Catch the coastal migration as the butterflies head south

Such coastal migration is quite fascinating to watch. It invariably happens when the weather is sunny with light west to south-west winds. As the wind drops over the promenade, cliff or sand-dune, it leaves a ‘pipe’ of calm air along which butterflies and other insects such as dragonflies, hoverflies and bees can move southward without being buffeted around too much. I imagine it’s a bit like the space under a waterfall.

Sometimes hundreds and occasionally thousands of insects pass within this pipe each hour when the conditions are right. Of course, a ‘pipe’ idea is somewhat idealistic as the coastline is far from straight, and the sheltered space is broken from time to time. Individuals may also fly out of the stream, take a break, and look for a nectar meal.

Sometimes butterflies appear to be able to skim like surfers on top of the falling wind current and use it to glide long distances, enabling them to conserve precious energy on a journey which might take them as far as the Mediterranean.

Butterfly migration like this occurs most years between mid-August and mid-October whenever conditions are just right. Whilst the majority of our small tortoiseshells stay close to the area in which they were born and then go into hibernation until next spring, a proportion head south, together with the majority of our red admirals.

However, brimstones, peacocks and commas tend to hibernate as butterflies rather than risk migrating to warmer climes. Other species of butterfly spend winter as eggs, caterpillars, or chrysalises. This autumnal southward movement is concentrated on the coast, but it actually occurs all over the county.

One reader asked about what plants were attracting so many late butterflies into my garden. Well, mainly buddleia. I have nine shrubs, of which two are miniatures in pots. Buddleia thrives best if you cut it back to a foot or two each year any time between November and early June.

A November cut usually flowers in July, a June one in September/October, and the rest in between. I cut at roughly monthly intervals to ensure buddleia flowers are available for a longer season.

The next most popular autumn flower is the ice plant. A patch of just two or three plants has been attracting 20 or more butterflies at a time, including holly blues. After that I think the more colour you have in your garden the better. Several butterflies have even visited our hanging baskets of geraniums including a fine brimstone.

I dug up part of my lawn last winter to plant two beds of meadow flowers and grasses. They were at their best before any butterflies appeared this year, but were a great boon for the bees and hoverflies.

Finally, don’t forget to leave at least a few dandelions, especially in spring. They provide an important nectar source for small tortoiseshells and peacocks.

Contact www.yorkshirebutterflies.org.uk