Systematic List114Shetland Bird Report Shetland Bird Report 2011

Transcription

1 114 Systematic List114Shetland Bird Report Shetland Bird Report 2011 Shetland s breeding seabirds in 2011 compiled by Martin Heubeck & David Parnaby from data supplied by University of Aberdeen (SOTEAG), Fair Isle Bird Observatory, Foula Ranger Service, Natural Research Projects, Royal Society for the Protection of Birds, Scottish Natural Heritage & Shetland Ringing Group Shetland has some of the most spectacular coastal seabird colonies in the British Isles, while our moorlands hold nationally important populations of Red-throated Divers and skuas. For well over 30 years, Shetland s breeding seabirds have been some of the most closely monitored in the country, thanks to the long-term commitment of Scottish Natural Heritage (SNH), Fair Isle Bird Observatory (FIBO), Shetland Oil Terminal Environmental Advisory Group (SOTEAG), Royal Society for the Protection of Birds (RSPB), Shetland Ringing Group (SRG) and, more recently, the Foula Ranger Service (FRS). Each organisation has traditionally presented results in unpublished annual reports, while summaries for most species have appeared within the Systematic Lists of the Shetland Bird Report and the Fair Isle Bird Observatory Report, with the latter including a short section on seabirds from Early in 2012, these groups agreed to produce a single annual summary of the results of monitoring of breeding seabirds, of which this is the first. The intention is to present data and interpretation in a Northern Gannet, Hermaness, May John Moncrieff manner that is clear to the reader, helps facilitate comparison between species and years, and provides a one-stop published record; more detailed information will still be available in annual reports of individual organisations. Not all species receive the same level of attention, and it is hoped this summary will emphasise gaps in our current knowledge and stimulate initiatives to fill these, ideally using input from amateur as well as professional observers. Monitoring largely involves recording the same parameter each year, in a standard manner in the same study area, with casual observations adding usefully to the interpretation of results. The different organisations within Shetland complement each other well in this, both geographically and in the species studied, with considerable cooperation in certain projects. On Fair Isle, FIBO s monitoring of seabird numbers, productivity, diet and survival is carried out under contract to the Joint Nature Conservation Committee (JNCC) as part of the Seabird Monitoring Programme. As well as monitoring on Hermaness and Noss National Nature Reserves, SNH has a requirement to report

2 Seabird Articles Report 115 to the Scottish Government on the health of seabird populations on sites designated or notified for seabirds. This is a 6-year rolling programme using data collected by SNH and other organisations listed here, although only on the NNRs is productivity monitored. SOTEAG monitors cliff-nesting species at Sumburgh Head, Troswick Ness, Esha Ness and at Burravoe in Yell, as well as European Shags, Blacklegged Kittiwakes and Black Guillemots more widely. The RSPB reserves of Fetlar, Lumbister and Black Park on Yell, Gruney and Mousa are monitored by permanent and seasonal staff, who also gather data more widely. The diverse FRS work on Foula is supported financially by SOTEAG and RSPB, while SRG undertakes long-term studies of Red-throated Divers and storm petrels, as well standardised ringing of other species, again with some support from SOTEAG. More recently, the consultancy Natural Research Projects has collected data on divers, gulls and skuas in large moorland study areas on Mainland. As well as collating data, Shetland Biological Records Centre staff provide invaluable manpower on particular surveys. Where data have been collected in a standard manner, we have tabulated this over a 10-year period. With the exception of Red-throated Diver and skuas, sample sizes given for breeding success should not be taken to indicate population trends as the number and extent of study plots might have changed over time. Red-throated Diver Gavia stellata SOTEAG s bi-annual survey of a study area in Northmavine found divers present on 30 