Hooded Crow

Corvus corni

Light gray body
Glossy black head, throat, wings, tail and thigh
Black bill, legs and eyes

Listen to its call.

On the pier at Kyleakin on the Isle of Skye, these birds are more abundant than gulls. I frequently watched them soaring in the wind while constantly scavengering for food during my time there this winter. One of their favourite pastimes was dropping molluscs on the concrete to crack them open.

Learn more about the Hooded Crow.

Rook

Corvus frugilegus

Appearance
Large black bird
Large grey-black bill, with bare grey-white skin around base
  
Listen to its call. 

I saw a large number of these birds in the fields along the river trail between Ware and Hertford. I determined they were Rooks for the following reasons: 1) "untidy" leg feathers, 2) bare grey-white skin at base of bill, and 3) Rooks are sociable birds while Carrion crows are usually found alone or in pairs.

Learn more about the Rook.

Jackdaw

Corvus monedula

Appearance
Small black crow
Silvery sheen to back of head
Pale grey (almost white) eye

Listen to its call.

While walking along the Lea River from Ware to Hertford in Hertfordshire, I saw this bird in a nearby field along with a substantial number of larger crows. The pale eye as well as the size distinguished this bird from the others. It wasn't until I reviewed the pictures later that I noticed the grey nape and shoulders.

Learn more about the Jackdaw.

Starling

Sturnis vulgaris

Appearance:
Medium-sized passerine bird
Short tail
Pinkish legs  
Summer
       Iridescent black plumage
       Yellow bill  
Winter (pictured)
       Brown-black plumage speckled with white
       Black bill

 Listen to its call.

A pair of these birds were trying to have a little bath in the boating lake in Regent's Park this afternoon. Unfortunately, their efforts kept being thwarted by a Mute Swan trying  to bite them. The Starlings weren't too upset by this though, as they continued to run back and forth to the water between nips.  

Learn more about the Starling.