Wardens’ Report iii Introduction to the Skokholm Island Annual Report 2017 iii The 2017 Season and Weather Summary v Spring Work Parties vii Spring Long-term Volunteers viii Spring Migration Highlights viii The Breeding Season x Autumn Migration Highlights xi Autumn Long-term Volunteers xii Autumn Work Party xii Skokholm Bird Observatory xiii Digitisation of the Paper Logs xiii Ringing Projects xiii Visiting Ringers xiv Birds Ringed in 2017 xv Catching Methods xv Arrival and Departure Dates xvii 2016 Rarity Decisions and DNA Results xvii Bird Observatory Fundraising xviii Acknowledgments and Thanks xviii Definitions and Terminology 1 The Systematic List of Birds 1 Anatidae Geese and Ducks 1 Phasianidae Quail 7 Gaviidae Divers 7 Hydrobatidae Storm Petrel 7 Procellariidae Fulmar and Shearwaters 17 Podicipedidae Grebes 31 Threskiornithidae Spoonbill 31 Ardeidae Bittern, Grey Heron and Egrets 32 Sulidae Gannet 33 Phalacrocoracidae Shag and Cormorant 34 Accipitridae Hawks, Hen Harrier, Red Kite & Buzzard 36 Rallidae Water Rail, Moorhen and Coot 39 Gruidae Crane 41 Haematopodidae Oystercatcher 42 Recurvirostridae Avocet 43 Charadriidae Plovers 44 Scolopacidae Sandpipers and allies 45 Laridae Gulls 57 Sternidae Terns 75 Stercorariidae Skuas 76 Alcidae Auks 77 Columbidae Pigeons and Doves 94 Cuculidae Cuckoo 95 Strigidae Short-eared Owl 96 Apodidae Swift 97 Upupidae Hoopoe 97 Picidae Wryneck 98 Falconidae Kestrel, Merlin and Peregrine 98 Corvidae Crows 100 ii | Skokholm Annual Report 2017 Paridae Blue Tit 106 Alaudidae Skylark 107 Hirundinidae Swallow and Martins 108 Aegithalidae Long-tailed Tit 111 Phylloscopidae Phylloscopus warblers 112 Acrocephalidae Acrocephalus and Melodious warblers 118 Locustellidae Grasshopper Warbler 121 Sylviidae Sylvia warblers 122 Regulidae Firecrest and Goldcrest 126 Troglodytidae Wren 128 Sturnidae Starling 128 Turdidae Thrushes 129 Muscicapidae Chats and Flycatchers 131 Passeridae House Sparrow 139 Prunellidae Dunnock 139 Motacillidae Wagtails and Pipits 140 Fringillidae Finches 146 Parulidae Myrtle Warbler 151 Emberizidae Reed Bunting 152 Calcariidae Lapland Bunting 153 The Non-avian Report 154 Invertebrates 154 Dragonflies and Damselflies 154 Beetles 156 Moths 156 Butterflies 184 Amphibians 191 Mammals 191 Rabbit 191 Bats 193 Seals 195 Cetaceans 196 Fish 199 Plants 200 Other Species 201 Observers, Photographers and Literature Cited in the Text 202 Wardens’ Report Introduction to the Skokholm Island Annual Report 2017 The 2017 season will be remembered as a record breaker, partly due to some extreme weather and, to a certain extent as a direct consequence of the weather, partly due to the number of different bird species encountered. There were six additions to the Island list, the most added in any year since the nine of 1990; Bittern, Cattle Egret, Crane, Avocet, Marsh Warbler and Myrtle Warbler took the Skokholm total to 295 species. Climate change is in part responsible for changes in the distribution of the former four species, all of which are likely to occur more regularly in the future. The Myrtle Warbler, a stunning male which sang in the Courtyard on 18th June, was only the fifth British spring record. Whereas the last North American passerine to occur in June, the Swainson’s Thrush of 2015, arrived on the back of a deep area of low pressure which tracked quickly across the Atlantic, the arrival of our latest ‘yank’ was harder to explain, although a low had crossed a week earlier. The most notable weather event of the year had a more easterly origin, indeed Ex-hurricane Ophelia had proven the easternmost major Atlantic hurricane of the satellite era. iii | Skokholm Annual Report 2017 The morning of 16th October dawned calm and humid, with unusually hazy skies the result of Iberian forest fire smoke and Saharan dust brought north by a system which in the afternoon delivered hurricane force southerly gusts and produced a phenomenal sea. Waves which were covering the 16 metre tall St Ann’s Weather Beacon approximately every ten seconds were large enough to lift debris up Skokholm’s southerly cliffs and through the Lighthouse. The resulting damage was unprecedented, with windows smashed, doors torn open and an entire upstairs window frame cast inwards, whilst torrents of seawater washed through the corridors and ran down the central stairwell. Boarding up the holes was all that could be achieved before the departure of staff; the repairs will be a job for the 2018 season. One of the more notable items discovered amongst the wreckage was a piece of lantern glass, almost certainly a shard of the original lantern pushed over the cliff by Trinity House in the 1960s; it was somewhat ironic that a prism thrown into the ocean forever returned 50 years later to smash its previous home. Ophelia did not only bring destruction to Skokholm’s shores; the