Large-billed Crow
Corvus macrorhynchos
The large-billed crow is relatively large all-black corvid. It is 46–59 cm (18–23 in) in length and 450–1,000 g (16–35 oz) in weight. It has a large black bill with an arched culmen. The base of the culmen is hidden by a layer of overlapping black rictal bristles. The glossy black plumage has a purple sheen. The bases of the neck feathers are pale grey. The throat has elongated hackle feathers. The irises are dark brown and the legs are black. The sexes are similar in plumage but the female, on average, is smaller than the male and has a less arched culmen. Voice: The voice is similar to the house crow to which it is closest, but deeper and usually more resonant and described as the usual loud "caa-haa-caa". However, it makes a range of calls, some which could be described as "cau cau" and others that could be mistaken for a woodpecker drumming.
ID text from Wikipedia, CC BY-SA 4.0
Rook
Corvus frugilegus
The rook is a fairly large bird, at 280 to 340 g (9.9 to 12.0 oz) adult weight, 44 to 46 cm (17 to 18 in) in length and 81 to 99 cm (32 to 39 in) wingspan. It has black feathers that often show a blue or bluish-purple sheen in bright sunlight. The feathers on the head, neck and shoulders are particularly dense and silky. The legs and feet are generally black, the bill grey-black and the iris dark brown. In adults, a bare area of whitish skin in front of the eye and around the base of the bill is distinctive, and enables the rook to be distinguished from other members of the crow family. Voice: The call is usually described as caw or kaah, and is somewhat similar to that of the carrion crow, but less raucous. It is variable in pitch and has several variants, used in different situations. The call is given both in flight and while perched, at which time the bird fans its tail and bows while making each caw.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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