How dynamic is the membership of bird flocks?

Obviously the answer depends on the species. Some types of birds don’t flock at all.

But amongst flocking types, does any given flock tend to have the same members for weeks or months or years? Or do individuals switch between flocks easily and often? e.g 2 flocks of ~20 Mallard ducks land on a pond. An hour later on ~20 take off as a flock. Was this necessarily the A or B flock from before, or is it a more-or-less random assortment of birds from each?

I’m particularly interested in Canada geese & Mallards as locally these are our most common flocking birds. But any info on any common North American birds would be interesting.



Bueller … ???

As a general thing, it’s fairly dynamic. There are flocks composed of family members or social groups that will stay together over long periods of time, but in large groups of waterfowl its pretty flexible.

Awesome. Thanks. I rather suspected that was it.

Our local Canada goose population has just reproduced and we’ve got families with 3 to 10 goslings all over the place. Damn they grow fast! So I got to thinking (always dangerous)…

I started from the question of how Canada geese identify their mate out of a group. Which then led me to wonder how they identify flockmates. Which then led to the thought that if they didn’t really recognize any individual other than their mate or juvenile offspring, how could a flock keep any sort of consistent membership. Which led to the question of whether a flock even does have any sort of consistent membership. etc.

Bird behavior is an interesting topic, but I don’t know how to hunt up more info beyond the superficial wiki entries on various species.

They may all look pretty much alike to us, but birds may be able to identify individuals the same way we do: by subtle (to us) differences in appearance and in voice.