There is a Peregrine site in London that I visit pretty regular, obviously more so in the breeding season, the pair are in a relatively unique habitat, there are so many feral pigeons in and on the main structure, the pair have little need to hunt further afield.
At my last count, 650 left the roost starting at dawn, departing over a period of an hour with the main surge happening in the first 30 minutes, at the moment it is the Tiercel who is doing the hunting from the structure, it is truly spectacular to observe.
With this many ferals inside, year round breeding takes place, even in mid winter, recent events have shown that the Peregrines have not only adjusted, learnt and taken advantage of another food source, but have also exploited it.
In 2010 I observed the Tiercel fly into the inside of the structure and he then landed on a girder, I did not think at the time, that his positioning was deliberate and intentional, he had already fed and was going to lay up. By coincidence there just happened to be a feral pigeon nest about 2 metres away at the junction of a girder, inside were 2 ¾ grown juveniles. I expected him to lay up as his crop was full, instead he reacted to the presence of the juvenile ferals. He quite simply waddled over to the nest and grabbed one, it was quickly dispatched and then taken to a stash point, obviously for later feeding or prey for the Falcon.
At the time I thought that it was a one off but recently I have seen him flying round the structure, sometimes low down and landing near likely pigeon nest sites, ie – holes, niches and ledges, he was searching, in short, it looks as if he has learnt to exploit it. Carrion Crows, even Magpies I know have this level of intelligence but never suspected Peregrines could learn and adjust there hunting behavior to take advantage of an easy food source.
Recently after observing a nest relief very early a.m, I watched the Falcon emerge and then for 10 minutes she preened, at the end of this she started to head bob as they do, intently looking around, behavior was obviously looking to hunt. I presumed there was no stashed prey available so suspected that she would go up and hunt. As I watched her she took off and disappeared round a corner, and then emerged 2 minutes later with a ½ grown feral pigeon juvenile, she then landed on a wall. The prey was intact and was not already plucked and half eaten.
This made me think, has she learnt from the Tiercel, or vice versa, the area where she retrieved the prey was not a known stashing point of the Tiercels, they have there points which they use regularly. In short, I do not think she retrieved stashed prey so it is possible that she has adapted to an easier food source also.
Certainly very surprising and I cannot recall hearing of this before, as I have said before, no 2 pairs behave the same and they can be totally unpredictable. New behaviour is coming to light all the time in urban pairings, a few years back, who would have thought that they regularly hunt at night to exploit a food source?