lochs, with breeding confirmed on 21, compared to averages during the previous decade of 26 and 16, respectively. The outcome of breeding attempts was not recorded. On Hermaness, 4 pairs hatched at least 6 chicks; one was definitely predated by a Great Skua, 2 possibly by Otters Lutra lutra, and just one was assumed to have fledged. On Fetlar, 6 single-chick broods were confirmed from 22 breeding pairs; 5 were assumed to have fledged and, from remains found, it was concluded that 4 eggs had been predated by birds, and one very small chick may have starved. On Lumbister and Black Park, 5 broods were confirmed from 11 breeding pairs. It was thought that 5 eggs had been predated by birds, and 3 chicks had been predated, possibly by Otters, and only 2 were assumed to have fledged. On Foula, one pair fledged a chick from a site that had not been occupied for about 40 years, while the only pair known with 2 chicks lost both in mid June, but relaid by late July (unsuccessfully). As part of a long-term programme of monitoring diver occupancy and productivity, Natural Research Projects monitored 113 lochs in central, west and north Mainland where breeding had occurred at least once during Single pairs were confirmed breeding on 69 lochs, 43 pairs hatched at least one chick and 39 juveniles were assumed to have fledged, giving breeding success of 0.57, a similar figure to 7 of the previous 8 years. Red-throated Diver breeding attempts and breeding success in monitored areas. Study area Hermaness (reserve) 6; ; ; ; ; ; ; ; ; ; 0.25 Fetlar (all island) 24; ; ; ; ; ; ; ; ; ; 0.23 Lumbister (reserve) 10; ; ; ; ; ; ; 0.18 Foula (all island) 10; ; ; ; ; ; ; ; ; ; 0.45 Mean success Red-throated Diver pairs with chicks in SRG study areas in late July and early August, and the ratio of one to two chick broods. SRG study area Unst North Roe Eshaness Bressay Total Ratio 1:2 chick broods 1:0.48 1:0.53 1:0.32 1:0.74 1:0.31 1:0.31 1:0.50 1:0.73 1:0.55 1:0.20

3 116 Systematic List116Shetland Bird Report Shetland Bird Report 2011 SRG s core study areas were checked between 21st July and 5th August. The total number of pairs with one or 2 chicks was higher than in , but still lower than the average of 42 in , and fewer broods of 2 chicks were recorded than in any year since the study began in Seven fish were seen brought to chicks, one Greater Sandeel Hyperoplus lanceolatus, 5 gadoids (possibly Saithe Pollachius virens) and one flatfish. The scarcity of broods of 2 chicks may be related to a lack of Lesser Sandeels Ammodytes marinus, the preferred prey. Northern Fulmar Fulmarus glacialis A census of Hermaness found 38% more apparently occupied sites (AOS) (6,723) than in 2006 (4,879), when there had been a large reduction since the previous census in 1999; many areas were not counted until late July, by which time the number of AOS might have declined from June. In contrast, a similar census of Noss, completed by 22nd June, recorded 15% fewer AOS (5,248) than in 2006 (6,144). On Fair Isle, a whole-island census recorded 29,640 AOS, a 6% increase since 2006 (27,896), although there were 20% fewer AOS in the population monitoring plots (303 AOS) than in 2010 (377). There were significant decreases since 2010 in the number of AOS in SOTEAG s population Northern Fulmar, Compass Head, June Roger Riddington monitoring plots. Fulmar breeding success has been calculated by 2 methods, both of which involved counting the number of chicks present in study plots in mid- August. This figure is then divided by either the number of AOS that were occupied on each of 3 visits Northern Fulmar population monitoring and breeding success. (a; number of plots) the number of sites occupied on 3 successive visits to breeding success plots in late May and early June (b; number of plots) the mean number of AOS on 5 visits to population monitoring plots during June. Breeding success is expressed as the number of chicks present in mid August, divided by (a) or (b), and given as the mean of plots. The percentage change is given for population plots only. Colony Hermaness (a; 3) Breeding success Burravoe, Yell (b; 1) % Breeding success nc Eshaness (b; 6) % Breeding success Noss (a; 3) Breeding success Foula (a; 4) Breeding success Troswick Ness (b; 6) % Breeding success Sumburgh Hd (b; 3) % Breeding success Fair Isle (a; 5) Breeding success Mean success (a) Mean success (b) The number of Fulmar chicks ringed on the holm in Brindister Loch. Brindister Loch holm Chicks ringed

