth parts of a rag-worm are uniquely made out of a rich protein bound together with zinc, which is not fully understood but there is research into how the material could be used in engineering.
The past couple of weeks have seen the disappearance of some species and the arrival of others. While a lot of the pink-footed geese have continued their journey further south to NW England and Norfolk, the Basin still holds a roost of up to 30,000.
An excellent way to view the geese is to head for the railway station bridge at around 4.30pm and wait. The birds have been feeding out in the stubble fields in reasonably small groups but when the light begins to fade they head back to the safe haven of the Basin - relatively free from predation by foxes. Different groups tend to join together until they reach the basin in a flock of up to 10,000.
The whooper swans making their way from Iceland have arrived in more reliable numbers now with at least 30 being seen regularly and this number will grow to around 130-150.
The shallow pools in front of the visitor centre have started to attract some eye pleasing birds including teal - the males with beautiful chestnut colored heads and green eye patches, the females looking like classic females ducks - lots of speckled brown but smaller than some others.
Other regulars include snipe, heron, kingfisher and widgeon. All these can be seen easily from the Bank of Scotland Hide at the bottom of the visitor centre car park.