Canterbury rook population




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CANTERBURY ROOK POPULATION

- TREND MONITORING 2009.
Environment Canterbury monitors rook (Corvus frugilegus) numbers annually; estimates on numbers have been recorded since 1983.
The rook is a highly gregarious bird species, foraging daily from either breeding rookeries or communal winter roosts. During the breeding season all birds live in rookeries, often the same sites as used in the previous season, unless disturbed.
They have no natural predators in New Zealand. They are extremely intelligent and quickly become wary, especially after being persecuted. Rooks are omnivorous their feeding forays can range up to 20 kilometres, with cereals at all stages of the crop, recently cultivated land and stands of walnut trees being preferred feeding sites, In the large numbers that they were present in rooks severely damage or destroy newly emerging crops or pasture.

Although rooks do feed on grass grub and porina caterpillars their impact on these pest populations would be negligible.

Rooks are listed under the “Total Control Pest Programme” section of the Regional Pest Management Strategy (2005) with an objective of destroying all rooks within the Canterbury region before 2015.

One of the principle measures to achieve this objective is to monitor all known rookeries and reported sightings annually, to assess numbers and the degree of success of any previous season control operations.



This assessment generally takes place in October/November each year. Birds are breeding at this time, which provides a good opportunity to obtain an accurate count on paired birds and nests. Usually the number of nests at each site is multiplied by 3.5 to provide an estimate of total bird numbers. This factor allows for the breeding pair plus the non-breeding juvenile rooks hatched from the previous year. This monitoring system is used nationally. However bird numbers are so low in Canterbury our count is of individuals.








Canterbury Annual Rook Census












































































 










1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

BANKS PEN

1239

238

6

10

4

1

0

0

0

0

0

0

0

0

0

0

PLAINS

294

9

34

19

16

8

7

4

5

5

* 5

* 5

* 5

* 2

2

1

ASHBURTON

66

91

18

24

14

12

8

4

4

3

5

* 5

* 4

0

0

3

SELWYN

24

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

KAIKOURA

18

10

3

2

3

3

3

4

7

6

0

0

6

1

2

* 1

WAIKARI

0

0

0

0

0

0

0

7

5

7

11

10

11

4

2

2

TIMARU

 

0

0

0

0

0

0

0

0

0

0

2

3

* 3

* 3

* 3

0




TOTAL

1641

348

61

55

37

24

18

19

21

21

23

23

29

10

9

7



















































































































* = estimate, no birds confirmed during census but presumed in locality.






















Rook Sightings over Last 12 months plus Control Attempts & Rooks Destroyed.

Sightings: 2008-2009.

Waikari. Hawarden, Masons Flat 23/7/2008, 3 birds reported – lost/moved.

Grid Ref E.2473478-N.5813692.
Waikari. Hawarden, Murray’s road 22/9/2008, 2 reported, 1 destroyed- 1 lost.

Grid Ref E.2474345-N.5814258.


Kaikoura, Inland Road 25/10/2008, 2 birds reported – lost /moved.

Grid Ref E.2560600-N.5769365.


Plains. Kirwee, Essendon Road 25/11/2008, 1 bird reported

One Destroyed by contractor. Bird collected.

Grid Ref E.2438678-N.5741868.
Plains. Darfield, Bealey road 25/11/2008, 2 birds reported – lost/moved.

Grid Ref E.2443023-N.5740325.



Sightings: 2009-2010.

Plains. Darfield, Greendale Rd. 4/6/2009, 4 birds reported.- control attempted,

no confirmed kill but 1 possibly 2 suspected.

Grid Ref E.2436795-N.5743185.


Ashburton, Maronan Ealing Road. 24/8/2009. 3 birds reported,

2 seen on inspection

Grid Ref E. 2386448- N.5694780.
Waikari, Pyramid Valley, 28/9/2009. 2 birds reported by landowner

Grid Ref, E. 2477375. N.5804310.


Waikari, Kingsmoor. 14/10/2009. 2 birds possibly 3 reported by landowner

Grid Ref, E. 2474730. N. 5819430.


Waikari, Stonybrook, 11/10/2009. 2 birds reported by landowner

Grid Ref, E. 2472740. N.5815850.


Plains, Bealey Road, 27/10/2009. 2 birds reported by landowner.

Grid Ref, E. 2443020. N.5740600.


Plains, Highfield Road, 28/10/2009. 2 birds reported by landowner

One destroyed by landowner, Bird collected. One lost.

Grid Ref, E. 2447700. N.5753535.

Control:

Two birds were known to have been destroyed over the last year.

One at Kirwee, Essendon Road, 25/11/2008. An Excel contractor following up on a reported sighting of a single bird feeding in a worked paddock was able to accompany the tractor driver and destroy the bird from the tractor.

The other bird was one of two seen by a landowner in the Plains district, again feeding on a worked paddock on Highfield Road, 28/10/2009. The landowner managed to shoot one bird, attempted to shoot the other with a shotgun but it escaped.


No known successful fledged chicks were raised this year, some birds built nests but failed to lay or incubate eggs where control could be initiated. It is possible that some of the lost birds may have reared chicks, but we rely largely on the public to inform us of new nesting sites.

Due to the now uncommon sight of rooks and perhaps the general unfamiliarity of the bird to the public it maybe likely some birds remain unreported.


Brent Glentworth

Biosecurity Team Leader

3 November 2009.





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