Why are crows carrying twigs in autumn?

October 5, 2021 5:23 AM

I live in the UK near a rookery (nesting site of rooks). I've seen rooks on 5+ occasions in the last week flying around with twigs. Could they really be building nests now in preparation for next spring or is something else going on?
posted by Lucy_32 to Science & Nature (9 answers total)

I'd guess that they're doing repairs. Nest-building does tend to be a spring thing, but the nests are maintained over many years, so I'm sure they must collect twigs at other times. It's been windier lately, so perhaps they're gathering twigs that have fallen from the nests.
posted by pipeski at 6:28 AM on October 5, 2021

I don't know the answer (repairs seem plausible though), but the Woodland Trust might be interested in your observations: scroll down to "How do rooks breed?" on their page about rooks.
posted by ManyLeggedCreature at 7:37 AM on October 5, 2021

According to this link, crows only use the nest once, so probably not nest maintenance (?). However, here it says that in the fall the crows form "large communal roosts". More information about the communal roosts here. This info is for American crows, but Hitchcock was British, so probably applies to British crows too?
posted by Dotty at 8:09 AM on October 5, 2021

You aren't the only one to have noticed this over the years - this book written by a naturalist in 1829 mentions similar behaviour in autumn and concluded it was repair work. This book from 1866 thought the same. Although by contrast, this more recent study from 1990 didn't find evidence of autumn repairs.
posted by greycap at 8:16 AM on October 5, 2021

Corvids (crows and their relatives) sometimes play with sticks. There are a lot of accounts of ravens doing things like dropping sticks in midair and catching them. The only mention I found of rooks playing with sticks was on this page from the British Trust for Ornithology. But according to that page, they do it. So it's possible that the rooks you saw were just carrying sticks around for fun.
posted by Redstart at 8:28 AM on October 5, 2021

It could be a lot of things. Perhaps as tools or toys as noted already, or maybe the very warm autumn we've had is confusing them. Jackdaws also nest nearby to rooks and are often easily mistaken for them, especially from a distance, and their nest building season can last into late summer/early autumn.

I would definitely take photographs or footage if you can and see if the Woodland Trust is interested in it. The truth is we don't really know what's going to happen to seasonal behaviour like this as our climate warms up so any information is useful!
posted by fight or flight at 8:52 AM on October 5, 2021

I can't find a decent link, but my understanding is that a combination of day length and a few warmer days makes the birds think it's spring. They will soon change their ways.
posted by StephenB at 10:25 AM on October 5, 2021

I would ask this question on Reddit. I know, Reddit can be a cesspool of filth and garbage. But it also has some very interesting and informed communities. I'd search ornithology, corvids, etc and try to find a subreddit that is frequented by experts.
posted by SoberHighland at 10:27 AM on October 5, 2021

Thanks for the replies, very interesting. I'm not sure how greycap managed to find those references! I haven't seen any the last few days, perhaps they have indeed realised that it's not spring. I'll get in touch with Woodland trust in case they are interested.
posted by Lucy_32 at 8:47 AM on October 12, 2021