The bristle head crows

Carrion Crows have a complex social structure. Territory-owning Carrion Crows remain paired year round, often flying and feeding together or not far from one another. They remain near their nest during the breeding season, although they may range wider outside this period. Birds that don't hold a territory form part of a loose flock that roosts communally, usually in large trees. Both male and female of a pair participate in territory defence, keeping other crows (or potential predators) away from the nest. Males have a more prominent role: if a male loses his mate he is able to defend the territory until he remates, but a female losing his mate will also lose her territory, as she would rapidly be evicted by other pair.
In one of my local parks there is a very high density of Crows. There are several territories, but the park is also the main ranging area of the non-breeding flock (where there is also a winter roost). There are a lot of interactions going on, but without ringed birds, it is hard to make sense of what is actually happening. Yesterday, I observed several interesting interactions. First, a Black-headed gull appeared most annoyed with a Carrion Crow and mobbed it repeatedly, dive-bombing on it when the crow tried to stop on an aerial. The crow did not vocalise and deftly avoided the gull attacks. Later, I heard the rattling call of a crow and watched a chase between two crows, one of them calling with the call I usually associate to mobbing a raptor. Crows, it appears, can use this vocalisation to fend off conspecifics.
 Finally, I watched a Crow it an amazing display: its head feathers raised, bill pointing down, looking really at its best. After taking a few photos, I realised it's partner was walking nearby using the same posture. Today I learned about this display in 'The Crows' by Franklin Coombs. It is called the 'Bristle head' display. It is a territory-owner display, used in territory boundaries to signal their occupancy, and also aimed at intruders within the territory. Both members of the pair display while they walk about. There is no vocalisation. Territory intrusions mostly occur during the spring, but there is also a peak in October-November.
 I can only presume that this pair of crows are a pair ot territory owning breeders. They do look in great shape!

This is a still from a video, which shows both members of the pair with their 'bristle heads'.

A side view of the displaying crow. 

This photo is a bit overexposed, but it shows the details and metallic iridescence of the crow really well.

Opportunistic crows

 Corvids are omnivorous birds and display a very flexible and opportunistic feeding behaviour: they will exploit coastal resources when near beaches, will actively search for nests in the spring looking for eggs or chicks, will take advantage of human scraps, feed on roadkill or other carrion, or look for worms and other invertebrates on fields and woodland floor. They show a remarkable inventiveness regarding looking for food, leading in some species to an understanding of the manufacture and use of tools. Rooks are able to add stones to a beaker with a little water where food is floating until the water level rises enough for them to reach the food. Caledonian Crows craft tools - including hooks - from leaves and twigs and use then to fish out grubs from trunks. Other species, like Jays, have extraordinarily precise spatial memory, which allows them to cache food surplus for use later.
  In general, corvids are dexterous birds. They have excellent foot-beak coordination and often use their feet when feeding, to hold down a piece of food so that they can pick bits with their beaks, as the Carrion Crow above. In experimental set ups, Ravens are able to reach meat tied to a a long string by alternatively pulling with their beaks and stepping on the loops of the string with their foot.
Their catholic food preferences and ingenuity have undoubtedly allowed them to adapt to living near people, and some crows species, like the Carrion Crow are common in towns, cities and agricultural land.

 Carrion Crows and a Greater Black-Backed gull feeding on a dead seal pup and afterbirths on a Grey Seal colony

I saw this Carrion Crow flying with a Woodpigeon's egg on its beak. It landed and quickly opened it up and ate the contents 

The predated egg shell

Carrion crow searching for a nest while a blackbird gave alarm calls nearby

Crow feeding on a chick 

Rooks and Carrion Crow feeding on a beach

A short video of a pair of Carrion Crows feeding on the leaf litter

More information
Bird, C., & Emery, N. (2009). Rooks Use Stones to Raise the Water Level to Reach a Floating Worm Current Biology, 19 (16), 1410-1414 DOI: 10.1016/j.cub.2009.07.033

Hunt, G., & Gray, R. (2004). The crafting of hook tools by wild New Caledonian crows Proceedings of the Royal Society B: Biological Sciences, 271 (Suppl_3) DOI: 10.1098/rsbl.2003.0085

Heinrich, B., & Bugnyar, T. (2005). Testing Problem Solving in Ravens: String-Pulling to Reach Food Ethology, 111 (10), 962-976 DOI: 10.1111/j.1439-0310.2005.01133.x