Two prickly customers

January 19th 2018

I should clarify at the outset that the ‘Two prickly customers’ does not refer to this article’s contributors!

Having cleared that up I can safely continue – these images of the dead fruiting heads of composites were taken recently by David Haines, as part of early trials in ‘stacking’ digital images.

On the left is spear thistle Cirsium vulgare (constructed from seven images) from Culkein Drumbeg (NC1133), while on the right is burdock Arctium minus (constructed from thirteen images) from the side of Loch Drumbeg (NC1132).  Both bear rigid spiny involucral bracts which dissuade animals from grazing the heads before the fruits can be dispersed, but there the similarities between the two end.

The fruits of spear thistle, like those of many composites, have feathery pappus hairs sprouting from the top of the ovary.  These hairs spread, when the fruits are ripe and the air is dry, forming rigid parachutes and the means by which they are wind-dispersed, the well-known thistledown.

Those of burdock also bear pappus hairs, but they are short and cannot function as parachutes.  So seed dispersal in the case of  burdock is by the hooked bracts catching in the fur of passing animals, the whole head, or burr, is detached and the hard black fruits are gradually shaken out as the bearer travels further afield.

Both plants are usually found in disturbed ground and neglected gardens in Assynt, occasionally way up in the hills, but spear thistle is much more widespread.  Burdock is a tap-rooted perennial that persists where it gets a foothold; spear thistle is a biennial, which just produces one set of flowers and fruits; contrasting strategies for life.

Of course it should be noted that their defences do not protect either from the predations of birds, in particular goldfinches.

Ian M. Evans

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Recent Sightings

House Martin

two birds nest building on Drumbeg Hotel (DAH) (25/05)

Greylag Goose

eight adult birds with 15 goslings Loch Drumbeg (DAH) (25/05)

WALRUS - NOT AN ASSYNT SIGHTING BUT -

UPDATE The Walrus was spotted yesterday, the 24th, in Wick harbour. --------------------------------------------- You may have seen in the news that the Walrus which was first reported from Orkney on 9th March was spotted on 16th May, near Kinlochbervie. If it should turn up in Assynt it would be very much appreciated if you could quickly let us know on assyntwildlife@gmail.com. We can then let those that are monitoring its condition know. We would also ask that you do not do anything which will disturb the animal and please keep dogs on a lead and well away from it, thank you. (25/05)

Slow-worm

single seen in Ardvar garden (Beccy Garvie) (24/05)

Harbour Porpoise

six off Bay of Stoer (DAH) (24/05)

Long-tailed Duck

two male birds, one in summer plumage, Bay of Stoer (DAH) (24/05)

Common Tern

three birds feeding Bay of Stoer (DAH) (24/05)

Small Tortoiseshell butterfly

single on nettles Culkein Drumbeg and two flying near Stoer (DAH) (24/05)

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