Alpine Accentor

The alpine accentor is a small robin-sized passerine 15–17.5 cm long, slightly larger than its relative the dunnock, native to Eurasia and North Africa and found throughout the mountains of southern temperate Europe, Lebanon and Asia at heights above 2,000 m. It has a streaked brown back somewhat like a house sparrow's, but adults have an all-grey head and red-brown spotting on the underparts, and a fine pointed insectivore's bill; young birds have browner heads and underparts (Wikipedia, general species account).

It builds a neat nest low in a bush or rock crevice, laying three to five unspotted sky-blue eggs. The mating system is of particular interest: home ranges are occupied by breeding groups of three or four males with three or four unrelated females, a socially polygynandrous system in which females seek matings with all the males, though the alpha male may defend her against matings from lower-ranking males, and males in turn seek matings with all the females (Wikipedia, general species account).