It’s a wonder we all don’t meet up on the top of hills or mountains! It’s such a great way of finding someone: just keep going up until you get to the top, and I’ll be there! Seriously though, hill-topping, as it is called, is where male butterflies aggregate on or near the highest places in their habitats, and wait for receptive females to fly uphill towards them. It is an excellent way of concentrating the numbers of an otherwise low density species, and a good strategy for meeting members of the opposite sex, as long as they are instinctively inclined (sic) to move upwards.
In some, but not all, cases the males become territorial, challenging and chasing away other males, defending a display site where females visit to choose males with which to mate. Such sites have also been called sexual rendezvous points (Cannon, 2019). I have had the good fortune to visit two hill-topping sites – both of which are in Galicia in NW Spain – on a regular basis in recent years. One is used throughout the summer – over three generations – by Swallowtail butterflies, Papilio machaon hispanicus; the other is a site where Large wall brown butterflies, Lasiommata maera, gather in the spring and early summer to find partners. Both species are well known hill-topping butterflies.
Hotel Semáforo de Bares
The first site is a small granite hill (210m above sea level), very near to Cape Bares (Cabo de Bares) in Galicia. Punta de Estaca de Bares, as it is called in Spanish, is the northernmost point of Spain and the Iberian Peninsula, and a great spot for bird-watching. There is an old semaphore station at the top of the hill, now a delightful small hotel called Hotel Semáforo de Bares, with panoramic views over the sea and Cape Bares.
Male swallowtails are to found throughout the summer at this site, where they establish territories for meeting females. They perch on prominent sites, such as rocks or stems of grass (below).
Marsh fritillaries also congregate at this site (below).
Mirador Da Miranda
The second site is a scenic lookout point – called a mirador in Spanish – situated above the Ría Ortigueira, which runs northwards into the Bay of Biscay, near the town of Cariño (below). It is 498m above sea level and is a windy place; there is often a cloud which forms above the hill, even on otherwise sunny days, so it is not ideal for butterflies. Yet they congregate here.
Many people drive up here to admire the view, but perhaps not many of them know that it is great site for hill-topping butterflies, as well as other species, including bees and wasps! The bees and wasps may however, just be enjoying the nectar from the abundant heather (see below)!
The Large Wall Brown is a classic hilltopping species, which has been recorded at quite high altitudes, for example in the Atlas mountains (Morocco) and at 2,900m in the Sierra Nevada (Southern Spain). They are not particularly easy to photograph at this site, as they tend to fly off and sit on a rock, in a precarious situation (for humans that is, not butterflies!).
There are not large numbers of Large Wall browns at this site, but they are a regular feature, particularly on the granite walls of the lookout point itself (below).
Female Large wall browns can also be seen at this site, so presumably they have flown up the hill from the surrounding areas (next two photos).
Not all species found at or near the top of hills, mountains of ridges are actively engaged in seeking mates however. The lovely heather around this site is often full of Red Admirals, Peacocks and Painted Ladies.
Butterflies are quite picky about their hill-topping sites, and changes to the topography or vegetation can, it is said, put them off using it! Degradation and loss of habitat is happening all around us in the world, but I doubt that saving hill-topping sites is top of the list of priorities when developing scenic land for hotels or whatever!
Cannon, R. J. (2019). Courtship and Mating in Butterflies. CABI. Hardback | 392 Pages | 9781789242638
Tolman, T. (2008). Collins butterfly guide. HarperCollins UK.