Enjoyed a very full and eventful day exploring the south end of Shetland mainland. The day started with three juvenile Wheaters flitting around the bushes in the hotel car park. Offshore, over 50 Shags were feeding in unison on what was presumably a shoal of fish moving across the bay (Fair Isle was clearly visible in the distance). At the entrance to the hotel, a Lapwing had a tiny chick in the field where it was mobbing a Herring Gull last night.
First birds seen at the Sumburgh Head car park were two Twite flying overhead. The cliffs beneath the car park held nesting Puffins (including adults bringing in fish and nest material, and juveniles at the burrow entrances), Guillemots (with some half-grown chicks), Shags, Kittiwakes (including some brooding young), Fulmars (ditto), Rock Doves and Starlings (including a nest of begging young in a rock crevice). Cruising by were passing Gannets and hunting Great Skuas and Greater Black-backed Gulls. Birds (and mammal) species on the grassy areas and dykes included Oystercatcher, Curlew, Rock Pipit, Meadow Pipit, Starling, Blackbird and Rabbit.
Nearer the lighthouse were all the previous species plus Hooded Crow, Razorbill, Black Guillemot, a Shag's nest containing two chicks and a bleached Painted Lady. Starlings had noisy young in the roof of a derelict out-building. Four Great Skuas offshore were watched squabbling over a dead auk.
The sandy bay at Grutness held a good selection of feeding birds consisting of Red-throated Diver, Eider, Shag, Razorbill, Common Gull, Herring Gull and Arctic Terns from the neighbouring colony. The area around the colony held both half- and full-grown juvenile Arctic Terns, newly-fledged Common Gulls, an adult Ringed Plover (followed by three immatures), two summer-plumaged Dunlin (one carring ring number L45, indicating that it had been ringed on the Dyfi estuary) and three Redshank. A Raven cronked overhead.
Loch of Spiggie held at least 35 bathing Great Skuas with other birds resting in adjacent fields. A breeding Mute Swan pair (apparently one of only two on Shetland) had two cygnets while eight Greylag Geese were on the opposite shore. The land bridge at the northwest end of the loch gave a good view across Muckle Sound to Foula. 
Other lochs we visited held a breeding pair of Whooper Swans with seven cygnets (a sight more typical of Iceland than Scotland) and an unexpected summer-plumaged Slavonian Grebe consorting with 23 Tufted Ducks. While we watched that loch, 50 Curlews flew over. 
The moorland above Dalsetter held Golden Plover, Skylark and a remarkable inland colony of  Arctic Terns. Also there were flowering Heath Spotted Orchid, Bog Asphodel, Cotton Grass and Ragged Robin plus a Shetland Bee. Meanwhile Loch of Clumlie held approximately 100 Greylag Geese.
The pull-in overlooking the tombolo connecting St Ninian's Isle to the mainland held another Painted Lady and a singing (Shetland) Wren. Finally, Rerwick Bay had 22 Common Seals, four Grey Seals, six Eider and two Black Guillemots. The roadside veges there were alive with flowering Tufted Vetch, Purple Marsh Orchid, Sheeps' Bit, Tomentil and Self-Heal.
The day ended with a walk along the foreshore west of Sumburgh Head where Redshank, Snipe, Oystercatcher, Curlew, Wheatear and Arctic Tern were all potential breeders. Meanwhile, Painted Lady butterflies were present at Sumburgh Head and Grutness Beach.