Brodificoum and kiwi chicks

[Dave Houston]

Hi,

Can anyone please tell me whether any kiwi chicks have been killed as a result of Brodificoum poisoning and if so how long after the poison was laid and using what technique did this happen?

Also, if using brodificoum to poison an area what is the recommended time lapse before it is thought to be safe to reintroduce species such as kiwi chicks.

Any information on this would be much appreciated.

Cheers

Jo Tilson
Project Co ordinator

Paparoa Wildlife Trust
www.pwt.org.nz
Ph 03 7324455  / 021 330330

Hi Brad,
 
In central Northland we used brodifiacoum in bait stations for 7 years in a c.50ha bush patch and monitored the survival and productivity of Brown Kiwi cf nearby forest patches treated with predator trapping, Operation Nest Egg or doing nothing (non-treatment). The early part of this work was published: Robertson, HA; Colbourne, RM; Graham, P; Miller,PJ; Pierce, RJ. (1999). Survival of brown kiwi (Apteryx mantelli) exposed to brodifacoum poison in Northland, New Zealand. NZJ Ecology 23: 225-231.
 
Subsequent work showed that one chick, killed by a stoat, had liver residues of 0.69ppm, which may have eventually proved fatal (we don't know LD50s for brodifacoum or other toxins)  but this sort of level was probably due to it eating bait(s) directly, as happened with a transmittered Little Spotted Kiwi on Kapiti (not shown in the tables for some reason - see below). Traces of brodifacoum were found in chicks, adults and even eggs; however the quantity of brodifacoum used at Rarewarewa was far higher than the sort of one-off type operation that it sounds like Jo is contemplating.
 
Despite the risk of brodifacoum getting into kiwi, we concluded in 1999 that the benefits to kiwi outweighed the costs, because chick survival was so much better than non-treatment because of the excellent control of stoats and feral cats. With later detection of brodifacoum in more adults and in eggs, we may have been a bit more cautious about the balance following prolonged use of brodifacoum, because of the bioaccumulation; however, I would still say that the benefits outweighed the costs.
 
For the sort of one-off operation that Jo is contemplating (I presume for clearing pests from a predator-proof enclosure), then I think brodifaoum poses a very low risk to kiwi, especially if they are not present until a month or two after the poison is laid, or if done as a bait station operation. Certainly the impact should be less than than aerial baiting operations over an existing kiwi population. On Red Mercury Island, none of 9 radio-tagged kiwi died from direct poisoning from aerial poisoning of rats(Robertson, HA; Colbourne, RM; Nieuwland, F. (1993) Survival of Little Spotted Kiwi and other forest birds exposed to brodifacoum rat poison on Red Mercury Island. Notornis 40: 253-262.), but in a double aerial application on Kapiti Island, 2 of 10 radio-tagged LSK died after exposure to brodifacoum (one from apparently eating baits, the other of unknown causes as it was deep in a rock pile and decayed by the time it was excavated). Subsequent analysis came up with an estimate that 8% (3-19%, 95% CI) of all LSK died during the rat eradication on Kapiti (Robertson, HA; Colbourne, RM. (2001) Survival of Little Spotted Kiwi exposed to the rodenticide brodifacoum. Journal of Wildlife Management 65: 29-34); however, this estimate has been further refined by adding better information on natural survival rates of LSK to 4.7% (0-15%) (Robertson, HA; Colbourne, RM. (2003) Survival of Little Spotted Kiwi (Apteryx owenii) on Kapiti Island. Notornis 51: 161-163.).
 
I hope this helps,
 
Hugh Robertson

[Steptoe]

Been away , catching up on old subjects.
This may or may not be of some relivence.
We bred captive kakariki and a couple other exoric species...
.A King Parrot  got into a safely room cage where Brodificoum pelts where laid, and chewed up the whole block. It was over24 hrs before the insident was descovered.
The diet we feed is high in Vit k1
We had accepted we would loose the bird as had everyone else, but administered vit k1 as per vet recommended does for a dog per weight.
The result wa the bird didnt even get sick or have any symtoms.
This was put down to the added vit k in our birds diets, before comsuming by the king parrot.

So the though I have is if it was possible to supply kiwi/chicks, without acces by vermin, vit K before any Brodificoum baits are put out.

[Dave Houston]

Interesting idea, but I can't see how one could introduce vitamin K into the diet of kiwi without also making it available to the rodent population and thus perhaps raising their Brodificoum tolerance.  One could directly administer vit. K to the kiwi, but if you're going to do this then you may as well keep all the birds in captivity while the operation is ongoing, something probably not achievable.

[Steptoe]

but I can't see how one could introduce vitamin K into the diet of kiwi without also making it available to the rodent population

You cant see it, I cant see it....but that doesnt mean some else reads this, shakes their head, thinks we are a couple twits and comes up with a simple soln ...
All those posts about traps, stopping some species or other getting in....lots of very inovative people in this country.

Bsically it woulds be hard to supply stuff like broccoli stems over a long engough period to make any difference.....
But a bit, 1 keneral corn, dipped in butter,  then dipped in a ..less than a 1/4 match head of vit k, throw down the kiwis hole for a coupe days before hand may work very well....or bit of worm, maybe far more suitable.