Notable instances of pigeon intelligence I have witnessed:
A baby pigeon was nursed by a kind family who went on a two week holiday. When the family came back from the holiday the pigeon remembered who they were and followed them around whilst cooing cheerfully
A pigeon that flew into a window in South East London. Once it recovered from its fractured skull it appeared to learn from its mistakes as it was never observed to fly into a window again
Pigeons in Clissolds Park recognising the people that regularly come to feed them and flocking around them every time they come to the park
A child who fed a pigeon on a regular basis, the pigeon witnessed the child being bullied and swooped in and pecked the bully on the back of the head until the bullying stopped

More interesting stuff,
Best yet,Carnivorous tendencies
There has been an increase in the number of reports of pigeons pecking each other over the last few years. Our current hypothesis is that this may be related to pigeons getting used to eating fried chicken, it is possible that this may have given them a taste for bird and that they are starting to suspect that they themselves are birds. It is thought that if they make the connection, that this may lead to chaos and the eventual extinction of the pigeon.
Stealing food, raiding females, chasing for fun, mating whenever possible etcAn average day for a pigeon
In order to get a good grasp of what pigeons do on an average day I engaged in observational research with behavioural coding. There were a number of methodological difficulties which had to be overcome: the main issue being that pigeons do not like being followed, they have a tendency to run away and if they get spooked they can also fly away. In order to overcome this issue the volunteers dressed up as trees and stood very still, this was found to be suitably effective and also had the added benefit that some tourists thoughts that we were 'living statues' and took photos of us and left piles of coins at our feet.
The experiment revealed that pigeons spend over a third of every day sleeping. The next most common behaviours involve eating food (or at least pecking the floor - it's not always possible to tell if there is anything there). The third most common activity pigeons took part in was playing cops and robbers (chasing or being chased), we hypothesise that there are several reasons for this behaviour:
Mating - male pigeons like to display their virility by charging around on a testosterone fuelled mission in a bid to impress their female counterparts.
Fighting - squadron leaders lead their troops on daring raids to steal food and female pigeons from rival gangs
Playing - sometimes pigeons get bored and chase each other for fun. This may be inspired by the myriad car chases in recent Hollywood films. This behaviour is thought to be linked to the increase in outdoor screening of films that has been observed in London over the last couple of years.
