On the 28th 7 Buzzards were soaring together over the reserve car park, with more birds displaying over the local woods. The male Kestrel is still around the reserve. The female Sparrowhawk is being seen more often, especially in the evenings. The Peregrine caught a Black-headed Gull on the estuary on the 27th this is being seen more regularly too.
With the temperatures increasing, the duck numbers are decreasing. Totals this week include 6 Pochard, 5 Tufted Ducks, 2 Gadwall, a Goldeneye and about 25 Teal. Perhaps many of them have already started heading north to their breeding grounds.
6 Black-tailed Godwit, a Dunlin and a Knot joined the increasing roost numbers of Curlew, Redshank and Oystercatcher. Little Egrets have increased to 6 this week.
There are now up to 7 Lesser Black-backed Gulls in the roost, with hundreds of Black-headed Gulls, Common Gulls and Herring Gulls.
A Chiffchaff was seen on the 24th. There is an increasing flock of about 30 Siskins in the wildlife garden with a Lesser Redpoll occasionally seen with them. Reed Buntings are calling from the reed tops now and Song Thrushes are singing around the reserve.
It wont be long until we get out first Wheatears and Sand Martins back.
For information on our work to eradicate the invasive weed 'crassula' on our shallow lagoon, next week, please follow the link below.
Next week sees the start of a major project at RSPB Conwy, undertaking one of the biggest changes to the reserve since its creation almost 20 years ago. We need to tackle an invasive non-native plant, marketed as Australian swamp stonecrop or New Zealand pygmyweed, but usually referred to by its scientific name, Crassula helmsii.
Away from its native Antipodean home and with nothing to keep it in check, Crassula spreads rapidly through waterbodies and around the margins. At Conwy, we lost our educational wildlife pond to the weed in 2009 but subsequently found Crassula in the Shallow Lagoon (in front of the coffee shop). It has since spread to the Deep Lagoon. The only proven way of eliminating Crassula is with prolonged flooding with saltwater.
What we’re doingThe lagoons are a couple of metres above the height of the estuary, so just opening up the sea wall isn’t an option. On the highest tides in early March, three huge pumps will fill the Shallow Lagoon from pipes across the seawall, opposite the coffee shop.
Access arrangementsWe'll have to close the estuary track for a few days while this operation is underway, but will keep all the hides open. Between Monday 5 and Monday 12 March, there will be no access along the estuary track between the Benarth Hide and the car park, so the circular walk will be partly-closed (if you go to Benarth Hide, you'll have to come back the same way).
Will it work?Providing we can maintain sufficiently high water levels and keep the water salty enough, we should eliminate Crassula from the shallow lagoon, as has been achieved successfully at our Old Hall Marshes reserve in Essex.
We have just a few days when the tides are high enough to pump water onto the lagoon, and we will raise the water about a metre above its current level. It may prove necessary to top-up the lagoons with more water from the estuary later in the year. We can also pump from the Afon Ganol, but this is fresh water and so raising the water level this way will reduce the salinity.
What does it mean for wildlife?To eliminate the Crassula, we'll be keeping water level in the Shallow Lagoon high and salty for at least a year, which will mean some changes for wildlife. We've assessed the impacts on our key species, and expect that most waterbirds won’t mind. Some ducks, such as shoveler, that prefer freshwater may not visit, but we may get ducks such as pintail. While the water levels remain high, there will be less mud for waders to feed, but this is a temporary measure. Initially, the reeds may not like it, but they'll be dying back for the winter soon and it's an impressively tough plant that is quite capable of growing in brackish conditions, so we hope they will recover.
We’ll also have to fill the bridge pond with saltwater, just in case there’s Crassula in there, as it is connected to the Shallow Lagoon. That’s bad news for any dragonfly larvae, but we created several new freshwater ponds earlier this year as alternative habitat.
The long-termWe’ll continue to monitor salinity, water levels and Crassula throughout the year. We’re aiming for salinity levels between 15 and 20 parts per thousand (ppt). By comparison, sea water is 35 ppt, but the water in this part of the estuary is less salty. Once we have filled the Shallow Lagoon, we will have a better idea about whether it’s feasible to fill the deep lagoon. This is a much bigger operation as we’d have to empty the fresh water first, and have to pump a lot of water during just a handful of high tides. The Crassula in the Deep Lagoon is above the waterline, so we can treat it with a herbicide until we decide whether flooding with seawater is possible. This means that we’ll need to keep the water level at its current, reduced level for now.
We have still to determine the long-term management of the lagoons. The lagoons at Conwy have some other problems, besides the Crassula: it’s proved challenging to maintain water levels during extended dry periods and the mud lacks invertebrate food for breeding and roosting waders. The initial flooding will give us a chance to determine whether maintaining brackish conditions is the best option in the long-term. We'll be keeping the blog updated with news of the work, and with such a significant change, it will be interesting to see the transformation through 2012-13.
We would like to thank Environment Agency Wales and the Countryside Council for Wales for their help with this project.
It has been a good week for raptor sightings. A Peregrine has been hunting over the reserve frequently and sat in front of the Carneddau hide on the weekend. The male Kestrel is still about, roaming around the reserve. A female Sparrowhawk has been seen chasing the Starlings in the evening roost and circling high over the reserve in the day. Buzzards are showing more frequently, displaying over the nearby woods. 4 Ravens have been calling over the reserve.
A pair of Chough flew over the coffee shop on the 21st, possibly the same pair as a few weeks ago.
Waterfowl numbers dropped this week. A Greylag Goose dropped in with the Canada Geese on the 17th.
A Water Rail has again been showing well from the coffee shop.
Wader numbers are still good with high counts being a Knot, 13 Black-tailed Godwit, 13 Ringed Plovers and 65 Dunlin.
2 Rock Pipits were on the estuary on the 17th. One was of the Scandinavian subspecies ‘Littoralis’ different from the one two weeks ago. A male Linnet was on the estuary with it. A Lesser Redpoll was still in the wildlife garden with the Siskins.