It is largely due to the constant rain we had for almost a year until the early summer. Many caterpillar larvae failed, food for many birds, blue tit nesting largely failed with nonfood for the young. Butterfly’s the same the rain had a massive effect, they have shown a bit of late but nothing like the numbers there should be.
but blackbirds and robins that feed on worms etc have thrived because of the wet damp weather.
when hiking, the peat bogs have not dried out this year, still very boggy and still water running off the moors and hills, can see big problem with floods if we have an autumn, winter and spring like the last couple.