Although the mornings feel autumnal (today was the first morning with a jacket over my t-shirt since June!), afternoons this week have been like mid-summer: warm sunshine that has encouraged the last of the butterflies, bees and dragonflies to take to the wing. Our weekly flying-insect survey recorded comma, speckled wood, common blue, small white and green-veined white on Friday, plus a probable hornet hoverfly, a third site record in the wake of two last summer.
An insect that is easier to spot are the caterpillars of alder sawfly. Like little snowflakes, these white, fluffy larvae are munching their way through the alder sapling leaves in the car park. They disguise themselves as bird droppings to avoid being eaten, though the white powder does eventually rub off, revealing a pale green body.
Bird of the week was the second pectoral sandpiper of the Autumn, found and identified by call (but not seen) by former warden Mike Duckham on Monday (12th) evening. It was seen on Tuesday morning, but not again. Thursday (15th) proved a good day for waders, with little stint, curlew sandpiper, grey plover, knot, greenshank, common sandpiper and 40 dunlins. Several of these remained to the weekend, with two bar-tailed godwits on Saturday (17th).
Our long-staying great white egret was joined by a second bird on Wednesday, so perhaps we've had two for a while, just not together? A spoonbill flew over the reserve on Wednesday (14th) and Thursday (15th), but headed upriver and wasn't seen to land. The flush of small fish into the estuary, featured in last week's blog, brought four Sandwich terns on Tuesday (13th) and 20 on Thursday (15th), plus 44 cormorants, a high count for the south side of the bridge. A guillemot was another unusual visitor to the estuary on Thursday, perhaps lost in the sea fog that enveloped the coast that day. Our long-staying garganey was seen on Wednesday (14th) and Saturday (17th), with a pintail and two choughs also recorded on Wednesday.
Summer migrant songbirds are feeding up before continuing their journey south. There were lots of blackcaps on the elderberries this morning, and earlier this week we've seen wheatears (five on Thursday, and singles daily since), redstart and white wagtail. Kingfishers have been spotted daily, with up to three present.
A yellowhammer was a great find last Sunday (11th), feeding on seeds in front of the Tal-y-fan Hide, with goldfinches and linnets. Sadly, they are all too rare a sight in this part of the county now.
The focus of birding interest on the reserve is often the lagoons, scrub and grassland, but this week's spectacle is in the estuary. We've noticed it each day on the incoming and outgoing tide: many hundreds of birds in a feeding frenzy in the channel closest to the saltmarsh. Black-headed gulls, herring gulls, grey herons and little egrets are all involved, noisily feeding in the water. We think it's because of a huge influx of either sprats or mackerel, as both have been seen in abundance on local shorelines recently. One fisherman told us that he'd never seen anything like it in his lifetime. This morning, 124 little egrets were among the throng, a record count for the reserve - the graph of peak annual counts illustrates how little egrets have become increasingly abundant on the river, with numbers typically peaking in late summer. We love this photo by Dave Williams, on our Flickr page.
It's all gone a bit 'back-endish' this week, with temperatures falling and an autumnal feeling to each morning. Many of the summer warblers have already left us, though there are plenty of chiffchaffs around the trails. House martins, too, are still feeding over the water, but far fewer swallows. There were 28 wigeon on the reserve this morning, fresh arrivals from the north, and a goldcrest today is also an indication of the changing seasons. It's been a good week for wagtails, with a few white wagtails dropping in from Iceland as they head south, and up to 120 pied wagtails also on the move, probably from Scotland.
The long-staying garganey and great white egret remain here, although the latter seems to spend more time in the estuary than on the lagoons now. A male common scoter has frequented the Deep Lagoon since Tuesday (6th), a scarce but annual visitor here. A wheatear was a nice sight on the Paddocks on Wednesday (7th), while this week's waders include spotted redshank and curlew sandpiper (both until 4th only), greenshank, ruff, green sandpiper, knot, whimbrel, green and common sandpiper, and ringed plover. 20 goosanders on the estuary was a high count for the site, while a yellow-legged gull on Monday (5th) was a good find, as was a count of 27 Sandwich terns on Saturday (3rd). Six barnacle geese, of unknown origin, were on the lagoons on Wednesday (7th).
After mentioning in last week's blog that migrant hawker dragonflies had been seen mating, a female was ovipositing (egg-laying) in one of the ponds this week, which we're sure is the first breeding attempt here. Look out for common darters too, ekeing out the last of the warm sunshine to bask on rocks and handrails.
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.