The all black appearance of the Carrion Crow means it is easily confused with the Rook. The curved bill and lack of a bare throat differentiates it from the Rook, as does the call and keeping its nest in a discrete territory rather than in a colony. The bulky stick nest, placed high in a tree, is usually conspicuous before leaves appear. In Pembrokeshire they also nest on cliff ledges.
The estimate that accompanied the 1984-88 survey was based on the distances between nests in a small number of random localities. With no other information available at the time, this was used to calculate a county total breeding population of 18,000–21,000 pairs. With the benefit of hindsight this is now considered to be an inflated total. The 1988-91 National Atlas showed Pembrokeshire contained Carrion Crows at maximum abundance and if their UK average density is adjusted to allow for this, suggests a county population of about 10,000 pairs, which seems realistic. The 2003-07 survey found no marked difference in distribution from the 1984-88 survey, so there has probably been no change in the size of the population.
Graham Rees
Fieldwork 2003-07 (based on 490 tetrads)
Red = breeding confirmed = 354
Orange = breeding probable = 51
Yellow = breeding possible = 48
Total tetrads in which registered = 453 (92.4%)