Distribution and numbers of the rook (<i>Corvus frugilegus</i> L.) in the North Island of New Zealand

Bull, P. C.; Porter, R. E. R.

doi:10.1080/03014223.1975.9517863

Cited by 5 publications

(12 citation statements)

References 4 publications

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“…For example, dung beetles (Scarabaeidae) are an impO'rtant food of rooks in Britain (Holyoak 1972), whereas in Hawke's Bay fly larvae are the malin inhabitants of dung, and are taken in large numbers. However, this does not explain the slow spread of rooks (Bull & Porter 1975) to other parts of New Zealand with seemingly the same conditions. Rooks in New Zealand are fDund in largest numbers in areas with soils suitable for growing cereals and o.ther crops (Bull 1957).…”

Section: Discussionmentioning

confidence: 88%

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Food of the rook (Corvus frugilegusL.) in Hawke's Bay, New Zealand

Porter¹

1979

New Zealand Journal of Zoology

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ThroughDUt a year gizzards from 160 adult and juvenile roDks and 105 large yDung in rDDkeries were cDllected frDm Hawke's Bay. The main fDDds were invertebrates (especially Diptera larVae and CDleDptera aduhs) during the warmer mDnths and walnuts and aCDrns in autumn and winter. When these fDDds were scarce cereals were taken, mainly frDm stubble. Other impDrtant fDDd items were carriDn, earthwDrms, peas, grass, and clDver. FDDds fed to' yDung rDDks were similar to' thDse eaten by adults except that the yDung were fed more 'striped dung fly (Hybopygia varia) larvae (P < 0.025) and fewer blow fly (Calliphoridae) larvae (P < 0.025). INTRODUCTIONRDDks (Corvus frugilegus L.) were intrDduced intO' Hawke's Bay dUl'ing the 1870s (WellwDod 1968). Their initial increase and spread were SIDW, but by 1965 there were 9000--10 000 breeding birds in the district (Bull & PDrter 1975). They sDmetimes caused cDnsiderable damage to' cereals (especially maize, Zea mays), peas (Pisum sativum) , pumpkins (Cucurbiia maxima), and walnuts (Juglans nigra). SDme peDple felt that these IDsses were Dutweighed by the birds' value in destrDying gress grub (Costelytra zealandica) and Dther pasture pests. This cDntroversy has persisted in New Zealand fDr nearly 50 years, and cannDt be resDlved withDut detailed information Dn the diet Df rDDks. Until recently it had not even been cDnfirmed that they eat grass grub.BrDadly based research was therefDre undertaken to' determine the role Df rDDks in the agricultural eCDnDmy Df Hawke's Bay. The study cDvered numbers and distributiDn (Bull & Porter 1975), feeding habits, mDvements (Purchas, in prep.), reprDductiDn (Purchas 1979), and cDntrDI methDds (Bull 1975, Purchas 1976. This paper deals with the diet Df adult roDks and dependent and independent juveniles. The gizzards were remDvedand placed in 75% ethanDl, Dr the whDle roDk was deep-frozen within 2 h Df collectiDn. Later, the cDntents Df each gizzard were remDved and the vDlume was determined by displacement. Debl'is in the gizzard lining, particularly earthwDrm chaetae, was washed intO' a petri dish and sDrted. The rest Df the cDntents were placed Dn a 0.5 mm s,ieve, washed with water, and then examined under a X 10-40 binDcular micrDscDpe. Anter all major items had been sDrted and (if possible) cDunted, the volumes Df the majDr cDnstituents were estimated separately as tenths Df the tDtal volume. The less important items were pDoled and together estimated as tenths Df tDtal volume. The freque,ncy Df Dccurrence of fDDd items 'in the monthly sample of gizzards -and the me"n number Df insects in gizzards were calculated. STUDYInsects were cDunted and identified from parts resistant to' digestJion, such as heads, thoraxes, and the posterior spiracles of Diptera larvae. SDme insects were sent to' specialists for identificatiDn.The volume Df fODd actually ingested was not *Free-flying young that had left tb-: rDokery were pDoled wi,th adults 5:30 Zoology, 1979, Vol. 6 estimated, because of the difficulty of interpreting items such as earthworms,...

