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). The population trend appears to be increasing, and hence the species does not 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.
The global population is estimated to number > c.16,000,000 individuals (Rich et al. 2004). The European population is estimated at 611,000-1,160,000 pairs, which equates to 1,220,000-2,320,000 mature individuals (BirdLife International 2015).
This species has undergone a large and statistically significant increase over the last 40 years in North America (166% increase over 40 years, equating to a 27.7% increase per decade; data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007). In Europe, trends between 1980 and 2013 show that populations have undergone a moderate increase (EBCC 2015).
The species is a habitat generalist, breeding throughout forested and open coastal, steppe, mountain, tundra and cliff regions of the Northern Hemisphere. It generally occupies more open habitat in the south and north portions of range where cliffs, sparse trees and human structures provide nest locations. In middle latitudes it is generally found in coniferous and broadleaf forests, where tree-nesting often more common than cliff-nesting. It is abundant in temperate (coniferous) rainforest along the north Pacific coast of North America. It generally avoids large cities but is abundant in Anchorage, Alaska and locally abundant in California metropolitan areas (Marzluff 2009). Egg-laying begins in late February over most of its range, although further north in Greenland and Siberia it begins later in April (Madge and Burn 1993). The nest is a large and bulky platform, made from dead sticks, lined with fine roots, grass, string and other bits of rubbish, and with mammal fur to make an inner cup. It is placed in the stout, lower branches of a tree, on a steep cliff, or on an artificial structure such as a utility pole, building, sign, radio tower, abandoned vehicle, oil derrick, bridge, irrigation pipe or windmill. Clutch size is typically four to six eggs. It is an opportunistic scavenger, consuming a huge variety of animals and plants. It preys on adult and nestling birds, eggs, small mammals, sick and dying larger mammals, toads, snakes, juvenile turtles, fish and invertebrates. It also scavenges garbage and slaughterhouse offal, dung, and nearly any kind of carrion and some plant matter is also consumed (Marzluff 2009). The species is mostly sedentary but northern populations are liable to move south in winter (Hagemeijer and Blair 1997).
From mid-1600s to mid-1900s or later this species was widely persecuted due to fear and superstition, resulting in European populations being reduced, often to point of creating gaps in the species's distribution (e.g. throughout much northern and central Europe). Persecution still continues in Iceland and Greenland but throughout the rest of Europe it is much reduced, allowing the species to recolonize areas it was previously extirpated from. Increasing populations of this species in much of western U.S.A. have led to conflict and targeted killing campaigns with large numbers shot and poisoned in California, Oregon, Utah and Nevada with limited and short-term benefits to crops and other wildlife (Marzluff 2009). Currently, intensive farming, the removal of woodland and human disturbance may also affect the species (Hagemeijer and Blair 1997).
Conservation Actions Underway
Active reintroduction efforts and increased subsidization, have aided its return to parts of Germany, the Netherlands, south-east U.S.A. (Marzluff 2009) and the Czech Republic (Hagemeijer and Blair 1997).
Conservation Actions Proposed
Although this species is not threatened the continuation in fall of persecution and the preservation of woodland stands within the landscape would help this species recover from past declines. Encourage land managers in North America to adopt non-lethal methods of deterring ravens from agricultural areas, rubbish dumps and other sites (Marzluff 2009).
Text account compilers
Butchart, S., Symes, A., Ekstrom, J., Ashpole, J
BirdLife International (2019) Species factsheet: Corvus corax. Downloaded from http://www.birdlife.org on 16/06/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 16/06/2019.