Irish butterfly populations are showing signs of a decline
While on a walk down a country lane on one of the dry, warm, sunny and calm days that marked the Easter weekend, it was nice to see several species of butterflies on the wing in the space of a kilometre or two.
The Peacocks were particularly noticeable and are arguably the most colourful member of the 30 or so insects that comprise Ireland's butterfly fauna. With a global range that extends from Ireland to Japan, these common and widespread butterflies hibernate as adults and emerge of the first warm days of late spring heralding the changing of season. Their striking colours and their large eyespots are indeed spectacular.
Named after their eyespots reminiscent of those on the display feathers on the huge tails of the peacock bird, the purpose of the markings is a subject of debate. One interpretation of the eyespots on butterflies is that the insects may flash their wings when threatened by a predator to alarm or deceive it or to draw its attention away from the more vulnerable body parts.
Obviously, the purpose of eyespots on the display feathers on the extravagant tails of male Indian peafowl are unlikely to play a role in deceiving any potential predator of these turkey-sized birds. It is much more likely and is generally accepted that they are display aids in communication and courtship among other members of the same species.
With so many species under threat and with many wildlife populations in steep decline, it is nice to know that the Peacock butterfly is bucking the trend; its numbers are increasing, and its range is expanding.
The Irish Butterfly Monitoring Scheme, organised by Tomás Murray at the Waterford-based National Biodiversity Data Centre, began in 2008 so the details of the scheme are now well established. The recently-published Newsletter No 11 reveals that last year, 110 volunteers walked 115 transects and recorded more than 46,000 butterflies. Peacock and Silver-washed Fritillary showed the strongest growth in populations, whereas the Small Heath experienced the strongest decline.
The overall trend in Irish butterfly populations since 2008 shows a decline of 6% but as a consequence of the dry and warm weather experienced in 2018, overall populations of our commoner and widespread species were up by 29% last year.
Full details, together with species by species fast fact files, are in Newsletter No 11 of the Irish Butterfly Monitoring Scheme that can be accessed at http://www.biodiversityireland.ie/latest-news/.