4 in late May and early June (marking and numbering the sites on large-scale photographs), or by the average of 5 counts of AOS in June. Neither method is perfect as both figures for the number of AOS will include a proportion of non-breeders, which should be lower in the marked photograph method, resulting in a higher productivity figure. At Hermaness, most chicks that hatched appeared to survive to fledging. Egg predation by Northern Ravens was noted at Foula. Productivity was particularly low at one plot at Noss (0.07) where predation of adults by Northern Ravens occurred. Adults were notably absent from Sumburgh Head in the first days of August, although had returned by 15th. Overall success at the different colonies was slightly higher than the average for , whether using the marked photo method (mean of 0.37) or the 5 June counts of AOS (0.36). Manx Shearwater Puffinus puffinus No attempt was made to check for breeding presence on Fetlar due to lack of time and unfavourable weather conditions. The species is no longer believed to breed on Foula, although birds are occasionally heard calling in flight at night. European Storm Petrel Hydrobates pelagicus On Noss, the first bird was heard responding to a tape lure on 6th July, the first date tapes were played. A survey of the island on 12th-19th July elicited a total of 20 responses from birds in nest cavities around the boundary dyke. From Mousa, Hannah Watson (University of Glasgow) reported: The season started a little slower than in 2010, although the rate of egg-laying picked up rapidly and by 7th July 80% of pairs were incubating compared with 63% on the same date in Hatching success was no different Seabird Articles Report 117 European Storm Petrel, Mousa, July David Gifford to 2010 but chick survival was 18% lower. Most nestling mortality occurred during the brooding phase when the off-duty parent is under pressure to find sufficient food close to the colony and return to provision the chick every night. Observations of many semi-torpid chicks, left alone at only 2-3 days old suggest that adults were struggling to find sufficient food close to the colony and/or were unable to return to the colony due to bad weather. Overall productivity was 0.45 chicks fledged per pair, compared to 0.56 in The SRG monitoring sites on Mousa were visited on 14th September when 30 chicks were ringed, below the average for (39). One further chick was too small to ring, one site held a dead chick, adults were still incubating at two sites, and 21 sites had failed. The oldest chick was about 5 days from fledging, suggesting timing of laying had been normal but with rather poor success. The same sites are checked each year but actual breeding numbers are unknown. Elsewhere, birds were heard responding to playback of Leach s Storm Petrel call from burrows on Gloup Holm (1 burrow), Gruney (1) and Fair Isle (6), during surveys for Leach s Storm Petrels on these islands in June, July and August. The number of European Storm Petrel chicks ringed at monitored nest sites on Mousa. Mousa Chicks ringed

5 118 Systematic List118Shetland Bird Report Shetland Bird Report 2011 Leach s Storm Petrel Oceandroma leucorhoa In June, July and August, 19 sites on 10 islands were surveyed for occupied burrows using call-playback methods. In total, 14 occupied burrows were found, 13 on Gruney and one on Gloup Holm and each was examined using a 1.5 m long endoscope. Most proved too deep to check conclusively but, of 4 burrows on Gruney, 2 held non-breeders, while on 3rd August one held an adult and a tiny, entirely downy chick, and one held an adult and an egg. More petrels responded to call-playback in August than in June and to find one adult with an egg and one adult with a very young chick in August was unexpected and suggested relatively late breeding in There were no responses from 9 areas checked on Fair Isle (Miles et al. 2012). Northern Gannet Morus bassanus The Fair Isle population increased by 3% from 3,968 AON in 2010 to 4,085 AON in 2011, in line with the long-term trend of steadily increasing numbers, except in 2008 and 2010 when population