Glamorgan Bird Club Rookery Survey 2022/23

Rooks have been in decline across the UK, but appear to be declining faster in Wales than anywhere else. In December 2022, they were moved directly from the Green to the Red list in the new Birds of Conservation Concern Cymru, making Rooks one of the species of highest conservation concern.

Early in 2022, in order to establish a robust Rook breeding population estimate for Wales, the Welsh Ornithological Society (WOS) launched a two-year all-Wales survey. Glamorgan Bird Club (GBC) decided to run its own survey alongside, and in support of, the WOS survey.  

In spring 2022 and spring 2023, birders across Wales were out looking for Rooks and their rookeries and, thanks to over 50 local volunteers, many of them GBC members, we now have a picture of where, and how many, Rooks are breeding in Eastern Glamorgan.

Background to both surveys

Volunteers were asked to visit all areas of suitable habitat for breeding Rooks within specially selected ‘tetrads’ (2km x 2km squares) between early March and mid-April and to count the nests in the active rookeries they found. WOS’ survey focused on visiting tetrads surveyed in previous UK-wide Rook surveys (in 1975 and 1996), as well as a sample of tetrads occupied by Rooks in the 2007-11 Bird Atlas. 

The aim of the GBC survey, as well as adding value to the WOS survey, was to attempt to map all the active rookeries in our region. The tetrads chosen for its survey included all those with Confirmed, Probable or Possible breeding Rook records in the 2007-11 Atlas, plus other tetrads with known Rook breeding after 2011. Birders could also report individual rookeries they happened to come across while out in the field or even during journeys in the car. 

Initial results

In total 122 tetrads (49 WOS and 73 GBC) were surveyed in Eastern Glamorgan in spring 2022 and spring 2023. Surveyors taking part, including students from Cardiff University Ornithological Society and Bridgend College, between them found 1,392 Rook nests in 69 rookeries. Rooks used multiple tree species for nesting but the most popular locally appear to be Ash, Sycamore, Scots Pine and Beech. The map of the surveyed tetrads is shown below.

St Brides Major (SS87X) is the unofficial Rook capital of Eastern Glamorgan, with 148 nests spread over 8 rookeries. Aberthaw (ST06I) came a close second with 135 nests over 3 rookeries and Marcross (SS96J) was the only other tetrad with over 100 nests (103 over 2 rookeries). 

What happens next

Records for all 122 tetrads surveyed in Eastern Glamorgan have been submitted via Cofnod to WOS. Data checking and editing by WOS is underway. Once completed, the Wales-wide data will be passed to the BTO (British Trust for Ornithology), which has been retained to carry out analysis of the data. BTO’s report to WOS is expected in late 2023 and the results will be included in a paper to be written in late 2023/early 2024 and published by WOS in its Milvus journal in spring 2024.

Separately, once WOS has concluded data checking and editing, GBC will look to carry out its own review of the data for the combined WOS/GBC surveys in Eastern Glamorgan and a summary of the results will be published.

Acknowledgements

Sincere thanks to all surveyors (GBC members and others) who contributed to the WOS and GBC surveys in Eastern Glamorgan in 2022 and/or 2023. Your efforts really are appreciated. 

Finally, a special mention to Rob and Linda Nottage who between them surveyed a remarkable 15 tetrads over the two years of the surveys.

Daniel Jenkins-Jones (WOS Survey Local Organiser) and Ceri Jones (GBC Survey Organiser)