EOS technology does the job.

Because of the strong winds, and associated  heavy rainfall, Bruno and I didn't head across to Worth Marshes RSPB Res until well after 10.30 hrs this morning. Even as I parked the van there was still a few drops of rain in the breeze, but we headed off, along the Pinnock Wall, towards the main floods beyond the Great Wood. A Chiffchaff and a Lesser Whitethroat were active in the hedge besides the horse paddocks, as we set off, and I was surprised, yet delighted to spot a lone Swift battling the conditions high over the Great Wood. A September record isn't something I always achieve these days. Crossing the small drain, via the wooden footbridge, it was nice to spot a Greenshank, two Wood Sandpipers and a Little Ringed Plover on the first pool we passed. A Green Sandpiper called loudly as it flushed from a small body of water in the adjacent field, whilst a Little Egret was stalking the margins of the bigger pool as I looked across towards the railway line. A few dragonflies were on the wing in sheltered spots, these being Migrant Hawkers and Common Darters, for the most part, but I did encounter a Willow Emerald Damselfly, which was a unexpected surprise. It wasn't, however, until we'd passed the Great Wood and were headed towards the double gate viewing area that I spotted another couple of Swifts. It quickly became apparent that there were a dozen, or so, hunting low over the surrounding landscape and I grabbed the camera in order to attempt to capture a useable image, or two.

Far superior to anything I've obtained previously. This image clearly shows the pale
 fringing to the coverts, on both wings, indicating that this bird is a juvenile.

They were not the easiest of subjects to keep in the viewfinder, yet I can have no complaints about the ability of the EOS 90d and 100-400 mm USM IS lens combo to capture record shots under the prevailing conditions. With the skies darkening ominously we retraced our tracks and got back to the van, around 12.50 hrs, just before the next belt of heavy rain arrived. It had been a very successful outing all round.