Increased Bird Aggressiveness: Is There Something Ominous Going On?

Posted on June 17, 2005 by Dave Pollard

Perhaps it’s just because I’m paying closer attention, but in the past few months I have observed an alarming number of instances of groups of small birds savagely and relentlessly pursuing and attacking larger birds. The first time I noticed it I put it down to defence of the nest, mates or young, but I have seen it so often lately, and in such Hitchcockian extremes (I watched a crow fleeing frantically from a dozen much smaller birds, for a full fifteen minutes, and heard it utter what were obviously anguished cries of pain at the ferocity of the attack) that I’m wondering if there’s something more sinister going on. I understand redwing blackbirds are known to gang up on crows, but on at least two of these occasions the gang-attack ‘victims’ have been jays and even hawks. I’ve seen a raft of instances where birds attacked others with such frenzy that both the attackers and victims flew recklessly into oncoming road traffic.

These avian participants are so common in the summer here that I’m sure I would have noticed this phenomenon before if it had been anywhere near as frequent or belligerent. And this week’s CSM reports an increase in bird-on-human and bird-on-car attacks as well, and chalks it up to encroachment on bird habitat. Has anyone else notice increased bird aggressiveness? Anyone have any theories or even intriguing hypotheses? Might there be a connection to the surge in West Nile Virus among some of these birds?

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19 Responses to Increased Bird Aggressiveness: Is There Something Ominous Going On?

John Evans (SYNTAGMA) says:

June 17, 2005 at 08:05

I wonder if it’s an instinctive reaction to pressures on birds’ environments by human activity. Aggression arises from stress. There might also be a chemical agent here, and, since birds are descendants of dinosaurs it’s perhaps not surprising. Here in England there are regular stories on news bulletins of gull attacks near the sea. Apparently, feeding them leads to a “rights” culture similar to humans dependent on welfare benefits. Fascinating topic.
Myke says:

June 17, 2005 at 09:08

At our home in the northern suburbs of Atlanta the small birds are aggressive when threatened. Crows eat eggs and chicks of smaller birds, which is why small birds gang- attack crows. Hawks kill and eat birds, including crows. Recently I’ve witnessed several bird species ganging up on a snake (http://www.mykesweblog.com/2005/05/nature_in_the_b.html). I also seen birds screaming at a hawk as it was killing a rabbit (http://www.mykesweblog.com/2005/05/nature_on_the_g.html).The alliances are dynamic, like humans — the enemy of my enemy is my ally. For example, blue jays help small birds harass hawks, owls, cats, and snakes, but blue jays will eat eggs (and maybe chicks) of smaller birds. The crow-magpie-blue jay family are very intelligent and quick to act on opportunities.
Rayne says:

June 17, 2005 at 09:28

Could be West Nile, if it has negatively affected the population of larger birds. I note that the state government here has asked for carcasses of crows and bluejays, but never wondered whether until now whether it was because they were the most affected. Not noting any change in small-to-medium-sized bird population here. I wonder whether the violence you’re noting presages a near-term shift in population in the other direction — a collapse of small birds. Avian flu?But I’ve also noted a BIG change in Canada geese, much larger numbers than I ever remember. I’ve told my kids to stay away from them and their spoor since their migratory habits might make them more likely to care viruses. Again, another collapse presaged?
Jean-Sebastien says:

June 17, 2005 at 10:40

It is a common behavior of birds to attack larger birds that could eat their eggs or nestlings. Birds of prey are almost continuously bothered by smaller birds (even by crows). When you enter a wood and hear a flock of crows or other smaller birds calling and flying in a bizarre manner, you have a good chance of spotting an owl or an hawk! I cannot remember the english word for this behavior but in french we call it «houspiller».It dont think that your recent observations of «violence» among birds is caused by human pressure, pollution or West-Nile Virus. I think that there might be more birds nests around your house than usual. If, for some random (or not) reasons, more birds nests neirby your house this year, you are more likely to witness aggresive behaviours among birds.
Barbara W. Klaser says:

June 17, 2005 at 11:01

We have a lot of crows in our neighborhood, and right now, with young birds just about ready to leave the nest, the other birds, especially mockingbirds, are incredibly aggressive. I’m noticing it more this year, too, but maybe there are more nesting birds. We had a lot more rain–more insects–more seeds for food, this year.
David says:

June 17, 2005 at 11:15

West Nile swept through Colorado two years ago and had an especially drastic affect on the population of all members of the crow family. I’ve always been amazed by the irony of tiny sparrows fighting off large hawks, but I’ve also noticed more this year, of attacks by, and against red-wing blackbirds, jays, and magpies, etc. I think I’ve noticed it more lately just because the crow bretheren are staging a comeback in numbers this year compared to the last two.Still, I have to laugh every time I see it. I thought it was just teenagers that acted this way …
Berlin says:

June 17, 2005 at 11:36

I believe it is a mob mentality in birds.
Jon Husband says:

