This lake has taken over from Queenford for numbers of water birds but, somewhat surprisingly, rarities still seem to stick to Queenford. This could, of course, be simply that Queenford is watched by many more people than The Allen Pit. Being very close to the Thames the Allen Pit ought to encourage migrating birds using the "Thames route" to pop in. I suspect, partly based on observation, that when migrating birds hit that part of the Thames that heads almost due west, when they want to go north, they branch off up the Thame which does head in a northerly direction.

In winter this water plays host to a large number (well over 1000 on some occasions) of Wigeon sometimes with Pintail associated. Most of the other common ducks can be seen including Gadwall, Shoveller Goldeneye and Teal. Together with Whittles Pit it is the favoured area for Goosander and it is always worth searching for the occasional Smew and Red-breasted Merganser. Ruddy Ducks turn up from time to time (put that gun away!). The grass and bushes around this lake are favoured by wintering Redwing and Fieldfare. Spring migration usually turns up a good selection of warblers and Terns and Hirundines spend some time hawking over the water. If the water level is low enough to expose some mud round the edges it can produce a few waders, Greenshank, Common Sandpiper and Redshank being seen in recent years. Summer is a quiet time with only the resident breeding Coot, Mallard, Tufted Ducks and Great Crested Grebes in attendance perhaps with a flash of the Kingfisher over the water. Autumn sees the gradual return to winter numbers of birds sometimes with a temporary influx of common waders and Terns.

Rarities seen on this water include Avocet and American Wigeon. The latter, to my mind of doubtful origin, a female present from March 1998 at least to June 1999. A Water Pipit was also seen on the grassy bank between the two lakes.