Recording the visible migration of migrant Butterflies
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Anyone with an interest in the visible migration of birds, will probably have noted Red Admirals and Painted Ladies, moving south during September and October.

Only 30 or 40 years ago, the fact that there was an observable and distinct southerly migration by migrant butterflies, was little known and largely dismissed as fanciful speculation, with little evidence to confirm it as an actual event.

It is however an annual Autumn phenomenon, although the nature of any southerly movement is dependent on the number of migrants arriving here in the Spring. Spring butterfly migration is usually less distinct, although there have been two exceptionally huge invasions of Painted Ladies into the UK during early June 1996 and more recently in late May 2009. An average year typically provides very small numbers of both migrant Nymphalids, with the Red Admiral being the more regular of the two.

 
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Autumn migration is an annual event, but numbers vary from year to year. Red Admirals make up the greater percentage of all migrants recorded and peak in September. Painted Ladies generally peak a month earlier in August and Clouded Yellows in September.

Choosing a suitable watchpoint

The key to observing and recording the visible migration of migrant Butterflies is to seek an open vantage point. Suitable sites can be found pretty much anywhere, and it often helps if there are hedges that run north to south as butterflies typically track along these. Open fields and large bodies of water are well worth watching, where the observer should position themselves at the southern or south-western end and scan low over the ground or water. Migrants generally fly very low (within 60cm above ground/vegetation level).

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  Observing and recording techniques

Scanning with binoculars will reveal distant butterflies and a good day will involve small, loose groups flying through, but single butterflies make up the majority of any count. To make the data more useful, the counting period can be divided up into hours. This method will show when peak numbers moved through, something that can help when planning future watches. Purposely recording butterflies actively migrating, is not a pastime that comes with instant success and high numbers.

As already mentioned, a fine September day will usually produce a steady trickle of Red Admirals, Painted Ladies or even the occasional Clouded Yellow moving south, low over the ground. It is not totally usual to have a wider variety of species moving through on the same day and the trigger for this when it does happen, seems to be very hot (over 25C) or dry weather conditions over the previous few weeks.

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Of course nothing can ever be guaranteed. After the huge Painted Lady invasion of May 2009, hopes were high that even larger numbers would move back south again in August. In the end, the forcasted event largely failed to materialise, and although we did record some Painted Ladies moving south, any similar counts seemed to have been missed elsewhere.
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Date 03/08/03 .. Eakring Flash .. Red Hill .. Total
Species .. 10:30am-11:00am .. 11:10am-13:10pm .. 13:10pm-14:40pm .. 14:40pm-15:40pm .. ..
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Painted Lady .. 14 .. 339 .. 254 .. 99 .. 716
Large White .. 2 .. 68 .. 102 .. 9 .. 179
Red Admiral .. 2 .. 50 .. 75 .. 9 .. 134
Peacock .. . .. 40 .. 60 .. 6 .. 106
Small White .. 5 .. 20 .. 30 .. 4 .. 54
Small Tortoiseshell .. . .. 16 .. 24 .. 7 .. 47
Green-veined White .. . .. 16 .. 24 .. 2 .. 42
Comma .. . .. 1 .. 1 .. 1 .. 3
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Our best day for Autumn butterfly migration was August 3rd 2003. Biggest surprise of the day were the 106 Peacock and 47 Small Tortoiseshell, all following the same direction as the primary movers - 716 Painted Lady, 179 Large White and 134 Red Admiral. In all, a total of 1,281 butterflies of eight species moved low south-west in five hours of continuous observation. The table produced above, shows the accumulated totals from the two vantage points used, during the times given on the day. September 30th 2000 was another notable date when 82 Red Admiral and a single Clouded Yellow were recorded.

Getting a decent total is often a matter of luck. The weather has to be right on the day and of course, the butterflies have to be there. A fine, sunny day in September should reap rewards and such a day after a period of poor weather, will often produce the best results. Red Admirals tend to dominate any counts made in September, with Painted Lady peaking a month earlier in August. September is the best month for Clouded Yellow, based on our records.

Migrant butterfly records

The following list of our own records, refers only to butterflies recorded actively moving through a site.

