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Published: 2001-02-21 00:00:00

Environment Waikato has treated 115 rook nests in the north Waikato and Taupo districts as part of a new, aggressive approach to eliminating the pests.

This week’s Biosecurity Committee meeting heard that rooks had become an agricultural threat in the Waikato and many other regions, feeding on and devastating emerging crops. They also tore silage wrap and ate walnut crops, and were listed as a pest of regional significance in the Regional Pest Management Strategy.

Animal Pest Programme Manager Peter Russell said the aim of the control strategy was to contain rook numbers and eradicate them from the Region by June 1999 but this was not achieved due to a number of unknown rookeries recently discovered through greatly improved survey methods.

The revised strategy set a new eradication date of June, 2004.

To find the birds, more than 8000 survey forms were mailed to people in the north Waikato and Taupo areas, followed by an aerial survey before control work was done. As a result 10 new rookeries were found, making a total of 31 known sites compared to 21 in 1999. Four were not used and eight were destroyed early in the breeding season.

While it was difficult to determine the number killed, staff were confident that all existing rookeries were targeted and high kills observed at all sites. The operation cost $66,000 including $10,000 for the survey.

Mr Russell said the survey had great value in updating the database and getting the community involved in the eradication programme. Aerial treatment during the breeding season was still the most effective control method, although the extended breeding season and periods of stormy weather added to the cost this year.

A significant drop in the number of nesting birds was expected in the 2001 breeding season as well as growing community support, he said.