expansion was relatively rapid. Breeding success remained fairly high and stable at Hermaness, and at Noss where the plot sizes were reduced to cope with increasing numbers; the plot areas used in held 614 AON in mid June Breeding success also continues to be relatively high on Fair Isle, above 0.60 in all years with data from Great Cormorant Phalacrocorax carbo At Eshaness, 15 nests were counted on the Brei Wick and Heads of Grocken stacks from the opposing clifftop on 12th May, but a few nests may have been out of sight at the rear of the stacks. European Shag Phalacrocorax aristotelis Whole-colony counts of nests at No Ness and Sumburgh Head (27th May) and Muckle Roe (9th June) all suggested extensive non-breeding. Counts on Noss on 5th June and 4th July supported this, locating a total of 66 AON; on the latter date 139 adults, 6 immatures and 32 juveniles were recorded, suggesting breeding success was 0.48 at most, and almost certainly lower. Northern Gannet breeding success (chicks fledged per AON) in monitored plots at Hermaness, Noss and Fair Isle. Colony Hermaness AON (3 pl.) Breeding success Noss AON (4 plots) Breeding success Fair Isle AON (4 plots) nc 254 c Breeding success nc Mean of all colonies Counts of European Shag nests made from the sea or from land AON on Noss, trace nests included elsewhere. Island / Colony Muckle Roe (sea) Noss (land) No Ness (land) Sumburgh Head (land) European Shag breeding success in study plots at monitored colonies (AON; chicks fledged per AON). Figures in italics are estimates. Island / Colony Foula 60; ; ; ; ; ; ; ; ; ; 0.71 Mousa 25; ; ; 1.04 Sumburgh Head 197; ; ; ; ; ; ; ; ; ; 0.28 Fair Isle 53; ; ; ; ; ; ; ; ; ; 0.11

6 Seabird Report 119 At Sumburgh Head, 141 incubating pairs were recorded in success plots during the season (222 in 2010), chicks were seen in only 33 nests, and 24 pairs fledged young; breeding success of 0.28 was the lowest since monitoring began in While bad weather contributed to this, with many breeding attempts ending during a period of gales, rough seas and prolonged rain in the 4th week of May, clutches began to be abandoned before this and it is likely that only the highest quality adults persisted with breeding. At Burravoe, Yell, brood sizes on 13th July were higher than at Sumburgh at the time, suggesting a better breeding season there, while at Westerwick on 14th July, 24 of 53 nests were still incubating, suggesting many had been washed out in late May but that a high proportion of pairs relaid. Breeding numbers were also low on Foula, but success there and on Mousa was higher than at Sumburgh, although fewer checks were made of the plots at these colonies than at Sumburgh Head and a higher proportion of breeding attempts will have gone undetected. On Fair Isle, the breeding population has declined severely and the number of AON in success plots is now very low (20 in 2011, 68 in 1986). There has been a gradual decline in breeding success since 1986, and the figure for 2011 (0.11) was the second lowest on record, after 0.03 in Arctic Skua Stercorarius parasiticus The single territorial pair on Hermaness had a chick on 6th July, which was not seen subsequently and assumed to have died. On Fetlar, there were no territorial pairs in the Lambhoga or Funzie Ness plots, but 5 pairs at Strandburgh Ness, although only 3 remained by 9th June and no fledged young were recorded. One of the 2 pairs on Noss had its clutch predated, while the other fledged a single young. On Foula, only 32 of the 41 territorial pairs laid (mean clutch size 1.63), 11 chicks were found but none fledged and most adults had left the island by 12th July. A pair on Mousa established a territory Arctic Skua, Clumlie, June Jim Wood but didn t lay a clutch. Elsewhere, a minimum of 4 young fledged from territories in the central and west Mainland, and at least 8 more were at the large chick stage in July, but with the outcome unknown. On Fair Isle, there were 59% fewer AOT than in 2010 and no chicks fledged, only the 4th season of zero breeding success in the past 23 years. Great Skua Stercorarius skua On Hermaness, the first chick was seen on 22nd June and the first fledged young on 6th August; productivity was low compared to the mid 1990s, when it averaged 0.95 in On Fetlar, 38 young fledged from 56 AOT