June 17, 2005 at 14:10

I do think there’s something going on. I walk quite a bit, and get *buzzed* by crows/blackbirds quite often, and have increasingly often seen geese in Stanley park and English bay, etc. being aggressive.
Jay says:

June 17, 2005 at 17:59

I’m located in Phoenix, AZ. I can’t compare this year to previous years, but I did notice a (lone!) sparrow attacking a hawk for the first time this year. I was amazed the hawk didn’t just bite his opponent in two; he just sat atop his telephone pole and took it.
Oliver S says:

June 17, 2005 at 18:17

(Another observation from the Vancouver area).I’d say over the last two years I’ve noticed crows being much more aggressive; singles or pairs will follow me for blocks at a time pretty regularly, dive-bombing, flying by your head from behind; pretty surreal initially.This year I’ve come across, for the first time I can remember, two sets of bird remains, that, for all that is left of them, appear to have been crows (typically lots of feathers and some bodily remains). I suppose it could have been cats, though, not having seen the actual events.All in all, I’ve noticed increasing wierdness with birds in the Vancouver area, and the appearance of new types of birds that I’ve never seen/heard before. Not sure about the “encroachment” hypothesis; Vancouver isn’t really a city of sprawling growth and everything I experience happens in well-established neighbourhoods…
Kim says:

June 17, 2005 at 19:39

I’m in Maine. A couple of weeks ago, an insistent noise at my kitchen window turned out to be a bird (I’m not sure what kind, forgive my ignorance). This bird was persistant, to the point of banging its beak at my window. When I or my brother would go to the window, it would fly away. When we would leave the window, it would come back. The banging started to become part of my routine. In the morning, before I headed out to work and there he was to greet me when I would get home from work.Finally, I drew the shade and this stopped him. I’ve since raised the shade but it seems he’s moved on.For me, this whole thing was very strange to me. I began to wonder if the bird didn’t have some weird disease, but really I have no knowledge on such things, just speculations.
Zach says:

June 17, 2005 at 20:20

Yes! Birds have been furiously attacking my house! They dive bomb my windows like Kamikaze’s, then bang! Thud. <narrow eyes> Something is definitely going on. </narrow eyes>
john says:

June 17, 2005 at 21:39

That’s the weirdest thing – just tonight I saw three red wing blackbirds relentlesly attacking a crow.
Wendy Farmer-O'Neil says:

June 18, 2005 at 00:22

Funny you should mention this. Just last week I witnessed (Vancouver Island) a bald eagle attacking a seagull. The seagull seemed near to exhaustion when two crows winged in and started aggressively attacking the eagle. They distracted it from the seagull, which escaped, and then continued to attack and chase the eagle until I lost sight of them (they continued to follow it inland). I thought it very unusual…quite exceptional in my experience anyway. I blogged a while ago about how the blossoms and bees here seemed to be on overdrive…as if they know something bad is coming and are making the most of the time they have left. Isn’t there something in chaos theory about populations booming just before a collapse? I hope I’m wrong…Wendy
John Evans (SYNTAGMA) says:

June 18, 2005 at 05:57

Kim, I’ve also had that banging on the windows by seagulls. I think they see their own reflection in the glass and assume its another gull. Whether they’re responding aggressively or as a mating ritual, I’ve never been sure. Probably they’re trying to figure out why the “other” bird does exactly what they’re doing. :-)
Tim says:

June 18, 2005 at 14:05

It’s Birds!!!!!! :)
Rayne says:

June 18, 2005 at 15:35

Hmm. Had another thought about this…wonder if West Nile adversely affects segments of the larger bird population or even the smaller birds, so that more aggressive birds in the large bird group die off or the less aggressive birds in the small bird group die off? Could be spotty, depending on the spread of the virus and on the rebound/recovery after infection has spread throughout the community.
Yves Grassioulet says:

June 20, 2005 at 06:34

How is it that your post on birds’ agressiveness brings out so many replies?
Mike says:

June 20, 2005 at 08:29

Mobbing behavior, when smaller birds team up to harry a larger one, is common in many bird species, from corvids (crows, jays, etc.) to songbirds. Birds mob when they feel threatened by a larger predator. They also mob when they feel that their nests or young are in danger.Stories of birds like grackles or crows attacking humans have definitely spiked this year. These attacks have occurred during breeding and nesting season, so I would assume that they are related to brood protection. The simple answer is to blame these attacks on habitat encroachment. However, the actual dynamic is a bit more complex since the aforementioned birds are as opportunistic as humans are as far as habitiat goes. Well-adapted to urban environments, grackles, crows, ravens, blackbirds, and jays thrive everywhere we do. Since those of us who live in cities basically live on top of each other, interactions can get tense, especially when our kids may be threatened. I’m inclined to look at these isolated incidents as examples of highly adaptive organisms defending their territory, rather than signs of impending ecological collapse. What we don’t hear about too often in the news are the countervailing cases where humans attack birds, whether with construction equipment, bb-guns, chemicals, or, as occurred a few times this year between humans and mute swans, fists, knives, and sticks.