Wednesday, 22 August 2018

Migratory Monarch Butterfly Blown Off Course!

Islay has been gifted with a lucky sighting this weekend by Jane Taylor, who spotted this Monarch butterfly (Danaus plexippus) near Bridgend! This exquisite pollinator is a migrant, most likely arriving from either North America, Western North America, Southern Canada, Florida or Mexico and will travel thousands of miles on migration. When migrating south along the east coast of the USA, they can get picked up by westerly winds and blown across the Atlantic, just as happens with several species of birds.

This butterfly is unmistakable by its size compared with any British butterfly, with a wingspan of 3.5–4 inches (8.9–10.2 cm) and by its orange upper-wings, with multiple black veins and margins, being narrower and lighter in the males. There are a series of white spots near the wing tips and wing borders. It can also have orange spots at the tips of the forewings. The underside is similar but with a yellow-brown colour on the forewings and hindwings instead of orange.The white spots also appear to be larger in size. The Monarch will alter its aesthetic before and after migration, starting off as a brighter red with longer and narrower wings, then fading and shortening towards the later migration stage. The male is often slightly larger than the female and will have either a black patch or dot on the androconial scales of the hindwings. The females have thicker wings than the males to compensate for their smaller body size and to help reduce energy loss during flight.

If the Monarch butterfly is ever seen within the UK, like Jane has seen near Bridgend, they are usually accidental migrants, not turning up every year, and so are a treat to spot! This species is found on agricultural land, pasture land, prairies, gardens, woodlands and roadsides. Monarchs use mountain forests in Mexico to migrate to for their winter habitat. The main threat to them lies in the forest also being a natural asset and resource for human use. Climate change will also affect their migration flight such as wintering grounds becoming colder and summer breeding grounds becoming warmer, thus shifting the migratory pattern.

The Monarch butterfly is unfortunately decreasing in population due to the above threats and the use of herbicides and pesticides on land. The U.S. Fish and Wildlife Service is currently undergoing research to decide by 2019, if the species should be protected under the Endangered Species Act. In Ontario, Canada, the species is listed under Species of Special Concern; however, in 2016 it was proposed to move the species into the endangered list for Canada, due to the drop in population.

There are, however, efforts being made to conserve this species and its habitat. The restoration of appropriate habitat in woodland glades for increased herbaceous ground cover for host and nectar plants, providing monarch-friendly seed mixes such as milkweed and controlling the timing of habitat management such as mowing to reduce compromising the species. These are only a few efforts among many more strategies. Fingers crossed for their conservation status change and an increase in population trend!

Although not common to find in the UK, keep your eyes pealed for any unfortunate Monarchs blown off the migratory path! In years when one is seen, it is usual for several others to turn up in different places.

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