Butterfly Explosion by NCT Senior Ecologist Georgia Beyer
The Caper White Butterfly Migration
Top photo: Male Caper Whites. Georgia Beyer.
If you live in northern NSW you might have noticed huge numbers of caper white butterflies a few weeks ago. The air was thick with them while their great migration took place.
But what is the caper white migration? The caper white is known from all states and lives mainly west of the Great Dividing Range (1). Beyond that, observations are varied and theories conflicting.
There are reports of high numbers migrating to south east Queensland every 6 to 10 years (2). Some report southerly migrations to Victoria and Tasmania then returning north again (3). An easterly migration was observed in Canberra (4) and some say the sexes migrate separately (5). One report is of high numbers aggregating on headlands before flying out to sea (6).
My own observations include hundreds migrating south along the coast at Brunswick Heads in October 2007, and a northern migration against a strong wind at Brunswick Heads in October this year.
In 2004 the Sydney Morning Herald reported “Mystery shrouds butterfly's southern suicide flight” (8). It wasn’t known why the caper whites were migrating to Victoria where few survived to make it back north. Suggestions included a lack of food elsewhere or a genetic memory of a time when food sources were abundant in the south.
Some say the caper whites were blown off course by the strong westerly winds (7). Some suggest the warm humid conditions brought them to the coast (9), others that they could be looking for their host caper plants (2, 9).
In his field guide, butterfly expert Michael Braby gives a good summary; ‘movement patterns are complex and not fully understood’.
Whatever the true factors are, we are very lucky to witness such amazing clouds of beautiful butterflies in spring time.
1 – Michael Braby. The Complete Field Guide to Butterflies of Australia (2005)
4 - bioacoustics.cse.unsw.edu.au/archives/html/canberrabirds//2015-11/msg00144.html
8- www.smh.com.au › Specials › Science
9 - www.brisbanetimes.com.au › News › Queensland