Butterflies

The 2006 season was notable for three new species being recorded in the area - an unprecedented happening. The Brown Argus was expected to move in, but sightings of a White Admiral and of a Silver-washed Fritillary astonished the observers, although now we know these two butterflies were recorded in other unexpected places in 2006.

Butterflies were seen from February to December. Over 60 people sent in records, over 5000 in total, more than ever. This was unexpected as the season started badly. The period to the end of April was poor, and numbers were no more than average by the end of June. However the second half of the year was particularly warm, and butterflies were seen on all but one day of 'summer' (July-September). October was one of the best ever recorded, and November and December were exceptional.

Our indifferent spring meant that some early species such as Brimstone and Orange Tip did relatively poorly, and also that the first generation of the two-generation Common Blues were few in number. However the single-generation Common Blues in Upper Wharfedale showed few ill effects.

The nymphalids generally had excellent years, particularly Red Admiral, the most common butterfly for the first time. Small Tortoiseshell remained less common then Peacock, but Comma improved, with a number of new sites. Painted Lady recovered from the 2005 slump.

Of the localised residents, Dark Green Fritillary and White-letter Hairstreak did well, and Holly Blue continued to improve. Purple Hairstreak and Northern Brown Argus were satisfactory, with good numbers of NBA being seen on two occasions. There was another unconfirmed sighting of Dingy Skipper - really a specimen or a photograph is needed before the presence of this uncommon butterfly can be accepted.

The browns all did well, including the nationally threatened Wall. A Gatekeeper sighting in Upper Wharfedale was noteworthy, suggesting a further expansion of range.

Clouded Yellow was seen in more places than it was in 2005, and there was one sighting of the Camberwell Beauty, a very uncommon migrant.

The General Picture

The varied scenery of Wharfedale ensures we have a reasonable range of native species, although with few rarities save the Northern Brown Argus, a small brown butterfly to be seen in June, well established in the upper dale.

Wharfedale hosts all of the commoner migrant species form time to time, nearly every year the Red Admiral and the Painted Lady , sometimes the Clouded Yellow, and very occasionally the Camberwell Beauty.

Study of over 50 years butterfly records compiled by the Wharfedale Naturalists Society reveals a substantial increase rather than decrease in the number of species seen, perhaps due to the effects of global warming, certainly due to species such as the Comma moving North. The incomers seem to be thriving, and a steady increase in the number of colonies is typical. For some long-term residents however, such as the Common Blue, habitat loss and degradation has meant the extinction of local colonies and there is concern over the increasing isolation of the remainder.

Estimation of the size of colonies year on year is difficult and only qualitative information may be derived from our records. An earlier review looking back over 23 years by our former president Freda Draper showed two species now common, Orange Tip (prior to 1970) and Peacock, to have been markedly scarce. Brimstone and Holly Blue were then very scarce but are now seen yearly. Turning to the 2000-2003 WNS records, counts in the hundreds of the incomers Small Skipper, Gatekeeper and Ringlet have been obtained. In 2003 confirmation that the Speckled Wood has bred in Wharfedale was obtained for the first time, and by 2006 it has become a common sight in our dales.

Year on year more sites are being found for the three elusive Hairstreaks that are resident here, Green, Purple and White-letter. The spectacular Dark Green Fritillary, long thought to have been lost from the area, is now seen each year and seems to be breeding on a few sites in Upper Wharfedale.

However after looking at the 1979 survey it appears that several species may now be present in smaller numbers. These include Wall and Small Heath. Then they were designated ‘common’ or ‘frequent’. In 2006 neither of them appeared in the 15 most seen butterflies in our dales.

Since the use of transects - walks to a set pattern to estimate numbers more accurately - is well established, three have been developed in Wharfedale. Two monitor important Northern Brown Argus sites near Grassington and are run by Butterfly Conservation. The third monitors the changes taking place in a reclaimed brown-field site in Burley-in-Wharfedale and involves the Society and Butterfly Conservation.


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