I often end my blog posts with “more on this to come” or “to be covered in more detail later”, and while these comments are always included with the best of intentions, they seldom come to much. I sift through such a stack of material every day and only odds and ends actually make it onto this blog, so that while there is plenty of good stuff behind the scenes, it is quickly washed off downstream and lost, particularly at this time of year when I can hardly drive a mile in the car without stopping and getting the binoculars out.
But it is worth describing the effects of an irritating buzzard on a big lek near Strathbogie a fortnight ago. I arrived in the half light, watching twenty blackcock literally humming with delight on the opposite hillside. Greyhens came in and out like fireworks, drifting back and forth over the steep face while the cocks fought it out on the short blue frosty grass.
A buzzard drifted past in the stillness, ignoring the lek with a callous indifference and settling on the top stones of a dyke a few hundred yards away. Several minutes later, a second buzzard came past, and this bird was decidedly intrigued by the displaying cocks. It changed direction and coasted in for a closer look, finally passing right through the middle of the lek like a bowling ball through skittles, sending all the cocks off in a flutter. They didn’t go far, but the low-altitude inspection was not appreciated. This buzzard then landed nearby and spent the next twenty minutes passing to and fro over the displaying cocks, buzzing them and generally making a nuisance of itself. At one stage, it actually made for a specific blackcock and lowered its talons as if to grasp it, but it broke away when the cock burst up into the air. Despite what we are told by the conservation charities, buzzards can and do kill blackcock, but this was a half-hearted, speculative gesture of ill-will rather than a determined attempt to catch and kill.
In due course, the buzzard landed right in the middle of the lek. The blackcock soon got used to it, and some began to display within a few feet of it. Every now and again, it would chase a blackcock away by bouncing towards it on foot, but the spectacle was becoming ridiculous and the lekking birds no longer showed any fear or frustration. They just accepted this intruder as a marginally irritating diversion to the morning’s activities, and after a few more low-level strafes, the buzzard vanished into the clear blue morning sky, heading off towards one of the classic Aberdeenshire granite tors which marked the horizon to the South. All the while, the first buzzard I’d seen had shown no interest in the lek whatsoever, implying a certain degree of mood or personality between individuals.
This had been an interesting incident, if only because the birds were so accepting of the intruder. They didn’t like being bothered by the buzzard, but they accommodated it. I have seen similar feints and silliness in Galloway which resulted in the entire lek being cancelled and the black grouse deserting altogether. This is probably related to the concept of safety and confidence in numbers, particularly since a Galloway lek seldom holds more than three or four cocks and this lek was more than five times as large. But it also implies that black grouse, like many other species, reach a critical mass in population which makes them less concerned by predators.
Galloway birds know what can happen if a bird of prey gets too near, and their reaction to pressure is abject terror and cowardice. Perhaps in this way, a depressed or failing population of black grouse is more effected by predation pressure (by which I mean disturbance as much as actual death). Even if they don’t actually kill birds, predators make small numbers of black grouse more timid and nervous, which leads to less confidence and all kinds of other detrimental and unquantifiable knock-on effects. I’ve written on this blog before about nocturnal lekking, and birds revert to all kinds of deviant strategies for avoiding predators when they are reduced to a small handful of individuals.
When lapwings breed together, they make tight colonies which are capable of joining forces to see off crows and nest-raiders, but when their numbers fail and there are only a few pairs, their eggs are easily stolen. It makes sense that a healthy population of black grouse is better able to deal with predation pressure than a few scattered individuals, and this must form part of the so-called predation trap which prevents small populations from becoming bigger.