I made my third visit this year to Dry Sandford Pit
reserve, Cothill, on Sunday. Although the breeze could be heard in the branches of the trees overhead, it was still and very warm, at the foot of the old quarry face, and my visit turned into an excellent butterfly-watching experience. Another sign of Spring was the persistent calling of Chiffchaffs from vantage points high in the trees.
My first surprise was to spot a rather small male Orange Tip
, patrolling the length of the quarry face. I think it was the earliest date that I have seen an OT at this site. Occasionally, he paused to rest or to nectar on the Violets, which are abundant this year:
The Peacocks and Commas that I had seen on earlier visits were also present but I did not spot any Small Tortoiseshells. I took an unusual view of a Peacock
, which shows both the cryptic underside markings together with light shining through from the upperside markings.
By far the major interest during my visit was provided by male Brimstones
, which were enjoying the large area of Primroses near the entrance to the reserve.
I decided to watch these in some detail, as they flitted from flower to flower seeking nectar. The rest of this entry takes the form of a ‘photographic essay’, covering my study of their behaviour. Most of the photos were taken using the high-speed frame-rate of my Olympus E-M1 camera and I’ve provided more photographic details at the end of this entry, for those who may be interested.
These butterflies have an unusually long proboscis, which enables them to penetrate deep into the tube of the primrose flower in order to find nectar. The amazing versatility of this proboscis is illustrated in the following sequence of photos, taken as individuals approached the flowers, unfurling their probosces in flight. Please click on each group of photos to see the details more clearly.
When the butterfly lands on a flower, the proboscis is extended fully and inserted past the ‘Style’ at the mouth of the tube. A detailed description of the structure of the Primrose flower can be found on the Devon Biodiversity Action Plan
My next photo sequence shows a Brimstone visiting a pin-eyed flower, where the proboscis has to be pushed past the pinhead shaped Stigma as the butterflies reaches down deep into the flower, to find nectar:
When the proboscis is withdrawn, pollen grains from the Anthers, placed half way down the flower tube, adhere part-way down the proboscis, as shown in the following photo. From here they are readily transferred to other flowers, especially those of the ‘thrum’ variety.
I also took a close-up view of a butterfly's head, where the proboscis can be see disappearing deep into the flower:
Some of my high-speed photo sequences captured the moments when the Brimstones showed their elusive upper surfaces, as they approached flowers, as seen in the following pair of photos (click to enlarge
The economy of movement as these butterflies moved rapidly from flower to flower within a single cluster was remarkable to observe Sometimes only a single wing beat was sufficient to propel them between flowers and, even at 10 frames per second, only five frames (0.5 sec) covered the transitions between flowers, as seen in the following animation
I hope that others will enjoy these sequences, which illustrate the relationship between the butterfly and the flower, by which the pollinator receives its ‘reward’ in the form of nectar.
My final group shows the last sequence that I took, as the Butterfly disappears out of the frame.
What a great start for me to the new season Technical Information
All my photos were taken using my Olympus OM-D E-M1 camera, fitted with a Leica 100-400 mm lens.
This lens provides an angle of view equivalent to that obtained by an 800 mm lens on a 35 mm camera. It also offers a close-focus capability to within 1.3m, where it delivers almost macro capability, coupled with a long stand-off distance. This is extremely useful when photographing nervous subjects, such as Spring-time butterflies.
In order to capture the high-speed sequences shown in this post, I made use of the electronic (silent) shutter in the camera, which provides a shooting rate of 10 frames per second. I also set continuous focus-tracking (C-AF), which uses the on-sensor phase-detection system, to adjust focus to follow a fast-moving subject. When shooting in RAW mode, the buffer holds around 40 images before the shooting rate slows down.
I prefer to use RAW + JPEG mode in the camera since, although the Olympus usually provides excellent JPEG results, the RAW image can be useful for ‘difficult’ subjects, in which I include pale-coloured butterflies in bright sunlight. Most of the photos I show in this post were taken directly from the JPEG results but, in a few cases, I processed a RAW image, where there were extremes of contrast, to be controlled in post-processing.
To ensure a reasonable depth of field, I used Aperture-priority mode, setting the aperture to f/8, which still allowed a shutter speed of around 1/2,000s in bright sunlight, at ISO 640.
I was pleasantly surprised by the success rate the camera achieved, in what was for me an experimental photographic trip. After using my Olympus camera in a wide range of conditions, I have become increasingly confident in its ability to produce good results under difficult conditions, from tropical rainforest to winter birding trips.