Swallows, Ravens & Buzzards

Having just returned from my holiday in North Wales (crap weather but some good tweeters), I wonder if anyone can answer the following couple of questions ?

Just by the rear of the cottage we stayed in was a field in which the local farmer grazed his cattle. The field was quite poor having been overgrazed and it being on damp poorly drained soil did not help either. Right next to the fence that divided the field from the garden of the cottage were some patches of Rush (Juncus sp). I noticed that the local Swallows had developed a method of feeding directly from these patches of Juncus. They would fly into the wind and hover over the Juncus until they spotted (or perhaps scared) an insect into moving and then they would fly down and pick the insect off the plant. We watched them many times doing this in bad weather when no insects were flying. The second feeding habit we noticed was that as soon as the cows were let back into the field after being milked the Swallows would appear and fly low down between the grazing cattle picking up any insects that the cattle had disturbed. I have stayed in this cottage twice before and have never noticed either method feeding before, this year had appalling weather and I assume the Swallows found this the only way of obtaining food at times in bad weather ? Are both these methods usually seen in feeding Swallows in the UK ?

Second question: Having become very interested in Ravens after spending many hours watching them on the Llyen peninsular this summer I wish to purchase a book about them. I know various titles are out there but does anyone have a recommended title they would suggest I buy ?

Third question: having watched lots of Buzzards and Ravens this summer in close proximity, why do Ravens not chase or harass Buzzards flying near their patch ? Most other corvids seem to chase any bird of prey they see but Ravens & Buzzards seem to co-exist quite happily.