Today I watched two examples of aggressive behaviour that brought home to me how little I know about even the most commonplace of our birds. The sparrows were particularly quarrelsome this morning: a whole bunch of them squabbling noisily between themselves. They were really quite vicious to each other but appeared oblivious to the other birds, all peacefully feeding and doing their own thing. There was plenty of food available so they weren’t quarreling over shortages; in fact, they were chasing each other in, out and between the pots on the balcony – not in the immediate vicinity of the feeders at all. I assume it was breeding-related. One female sparrow in particular seemed especially desirable. There was a lot of argument between potential suitors, perhaps!
When I started reading up a little I realised that actually, I didn’t observe that closely what each bird was doing within the situation, or how many of each gender were involved. I’d have learned more if I had. I now understand, for example, that sparrows are monogamous and that often it’s the females who fight between themselves to keep other rivals at bay. I also learned that the size of the male house sparrow’s black bib is significant. It may be that it’s a sign to fellow sparrows of its power and strength; certainly it would seem that the bib grows larger with age. I’ve noticed birds where the black bib has really caught my attention. Next time that happens I’ll view that sparrow with more respect!
The second behaviour, that I witnessed later in the day, was mobbing. I’ve never seen this before and didn’t recognize it as such at the time. There was a lot of noise, and a buzzard was flying fast and hard with a pair of rooks/crows – corvids certainly – not only in hot pursuit but attacking it. I was astonished that a bird the size of a buzzard should seemingly be cowed by crows. Now I understand that this mobbing behaviour is common among certain birds. Crows are particularly adept at mobbing and buzzards are the most hapless of birds of prey when it comes to enduring it. Corvids are aggressive and highly territorial; the buzzard is perceived as a threat to its young and/or its territory. The noise may also serve as a warning to other corvids that a predator is in the vicinity. What I saw today involved just a couple of crows, sometimes there can be many more, intent upon just the one victim.
Buzzards may have the advantage in size and dexterity but they are delicate birds and will avoid confrontation where possible. Mobbing rarely escalates into physical contact; the woeful buzzard simply makes a hasty retreat. I think I would do the same, faced by these angry and determined birds. It does not do to get on the wrong side of a crow!