February 9th, 1999

A number of predators use the school grounds and although it is possible to observe some of these, such as kestrels, during the daytime those that hunt at night-time present more of a challenge. One of these is the tawny owl.

During the warmer months, individual tawny owls can be located in the trees at the end of the cricket field but for much of the year it is more difficult to find evidence of their presence. Fortunately, tawny owls regurgitate 'pellets', which contain the undigested fur and bones of their prey, and these drop to the ground below their favourite perches. Careful searching will usually uncover some of these below the trees where the owls are normally seen.

The bones illustrated on this page come from several pellets that I picked up during the past week. Most of the images are much larger than the original bones. The largest ones, from the legs, were as much as twenty five millimetres in length but some of the teeth were only one or two millimetres long. Despite their small size, the bones exhibit a number of interesting features when viewed through a hand lens. For instance, tiny ball joints can be seen on some of the leg bones and a variety of types of teeth can be seen. The lower jaw bones survive the digestive process more readily than some other bones, such as ribs, which were almost absent from the pellets examined, and these are particularly useful when trying to identify the prey species.

Most of the pellets that I have found recently seem to be quite old. It may be that the tawny owls do not always use the grounds or it may be that the increase in population during the summer months, when the young will also be present for some time after fledging, leads to more evidence of the presence of this species at this time. Although I often hear little owls in the grounds, I do not hear tawny owls very often. A concern at the moment is that modern farming machinery is damaging an old, ivy-covered ash tree which grows in what used to be a cricket field and is, I believe, probably a favourite tree for the tawny owls. Recent ploughing of the field has severed a number of roots on the tree, one as thick as a person's thigh, and this must bring closer the day when the tree will fall down or when the farmer will decide that its poor condition merits it being chopped down.