Black fu­ture for rooks

Clare Wishart says she is a ‘‘rook en­thu­si­ast’’. New Zealand has many of the black birds, but re­gional coun­cils plan to ex­ter­mi­nate them. Farm re­porter Jill Gal­loway re­ports.

Manawatu Standard - - In Land - Pic­tures:

One col­lec­tive noun for rooks is a ‘‘sto­ry­telling of rooks’’. They are noisy with their dis­tinc­tive ‘‘kaah’’ call. The col­lec­tive noun for crows is a ‘mur­der of crows’ and if re­gional coun­cils have their way – it could be a mur­der of rooks.

That is be­cause re­gional coun­cils and many farm­ers see the rooks as pests. Hori­zons, the Manawatu/Wan­ganui re­gional coun­cil, says most se­ri­ous is the dam­age they cause to farms by eat­ing and de­stroy­ing newly sown ce­re­als, wal­nuts, acorns, pump­kin seeds and oc­ca­sion­ally pota­toes and fruit.

The en­vi­ron­men­tal man­ager biose­cu­rity and re­sponse, Bill Mar­tyn says it has gone from want­ing to limit rook num­bers – to erad­i­ca­tion.

‘‘They’re known to be de­struc­tive of crops, and we can now look at erad­i­cat­ing them, be­cause it is now pos­si­ble with mod­ern tech­niques.

It’s the change from con­trol­ling rook num­bers to erad­i­ca­tion that has up­set Clare Wishart.

‘‘I’m a rook en­thu­si­ast. While I don’t have a prob­lem with con­trol­ling the num­bers, I do with killing all the rooks.’’

She says many New Zealan­ders have no idea this is home to rooks. They are mem­bers of the corvi­dae fam­ily, along with crows and ravens. They are about the same size as a large mag­pie and have glossy black plumage, with a slightly pur­ple tint.

The corvi­dae fam­ily are the most in­tel­li­gent birds on Earth – their brain to body ra­tio is the same as dol­phins and hu­mans.

They’re smart – the Ein­steins of the avain world. In the jour­nal, Cur­rent Bi­ol­ogy, re­searchers say crows in New Cale­do­nia used tools (a short stick), to get at other tools (a long stick), which they can then use to get food. And they ap­pear to solve prob­lems with rea­son­ing, rather than brute force.

Un­like oth­ers in the corvi­dae fam­ily, rooks are gre­gar­i­ous. They roost to­gether in colonies called rook­eries. They nest in high trees and usu­ally feed in flocks.

They are too smart to lose many birds to shoot­ing or ground poi­son­ing, and af­ter they be­came ‘‘bait shy’’, re­gional coun­cils have used he­li­copter poi­son­ing of the rook­eries in­stead.

Poi­son is dropped – it in­cludes a pe­tro­leum jelly sticky in­gre­di­ent to carry the poi­son DAC 1339 and it is sprayed, as the ap­pli­ca­tor dan­gles uder a he­li­copter – straight into the rooks’ nests.

The birds preen them­selves and die, but af­ter sev­eral days of agony and fail­ing or­gans Ms Wishart says. The poi­son hits the fe­males, who stay in the nest with their young, and the chicks. Be­cause of that, it is thought there are more male rooks than fe­males in Hawke’s Bay.

Rooks were in­tro­duced to New Zealand in 1862 to con­trol in­sects. There were lib­er­a­tions in Auck­land and Nelson, which failed, as well as the suc­cesses of Hawke’s Bay and Can­ter­bury.

‘‘Fifty years af­ter their in­tro­duc­tion, rooks in Hawke’s Bay had spread only 30 kilo­me­tres, while 100 years af­ter their in­tro­duc­tion in Can­ter­bury, they had spread only 50 kilo­me­tres,’’ Ms Wishart says.

They were in­tro­duced to eat in­sects, and she says that is ex­actly what they do.

‘‘A rook diet in­cludes a whole host of pas­ture pests, in­clud­ing wee­vils, striped dung flies, grass grubs and blow fly lar­vae as well as wasps, moths and mos­qui­toes.’’

They also kill and eat mice – the good they do has never been cal­cu­lated against the dam­age.

She says re­search shows the rooks only turn to newly sown crops when their beaks can’t probe the ground be­cause of win­ter frosts or sum­mer drought – and in na­ture, that is called sur­vival.

But hu­mans see that dif­fer­ently and for some of the time, the birds com­pete for the same food source.

‘‘So the rooks have been la­belled pests. Even though the ma­jor­ity of time, they are killing un­wanted in­sects.’’

A rook dam­age sur­vey was car­ried out in Hawke’s Bay in 1969 and of the 400 replies, 46 per­cent said they had suf­fered crop dam­age. ‘‘This was said to be $823 for each of th­ese 187 ratepay­ers. But it in­cluded their es­ti­mated time spent on bird scaring and con­trol, the cost of guns, am­mu­ni­tion, poi­son and scare­guns.’’

As a di­rect re­sult of the sur­vey pa­per, Ms Wishart says ‘‘a rook holo­caust be­gan and 86,000 rooks were shot or poi­soned in Hawke’s Bay’’.

Then the re­main­ing 5000 birds spread their wings, and many moved out of the re­gion.

She says far wider dis­perse­ment meant rooks have been seen over much of the North Is­land, as well as Otago and even on the Chathams and Ste­wart Is­land. A rook­ery has even set up base on Waiouru Mil­i­tary Camp land.