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        Spring migration records   Autumn migration records
... ... Species ... Date ... Total ... Direction ... Date ... Total ... Direction
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59.023 1590 Vanessa atalanta Red Admiral   15/06/17   1   N            
59.024 1591 Vanessa cardui Painted Lady   14/06/17   1   N            
59.023 1590 Vanessa atalanta Red Admiral ... 24/05/17 ... 1 ... N ... ... ... ... ... ...
59.023 1590 Vanessa atalanta Red Admiral ... 22/05/17 ... 1 ... N ... ... ... ... ... ...
59.023 1590 Vanessa atalanta Red Admiral ... 18/05/17 ... 1 ... NE ... ... ... ... ... ...
59.023 1590 Vanessa atalanta Red Admiral ... 13/05/17 ... 1 ... N ... ... ... ... ... ...
...
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 03/10/16 ... 2 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 27/09/16 ... 1 ... SW
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 18/09/16 ... 4 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 13/09/16 ... 2 ... SW
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 11/09/16 ... 2 ... SW
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 07/09/16 ... 1 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 23/08/16 ... 1 ... S
59.024 1591 Vanessa cardui Painted Lady ... 08/06/16 ... 1 ... NE ... ... ... ... ... ...
59.024 1591 Vanessa cardui Painted Lady ... 07/06/16 ... 1 ... S ... 23/08/16 ... 1 ... S
...
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 11/09/15 ... 1 ... SW
59.024 1591 Vanessa cardui Painted Lady ... ... ... ... ... ... ... 11/09/15 ... 1 ... SW
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 06/09/15 ... 1 ... S
59.024 1591 Vanessa cardui Painted Lady ... 23/06/15 ... 1 ... N ... ... ... ... ... ...
59.024 1591 Vanessa cardui Painted Lady ... 05/06/15 ... 1 ... NE ... ... ... ... ... ...
...
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 12/10/14 ... 35 ... SW
59.031 1598 Polygonia c-album Comma ... ... ... ... ... ... ... 12/10/14 ... 1 ... SW
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 05/10/14 ... 7 ... S
58.006 1549 Pieris brassicae Large White ... ... ... ... ... ... ... 05/10/14 ... 1 ... S
...
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 15/09/12 ... 30 ... SW
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 09/09/12 ... 10 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 08/09/12 ... 9 ... S
58.006 1549 Pieris brassicae Large White ... ... ... ... ... ... ... 08/09/12 ... 2 ... S
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59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 11/10/10 ... 1 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 10/10/10 .. 2 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 08/10/10 ... 2 ... SW
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 04/10/10 ... 2 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 30/09/10 ... 1 ... SE
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 22/09/10 ... 1 ... SE
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 18/09/10 ... 1 ... S
...
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 09/08/09 ... 2 ... SW
58.006 1549 Pieris brassicae Large White ... ... ... ... ... ... ... 09/08/09 ... 109 ... SW
59.024 1591 Vanessa cardui Painted Lady ... ... ... ... ... ... ... 08/08/09 ... 12 ... S
59.024 1591 Vanessa cardui Painted Lady ... ... ... ... ... ... ... 09/08/09 ... 93 ... SW
59.024 1591 Vanessa cardui Painted Lady ... ... ... ... ... ... ... 06/08/09 ... 3 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 03/07/09 ... 1 ... S
59.024 1591 Vanessa cardui Painted Lady ... 30/05/09 ... 191 ... W ... ... ... ... ... ...
59.024 1591 Vanessa cardui Painted Lady ... 29/05/09 ... 748 ... NW & SE ... ... ... ... ... ...
59.024 1591 Vanessa cardui Painted Lady ... 28/05/09 ... 1,141 ... NW ... ... ... ... ... ...
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59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 13/09/08 ... 7 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 14/09/08 ... 1 ... S
