Scientific Evidence against Rooks

[Paul Shortis]

I see GRWC has been posting signs asking for rook sightings around the Wairarapa. Is there any scientific evidence that rooks should be classed as a pest species? Once again our regional council seems intent on spending ratepayers money on eradicating a seemingly harmless species while cats, mustelids and rodents go largely unchecked. Even if there is a scientific case against rooks, it seems they should be a lot further down the priority list. I am keen to tackle GWRC but first thought establishing the science (or lack of it) behind the campaign would be a good idea. So, is anyone aware that there is a scientific basis for rook extermination?

[sav]

Hi Paul,
As far as I can work out, there is absolutely zero "scientific" evidence. The reason that Hawkes Bay Regional Council (HBRC) gave me was that they are "potentially devastating" to crops like squash. HBRC have a budget of $100,000/year (!!seriously?) to eradicate Rooks over a ten year period.
At the same time they have no allocated funds for rat, cat or mustelid control, and they wholly ignore the beneficial influence that Rooks have on grazing land, due to them feeding on grass grubs.
So, I can only presume that a large vegetable grower in HB pressured the council some time ago to eliminate the Rooks - which after all are an easy, obvious target. In early 2022 they used a twin-engined helicopter for 1.5 hours at a quoted cost of $4000/hour to destroy 6 (SIX!!) Rook nests at Ahurriri.
It's disgraceful on so many levels.

cheers

[Jan]

I have long been against the weird antagonism [sp] that rural people have about rooks. They mostly eat invertebrates which are pasture pests like grass grubs, as Sav says. They do like newly sown crops, but so do pukeko and they are native. In the UK they are also persecuted, but it's totally unnecessary. They are really smart birds and a pleasure to know. I miss them from the Canterbury landscape. Nowadays that's all featureless grass, dairy cows, treeless and horrible.

[Jim Kirker]

A Papers Past search has articles about rooks damaging crops and even sheep. All anecdotal, but shows why farmers might want to limit numbers.

https://paperspast.natlib.govt.nz/newsp ... uery=rooks

[Jim_j]

While not wanting to be anti-bird on a bird website... the NZ Birds on-line website indicates that in the past, when they were in high numbers, they were a serious pest in agricultural areas.
I assume the aim is total eradication - hence the high cost to get rid of the last few.

While you can argue that with current numbers Rook are not a significant pest - and as stated may well do some good controlling grass grub etc - you could say the same thing about rats, stoats, possums etc - if there were only 100 stoats in NZ they wouldn't be a pest animal- but.... nek minute!!
I suspect s/c cockatoo & rosella might end up on the same path.

cheers
jim

[SomesBirder]

if there were only 100 stoats in NZ they wouldn't be a pest animal- but.... nek minute!!

I'm sure that they would be; tragically it took just one adult stoat to kill the entire population of South Island Tīeke at Orokonui Ecosanctuary.

[Paul Shortis]

Thanks to those who answered my query and many thanks Jim for the links to some amazing articles and claims against rooks. I particularly liked the assertion that rooks in Auckland had mated with introduced crows and both species had died out! I shall pursue the issue and report back!

[Jan]

It is interesting that rooks have long been persecuted in England. Since the agricultural revolution when feudal lords took over commoner's farm strips and started growing grain industrially, rooks became pests. They uprooted germinating
wheat and barley grown as a monoculture and rookeries that villagers relied on for getting young squabs for the pot, became fewer and fewer. All this despite the considerable good that these birds do in attacking invertebrate pests. It's the way we farm that makes certain species a problem. Industrial ways of farming are hopeless both for humans and wildlife. About time more mixed farming was reclaimed and that is becoming realised now.

[andrewcrossland]

I think the evidence is fairly clear that the damage done by rooks was over-rated and they’ve been targeted for eradication because it’s a pest control target that is achievable whereas most other vertebrate pests are likely impossible to fully eradicate. Apparently the big issue on Banks Peninsula was the damage they did to walnut crops. Now the walnuts are safe, they can drop from the tree and attract rats which love them even more than rooks!!

[Jake]

I've only seen Rooks feeding in stubble fields, or established pastures. I'd be very surprised if Rooks did much damage to direct-drilled arable crops. I think the idea has been that, unlike virtually every other exotic, it could be possible to eradicate them, thanks to their breeding strategy. I'm not convinced of their negative impacts either, but stay kinda neutral: I still add them to ebird, but don't follow up with council. 30 years ago, when you'd see a flock of >150, it'd be hard to say they weren't damaging

It might've been two years ago, a pair were breeding near Park Is. Napier: unusual behavior and probably a good strategy to avoid nest poisoning.