Tag Archives: Branta

Autumn Geese and a natural mystery

Autumn came in very slowly this year, but it turned quite cold quite quickly. However, now at last we are getting rain in proper autumn levels. We had proportionally very little rain all last winter, spring and summer. Finally the geese have started to arrive too. Here are two of the most common species, the Brent Goose (Branta bernicla):

and a flock of Greylag (Anser anser), with two Rooks (Corvus frugilegus) providing a sense of scale:

All of these birds are pictured at the famous Kilcoole Breaches and nature reserve.

There have been two noticeable trends this autumn – firstly there have been far less spiders than you would expect on average, particularly House Spiders. But all species seem to be lower in number than usual. The only spider species at normal levels, or apparently normal levels, has been the Garden Spider (Araneus diadematus), which is also the most obvious autumn spider:

    Conversely, there has been a population explosion of Brown Rats (Rattus norvegicus) which has been attributed to the long hot summer and the summer heatwave of May, June and July which almost led to a severe drought. The increased population of Brown Rats very likely has reduced the number of spiders, as rats and mice will happily eat large spiders. More rats equals less spiders.

However, from my own observations I disagree that the summer heatwave is responsible for the population explosion of rats – back in March, during the heavy snows, there was a massive surge in rat numbers. They were especially attracted to bird feeders. The winter had been very cold even before the snows arrived late, and it seems that this factor drew rats from the countryside towards human settlements in order to find food and warmth. But whatever the exact cause, there were a lot of them around, although numbers at last seem to be returning to normal: