Crows and Curlews

A mixed bag

A mixed bag

Having put the best part of a four inch nail into my foot while chopping wood last night, my Saturday has been doomed to limping inactivity and the prospect of a tetanus jab. To make the best of a bad job, I hope to turn this “dead” indoor time into a chance to catch up with my notes and paintings, as well as a blog post or two from the pipeline.

The curlews are having varying degrees of success on the hill this year, and while I was happy that I had an extra pair on my ground in 2015, their progress has been mixed. I know that the ravens have had at least one clutch of eggs away, and I have had to look on as the black pirates continue to prowl the open grass on the hunt for tit-bits. I daresay that most people would find it hard to understand the effect that this can have on a human bystander, but when you live for birds and see them trashed to failure year after year, it is a genuinely sad, depressing business. I have no doubt that this pair will try a second clutch, but in my experience of curlews, second clutches become more and more forlorn as the season progresses. The later they lose their first clutch, the less chance the second has – not only of hatching, but also of fledging as adults.

On a more positive note, the larsen traps have been catching very well, creating a black hole through which pairs of crows continue to vanish. It is interesting to see the shapes of territories expand and change as crows come and go, and the disappearance of a breeding pair makes the neighbours feel very prosperous for a few days, expanding their domain into the lands of departed birds until they too are caught and create further vacuums. When there is a big enough gap without breeding crows, gangs of non-territorial juveniles come through and these are soon caught as well so that there is never a situation where any crows can settle and breed. Studies show that the non-territorial birds are much less predatory than the nesters, and that egg-stealing is an acquired skill most finely honed in the mature adults than the juveniles. The nesting pairs are always my number one priority, but as long as it’s free to roam, any crow on the hill might bump into a nest.

There was some science published earlier in the year to suggest that trapping crows performs no overall ecological function and that it serves only to create a surplus of young gamebirds available for shooting later in the year. The study (as I understood it) suggested that crow predation is at its worst when the habitat is not in the best condition and gamebird nests are more easily found and raided. Killing the crows allows gamebirds to produce chicks in sub-optimal conditions, and while these chicks went on to provide sport for guns in the autumn, poor habitat (and over-winter predation/lack of feed as a result) would mean that there was no net improvement of game birds at a population level the following year. Essentially, the study argued that crows were merely the control mechanism by which poor habitat expressed itself, and that sustainable population growth depended on proper habitat more than crow control. The paper became pretty political and argued that we should not bother to catch crows at all, but the discussion of breeding habitat and nesting conditions was quite interesting.

Fair enough; I can see the logic behind the theory that killing crows produces a short term increase in the amount of grouse or partridges which might not survive the winter in poor habitat. To me, that’s a slightly different issue compared to when we talk about waders. Curlews and all manner of waders breed in the uplands and then migrate down to shore in the winter, so the quality of breeding habitat and its ability to protect adult birds in the winter is an irrelevance to them. There is no question that we should work to improve breeding habitat for waders as part of a long term solution to their decline, but these changes may take years and it is crucial that we hold on to what we have now. There is no shortage of data to show how quickly waders can vanish, and it is extremely difficult to get them back once they have gone. It is absolutely incumbent on land managers and conservationists to preserve what they have got by all means available to them.

Running larsen traps is not fun or glamorous, but it’s crucial. I currently spend an hour in the car every day checking and managing my traps not because I’m an slack-jawed yokel with a psychotic need to kill, but because at this stage of the game, inactivity is not an option.

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