First Butterflies!

Yesterday turned out to be the warmest day of the year, but was tempered by a strong south westerly wind. There were hints that a lot of the common summer migrants which had been held up by the recent bad weather would start to pour in. Reports of many Ring Ousels for example, along the Chilterns on Saturday suggested that it could be a good day, and for the first time in about two months Colin and i planned a trip out.
We decided to go down to Moor Green pits near Sandhurst where the overwintering Pallas's Warbler was still present and singing. I have only seen a handful of Pallas's over the years, and with only one or two spring birds, it was a very rare opportunity to hear a singing bird. We arrived around 0930 having seen several Brimstone butterflies on the way down. The pits did not seem to have many birds, apart from a pair of Egyptian Geese, an odd hybrid Goose and the usual selection of ducks that one would expect. Several Chiffchaffs were singing as we made our way down to the river meeting a local photographer waiting for the warbler. Not long after we heard the song-rather like a Willow Warbler but finishing a bit like a Wren. I managed to locate the bird flitting around in a Willow some 30 yards away the other side of the river. Got pretty good views, seeing the wing bars and the crown stripes despite the distance but it was out of camera range. It then disappeared but we manage to locate it about 30 yards to the west in conifers, before returning to the willow where it seemed to settle but as soon as i got the camera up it was off again. We left soon after as a big crowd had turned up and viewing space was a bit limited.
We then set off for Bison hill in the Chilterns, but as we were passing decided to call in at Wilstone reservoir as I thought that it might have some migrants, and the wintering Water Pipits were still around. As it turned out the wind had become very strong with waves breaking over the reservoir banks so there was no chance of seeing the pipits near the jetty. However there were small numbers of hirundines so we decided to do a circuit. Did not get much at all, more Chiffchaffs, some Blackcaps, but several Brimstones, and single Peacocks and Small Tortoiseshells were great to see.
 We eventually got to Bison Hill around 1330 and sent a good 90 minutes searching for migrants. The strong wind did not help and there did not seem to be many birds at all. However at the eastern end of the sheep field I heard two Ring Ousels and eventually saw them flying low above the trees on the northern side of the hill. Unfortunately despite searching we were not able to relocate them. We did find another Small Tortoiseshell though.