Rattling Behavior in Birds: What Causes It, How to Avoid It

Rattling behavior can be distinguished from mobbing behavior because the later is applied to any potential predator, while rattling is specific to an individual target. Many birds will mob owls and cats even if they are only asleep or resting, apparently because they think all owls and cats are predators. A kind of nest protection behavior similar to mobbing also happens when people walk by a mockingbird nest and the mockingbirds fly at their heads and at least pretend to peck at them. This often happens along city sidewalks when the birds are nesting in a tree over a commonly used sidewalk. But this isn't specific to the person, they will fly at anyone who walks by. Rattling, however is restricted to a particular object of fear, such as an individual who has been seen harming other birds.

A recent NPR interview with Professors McGowan and Marzluff discusses the peculiar but relevant ability of birds to recognize individual human beings, after only one traumatic incident. They reported that when they had been banding baby crows (which required that they catch the birds in the nest and then release them without harm), the parents would become very upset, and afterwards, flocks of crows would scream at the specific bird banders whenever they saw them in the neighborhood. They would be singled out for loud disapproval even when they were playing tennis with other humans in the area who were ignored.

They tested this by buying masks at a costume store (they tried a monster mask and a Dick Cheney mask) and they found that if they wore a mask when banding the birds, the parents would then scream at them when they wore that mask around the neighborhood. They tested this further to see what features of the mask were recognizable to the crows and they found that if they fastened the mask on upside down the crows would turn their heads upside down to get a better look at them, and then squawk away. This makes me want to annoy baby crows and then run around the neighborhood wearing an upside-down Dick Cheney mask, just so that I can watch all the crows turn their heads upside down and squawk at me. ok, not really, but who says science can't be fun?

What Causes Rattling
Konrad Lorenz wrote extensively on this subject in Studies of Animal and Human Behaviour, p. 6-11, and he describes the peculiar metallic rattling call directed by jackdaws at the object of alarm, which can be distinguished from their many other calls. He focused on what triggered the behavior. In his observations, it was the appearance of a bird (or something mistaken for one), being held in the hand, which triggered the response. He reports that the rattling response was provoked when jackdaws, which he kept for study, saw him holding another jackdaw in his hand, even though he wasn't hurting it. He also was targeted when they saw him carrying a pair of wet black bathing trunks through the garden. He surmised that the fabric of the bathing trunks which fell limply was mistaken for a dead bird. And he reported that some jackdaws attacked another crow, which they didn't normally have a problem with, when they saw it carrying an abandoned feather to add to its nest. He reports that "even the presentation of a single large black feather sufficed" to trigger the rattling response. Konrad Lorenz limited his observations to corvids, birds of the crow family, including crows, ravens, jackdaws, rooks and magpies.

My experience with flamingos and hawks
Rattling behavior is not limited to corvids. I used to volunteer in the graphics department at a zoo, and I was collecting flamingo feathers in the flamingo cage (with permission), but the hawk nearby saw me. He would have eaten a flamingo if he could except that they are too big and he was in a cage, still he has no sympathy for them. Nevertheless he began to scream at me when I came out of the flamingo cage with a handful of large very pink flamingo feathers, and after that he continued to scream at me whenever I walked by. This was very embarrassing, because he would pick me out of the common run of tourists in the zoo, even though I was on the standard walkway that went around the cages, and it made me feel quite conspicuous. This lasted about 30 days, and then he forgot me, to my great relief.

How to avoid being rattled.
Don't rob nests or otherwise harm birds. I'm guessing you weren't planning to anyway, but it used to be considered a perfectly normal sport for boys. I suppose if you have to band birds or handle them for some other (legitimate) reason, you might want to wear a mask. Scientists who handle baby raptors (hawks, etc.) wear helmets because those birds can strike you dead.

If you want to collect feathers, put them in a brown paper bag (not clear plastic) and try to be inconspicuous about it. Feathers are shed naturally and it does no harm to pick them up to use to make quill pens or for craft projects. But turn your back to any birds you see and put the feathers out of sight quickly. If any birds see you carrying a feather in your hand, they may think you ate the rest of the bird!

References
NPR report "The Crow Paradox" July 27, 2009 by science correspondent Robert Krulwich, in which he interviewed Kevin McGowan of Cornell University and John Marzluff of the University of Washington.

Lorenz, Konrad, Studies in Animal and Human Behaviour, Vol. I , transl. by Robert Martin, Harvard University Press, Cambridge, Mass, 1970.