Nature Notes – December 2017

On several days during November a Barn Owl has been out hunting over the hayfield in broad daylight – as early as 1pm. Although this is known from time to time, it is much more usual to see them hunting later in the afternoon (much later in the summer), say an hour before dusk. I have tried to get photographs, but although daytime the light has still not been good, so the pictures are not brilliant. There will be disadvantages in daylight hunting. For instance, I have watched Owls being mobbed at this time by another predatory bird, the Kestrel, so that their hunting is interfered with. It is suggested that daytime hunting may indicate that the owls are finding food harder to find.

The main prey in the hayfield is the Short-tailed Vole, or Field Vole, a creature that always lives in Grassland. In the food remains of Barn Owls in Sweffling and Rendham three years ago I also found very large numbers of shrews, both Common and Pygmy Shrews. This was echoed in the number of shrews brought in by our cats (but never eaten by them. Although predatory birds readily eat shrews, they seem to be distasteful to cats). However, for many months the cats have not brought in a single shrew. I hope to get some more owl pellets locally to see whether the shrews have become scarcer – perfectly possible as small mammals do go through quite large natural cycles in their numbers over the years.

Bullfinches are again very regular in the garden. Despite the male’s bright colours, they can be quite reclusive and hard to see. They do however have a very distinctive call, a soft, low- pitched single note, which although quiet does tell you that they are there. They have been busy eating the seeds of an ornamental Maple, little ‘helicopters’ just like small Sycamore seeds. Studies of Bullfinches have shown that in winter they rely heavily for food on the seeds found in the keys of Ash, which are rather similar. It is when seeds like these are scarce that they turn to the flower buds of fruit trees, where they can do so much damage. I presume that the great reduction in Ash trees as a result of the rapid spread of Ash die-back disease will affect the Bullfinch population. Bullfinches will also often eat the seeds of blackberries, after these have been neglected by other birds, and dried and shrivelled.

Flocks of Rooks flying to their winter roost in the woods towards Benhall are a feature of the winter evenings. These winter gatherings can be enormous. I have estimated well over a thousand gathering together. They must include birds from several rookeries and from quite a large area. They gather in mid-winter in tree tops, arriving in late afternoon. By late winter, however, they have taken to gathering, in smaller numbers, in the trees in which they will have their breeding rookeries. They share this winter roost with an equal number of Jackdaws, alongside which they can be seen feeding in the fields (although their nesting is quite separate – the rooks nesting in high trees and the Jackdaws in chimneys, old buildings and holes in trees.) With the rooks making their loud ‘caw’ and the Jackdaws ‘chacking’ (hence ‘Jack’) the noise from such a big roost can be quite impressive.

Geoffrey Abbott