in the Lambhoga plot (productivity 0.67), 32 from 36 AOT at Strandburgh Ness (0.88) and 10 from 15 AOT at Funzie Ness; there were signs of cannibalism, especially at Funzie Ness and Lambhoga. A search of the productivity plot on Noss on 7th August located just 11 chicks and Arctic Skua breeding success in monitored areas (AOT; chicks fledged per AOT). Island / Study area Hermaness (reserve) 7; ; ; ; ; ; 1; ; ; ; 0.00 Fetlar (3 plots) 9; ; ; ; ; ; ; ; ; ; 0.00 Noss (whole island) 7; ; ; ; ; ; ; ; ; 1.00 Foula (whole island) 101; ; ; ; ; ; ; ; ; ; 0.00 Mousa (whole island) 8; ; ; ; ; ; ; ; ; ; 0.00 Fair Isle (whole island) 60; ; ; ; ; ; ; ; ; ; 0.00

7 120 Systematic List120Shetland Bird Report Shetland Bird Report 2011 The number of Great Skua chicks ringed in a study area on Bressay. Bressay study area Chicks ringed Great Skua breeding success in monitored areas (AOT; chicks fledged per AOT). Productivity on Foula is calculated from chicks fledged per AON. Island / Study area Hermaness (one plot) 36; ; ; ; ; ; ; ; ; ; 0.47 Fetlar (sum of 3 plots) 66; ; ; ; ; ; ; ; ; ;0.75 Noss (one plot) 58; ; ; ; ; ; ; ; ; ; 0.13 Foula (one plot) 49; ; ; ; ; 0.66 Mousa (whole island) 22; ; ; ; ; ; ; ; ; ; 0.45 Fair Isle (whole island) 133; ; ; ; ; ; ; ; ; ;0.25 Mean no evidence of cannibalism, suggesting many pairs held territory but did not breed. On Foula, the 53 AON in the monitored plot had a mean clutch size of Of 38 chicks ringed on 21st-28th July, 3 were predated giving possible productivity of 0.66, but only 11 fledged and 3 unfledged young were found on 14th August, so this is probably an over-estimate. The number of AOT on Mousa was the lowest since 2005, although still higher than in On Fair Isle, there were 19% fewer AOT than in 2010, which contrasts with the long-term population increase on the island, which was particularly rapid between Eggs were first seen on 9th May and chicks on 8th June, but breeding success was 60% lower than in In the past 23 years, productivity on Fair Isle has been lower than 0.3 in only 5 years, all in the last decade. Just one chick was ringed in SRG s study area on Bressay on 5th August; a number of predated chicks were found and many adults had left their territories. Black-legged Kittiwake Rissa tridactyla Few counts were made of colonies around Mainland Shetland. At the Ramna Stacks, a small colony persists on Fladda; the total of 76 adults present on 18th June, and 18 trace nests in addition to the 25 AON, Black-legged Kittiwake breeding success in study plots at monitored colonies (AON; chicks fledged per AON). * more than one plot, mean success is given. Colony Hermaness * 139; ; ; ; ; ; ; ; ; ; 0.02 Burravoe, Yell 48; ; ; ; ; ; ; ; 0.19 Clett Head, Whalsay 80; ; 0.00 nc Noss * 186; ; ; ; ; ; ; ; ; ; 0.00 Foula * from ; ; ; ; ; ; ; ; ; ; 0.05 Ramna Geo, Burra 110; ; ; ; ; ; ; ; ; ; 0.00 Kettla Ness, Burra 102; ; ; 0.00 No Ness 53; ; ; ; ; ; ; ; ; ; 0.00 Compass Head 55; ; ; ; 0.00 Sumburgh Head * 177; ; ; ; ; ; ; ; ; ; 0.00 Fair Isle * 441; ; ; ; ; ; ; ; ; ; 0.00 Mean success Colony counts of Black-legged Kittiwake nests (AON) in colonies counted in Colony / Island Ramna Stacks Muckle Roe Foula Fair Isle

8 Seabird Report 121 suggests the colony was larger earlier in the season. At Muckle Roe on 9th June, the colony at Murbie Stacks was the only one remaining (10 birds were incubating, 11 standing at empty nests), although single nests were also recorded at 2 isolated geos. A census of Foula on 18th June confirmed that the breeding population there has halved since On Fair Isle, the whole island count of 1,438 AON was 60% lower than in 2008, and there were 52% fewer AON in success plots (81) than in 2010 (170). At the 10 colonies where breeding success was monitored, laying was 2-3 weeks later than in 2010, and a relatively low proportion of nest-building pairs laid (e.g. 65% at Sumburgh Head, c.f. 85% in 2010). Hatching success was low (e.g. chicks were recorded in 21% of nests at Sumburgh Head, c.f. 87% in 2010), and most colonies had failed completely by mid July; only at Hermaness, Burravoe, Yell, and on Foula did a few chicks survive to fledge, making 2011 one of the worst breeding seasons on record. On Fair Isle, this was only the 5th year of zero success since 1986, and no nests were recorded at 5 of