The conditions were ideal with 10-15mph westerlies blowing over the open saltmarsh while remaining cloudy and dry. The reedbed, where we were targeting the hirundines, was much more sheltered by the deeply eroded river banks. The timing of high tide wasn't perfect, coming at 19.45ish, roughly an hour and a half before darkness.
Curlew Sandpiper (Left) and Dunlin
We haven't quite worked out where all the estuaries waders, gulls, terns etc. go to roost. There are 1000's of birds at low tide but the vast majority head out the mouth of the river at high tide. The most likely location are the Skerries Islands off Portrush, which are 8-9km away and it is almost certainly where the gulls head; including the hundreds from further up river. The nearest shores of Lough Foyle are 13km away and are a possibility for waders, although it would be the turf fields of Myroe which would be most suitable for roosting, but the 20km seems unlikely (why bother return the Bann Estuary twice a day?). We have no idea about the Terns but the beaches of Magilligan Point (11-12km) or perhaps the Skerries would fit the bill.
What we do know is that perhaps up to 500-750 waders remain to roost in the estuary at this time of year, mainly Curlew, Black-tailed Godwits, a few Redshank and perhaps a couple of hundred Calidrids (a number seem to roost on the piers at the mouth of the river). The oxbow lake (very shallow, partially exposed mud) holds the main concentrations (when not disturbed) and seems to appeal to a wider range of species, perhaps due to the water being less saline and the more consistent levels. The oxbow lake is cut off from both rivers, sitting a few feet above high tide and surrounded by salt marsh and wet meadows.
Trying for roosting hirundines was a first for the site but the habitat (reedbeds) is much better than our usual site plus it is in close proximity to our Grangemore Sand Martin colony. I had created a net ride through the reedbed earlier in the year for Sedge Warblers, which was around 50 metres long but the high tide meant we could only use the last 12m. We added another 18m net running at the edge of the reeds to create another 'V' shape'. A Swallow and Sand Martin tape lure were placed in the centre.
The hirundines built around sunset and we managed a catch of 15 Swallow, 6 Sand Martin and 2 Sedge Warbler. There didn't appear to be many more birds about, so a decent catch. While keeping an eye on the other nets, we ringed and released the birds straight from the nets (still light) and closed up.
Just after dark, perhaps 300 waders appeared and descended on the pools giving us an initial big hit. We turned the tape off straight away as we were not equipped for too large a catch. The result was really pleasing with 20 birds in the nets of five species. The majority of birds were Dunlin (14) plus 2 Redshank and 1 Black-headed Gull but the real big surprise was 2 Ruff and a Curlew Sandpiper.
These two species were new ones to us and very unexpected. The Curlew Sandpiper is the first to ringed in Northern Ireland since at least 1977, possibly ever. In the same period there were only 4 Ruff ringed in Northern Ireland with the last one coming in 1983.
Grangemore Ringing Totals 31/08/2016
Black-headed Gull 1
Curlew Sandpiper 1
Sand Martin 6
Sedge Warbler 2
We plan to get out to Portstewart Strand at the weekend and are hoping for an arrival of some new birds. The next attempt at wader and hirundine roost catches will probably be next week if we can muster the manpower and work the weather and tides!
Curlew Sandpiper (right, top, bottom) and Dunlin