It was an aerial battle by Tillicoultry; a sparrowhawk closing rapidly upon the tail of a woodpigeon, as they both weaved over a field by the River Devon in a desperate tussle.

For a second, it looked like this female sparrowhawk had the upper hand and was about to pluck the woodpigeon out of the air, but the pursuit had been going on for too long, and the hawk tired and abandoned the chase. The woodpigeon was lucky, it had come within seconds of death.

It was proving an enjoyable walk, starting on the Devon Way at Tillicoultry, then cutting down to a field by the Devon, and crossing over the river by the old red bridge. A stunning maple nearby, its leaves turning scarlet, was most eye-catching. There were still some late flowers in bloom, including knapweed, as well as a tenacious monkey-flower. The most ubiquitous flower, however, was Himalayan balsam.

Bees and other pollinators find their flowers irresistible, and because of their depth, buzzing insects disappear completely inside, before emerging with their bodies coated in pale-powdered pollen. Indeed, when I first came upon bees feeding on Himalayan balsam many years ago, I thought I had discovered an unusual type of insect such was their ghostly coloration.

Himalayan balsam was introduced into gardens in the mid-1800s and soon escaped to colonise the countryside. It is particularly abundant along river courses because their exploding seed capsules (each plant can carry 800 or so seeds) can fling seeds a reasonable distance, which are then carried downstream in the water flow to colonise new areas.

Unfortunately, their tall invasive growth shades out native plants and the die-back of extensive stands over winter can leave riverbanks bare and exposed to erosion, which can lead to siltation of trout and salmon spawning grounds. In addition, while pollinators adore balsam, it creates a further problem in that their brassy blooms detrimentally lure nectar-seeking insects away from native flowers, upsetting the natural equilibrium.

In my new book charting a wildlife year on the River Devon, ‘If Rivers Could Sing’ (www.tippermuirbooks.co.uk), I highlighted of my anguish about the impact non-native species – such as Himalayan balsam and American mink – are having on the river.

I wrote: “As I stood on this river bankside, engulfed by the towering balsam, I could not help but feel fearful for the future of the river with such invasive threats; a ticking time-bomb of our own making, and one with the potential to cause great turmoil.”