the 10 monitoring plots. Black-headed Gull Chroicocephalus ridibundus The Tingwall Loch colony held over 100 pairs and good numbers of young fledged. There were 75 AON at a colony near Tingwall airstrip. Common Gull Larus canus Over 60 pairs bred at Tingwall Loch and reared a reasonable numbers of chicks, while 60 pairs at Sandy Loch fledged only a handful of young. At Garths Ness, 25 pairs fledged at least 20 young. On Foula, 7 pairs at the Groups quarry fledged 11 young, at least 4 of which were predated by a Great Skua. Lesser Black-backed Gull Larus fuscus There have been no breeding attempts on Mousa since 2004 when there were 4 pairs (10 in 2003 and 12 in 2002). Great Black-backed Gulls, Compass Head, May Roger Riddington European Herring Gull Larus argentatus In Lerwick, Shetland Islands Council continued its programme of nest removal from rooftops, but good numbers of chicks fledged from those nests not destroyed. On Noss, while productivity was relatively high at 1.33 (36 fledged from 27 AON), some fledglings were later seen to be predated by Great Skuas and a Great Black-backed Gull. Six pairs bred on Mousa, compared to an average of 14 pairs in Great Black-backed Gull Larus marinus On Noss, the first eggs were noted on 25th April and a total of 66 AON was recorded. The first chick was seen on 31st May, and a total of 45 fledglings were counted later around the island, giving a productivity of 0.68/AON. Common Tern Sterna hirundo At least 5 pairs nested at the Gremista marina in Lerwick but the colony was abandoned by mid- June. A handful of chicks fledged in the 2nd week of August from a small colony at Brindister Loch. None were recorded on Mousa all summer. None have attempted to breed on Fair Isle since 2005, when 3 pairs raised 3 chicks. Arctic Tern Sterna paradisaea Few were seen around Hermaness and there was no evidence of attempted breeding. On Foula, numbers peaked at c. 70 at the end of May but none attempted to breed. This pattern, with no evidence of attempted breeding, was repeated for all the key colonies in S

9 122 Systematic List122Shetland Bird Report Shetland Bird Report 2011 Mainland, and in most other areas of Shetland. Although a few pairs laid eggs, it would appear that very few, if any, hatched chicks and it is likely that no chicks were reared in the islands. Common Guillemot Uria aalge There were decreases in numbers since 2010 at all monitored colonies, although the extent to which low attendance by non-breeders, off-duty mates and failed breeders is contributing to declining numbers remains unclear. At Sumburgh Head, a few ledges have now been abandoned, but counts at the breeding success plot made at the same time as those at the population monitoring plots found that on average only 99 adults were present per 100 breeding pairs in 2011 compared to 147:100 in 2005, a very similar difference (-33%) to that observed in the population plots (-38%). Whole colony counts were of 1,186 adults at Gruney and the Ramna Stacks on 18th June (compared to 2,032 on 24th June 2001) and 4,960 at Sumburgh Head in 19th June (7,108 on 8th June 2010). In the single breeding success plot at Sumburgh Head, the first egg was seen on 29th April and median laying date was 9th May. Heavy swell on 8th May washed away c. 60 eggs, around 40% of the first eggs laid in the plot, and while most pairs relaid breeding synchrony was disrupted. The first bird was seen to abandon its egg in situ on 13th May, and by 26th May Arctic Terns, S Mainland, June David Gifford it was obvious that incubation shifts were becoming excessively long. Dead chicks were seen from mid- June, both in the plot and throughout the colony, and predation by gulls added to chick losses through starvation. Just 2 chicks may have fledged from 142 egg-laying pairs, by far the poorest breeding season since monitoring began. Sandeels comprised a higher proportion of fish brought to the colony at the chick stage than in , but not all of these in 2011 may have been intended chick feeds. The boulder colony at nearby Compass Head had failed completely by mid-june, and no chicks were ringed there this year. On Fair Isle, the first eggs were seen at the monitoring plots on 12th May and the first chicks on 7th June, but none fledged, the 3rd year of zero productivity since monitoring began in From 1988 to 2002 productivity was fairly high, fluctuating between 0.67 and 0.85, but since 2002 it has tended Mean June counts of adult Common Guillemots in study plots at monitored colonies and percentage change from 2010 to *all birds are monitored at Burravoe and Eshaness Colony / Island Hermaness % Burravoe, Yell * % Eshaness * % Noss % Troswick Ness % Sumburgh Head % Fair Isle % Total %