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Section: Discussionmentioning

confidence: 88%

“…The study cDvered numbers and distributiDn (Bull & Porter 1975), feeding habits, mDvements (Purchas, in prep. ), reprDductiDn (Purchas 1979), and cDntrDI methDds (Bull 1975, Purchas 1976. This paper deals with the diet Df adult roDks and dependent and independent juveniles.…”

Section: Introductionmentioning

confidence: 99%

Food of the rook (Corvus frugilegusL.) in Hawke's Bay, New Zealand

Porter¹

1979

New Zealand Journal of Zoology

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“…By the 1950s and 1960s, rooks were established in both pastoral and cropping lands in Hawke's Bay, and were most common in the central lowlands of the Heretaunga Plains, around Maraekakaho to the west, and north of Waipawa in central Hawke's Bay. During this time, rook numbers built up and their distribution widened (Bull 1957;Bull & Porter 1975). By 1969, there were at least 20 000 breeding adults in 128 rookeries distributed over c. 6000 km 2 (Bull & Porter 1975).…”

Section: Introductionmentioning

confidence: 99%

“…During this time, rook numbers built up and their distribution widened (Bull 1957;Bull & Porter 1975). By 1969, there were at least 20 000 breeding adults in 128 rookeries distributed over c. 6000 km 2 (Bull & Porter 1975). A few rookeries were also present in the adjacent districts of Manawatu, East Coast and Wairarapa (Bull & Porter 1975).…”

Section: Introductionmentioning

confidence: 99%

Distribution, abundance and control of the rook (Corvus frugilegusL.) in Hawke's Bay, New Zealand, 1969–2006

Porter¹,

Clapperton²,

Coleman

2008

Journal of the Royal Society of New Zealand

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“…comm. ), is now by far the largest in New Zealand (Bull & Porter 1975). The birds in this district eat a variety of insects which are harmful to seasonal crops and pastures (Porter 1979), but sometimes damage cereals (especially maize), peas, pumpkins, and walnuts (Bull 1975;Purchas 1980).…”

Section: Introductionmentioning

confidence: 99%

Predation by the rook,Corvus frugilegusL.,on larvae of the grass grub,Costelytra zealandica(White),in Hawke’s Bay, New Zealand

McLennan¹,

Macmillan²

1983

New Zealand Journal of Agricultural Research

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A method for quantifying predation by rooks on grass grub larvae was developed and applied in Hawke's Bay. The birds searched for grubs to a mean depth of 1.9 em by removing turf. As 65070 of the grubs in Field 1 and 40% in Field 2 were more than 2 em deep, they were not vulnerable to predation. Rooks were estimated to eat 22% of the grubs in Field 1 and 15.0% of the grubs in Field 2. These numbers were too low to prevent further loss in pasture production by grass grubs or to stop the next generation of grubs from increasing to severelydamaging levels. The rooks damaged the pasture seriously when they searched for grubs in the topsoil. The role that rooks might play in the control of other insect pests in Hawke's Bay is discussed briefly.

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Distribution and numbers of the rook (Corvus frugilegus L.) in the North Island of New Zealand

Cited by 5 publications

References 4 publications

Food of the rook (Corvus frugilegusL.) in Hawke's Bay, New Zealand

Food of the rook (Corvus frugilegusL.) in Hawke's Bay, New Zealand

Distribution, abundance and control of the rook (Corvus frugilegusL.) in Hawke's Bay, New Zealand, 1969–2006

Predation by the rook,Corvus frugilegusL.,on larvae of the grass grub,Costelytra zealandica(White),in Hawke’s Bay, New Zealand

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