Desperate feeding behaviour

We put fat balls out and mainly sparrows, starlings and occasionally blue & great tits. In the last two weeks we have observed an almost desperation in the feeding. Usually the fat balls last a couple of days but they're gone now in hours and we've seen a male blackbird feeding on them this morning several times. There's a desperation about the way they're feeding as though they're expecting to not feed for a while or bad weather. I've been a birdwatcher for years and never seen this behaviour. I'm also a gardener and have noticed a drop in caterpillars and greenfly/black fly. Is this a climate change adaption? Has anyone else seen this behaviour?