Rookeries survey 2013/2014

In 2011/12 it was commented on by several observers that some rookeries had either disappeared, or declined considerably in parts of Pembrokeshire.  In 2013 and 2014 birdwatchers were asked to count the nests in any rookeries they came across in the county.  No attempt was made to find all rookeries, or to visit all tetrads where rookeries had previously been recorded.

A minimum of 3,776 apparently occupied rook nests was recorded in 2013/14 from 138 rookeries surveyed. The largest rookery (at Dale) contained 178 apparently occupied nests (AON). The average rookery size was 27 AON.

Rookeries were recorded within 110 tetrads, which represented about 50% of the tetrads where rookeries were found during the 2003-07 Pembrokeshire breeding birds atlas survey (Rees et al. 2009). During the 2013/14 survey, rookeries were recorded from an additional nine tetrads where there was no evidence of breeding reported during the 2003-07 atlas survey period. However, all bar one of these had previously been confirmed to have breeding rooks in the first Pembrokeshire breeding atlas survey (1984-88) (Donovan & Rees, 1994).

At least fourteen rookeries were found to have 'disappeared'. These had ranged in size from 9 to 102 AON in a census of south Pembrokeshire rookeries undertaken in 1996 (Little and Level 1996). No alternative sites were found in the vicinity of these rookeries in 2013/14, although there was anecdotal evidence of two of them having attempted to relocate in the five years subsequent to their last being occupied.

If the population of 3,776 AON, from about 50% of the tetrads with confirmed breeding rooks in 2003-07, is a typical of the population across the remaining 50% of un-surveyed tetrads in 2013/14, then a total county population of at least 7,550 AON is possible. This assumes that the average rookery size in the un-recorded parts (e.g. in the northeast) is similar to that for the surveyed rookeries in the remainder of the county.  

Data from three previous censuses of the rook population (a BTO census of 1944-46, a Dyfed Wildlife Trust census of 1971 and a BTO census of 1975/76) suggested a population of between 8,000 and 10,000 pairs. Limited local surveys conducted over a period of 15 years in the 1980’s and 1990’s showed fluctuations in annual totals but stability overall. It was suggested that the population was still likely to be in this range in 2003-07 (Rees et al. 2009). Data from the 2013/2014 survey suggests a population closer to the lower estimate.

Orange squares show tetrads where rookeries were recorded in the 2003-07 atlas

Black circles show rookeries counted in 2013-14

Rook - 1949 status

Corvus frugilegus frugilegus

Resident and numerous.  Rookeries in 1945 were 147, containing 9,664 nests (James Fisher - BTO national survey). Marked spring migration at Skokholm during March and April.

R.M.Lockley, G.C.S.Ingram, H.M.Salmon, 1949, The Birds of Pembrokeshire, The West Wales Field Society

Rook - 2003-07

The Rook looks similar to a Carrion Crow but has a stepped forehead, a pointed bill, a grey–white area of bare skin around the base of the bill and loose flank feathers giving it a “baggy trousers” appearance. The large nest built of sticks is placed in the crown of a tree and several nests are grouped close to each other so that a colony is formed.

There have been many small shifts in the sites of rookeries in the county but no great change in overall distribution. Note the “Possible breeding” category has been omitted when assessing distribution, as Rooks recorded feeding in fields do not give any indication of the origin of their rookery. Site relocations have mostly been due to tree felling but in some cases are for unknown reasons. No complete county rookery census has been conducted during the last 30 years. 

Based on the three previous censuses a county population of between 8,000 and 10,000 pairs was extant over a period of 31 years. The BBS has indicated a 15% decrease in Wales between 1994 and 2007. However limited local surveys conducted over a period of 15 years in the 1980’s and 1990’s, showed fluctuations in annual totals but stability overall. On the information available, it seems reasonable to conclude that there has been no marked change in the Pembrokeshire breeding population and that a countywide census is desirable.

Graham Rees

 

Fieldwork 2003-07 (based on 490 tetrads) 

Red = breeding confirmed = 211

Orange = breeding probable = 3

Total tetrads in which registered = 214 (43.7%)

Rook - 1994

Breeding resident

Resident and abundant in all districts according to Mathew (1894), who noted that thousands perished in the severe winter of 1880. Lockley et al. (1949) also knew the Rook as resident and numerous.

They now nest throughout Pembrokeshire wherever there are suitable trees amid farmland, and are only absent from the mountain tops and the offshore islands, though they occasionally visit Ramsey and to a lesser extent Skokholm and Skomer.

The BTO census of 1944-1946 located a total of 9,664 nests in 147 colonies in Pembrokeshire. The Dyfed Wildlife Trust conducted a repeat survey in 1971 and found 10,109 nests in 281 rookeries. The BTO census of 1975-1976 logged 8,280 nests in 268 colonies. It would seem therefore that the Pembrokeshire population has been fairly stable for a long period; a sample census conducted by T.C.E. Hughes in 1986-1993 reached the same conclusion.

Saunders (1971) noted that the average rookery size had decreased between the 1944-1946 survey and that of 1971. He also noted that rookeries were sparse in the east of the county. The Breeding Birds Survey of 1984-1988 found that many areas in the east had since been colonised.

Lockley (1947) noted a regular south-west to north-east movement off the sea during March and early April. McCanch (1985) noted large scale departures to the west and north-west over the South Bishop during November 1975, including 350 on 6 November and 110 on 8 November. No other marked movements have been noted.

Fieldwork 1984-88 (based on 478 tetrads) 

Red = breeding confirmed = 220

Orange = breeding probable = 3

Total tetrads in which registered = 223 (46.7%)

Donovan J.W. & Rees G.H (1994), Birds of Pembrokeshire

Rook - 1970s breeding

Red = breeding confirmed

Orange = breeding probable

Yellow = breeding possible

Rook - 1980s winter atlas

The BTO winter atlas showed that Rooks were present in most 10km squares during the winters of 1981-82, 1982-82 and 1983-84.

The darker the colour, the higher the relative total count for each 10km square.  The darkest blue represents over 800 birds seen in a day.

Use of treeless coastal areas resulted in a winter distribution that was slightly more extensive than the breeding range.

Graham Rees

Rook - 1894

Species account from M Mathew, 1894, "The Birds of Pembrokeshire and its islands"

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