Bird's Foot Trefoil & the Common Blue Butterfly

[Perseus]

Hello,

Plant:

Common Bird's Foot Trefoil
Lotus corniculatus


Butterflies:

Common Blue
Dingy Skipper
Green Hairstreak
Réal's Wood White
Short-tailed Blue
Silver-studded Blue
Wood White
Clouded Yellow (probably uses the continental species and breeding
in the UK is unusual)

http://www.ukbutterflies.co.uk/foodplants.php

The Bird's Foot Trefoil is an interesting plant because it supports
vast numbers of the Common Blue Butterfly, which could be over a
thousand an acre in a good year.

It can be confused with Horseshoe Vetch.

This is an abundant plant on the meadows of Lancing Ring and the
middle slopes of Mill Hill.
In these areas it forms a yellow carpet after the Horseshoe vetch. In
the Lancing Ring meadows the plants is obscured by other herbs and
grasses.

It is also common on the lower slopes of Mill Hill and carpets will
occur in lightly grazed horse pastures on the Adur Levels and will
occur on verges and rough land in large numbers.
It is not nearly so common on the conservation pastures of Anchor
Bottom (needs searching for in patches), and on Southwick Hill it
does not occur on the lightly crazed all the year round cattle
pastures hardly at all.
On the commercial cattle pastures, previously used for horse grazing
where there were carpets of Bird's foot Trefoil, these were all
eliminated when cattle were put on.

However, this is common plant and may very well return later after
cattle grazing is stopped, although if it is persistent it disappears
(one field example). It is less fussy about habitat than Horseshoe
Vetch, but it is noted that both of these yellow legumes are
diminished by human trampling.

It is mostly wiped out by ploughing up the land. In hay meadows, it
is infrequent and this may be because of spraying.

On the Shoreham downs Dingy Skipper is not correlated with Bird's
Foot Trefoil but it it seems to correlate with Horseshoe Vetch.

Summary: On the downs above Shoreham and Lancing this plant supports
abundant (thousands in good years, hundreds in poor years) Common
Blue Butterflies, but on pastures the numbers per acre are only
frequent (20 - 100). On grass verges and road banks this butterfly
can be common.

Conclusion: Meadows are better than pastures for the Common Blue
Butterfly by a very large margin.

Adur Butterfly & Large Moth List
http://www.glaucus.org.uk/Butterfly-list2007.html

Cheers

Andy Horton
glaucus@...
Adur Valley Nature Notes
http://www.glaucus.org.uk/Adur2006.html
http://www.glaucus.org.uk/Adur2007.html
Adur Valley Nature Notes: November 2007
http://www.glaucus.org.uk/Nov2007.html

Adur Valley & Downs Gallery
http://www.flickr.com/groups/adur/pool/