Muddy edges = wader heaven

Each Summer, lots of visitors ask us about the water levels in the lagoons, especially those viewing from the Coffee Shop where the changes are most apparent. Some people suggest that there should be more water in the lagoons, but the birds think otherwise. As wading birds fly south from their short Arctic breeding season, they need invertebrate-rich mud to refuel. They will travel down to west Africa, so have some way to go yet.

Managing water at Conwy can be a challenge. The lagoons sit high (three metres) above the tidal river and there is no watercourse coming into the lagoons, so through the Summer, we are dependent on what falls from the sky. We try to fill the lagoons as high as possible by early April, so that ground-nesting birds will feel protected from the islands, the deep water deterring mammals such as foxes and badgers. As soon as the air warms up and plants grow, the water levels start to drop. A combination of evaporation (the sun and wind) and transpiration (by the reeds) lowers the level of the shallow lagoon by 1cm every day. You don't have to be a maths genius to work out that, in a lagoon only 70 cm deep at maximum, it can soon disappear.

The level can, of course, be offset by rainfall. Since 1 April, we have had 31.7cm of rain (almost exactly the same as 31.4cm in the same period last year), so this only partially compensates. But that's fine, because we don't want a lagoon full of water in late summer, we want plenty of sticky mud to feed passing waders. They will tell us whether we've got it right, by coming to Conwy, actively feeding and staying for a day or two. So, what do they think of it this week?

A little stint has been present since Sunday (and is still here today, 23rd) - thanks to Susan Morris for the photo; a curlew sandpiper was here yesterday (22nd); four black-tailed godwits have been feeding on the lagoon this week, and yesterday there were three bar-tailed godwits, two knots, 10 ringed plovers, whimbrel and greenshank, several of these having stayed over since Sunday. A couple of snipe have been actively feeding in the shallow lagoon and a green sandpiper was here on Friday.

A female/juvenile garganey was still present on the shallow lagoon this morning, having been reported sporadically over the last 10 days; and three black terns were present for a few hours on the island in front of Carneddau Hide last Friday (19th), the first here for several years (thanks to Henry Cook for the photo).

So, we think that the birds think we've got it about right. To find out what they're eating, we are doing the annual survey of benthic (mud) invertebrates this week; we got very muddy collecting the samples today, and our expert volunteers will be analysing them tomorrow.

Other highlights this week include a flock of 70 linnets on Sunday (21st); a juvenile spotted flycatcher reported today; the first raven of the autumn on Monday (22nd); the last swifts reported to us were on Saturday (20th) - will we see any more this year?

Emperor dragonflies and common darters have been flying in the sunshine; common blue butterflies have been abundant, as the new generation hatches; and our night-time trail camera recorded two otters together last night, which we are delighted about!