Last month I touched on the resurgence of the brimstone. Well, now it’s official: this has been the best season in 38 years of monitoring for this large and attractive butterfly, as the graph opposite shows indisputably. The line is now approaching verticality, and it will be interesting to see if it starts to level off next year, as such a meteoric rise is unlikely to be sustained for much longer.
With just seven territories on the monitored plot this year, numbers of spotted flycatchers are still in the doldrums following the population collapse in 2001, so it was very pleasing to watch a couple of families high up in the trees, flicking their wings, and launching brief, convoluted sallies into the gaps between adjacent trees in pursuit of flying insects. Like other migrants, they are now feeding avidly and putting on fat reserves in preparation for the exhausting journey back to Africa.
Late summer can be a good time to see large numbers of dragonflies, and this has been a better than average year with, at times, dozens of them patrolling the airspace above the rides. Like aircraft stacked awaiting permission to land, the medium-sized migrant hawkers tend to monopolise the upper feeding zone, some 15-25 feet up, presumably finding a rich source of food that is invisible to our poor eyes. Lower down the slightly smaller common darters restlessly pursue prey at head height, while the largest of our dragonflies, the much scarcer emperor, sensing that its size renders it invincible, barges heedlessly through the territories of all the smaller species.
It never ceases to amaze me how extraordinarily prodigal nature is when it comes to seed production. You only have to look at the drifts of thistle or willowherb down billowing across the countryside to realise that 99.999% of it is going to be wasted. At the moment you can witness evolution’s attempts to enable hornbeam to take over the earth, as the ground beneath some trees is thick with seeds; my crude estimate is that one tree may be producing hundreds of thousands of seeds, some of which will escape being eaten and germinate next spring, but with the likelihood that not one of them will give rise to a mature tree. This may seem ridiculously wasteful, but plants are at war with each other for resources and a place on this planet; the more seeds a hornbeam produces the more likely it is that it will perpetuate its genes through its offspring, compared to another hornbeam that only generates a modest seed crop. Much like an arms race spiralling out of control, the incentive is for plants to increase seed production until it reaches a point where the energy put into this effort adversely affects the health of the parent.
Brimstone feeding on hawkweed along one of the wood’s wide rides.
Spotted flycatcher – a declining species at Blean Woods (Photo courtesy of Dave Smith)
We spend 90% of net income on conservation, public education and advocacy
The RSPB is a member of BirdLife International. Find out more about the partnership
© The Royal Society for the Protection of Birds (RSPB) is a registered charity: England and Wales no. 207076, Scotland no. SC037654