10 Seabird Report 123 Common Guillemot breeding parameters in a single plot at Sumburgh Head. Breeding success is chicks fledged per laying pair. Sumburgh Head Laying pairs First egg date 23/4 10/5 13/5 11/5 8/5 4/5 4/5 2/5 2/5 29/4 Median laying date 9/5 21/5 23/5 26/5 19/5 11/5 16/5 10/5 9/5 9/5 Breeding success % Sandeels in chick diet 62% 53% 46% 46% 71% Common Guillemot breeding success in two study plots at Fair Isle. Breeding success is chicks fledged per apparently incubating adult. Fair Isle Peitron AIA Peitron success Da Swadin AIA Da Swadin success Mean success to be relatively low (< 0.5) or zero, especially so at Da Swadin where breeding numbers have fallen considerably since The number of fish brought back to chicks on a 24-hour feeding watch (27; 52% sandeels, 33% clupeids, 15% gadoids) was 78% less than in 2010 (122; 46% clupeids, 35% sandeels, 11% gadoids). Elsewhere, very few chicks were seen on the cliffs at Hermaness and Noss, and none were seen on the sea off Noss. Adult numbers appeared low on Foula, and only one chick was seen at east coast colonies there. Razorbill Alca torda There were decreases since 2010 at all monitored colonies, with the 2011 total being 68% lower than in However, there can be large daily fluctuations in colony attendance and a census count at Sumburgh Head recorded 204 birds on 19th June, c.f. 133 on 8th June No chicks were seen at Hermaness during the season, and none was seen on the sea off Noss, although success on Foula was believed to have been slightly better than for Common Guillemot. At Sumburgh Head, 47 incubating pairs were monitored, 7 were known to have hatched a chick but none were believed to have fledged. At Fair Isle, just one chick fledged from 63 breeding pairs in the Easter Lother monitoring plot. Mean June counts of adult Razorbills in study plots at monitored colonies and percentage change from 2010 to *all birds are monitored at Burravoe and Eshaness Colony / Island Hermaness % Burravoe, Yell * % Eshaness * % Noss % Troswick Ness % Sumburgh Head % Fair Isle % Total % Razorbill breeding success (chicks fledged per egg-laying pair) at a single plot on Fair Isle. Easter Lother Egg-laying pairs Breeding success

11 124 Systematic List124Shetland Bird Report Shetland Bird Report 2011 Black Guillemot Cepphus grylle Pre-breeding counts of adults along western coasts were hampered by persistent swell, and those at Hillswick Ness and between Mu Ness and Dale were of no use for monitoring purposes. The recent increase on Mousa appears to have come to a halt. Counts of around 200 adults on the island during the 1990s had halved by 2005 for reasons unknown, although predation at nests by an Otter, and its cessation after the death of the culprit, may be an explanation. The reduced count on the east coast of Fair Isle, between the North and South Lighthouses, was at odds with the trend of a gradual increase since Breeding success was monitored at nests in the boulder beaches on the east coast of Fair Isle from 1987 to 2000, but the use of these nest sites has since declined greatly and alternate, accessible sites have not been found. Allowing for all these factors, the Shetland breeding population appears to have increased since , perhaps by around 20%. Black Guillemot, Burravoe, Yell, July Brydon Thomason Atlantic Puffin Fratercula arctica On Noss, numbers seemed high but adults showed little interest in breeding, still bringing in nest material in mid-july. On Foula, numbers with chicks appeared very low, with only a few seen coming in with feeds, mostly of small larval fish, and none were seen carrying sandeels. At Sumburgh Head, the first recorded were 4 on 26th March, the puffincam pair first occupied their burrow on 14th April and laid on 6th May, but the chick was believed to have died at hatching. Few adults were later seen carrying fish, and it was thought a poor breeding