Everyone is familiar with migratory birds flying into Britain, but did you know that moths migrate here too? Surprisingly for such flimsy looking insects, some of the moths commonly see in our gardens may have travelled from places as far away as North Africa!
Most of the moths found in Britain are resident here, passing through all the stages of their life-cycle within the UK, but others come to our shores as migrants from continental Europe or further afield. Some of the moths that arrive from other countries are species that already live here, so they are just adding to the resident population. However, most of the migrants that come to Britain and Ireland are species that do not live here permanently. They may breed here after their arrival, but their offspring do not survive our winter.
One spectacular migrant commonly seen every year is the wonderful Humming-bird Hawk-moth. It really does look like a little hummingbird as it hovers at flowers to feed on nectar! Amazingly, it comes to us all the way from the Mediterranean and even North Africa. It arrives at any time from April to December, but numbers usually peak in August and September. Like all migrants, more are seen in hotter summers and when there are southerly winds. Some do breed here and it is possible that a few of the offspring now survive our milder winters.
Another very common migrant is the Silver Y, recognisable by the clear metallic Y shape on each forewing. This clever little moth has been tracked flying vertically upwards to hitch a lift on the faster high altitude winds! It is much smaller than the Humming-bird Hawk-moth, but newly arrived moths often behave in a similar way, hovering at flowers in the daytime to refuel after their journey. The Silver Y breeds here in large numbers and the British-born offspring then add to the population, which can be very high by the end of the summer, but none (or very few) of these moths survive the winter.
Other notable migrants which are seen every year, although in small numbers, are the Death's-head Hawk-moth and the Convolvulus Hawk-moth, both with wing spans of about 12cm (five inches). Some species, like the Crimson Specked, only occur in some years but may sometimes arrive in large numbers. Perhaps the most exotic looking migrant is the Oleander Hawk-moth, which only arrives in some years and even then in very low numbers.