First Grizzled Skippers

[Perseus]

Noted comments by Perseus re cattle grazing - all I can do is report what works for us!

People will see that views on the efficacy of grazing with cattle obviously vary. It is of concern to me that newcomers to conservation might be feeling a bit confused! I am always willing to discuss what we do by way of winter cattle grazing and the value of it on our Hampshire reserves. I can be contacted via the Hampshire Branch web site.
Lynn Fomison

North of Shoreham, we have a sheep grazed chalk downland site, turned over to conservation cattle grazing for half a century and Grizzled Skippers have not been recorded.

On a five acre chalk downland site that is rabbit grazed we have up to 25 Grizzled Skippers in an acre.

I have recently observed Silverweed growing out of a cow pat. As I suspected, I think cattle eat most of the food plants of the Grizzled Skipper but the seeds may pass right through them. In the short term you may find an increase or a surviving number of Grizzled Skippers. It really depends on the density of cattle. One mistake and overgrazing and you may find a wipe-out. I would definitely not advise cattle grazing on small sites and be wary of it on larger sites, without a previous history of it.

However, Grizzled Skippers in theory should survive and may even increase. Not so the blue butterflies though.

[Lynn]

Re Cattle grazing

Perseus is right to point out that cattle grazing can be disastrous.

IF it is done in the wrong way at the wrong time or is too heavy plants and butterflies will suffer. There are without doubt several species of butterfly that prefer ungrazed or lightly grazed swards and these need to be taken carefully into account.

At Magdalen Hill Down the Chalkhill and Common Blues seemed to have benefited. Until the winter of 1998 grazing was predominantly with sheep. That summer of 1998 numbers of CHB & CB on transect were 1895 and 175 respectively. By 2006 with annual grazing with cattle during the winter numbers had increased to 3236 and 394.

Whilst CHB’s have shown a more or less steady upward trend from the first transect figure of 437 in 1990 Common Blue numbers have varied quite a lot between a minimum of 262 in 1996 and a maximum of 424 in 2005.

Of course figures for both species took a large dip in the awful summer of 2007!

[Perseus]

I have Chalkhill Blues numbers for Mill Hill, one acre counts not cumulative for comparison purposes as the monitoring was the same and numbers vary from year to year.

I cannot compare cumulatative unless I know how the numbers were added up.

Chalkhill Blues had their best year recently in 2003. Their worst year was 2007. There are huge annual fluctuations this century. Generally, there seems to be a decline since 2003, which is not todo with management.

[Piers]

Apparently, samples of mature larvae taken and reared through in recent years from sites around the south of England reveal that Chalkhill Blue larvae are being heavily parasitised. I am not yet aware of what specie of hymenoptera is responsible, but watch this space for more details...

Felix.

[Perseus]

Apparently, samples of mature larvae taken and reared through in recent years from sites around the south of England reveal that Chalkhill Blue larvae are being heavily parasitised. I am not yet aware of what specie of hymenoptera is responsible, but watch this space for more details...

Felix.

Hello Felix,

I have created a thread for this subject at:

http://ukbutterflies.co.uk/phpBB2/viewt ... 733#p10733

This would be very interesting. There was no obvious explanation for the dramatic fall in numbers. 2003 was a good year for Chalkhill Blues. The numbers reduction was in subsequent years. However, 2003 may still not have been maximum numbers. Mill Hill recorded about 800 per acre, total in 20 minutes, in 2003. Numbers fell to 200 an acre in 2007.

In Germany, numbers have been more than this in the past. However, I would expect in England that 800 per acre was near the maximum nowadays.

The numbers of Common Blues have also fallen.

[NickB]

Strange to find thread on Chalkhills but there you go...
Interesting to see that the numbers of Chalkhill Blues seems to have dropped dramtically for previous peaks in good years from transect counts around the country. I walk the Fleam Dyke nr Cambridge where a few tens of Chalkhill Blues have been seen in the previous 2 years but have almost disappeared from counts in 2007. The nearby Devils Dyke, a generally thriving population, was also down on previous years.
I had assumed that it was just the dreadful cold spring and early summer that had accounted for their fall - a link to parasitic activity is interesting to note Particularly whether this is a normal level for this type of population or coincides with the fluctuations we observe would be worthy of further investigation.

[Jack Harrison]

Foulden Common Norfolk, 3rd May, three Grizzlies seen including pair in cop in NE corner of the reserve courtesy help from Adrian Riley who saw the first one.

I hasten to add that I HAD been looking in the right place but simply hadn't seen any until Adrian turned up. Then I subsequently found the pair by pure fluke.

Jack