season, with Pre-breeding counts of adult Black Guillemots at monitoring sites and percentage change is from 2010 to Counts in brackets were the only ones carried out that year, those not in brackets were the higher of two counts. Counts in bold were made in favourable sea/weather conditions. Those not in bold may have been low because of adverse sea or weather conditions, or because birds were difficult to flush from cliffs. West Coast Ronas Voe [101] [101] 114 [117] [112] 101 [137] 131-4% Hillswick Ness [238] [233] 266 [286] [293] [249] -15% Mu Ness Wats Ness 277 [276] [261] [273] 296 [336] [264] West Burra [186] [221] [230] [258] East Foula % East Coast Lunning [64] [67] % Levaneap 261 [273] [224] [271] % Kirkabister 153 [135] [164] [170] % Noss % Aithsetter [86] [95] [100] % Mousa 134 [108] [115] [99] 137 [158] [194] 182-6% Boddam-Virkie 137 [116] 123 [102] [121] [120] % East Fair Isle % West total East total Combined total

12 Seabird Report 125 Atlantic Puffin breeding success (chicks fledged per egg-laying pair) in a study plot on Fair Isle. Fair Isle Egg-laying pairs Breeding success predation of chicks by Herring and Great Blackbacked Gulls, and Hooded Crows. On Fair Isle, 2011 was not scheduled for a wholeisland count but the trend since 1989 has been of a gradual decline in numbers. In the productivity plot, eggs were first located on 4th May and chicks on 5th June, and breeding success was 18% higher than in Breeding success tended to be higher and less variable between 1987 and 2000 (14-year mean 0.72 ± 0.03 S.E.) than from (11-year mean 0.49 ± 0.06 S.E.), although in contrast to Common Guillemot and Razorbill there have been no years of zero productivity in the past decade. During a 24-hour feeding watch on 14th July, chick feeding frequency (86 fish loads, 1.68 feeds per burrow per day) was 70% lower than in 2010 (285, 5.85). Rockling Gaidropsarus was the most frequent prey type seen (72% of fish) followed by small sandeels (12%), compared to 2010 proportions of 36% small sandeels, 31% rockling and 12% large sandeels. Similarly, rockling and small sandeels predominated in food samples collected in 2011 (36% and 64%) and 2010 (20% and 63% of fish, respectively). The longest fish in these samples in 2011 were small sandeels (mean 31 mm), whereas they were large sandeels in 2010 (mean 111 mm), and the average weight of food loads (2.2 g) was the lowest since monitoring began in Since 2001, the average food load has exceeded 6 g only in 2005, whereas it exceeded 7 g in eight years between 1986 and In 2011, 50 colour-ringed Puffins were resighted from the year total of 106 colour-ringed individuals seen in 2010, giving a year-to-year survival estimate of 47% which was low compared with the estimate of 64%. From the year total of 127 colour-ringed birds known to have been alive in 2010, 71 were re-sighted in 2011 giving a year-to-year survival estimate of 56%, compared to the estimate of 80%. The long-term trend, shown by both methods of calculation, is that adult survival estimates were relatively high and stable from 1987 to 1999, but from 2000 onwards tended to be slightly lower. Acknowledgements We are extremely grateful to the following organisations and individuals for collecting and/or supplying the 2011 data on which this report is based: University of Aberdeen (SOTEAG) - Martin Heubeck and Mick Mellor; Fair Isle Bird Observatory - David Back, Sammy Fraser, Rob Hughes, Will Miles, Elisa Riera Miquel, Jason Moss and David Parnaby; Foula Ranger Service - Sheila Gear; Natural Research Projects - Mark Chapman, Simon Hulka, Digger Jackson; RSPB - Martha Devine, Pete Ellis, Rob Fray and Malcie Smith; Scottish Natural Heritage - Chris Dodd, Ruth McKee and Afra Skene; Shetland Ringing Group - Dave Okill and Roger Riddington. In addition, Newton Harper (RSPB) and Glen Tyler (SNH) helped check data from previous years. Reference Miles, W. T. S., Tallack, R. M., Harvey, P. V., Ellis, P. M., Riddington, R., Tyler, G. A., Gear, S. C., Okill, J. D., Brown, J. G. & Harper, N A survey of Leach s Petrels on Shetland in Scott. Birds 32: Atlantic Puffin, Hermaness, July Brydon Thomason M. Heubeck, University of Aberdeen (SOTEAG), c/o Sumburgh Lighthouse, Virkie, Shetland ZE3 9JN D. Parnaby, Fair Isle Bird Observatory, Fair Isle, Shetland ZE2 9JU