same weather system brought a significant influx to Britain of birds which had been working south through central Europe, most notably large groups of Hawfinch and Firecrest. On Skokholm this resulted in four Hawfinch sightings, the same number as had previously been logged since 1933, and an arrival of Firecrest which took the autumn total to the fourth highest on record. The rough seas brought record numbers of Sabine’s Gull to our surrounding waters. Even without the Ophelia related birds, it proved a remarkable year for Island rarities, with 14 species logged which had been seen on fewer than ten previous occasions; in addition to the Hawfinch records, there were 2017 sightings of Great Shearwater, Little Grebe, Great Crested Grebe, Honey-buzzard, Red Kite, Long-billed Dowitcher, Long-tailed Skua, Feral Pigeon, Long-tailed Tit, Western Bonelli’s Warbler, Radde’s Warbler, Dartford Warbler and Bullfinch. These, coupled with more regular Island scarcities such as White- fronted Goose, Red-breasted Merganser, Quail, Spoonbill, Coot, Pectoral Sandpiper, Pomarine Skua, Hoopoe, Wryneck, Magpie, Blue Tit, Yellow-browed Warbler, Melodious Warbler, Barred Warbler, Bluethroat and Richard’s Pipit took the Skokholm yearlist to an unprecedented 166 species, seven more than the previous Island record. It was also an excellent year for our breeding birds, with a pair of Short-eared Owl nesting for the first time since records began, two pairs of Peregrine nesting for only a second time and record Chough productivity, whilst the breeding populations of all three auks increased yet again. This report follows the same format as in the previous four years. It provides a full account of the 2017 season, documenting the fortunes of Skokholm’s breeding birds, along with an in depth record iv | Skokholm Annual Report 2017 of migrant birds and the non-avian wildlife recorded this year. Each avian species logged in 2017 is addressed separately and every piece of information we have gathered during the season can be found under that species title; thus details of first and last dates, numbers, breeding, ringing totals, ringing recoveries, specific projects and all other relevant information can be found in the one place. Following the success of our four previous online reports, the Skokholm Annual Report 2017 has again been produced in a free to download PDF format. For any readers wishing to contribute to our work, a ‘donate now’ button is available on the source page. The number of species logged in each year since 1926, with the ten most productive years in darker green, and the cumulative number of species logged on Skokholm (which had reached 295 by the end of 2017). 170 300 160 150 140 250 130 120 110 200 100 90 150 80 70 60 100 50 40 30 50 20 10 0 0 1926 1928 1930 1932 1934 1936 1938 1940 1947 1949 1951 1953 1955 1957 1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 2017 The 2017 Season and Weather Summary The season ran from 12th March to 9th November and we welcomed visitors from 17th April to 3rd October. After sailing from Neyland through heavy drizzle, we arrived to Skokholm in warm sunshine. However the remainder of March was dominated by damp conditions; rain or drizzle fell on nine dates, hail and thunder struck on the 21st and mist descended on three dates, whilst the temperature averaged a cool 8.5˚C. Winds were typically moderate, although a steady force seven between the 17th and 21st veered southwest from south-southeast and produced a lingering swell. The 23rd was the first dry and sunny day since our return and the first day of a calm and almost cloudless spell which lasted until the 28th, from when rain and mist again dominated. April saw much drier weather, with sunny conditions logged on 13 dates and precipitation only falling on seven; the majority of rain fell overnight, although squally hail and rain showers passed through on the 25th and persistent rain lingered for much of the day on the 30th. Light northerly winds were prevalent, with warm temperatures and glassy sea states enjoyed on over 60% of April dates; wind speeds only exceeded force four on the 25th, 29th and 30th when cooler conditions were also felt. Although the 1st proved a drizzly affair, sunny weather again dominated during May, with over two- thirds of dates proving to be pleasant and hot diurnal temperatures between the 24th and 26th which peaked at 22.8˚C. Gentle winds, typically from the easterly quarter, prevailed until the 12th, after which southwesterly or southerly winds became the norm; the only rough spell fell on the 15th and 16th when a southerly near-gale resulted in very rough seas. Mist enveloped the Island for much of v | Skokholm Annual Report 2017 the 23rd and 28th, rain was recorded on six dates and a thunder and lightning storm on the 27th saw very heavy overnight showers.