Raptors of Delight

Sparrowhawk recently spotted at Coombe Hill Nature Reserve by Zsuzsanna Bird

Being an ecologist can result in one taking an opinion that is diametrically opposed to that of simple logic. A classic example is that of the bird of prey populations that have made a spectacular recovery over the past 30 years. Surely more raptors must mean less songbirds? Not according to my understanding!

Studies of predator-prey dynamics have shown that there are often two characteristics of population curves; predator numbers are determined by the abundance of food and they reach a peak later than the prey species. In other words the more that there is to eat the more predators there may be! The total amount of prey in an area will be an important factor in determining the number of predators, but there is a time delay.

The British Trust for Ornithology has presented some important new information that contributes understanding to this model in its BTO News May-June 2010. In a piece entitled Are Predators to Blame? Stuart Newson and Stephen Baillie summarise their research that is published in full in the Journal of Applied Ecology 47.

‘In summary, for the majority of the songbird species examined, there was little evidence that increases in common avian predators and grey squirrels were associated with large-scale depression of prey abundance or population declines. For the majority of declining songbird species with unfavourable conservation status, population declines appear to be due to factors other than predation’.

In Gloucestershire, the numbers of many of our birds of prey have increased dramatically since I have lived in the county. Whilst it is true that species like the house sparrow, yellow hammer, nightingale, turtle dove and many others have achieved the undesirable red or amber status (in trouble), it would seem that the causes are often more complex than their immediate natural enemies. Habitat loss in the UK and overseas for migrant species, combined with disease and climate change may play a far more important role in determining population size.

So don’t worry about your local sparrowhawk, buzzard or kestrel, just marvel at their aerial grace and their subtle role in local ecology.

Welcoming New Supporters

Standing in a wonderful piece of flower rich limestone grassland, I could have been anywhere in Cotswolds rather than only three miles from Stroud. The valleys and coombs around Chalford are a precious hidden landscape which only the curious or those lost because of a confused SatNav are likely to experience. The effort that Margaret and I had put in (SatNav notwithstanding) was well worth it. Gloucestershire Wildlife Trusts’s nature reserves at Strawberry Banks and Three Groves Wood are absolute gems.

Strawberry Banks, which is managed in cooperation with the very committed owners, the Shorts, was the most fascinating on the night as dozens of common blue butterflies were flitting around our feet. This is not any exaggeration; I counted 12 butterflies within a few feet of me, remarkable!

I was actually working, although it was more pleasure than pain. The Trust has started to hold meetings with its newer members to help them to learn more about our work and to enjoy the wonderful nature reserves that their subscriptions support. Last week, through the hard work of Membership Development Manager, Alice and her team, over 50 members were greeted and shown around by a bunch of our hard working staff.

Two walking groups set off down through Far Oakridge towards the reserves. Each group had an expert guide; Jeremy Doe or Pete Bradshaw. I was in Pete’s group and I learned a lot, nature reserve management is more sophisticated than it used to be! After our 90 minute ramble we reassembled at the Butcher’s Arms for excellent refreshment and a short talk. All very pleasant.

The Trust has over 24500 members, making it one of the largest in the country. It is its members that have shaped and supported its strategies and actions over the last five decades. Last night it was clear why the Trust is still so well supported; effective local action for local wildlife by a local organisation. David Cameron could learn a lot from the Wildlife Trusts!