Their dis­per­sal meant the Tararua dis­trict, which had been rook-free un­til the 1970s, be­came home to some.

Hori­zons puts it this way. Mr Mar­tyn says a sur­vey of ac­tive nests shows they are spread be­tween Palmer­ston North and Tai­hape, but there is a clus­ter in Tararua and that is the hot spot, the coun­cil says.

‘‘Rooks are a par­tic­u­lar pest in Tararua Dis­trict, al­though they are wide­spread through­out the re­gion. We are al­ways keen to hear of new rook­eries es­tab­lish­ing, so please let us know.

‘‘Rooks are con­sid­ered a re­gion­ally un­de­sir­able an­i­mal, based on the im­pact th­ese birds can, and do have on our en­vi­ron­ment. There­fore Hori­zons car­ries out con­trol op­er­a­tions and mon­i­tor­ing of rook pop­u­la­tions at no cost to af­fected landown­ers.’’

Mr Martin says there are 1272 ac­tive nests in Hori­zons’ area.

‘‘You have to eval­u­ate if harm is be­ing caused. Then can you con­trol it?v Or can you erad­i­cate it at a re­spon­si­ble cost?’’

He says rooks are mainly a rural prob­lem, which is re­flected in the rat­ing for­mula for rook con­trol, with a tar­geted rate of 90 per­cent on all prop­er­ties over 4 hectares and 10 per­cent com­ing from gen­eral rates.

Hori­zons’ Pro­posed Re­gional Pest Man­age­ment Strat­egy is cur­rently un­der re­view. The strat­egy high­lights the path that Hori­zons thinks is the best di­rec­tion for pest con­trol into the fu­ture. The op­por­tu­nity to have your say is now.

How­ever, the ‘‘rook prob­lem’’, which Hori­zons be­lieves ex­ists, does not wash with Ms Wishart.

‘‘I have no prob­lem with the con­trol of rooks, but erad­i­ca­tion, which is openly pub­li­cised on re­gional coun­cil web­sites, that’s dif­fer­ent.’’

She says Christchur­ch’s rook pop­u­la­tion has al­ready been wiped out and cur­rently the Hawke’s Bay Re­gional Coun­cil plans to erad­i­cate all rooks by 2013. Hori­zons is plan­ning to fol­low suit, erad­i­cat­ing all rooks by 2020.

This ac­tion is not nec­es­sary, Ms Wishart says, and it is years since there has been a prob­lem with the num­ber of rooks.

Richard Porter, who is re­tired from the DSIR and Land­care Re­search, has re­searched rook pop­u­la­tions.

‘‘The rook pop­u­la­tion changed over from the dense pop­u­la­tion cen­tred in large rook­eries in a small area, to a less dense pop­u­la­tion, in small rook­eries scat­tered over a much larger area,’’ he wrote.

By the mid 1980s, es­ti­mated rook dam­age went to al­most noth­ing as in­di­cated by com­plaints re­ceived by the DSIR and pest de­struc­tion Board, Mr Porter said.

Low rook­ery num­bers means the birds do not pose an eco­nomic threat any more, he said.

A rook cen­sus is done by count­ing known nests and mul­ti­ply­ing by 3.5, but Ms Wishart be­lieves the birds are over­counted.

‘‘Rooks are not pro­lific breed­ers. An av­er­age of only 1-2 chicks sur­vive per nest each year and only one usu­ally makes it to fledge a few months later. There are heavy losses of both eggs and chicks.’’

She doubts all nests are used, so she says the birds are over­counted by re­gional coun­cils.

De­spite that, be­cause there are fewer of the birds and they are widely dis­persed, the eco­nomic threat of rooks has gone, Ms Wishart be­lieves. ‘‘Rooks can now be re­garded as part of the the large birds of the coun­try­side. At present and in the fore­see­able fu­ture, rook con­trol is prob­a­bly not war­ranted in most parts of the North Is­land.’’

Ms Wishart be­lieves that due to heavy poi­son­ings, the rooks’ days are now num­bered in New Zealand.

‘‘This is no longer con­trol of rooks. Erad­i­ca­tion is on the lips of most re­gional coun­cils.

‘‘But the New Zealand rook has been liv­ing here for more than 135 years and has earned its right to be here. Let’s not for­get most of the hu­mans liv­ing here – are all orig­i­nally im­ports. There is no case for posoin­ing them, sim­ply be­cause they are there.’’

On rook intelligen­ce, here’s what the Rev­erend Henry Ward Beecher, 1813-87, preacher, or­a­tor, and lec­turer, said.

‘‘If Man had wings and bore black feath­ers – few of them would be clever enough to be rooks or crows.’’

Robert Charles

Rook en­thu­si­ast Clare Wishart. She wants to see rook pop­u­la­tions con­trolled in New Zealand, but she does not want to see the birds wiped out en­tirely. Pic­ture:

Sup­plied

Young rooks in a nest. Re­gional coun­cils plan on erad­i­cat­ing all rooks.

An adult fe­male rook sits on eggs in her nest.

Rook poi­son­ing from a he­li­copter.

Murray Wil­son

Hori­zons en­vi­ron­men­tal man­ager biose­cu­rity and re­sponse, Bill Martin. Pic­ture

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