Today - six Great Northern Divers in Loch Roag just off Tolstachaolais slipway. At least three in rich adult summer plumage, the others juvenile. I’m not aware of seeing adults in summer plumage in Lewis before (perhaps I’ve not been attentive enough). I assumed they’d have departed for North America by now to breed. Do they migrate once in breeding colours or are they likely now to breed here? Can anyone share better knowledge on this? Thank you.