Bog Myrtle & Peat

Low Airie, Glenkens – 10/05/20

Ravens have risen to a position of prominence in the last twenty years – here in Galloway, they are fast becoming common after decades of obscurity. This has had a strange knock-on effect on carrion crows; the raven’s smaller and more cosmopolitan cousin which occupies a similar niche. The two birds seldom come to head-to-head in direct competition for food, but I have often wondered if the raven’s advance has come at the crow’s expense.

I had started to think that part of this relates to breeding. Carrion crows used to nest in safe, productive trees which were handed down between the generations. It was easy to catch these crows when the breeding season came, because their nests were always very easy to find. But in the last few years, many of these nest-sites have been overtaken by ravens. A raven could see off a crow any day of the week, but direct confrontation is usually avoided because ravens nest much earlier than carrion crows. When April comes around and carrion crows return to breed, they find their ancestral home has already been occupied for a month. There’s no point in arguing, so the crows move away to less promising spots and eke out their breeding season on scraps, often in deep forestry blocks. That has made it much harder for me to trap them, but it has also meant that they represent less of a threat to waders and ground nesting birds on the open hill.

But this evening I saw something new and altogether unexpected which adds a different flavour to the dynamic between two closely related corvids. As I checked on the cows, a raven came down off the hill and began to croak his way along the in-bye fields. There are some scrubby spruce trees in there, no more than twenty five or thirty feet tall. I only noticed him because he was being pursued by a noisy pair of carrion crows, both of which pressed him so hard that he was forced to roll over and show them his claws.

He flew directly towards one of the trees and abruptly plunged into it like a monkey, sending the crows into a state of uproar. They wailed and clamoured and hung around almost within arm’s reach, loud enough to tickle my curiosity. I set off walking towards the tree which stood about eighty yards distant, but this is very bad ground full of myrtle and heather, and it made for slow walking. By the time I was twenty yards away, the raven flew out heavily and made off for the hill again. The crows followed him, and I was left peering up at what seemed to be a nest in the topmost branches of the tree.

I usually have a pretty good idea of where crows are nesting, so this caught me by surprise, particularly since I have spent the last month working nearby and felt sure I would have spotted any nesting activity. That said, crows are hellish crafty around the nest, and they often take some winkling out. Monkey-minded myself, I decided to climb up for a closer look – easy work in an isolated spruce tree, provided you don’t mind a neckful of needles and twigs.

On reaching the nest, I found it sturdily built and neatly lined almost exclusively with birch twigs and pheasant feathers. Inside were the glistening remains of freshly broken egg white which, when I felt it with my fingertips, was tangibly warm. I also found several tiny fragments of a crow’s eggshell and a few little swirls of yolk. It seems beyond any doubt that I had just seen a raven raid a crow’s nest and consume the eggs.

It set me wondering how often this takes place, and what drove the raven to this kind of work. On the face of it, the raven had simply won himself a meal at the expense of weaker neighbours. But the two species are so closely related that the act felt almost like cannibalism – perhaps the raid was motivated at least in part by a grumpy refusal to share his patch with subordinates – what better insult than destroying a nest than to actually eat the eggs and really send a message?

Until this point, I had always imagined that ravens simply drove carrion crows out and displaced them to nest in less productive areas, but this experience would suggest that they might be able to suppress a population of crows. That’s probably quite a leap, but whether this behaviour is well documented or not, it does seem to imply that the relationship between the two species is complex. Having often found the remains of crows which had been killed by goshawks, the raven raid was another reminder that carrion crows occupy a strange niche which sometimes allows them to exert disproportionate harm on their prey and at other times exposes them to predation in turn. It would be foolhardy to arrive at any hard-and-fast conclusions from this single event, but if nothing else, it was a nice reminder that nature is beautifully fascinating.