Sunday, 25 July 2010

Sunday 25th.July 2010

Wall to wall cloud welcomed the morning of the Field Trip to High Elms , with Silver Washed Fritillaries being the main target . I left a bit early for a look at the Ash tree on the Common , but only got 4/5 sightings high up , no specimens coming down onto the lower vegetation . Leaving the car park , a brown flash by the barrier had me stopping and photographing a juvenile Robin , that was happy to sit and pose . This turned out to be the only shot I took today .
The weather was no better at High Elms , and the 19 species seen yesterday , in much better conditions , seemed like a dream . I was relieved when we made our first stop at a pathside Buddleia bush to find SWF and White and Red Admiral nectaring on the flowers . Burnt Gorse was bathed in cloud , but we managed to find the odd butterfly species and topped up with a few day flying moths . Right down the far end , a single Marbled White , Small Copper and Large Skipper raised the hopes of better to come . We actually got some sunshine , which increased the activity , so we headed for the first of the glades where the SWF lay their eggs . The SWF sightings increased , including females , but no egg laying was observed although one courting pair was seen . We did search for , and find , eggs that had been layed on a Scots Pine . More SWF sightings on the way to , and on the Orchid Bank , then one of the group spotted a small butterfly on a Hazel bush , and White-lettered Hairstreak was added to the list . This shot of the species was taken a couple of weeks ago . A second was found on the Orchid Bank itself , to be followed by a third after lunch in the Conservation Field , the advantage of many pairs of eyes .
The look around the Conservation Field did not produce any new species , but several fresh Brown Argus and another Marbled White were recorded .
By the end of the visit , the same 19 species of Butterfly that I recorded yesterday had been found , plus WLH , Holly Blue and the Marbled Whites , bringing the total count to 22 species , with a probable 23rd. , when Hairstreak sized specimens were seen in silhouette , high in an Ash tree , probably Purple .

4 comments:

Warren Baker said...

Greenie,

Ive learnt from you that Butterfly eggs overwinter, then hatch out the next year. However do you think the eggs could go through a second or even third winter?

This would explain to me why some years there are lots of butterflies about, when in the previous year there were hardly any butterflies about to lay any eggs

Greenie said...

Warren ,
SOME butterfly eggs overwinter as such , like the Purple Hairstreak .
I do not think , nor have I read that eggs could or would , go through 2/3 winters .
I have mentioned before that egg to adult ratio is very low , approx. 5 adults to every 100 eggs laid , in a bad year even lower , in a good year higher . To keep a constant population each mating pair need 2 of their offspring to make it to adulthood .
Depending on how a species overwinters - egg , caterpillar , chrysalis or adult , a mild Winter will mean more predators about , looking for food , whereas a cold Winter keeps the predators in hibernation too .
Heavy Winter rain causing flooding can wipe out a colony of a species that is in caterpillar or chrysalis form in or near the ground .
Also , cold , wet weather whilst a species is on the wing can cause breeding failure , as we know butterflies are active during warm , sunny periods .
If Ichneumon Flies have a good breeding season , Holly Blues are likely to have trouble as the Fly lays it's eggs in the HB caterpillars , and the hatching grub literally eats it's way out .
All these things , and many others all go determine how many Butterflies are about for us to enjoy in any given year .
Interestingly , your 2/3 Winter theory can be true of Dragonflies/Damselflies , some of whom can remain as larvae in the water if conditions are bad .
Hope this makes some kind of sense .

Ken Browne. said...

Hi Greenie.
Another good day's count of Butterflies. What I wouldn't give to see 19 species ina day. Well done.

Warren Baker said...

All makes sense to me Greenie :-)

I just wondered how I get from very few Butterflies one year, hence few eggs for the next year, to a big population the next year, out of those few eggs !