Williamson's Weekly Nature Notes April 15 2009

Half a dozen blackbird's eggs, song thrush and pheasant's eggs show where the thief has taken its trophies, broken into the shell and enjoyed a hearty breakfast.

I suppose they enjoy their Easter eggs as much as do we. Very often an old bird's nest in the hedgerows will contain broken shells where the magpie has dug in without bothering to carry them away. That may depend on how much fuss the rightful owner made during the attack on their property.

In the Arun valley last year I found a very unusual small pile of shells. They turned out to be redshank's eggs. Very few redshanks now breed in Sussex, about a couple of dozen pairs perhaps, and most appear unsuccessful, with hardly any young seen.

A few years ago when avocets tried to breed in Chichester Harbour I was somewhat horrified to see several magpies and crows hunting that small freshwater marsh near East Head where a pair of avocets had their nest right out in the open. Even if the eggs survived, the young would not.

This year I found two tawny owl's eggs broken into by crows. The owl had nested on an old squirrel's drey, so the two white eggs could easily be seen by the crows. The usual method of attack is for one crow of a pair to tease the owl and finally to make it chase away this tormentor. The other crow then steals an egg when the coast is clear.

Either that or take an egg after the owl has laid and left its treasure in the open. This of course can only happen when there are no proper nesting holes in old trees or even nest boxes put up in the woods. Wood pigeons make easy targets for magpies and crows.

But they are able to overcome this problem by having up to five layings in the season. Only the last one in August is usually successful. With only two small eggs for a sitting, the hen bird is not exhausted by the end of the season.

Also magpies and crows having finished their own breeding, do not really need such hearty breakfasts any more and find alternative food in so many other ways such as the harvest corn, dead birds and mammals, snails, larvae of insects like St Mark's flies, craneflies, and wild berries. But by then the damage has already been done.