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
BANKS PEN
PLAINS
ASHBURTON
SELWYN
KAIKOURA
WAIKARI
TIMARU
TOTAL
1994
1239
294
66
24
18
0
0
1641
1995
238
9
91
0
10
0
0
348
1996
6
34
18
0
3
0
0
61
1997
10
19
24
0
2
0
0
55
1998
4
16
14
0
3
0
0
37
1999
1
8
12
0
3
0
0
24
2000
0
7
8
0
3
0
0
18
2001
0
4
4
0
4
7
0
19
2002
0
5
4
0
7
5
0
21
2003
0
5
3
0
6
7
0
21
2004
0
*5
5
0
0
11
2
23
2005
0
*5
*5
0
0
10
3
23
2006
0
*5
*4
0
6
11
*3
29
2007
0
*2
0
0
1
4
*3
10
2008
0
2
0
0
2
2
*3
9
2009
0
1
3
0
*1
2
0
7
* = estimate, no birds confirmed during census but presumed in locality.
Canterbury Region Annual Rook Counts.
Total Birds Counted (logarithmic Scale).
10000
1000
3735 3658
4159
5381 5108 5303
4141
5559
3785 3816 3852
4239
1641
100
348
61
55
23
29
37
10
24
18
19
21
21
23
10
9
7
1
1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
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.