I suppose that the reason the countryside is as rich as it is is due in part to the opportunistic side of nature. If there is a piece of open ground then rapidly plants will begin to colonise it. Poppies and other "shaken dispersal" plants shake their seed heads violently so that seeds fly in all directions - only some will take root but the ones that do you can bet your bottom dollar are the ones that land in the most advantageous places for development. Similarly, little plants like violets will seed in a crack in the paving - just the right place to keep their feet cool.
The same applies to birds - a farmer ploughing a field will notice that the sky goes from empty to full of gulls at a rate of knots - where they come from it is hard to say, but ever the opportunist - the seagull will sense there is food around. And how long does a dead rabbit lie on the roadway before a crow or two are pecking at it?
Earlier in the year in a gale, our ancient plum tree broke across its middle and half of it fell down.
The wood has already been sawn up for the stove - plum wood is lovely to burn. (I suppose you could say that was the farmer being opportunistic). This morning the farmer called me to come and look what had happened to the spot where the branch had broken away. Lo and behold - fungi had already grown in it - not just one but a veritable little town of fungi roofs. And do you see - on top of the fungi an overhanging holly bush (laden with berries this year) has dropped a berry right in the middle. It will be interesting to see if it takes root. Watch this space.