A pair of swallows resting from parental duties; they have a nest underneath this structure at the Las Gallinas ponds in Marin County, California. Imaged with a Canon 1D mark II and a Canon 400mm f/5.6 L lens, kindly loaned by Mark Yuan. Thanks, Mark! I added a Canon 1.4x extender to give me about 560 mm focal length. Three images, please scroll down.
The female (on the left) was nicely focussed in the above shot; unfortunately I didn't have enough depth of field to include the male (right) in that sharp region.
Seemed to be a little disagreement here for a while, but after the squawking ended, everything settled down to domestic peace and tranquillity.
I carried out a brief, informal test of the Canon 400 f/5.6 prime and the 100-400 zoom, using a Canon 1.4x extender on both while at the Las Gallinas ponds. You can see the results here.
The image below was the result of about a hundred attempts to capture the flight of these amazing flyers on April 13, 2005 at the same location, Las Gallinas Sanitary Ponds in Marin County, California. They are so fast and so erratic in flight that it is very difficult to keep them in the viewfinder long enough to focus. This image was the best of the lot. According to Sibley's book, the white band across the tail indicates that the bird is probably a juvenile. Canon 100-400 L IS zoom at 400 mm plus the 1.4x extender plus a pretty tight crop.