Friday, July 27, 2012

Today I paid a visit to Waterperry Wood, part of the Bernwood complex of woods. Shortly after arriving a couple of Forestry Commission chaps arrived and started sticking up closure notices at the entrance to the wood. I got chatting to them and it sounds like tree thinning is to start somewhere at the far end of the wood on Monday. Over the next hour I saw 8 Emperors. These looked like an even mix of males and females. The females looking like they were egg laying while the males were Oak/Ash edging searching for mates.

After an hour a large low loader truck arrived carrying timber handling equipment. It was accompanied by one of the Forestry Commission chaps. He was only doing his job but to my horror he jumped out of his truck with a chain saw. He proceeded to fell a large chunk of one of the best broad leaved Sallow along the track. It was a Sallow that I had already seen a couple of females showing an interest in. It had to be done, or the lorry would not have been able to pass, but about a sixth of the tree was cut down.

Knowing that females had been laying on the tree I set about systematically searching the cut material for eggs. Several hours later I had rescued 10 Emperor eggs. A couple of these were very fresh but most were several days old as they had the purple bands fully developed. Hopefully I didn't miss too many but there are certain to have been some that I missed.

I think its interesting to kick around a few numbers to make a guess as to how many eggs are laid on this Sallow in a season. Approximately one sixth of the suitable egg laying habitat was cut down. This would imply that the entire Sallow currently holds about 60 eggs if you assume I collected all of the available eggs. If you work on the basis that only half of them were found then it implies a total of about 120 eggs. My guess is that we are about half way through the egg laying season. That would imply that that Sallow will holds between 120 to 240 eggs this year (or it would have done before the arrival of the chain saw).


Matthew Oates said...

Our thanks to Steve for the rescue operation! Odd that the females were favouring such exposed sallows, though the trees are (or rather were) densely foliaged, offering the essential degree of shade.

irisscientist said...

In agreement with Matthew, a great rescue job. I doubt however that laying would have been uniform across the entire tree, with females no doubt favouring particular portions of the Sallow in question. Matthew again however is the Guru on such matters. Statistical extrapolation of any data is extremely 'dangerous' without first knowing all of the elements of the equation!