A busy week on a muddy pool

Last week I wrote about how we manage the water, aiming to have lower water levels in late Summer and Autumn in order to provide feeding opportunities for migrating shorebirds. This week's birds suggest we got it about right!

Highlight of the Autumn so far was a pectoral sandpiper, the fifth reserve record but the first since 2008. A nice find on Wednesday (31st) by visitors on holiday from Scotland, lots of people had the opportunity to watch it feeding close to Tal-y-fan Hide before it disappeared early that same evening. The same patch of mud has hosted a curlew sandpiper since Tuesday (and still present today, Friday), and a garganey has been an almost constant feature here for the last couple of weeks (with possibly a second bird on the Deep Lagoon on Friday 26th). A juvenile spotted redshank was another good find on Thursday 25th, and has spent much of its time feeding in the mud close to Tal-y-fan Hide, and it too is still present today.

Click on the image above to see these photos in all their glory: spotted redshank (Dawn Micklewright), curlew sandpiper (Adrian Foster), pectoral sandpiper (Peter Shallcross), garganey (Dawn Micklewright)

The great white egret, here on and off since mid July, has been present again this week, but it seems to be spending more time on the estuary now, and can go missing for long periods of time. The lagoon has also provided a stop-over for dunlins (16 today), green sandpiper and ruff (1st), common sandpiper and black-tailed godwits daily, while a few whimbrels and ringed plovers have been on the estuary.

Small birds become harder to find at this time of year, and we haven't really yet had a 'fall' of migrant warblers. Chiffchaffs are quite vocal at this time of year, but others, such as blackcaps and willow warblers are present but can be harder to find. There are plenty of house martins still feeding over the lagoons, with a few swallows too, but the last swift reported was on 20 August. Good numbers of wagtails have been feeding on the saltmarsh and on the lagoons this week: mostly pied, but with a few white wagtails that are stopping off on their way back from Iceland. Other migrant songbirds include a wheatear on Tuesday (30th), spotted flycatcher (29th) and redstart (27th). We're starting to get more reports of ravens over the reserve, as they return to the coast for the winter, and our first autumn records of chough came last Friday (26th), with two flying over.

The warm days earlier in the week were great for insect-watching, and we were pleased to see Dylan Edwards' photo of two migrant hawkers mating, the first indication we've had of this species breeding at the reserve. Common darters are easy to spot around the Bridge Pond at the moment, and emperor and common hawker have also been seen. A painted lady last Thursday (25th) looked too fresh to have been a migrant from southern Europe, so perhaps hatched in this country, and there have been plenty of common blue, holly blue and speckled wood butterflies to see.

In late Summer each year, we take samples of mud (benthic) and water (nektonic) from the lagoons to find out what invertebrates and fish are living in there, and how abundant they are. This can tell us what birds are feeding on when they visit the reserve. The key measure is the biomass of the larvae of non-biting midge (chironomids), as this is what many of the smaller waders are looking for. Taking the samples is a messy job (Tim and Julian were snapped by Mal Delamare collecting the mud!) and analysing them is a really painstaking one - we're fortunate to have two expert volunteers, John and Rosie Solbe, who do this for us each year. They not only find and identify the invertebrates, they also measure the larvae (most are just a few millimetres long!). The benthic sampling showed an increase in the biomass (the weight of the inverts per sqauare metre) of chironomids in the Deep Lagoon, but a slight decrease in the numbers in the Shallow Lagoon (where waders are feeding most actively). We're still working on the results for the nektonic sampling, but found plenty of common ditch shrimps, which is what we assume the little grebes are eating.

Thanks to all the photographers who let us use their images - who knows what we'll get to see this week.