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59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 30/09/07 ... 2 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 29/09/07 ... 1 ... S
59.023 1590 Vanessa atalanta Red Admiral ... 04/02/07 ... 1 ... NW ... ... ... ... ... ...
...
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 22/10/06 ... 3 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 13/10/06 ... 2 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 25/09/06 ... 11 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 24/09/06 ... 12 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 25/07/06 ... 1 ... SW
59.024 1591 Vanessa cardui Painted Lady ... ... ... ... ... ... ... 25/07/06 ... 3 ... S & SW
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 22/07/06 ... 1 ... S
59.024 1591 Vanessa cardui Painted Lady ... ... ... ... ... ... ... 22/07/06 ... 1 ... SW
59.023 1590 Vanessa atalanta Red Admiral ... 18/06/06 ... 2 ... N ... ... ... ... ... ...
...
59.023 1590 Vanessa atalanta Red Admiral ... 20/06/05 ... 1 ... N ... ... ... ... ... ...
...
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 04/09/04 ... 1 ... S
59.024 1591 Vanessa cardui Painted Lady ... ... ... ... ... ... ... 03/09/04 ... 1 ... S
58.010 1545 Colias croceus Clouded Yellow ... ... ... ... ... ... ... 03/09/04 ... 1 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 03/09/04 ... 1 ... S
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59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 20/09/03 ... 47 ... S
59.026 1597 Aglais io Peacock ... ... ... ... ... ... ... 06/08/03 ... 2 ... SW
58.006 1549 Pieris brassicae Large White ... ... ... ... ... ... ... 06/08/03 ... 8 ... SW
58.007 1550 Pieris rapae Small White ... ... ... ... ... ... ... 06/08/03 ... 3 ... SW
59.027 1593 Aglais urticae Small Tortoiseshell ... ... ... ... ... ... ... 06/08/03 ... 8 ... SW
59.024 1591 Vanessa cardui Painted Lady ... ... ... ... ... ... ... 04/08/03 ... 51 ... S
58.006 1549 Pieris brassicae Large White ... ... ... ... ... ... ... 04/08/03 ... 36 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 04/08/03 ... 17 ... S
58.007 1550 Pieris rapae Small White ... ... ... ... ... ... ... 04/08/03 ... 7 ... S
58.008 1551 Pieris napi Green-veined White ... ... ... ... ... ... ... 04/08/03 ... 6 ... S
59.026 1597 Aglais io Peacock ... ... ... ... ... ... ... 04/08/03 ... 6 ... S
59.031 1598 Polygonia c-album Comma ... ... ... ... ... ... ... 04/08/03 ... 1 ... S
59.027 1593 Aglais urticae Small Tortoiseshell ... ... ... ... ... ... ... 04/08/03 ... 10 ... S
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 03/08/03 ... 134 ... SW
59.024 1591 Vanessa cardui Painted Lady ... ... ... ... ... ... ... 03/08/03 ... 716 ... SW
58.008 1551 Pieris napi Green-veined White ... ... ... ... ... ... ... 03/08/03 ... 42 ... SW
59.031 1598 Polygonia c-album Comma ... ... ... ... ... ... ... 03/08/03 ... 1 ... SW
58.006 1549 Pieris brassicae Large White ... ... ... ... ... ... ... 03/08/03 ... 179 ... SW
58.007 1550 Pieris rapae Small White ... ... ... ... ... ... ... 03/08/03 ... 54 ... SW
59.026 1597 Aglais io Peacock ... ... ... ... ... ... ... 03/08/03 ... 106 ... SW
59.027 1593 Aglais urticae Small Tortoiseshell ... ... ... ... ... ... ... 03/08/03 ... 47 ... SW
...
58.010 1545 Colias croceus Clouded Yellow ... ... ... ... ... ... ... 30/09/00 ... 1 ... SE
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 30/09/00 ... 82 ... S
58.010 1545 Colias croceus Clouded Yellow ... ... ... ... ... ... ... 23/09/00 ... 1 ... S
58.010 1545 Colias croceus Clouded Yellow ... ... ... ... ... ... ... 19/09/00 ... 1 ... SW
59.023 1590 Vanessa atalanta Red Admiral ... 19/06/00 ... 4 ... NE ... ... ... ... ... ...
59.023 1590 Vanessa atalanta Red Admiral ... 18/06/00 ... 2 ... NE ... ... ... ... ... ...
...
59.024 1591 Vanessa cardui Painted Lady ... ... ... ... ... ... ... 12/09/99 ... 1 ... SW
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 25/08/99 ... 22 ... S
...
59.023 1590 Vanessa atalanta Red Admiral ... ... ... ... ... ... ... 08/08/98 ... 2 ... S
 
Painted Lady migration in Spring 2009
Painted Lady migration in Autumn 2003
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