On Red Admirals and Migration

A couple of weeks ago I wrote about the fantastic Red Admiral that I am hoping will be around and about as soon as the weather warms up.  However, the reason that I was prompted to write about the butterfly was due to an interesting article that I read in the wonderfully informative British Wildlife magazine.

Whilst many nature lovers are aware of the satellite tagging that is now being done on all sorts of species, particularly the cuckoos and ospreys that have been tracked to Africa and back, you may not be aware that there are other ways to track the movement of species (particularly small, delicate ones such as butterflies).

Scientists have recently been investigating the levels of different isotopes of hydrogen found in the wings of Red Admirals across Europe.  These are taken into the body of the butterfly when, as a caterpillar it does what caterpillars do and eats.  Across Europe the normal foodstuff of a caterpillar will have different levels of these hydrogen isotopes.  Comparison of these levels with non-migratory species of butterfly then allows scientists to tell where the butterfly spent its time as a caterpillar.

The results of the work were very interesting.   Italian butterflies examined in autumn showed different isotope levels to non-migratory species.   This indicated that the butterflies had developed in northern Europe and migrated south.  Italian butterflies examined in the Spring had levels similar to those of local butterflies indicating that they were locally bred as a result of a winter breeding cycle and were not overwintering adults from further afield.  In addition there were also some individuals that seemed to have migrated from further south in the Spring.

In Northern Europe the examination of butterflies in the Summer appears to suggest that they had migrated from central Europe, whilst those examined in the autumn appeared in the main to be more local, but with some migration still occurring from the south.

So, in conclusion it would appear that butterflies move north to breed in the Summer and then move south in the autumn to breed into the winter months.  Will this change with the changing climate  and, as previously noted, an increased propensity for adult Red Admirals to overwinter in some northern parts of Europe?

Migrant Butterflies

When you think of migrant species, the word butterfly is not usually the first thing that pops into your head.  Whilst many of us have seen pictures of the mass migrations of Monarch butterflies in America, you may not realise that many of the butterflies that we see in our gardens each year have flown in from Europe or Africa.  (Although the recent coverage of the Painted Lady migrations on the fantastic Springwatch may have increased awareness of migratory butterflies.)

More surprising though is the fact that one of our commonest butterflies, the Red Admiral, is a migrant.  To confuse things still further though, it is also in some cases being classed as a resident.  Climate change and the warmer winters means that it is now able to survive winters as an adult in the south of the country (this includes Northamptonshire). Consequently it is often one of the first butterflies seen each year – often in January.

The Red Admiral is a striking and unmistakeable butterfly.  Its Latin name is Vanessa Atalanta, named after the beautiful and athletic goddess Atalanta, a famous huntress.  Atalanta tried to enlist with the argonauts but was turned down as Jason was worried about the presence of one woman on the ship.  She would go to such lengths to avoid marriage that suitors were challenged to a race, those who lost, the penalty not being a sufficient deterrent, being put to death.  She was eventually beaten after the love goddess Aphrodite took pity on a suitor and helped him distract Atalanta during the race.

The butterfly given her name can be seen throughout the year (although the first major migration occurs from mid-May to the end of June), in most habitats, throughout the country.  It will visit many flowers, switching from one favourite to another as the summer progresses, moving onto fruit and then ivy blossom in the autumn.  There would usually be a return migration in the autumn, but they are increasingly staying to overwinter in the south of England.

The food plant of the Red Admiral is the nettle, with the small, green egg laid on the upperside of a leaf.  When this hatches, the caterpillar uses silk to form a tent from the leaf on which it hatched, and, as it grows it pulls in more leaves to its tent and eventually makes its chrysalis in the tent.  After two and half weeks the black or yellow spiny caterpillar will emerge from its chrysalis as a stunning red, white and black butterfly.