Tuesday, 25 July 2006

Watch out for hummingbirds

Over the last few weeks I have received a number of telephone calls from excited householders, each describing how a tiny hummingbird has been visiting their garden flowers. These “hummingbirds” are not birds at all but a species of migrant moth that arrives in varying numbers each summer from continental Europe. Known as the hummingbird hawkmoth, after its habit of hovering to feed at the tubular flowers of a number of wild and cultivated species, it is easy to see why people think that it is a bird. The rather squat body is greyish-brown in colour, with darker markings at the rear and a neat row of cotton bud white spots along its flanks. The orange-brown wings are visible close to the body, but become a blur towards their tips; such is the rapidity of the wing beats. As such, the hummingbird hawkmoth is unlikely to be confused with any other moth, although the two – now rather scarce – bee hawkmoths share a passing resemblance.

It is during August and September that the largest numbers of hummingbird hawkmoths are reported from across the country. Although they can appear in any month, most reports fall between April and December. A small number of records from late in the winter presumably refer to individuals that have attempted to hibernate in houses or outbuildings, a behaviour that is well-known within the main part of their range. The arrival of these moths is usually associated with warm weather pushing up from the south. This weather also brings with it many other invertebrate migrants, including familiar species like the painted lady butterfly, silver-‘y’ moth and several species of hoverfly. In certain parts of the eastern Mediterranean, the hummingbird hawkmoth is considered a bringer of good tidings, a belief that did not go unnoticed by one writer who reported that a small swarm of these moths was seen flying low over the water from France to England on D-Day, 1944.

This day-flying moth tends to be on the wing on warm and sunny days. However, if it is exceptionally hot, then the moth will become torpid, not emerging until late in the afternoon once the temperature has dropped.  Individuals have been shown to return to the same flowerbeds over a period of several days, suggesting that they possess the ability to map the location of good nectar sources. Plants like phlox, buddleia, petunia and red valerian are favoured, although the female moths will also visit various bedstraws in order to deposit their eggs. So do keep an eye out for this delightful little moth over the coming weeks and do let me know if you have one visiting your garden this summer.

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