Swallows. That and the fact wild animal populations swing widely to extremes sometimes. I have been paying close attention to swallows in recent few years and t

Swallows. That and the fact wild animal populations swing widely to extremes sometimes. I have been paying close attention to swallows in recent few years and the numbers of them as well as the bugs they eat are skyrocketing in my area. When I moved to the area it was essentially empty field a couple hundred meters from anything. The farmer owning it converted a bit in the middle into residential building plots, a road was built, electricity hooked up etc. Most of the people that buy those plots do it as an investment so they don't do anything to them. I have observed over last 10 years how nature took over those plots. Hay that grows and is not mowed accumulates and besides being a fire hazard provides an environment for birds to nest in. Wild trees have grown to the point one wouldn't recognise it was a field a decade ago. I regularly have hedgehogs, hares, deer, lots of all kinds of birds (including a golden Eagle once). Every year there are huge numbers of swallows come in the spring. As of last 2 years there have been moose and even wild wolves. Yes, wolves, in a middle of Europe in 2022. I have photos of their dinner I once found in addition to other info. People don't realise nature is very resilient and it will move into every area that is not polluted with toxins. Even with toxins or radiation (like the famous Chernobyl exclusion zone) nature evolves to deal with it.