Last week, while out dog-walking, I came across kestrel perching on a hedge and then swooping down to find small prey on a patch of grass.

More than anything else, I felt very aware of our proximity to this regular visitor, much closer than the perimeter at which a wild bird would normally take flight. Unperturbed by our presence, she used her position to survey the nearby patch of field, frequently swooping down to pick up a morsel and then duly flying back to the lookout position on the hedge line.

Occasionally, the bird would run about the ground, rather comically – her light-coloured, feathery upper legs emphasised by a brisk, clownish running style.

I’ve lived around kestrels (Falco tinnunculus) for nearly 40 years and I’m still in awe of their legendary ability to hover; their uncanny ability to ride the wind such that, however their body undulates, their head remains absolutely fixed to its precise coordinate. Of course, I’ve seen them perching and surveying before – usually atop telegraph poles or street lights – and it’s little surprise that from there, they will swoop down to intercept any prey they espy. In all that time, I’d never seen a kestrel so close to the ground, for so long, swooping so repetitively and actually running around on the grass.

I was intrigued by the hunting method she employed and I was a little concerned that this individual was either too hungry to hover or possibly even physically incapable. It’s November and it would be hardly surprising if food is less abundant. Worms and insects often have to make up for a shortfall in protein – but was there a reason why this kestrel, usually a master of the skies, should be reduced to hanging around the free buffet?

When I got home, I did a few google searches and started to read up on kestrel feeding habits. In particular, I found this: The Hunting Behaviour of Some Farmland Kestrels by M. Shrubb (1982).

In it, Table 1 suggests that, over the winter months, farmland kestrels are almost twice as likely to ‘still-feed’ (from a perched position) than by hovering – with the proportions reversed over the summer months. It suggests (not unreasonably) that the need to conserve energy in harsher conditions is the main reason behind the change in strategy.

Hovering is, as you might assume, an energy-consuming activity, requiring kestrels to feed on upto eight small rodents a day, to survive. As long as food is abundant, their expert ability to hunt this way will sustain them. When it isn’t, they still-feed. Their legendary eyesight means that they can spot an insect from fifty yards.

Thanks to simply observing nature and hunting myself on the internet, I’ve learned something quite fundamental about a bird with which I considered myself to be quite familiar.

The real lesson is that we should never stop learning.