I walked along a stretch of the river and a stretch of canal today.

Nothing unusual about that. What was unusual for the season is that I walked there in daylight. More usually I pass that way on the way to one of our local supermarkets, and I generally go to those quite late when they’re less busy.

Being a bright, sunny Sunday there were lots of people. And of course there were lots of ducks. Some of the people feed the ducks: I saw this on the first stretch of river. Shortly after I crossed to the canal, where there were fewer people but more ducks, and as I arrived a number of ducks hastened (indeed, flew) towards me, landing alongside me. Evidently they’re so used to being fed by humans that they came to investigate one as soon as I appeared along their canal.

It set me wondering to what extent the duck population might be reliant on human food, particularly in the winter months. Are we sustaining a higher population than could exist naturally? If so, what other wildlife are they displacing: is this indeed affecting biodiversity?

I imagine the same kind of consideration applies to other efforts by humans to feed wildlife. The bird feeder in many a garden may be welcome to birds – not to mention enterprising rodents and perhaps others – that use it, and perhaps also their predators both domestic and wild, but what else are they then displacing?

It may be a drop in the ocean of human influence on the biosphere, but today it was both local and visible!