LC
Rook Corvus frugilegus



Justification

Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Population justification
In Europe, the breeding population is estimated to number 8,170,000-14,200,000 pairs, which equates to 16,300,000-28,400,000 mature individuals (BirdLife International 2015). Europe forms c.30% of the global range, so a very preliminary estimate of the global population size is 54,300,000-94,700,000 mature individuals, although further validation of this estimate is needed.

Trend justification
The population is suspected to be in decline following considerable decreases, especially in the east Asian populations (Madge and Burn 1993). In Europe, trends between 1980 and 2013 show that populations have undergone a moderate increase (EBCC 2015). However data collected for the European Red List of Birds shows that the European population has undergone a decline of less than 25% in 21.9 years (three generations) (BirdLife International 2015).

Ecology

This species prefers agricultural land, wooded steppe and riverine plains with fragmented woodland or stands of trees. It is also found in the fringes of cities, towns and villages with large trees (Madge and Burn 1993), and in city parks and churchyards (Madge 2009). In the winter it can also be found along the sea shore. It is a highly colonial species and breeds as early as late February in Britain but can breed as late as mid-April in European Russia (Madge and Burn 1993). Both sexes build the nest, which is a bulky structure of twigs and sticks and the cup is lined with roots, dry grasses and dead leaves. A nest may be repaired and reused for many years. Usually four eggs are laid but can range from two to seven. It is an omnivore; main food items are earthworms (Lumbricidae) and grain but it does take a wide variety of other invertebrates as well as vertebrates such as small lizards, frogs and small mammals, and eggs and nestlings of small birds (Madge 2009). It is less of a carrion-feeder than other northern corvids (Madge and Burn 1993). The species is resident over western and southern parts of its range and migratory in the north and east (Madge 2009).

Threats

Populations of this species have fluctuated since 1900. The main causes of fluctuations are changing agricultural land-use (notably the loss of extensive pasture), the application of pesticides and seed dressings (mercury) and persecution through shooting (Hagemeijer and Blair 1997, Madge 2009).

Conservation actions

Conservation Actions Underway
EU Birds Directive Annex II. There are currently no known conservation measures for this species within Europe.

Conservation Actions Proposed
Although this species is not threatened, monitoring implemented to assess population fluctuations and research into the impact of threats should be undertaken.

Acknowledgements

Text account compilers
Ashpole, J, Wheatley, H., Butchart, S., Ekstrom, J.


Recommended citation
BirdLife International (2021) Species factsheet: Corvus frugilegus. Downloaded from http://www.birdlife.org on 03/12/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 03/12/2021.