Although Guillemots at the southern edge of the range are known to return to the colonies in

autumn, usually only opportunistic observations of this behaviour are available. In the autumn of

2015 we took advantage of the live interactive cameras on the Isle of May, Fife to make systematic

checks of Guillemot colony attendance. Birds were recorded at dawn on 59 consecutive mornings

between 23 October and 20 December after which webcam images ceased due to lack of power on

the island. This prolonged period of attendance covered several periods of stormy weather and

appears unprecedented at this colony. Presumably local feeding conditions must have been

extremely favourable to enable the birds to spend so much time ashore

Harris, M.P.

Wanless, S.

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3Scottish Birds:  3–9Scottish Birds Records Committee report on rare birds in Scotland, 201136:1 (2016)The use of webcams tomonitor the prolonged autumnattendance of Guillemots onthe Isle of May in 2015M.P. Harris & S. WanlessAlthough Guillemots at the southern edge of the range are known to return to the colonies inautumn, usually only opportunistic observations of this behaviour are available. In the autumn of2015 we took advantage of the live interactive cameras on the Isle of May, Fife to make systematicchecks of Guillemot colony attendance. Birds were recorded at dawn on 59 consecutive morningsbetween 23 October and 20 December after which webcam images ceased due to lack of power onthe island. This prolonged period of attendance covered several periods of stormy weather andappears unprecedented at this colony. Presumably local feeding conditions must have beenextremely favourable to enable the birds to spend so much time ashore.IntroductionIndividuals of many species of pelagic seabird spend a relatively small proportion of the year atthe breeding colony and are often said to ‘only visit land to breed’. The Guillemot Uria aalge istherefore unusual in having a very variable pattern of colony attendance. Whereas in mostpopulations Guillemots do not return to the breeding ledges until March or April, at the extremesouthern end of the range in both the east Atlantic and east Pacific, birds start to come back tothe colonies from October onwards (Taylor & Reid 1981, Mudge et al. 1987, Boekelheide et al.1990). Indeed the earliest individuals return immediately after they have completed the mainmoult of the year, during which they are flightless, and are in full winter plumage with white facesand throats (Plates 2–4) (Harris & Wanless 1990a).Plate 2. Guillemots on the Isle of May, 21 October 1982 showing a range of plumages from full winter (extreme left)to almost full summer (extreme right). © Mike Harris.Scottish Birds:  3–94The use of webcams to monitor autumn attendance of Guillemots on the Isle of May in 2015From the 1960s to the 1990s Guillemots returned to the Isle of May National Nature Reserve, Fifeprogressively earlier such that arrival dates advanced from early November to the late Septemberor early October (Figure 1). However, since around 2000 this trend has been reversed so that inrecent years return dates have again been in early November (Sea Mammal Research Unit (SMRU)personal communication). During the 1980s, birds were sometimes present for many days inOctober but later in the autumn and in the middle of winter attendance became erratic with birdsoften absent for several weeks (personal observations). However, it was clear that levels ofattendance at the Isle of May and other colonies in eastern Scotland varied considerably betweenyears (Harris 1984, Mudge et al. 1987). Attendance also showed a clear daily pattern with birdsstarting to come ashore just prior to dawn and numbers peaking soon after. The time that theledges were occupied each day varied greatly from less than an hour to 3–4 hours and generallyattendance time was positively correlated with the number of birds ashore. Observations ofcolour-ringed individuals indicated that the birds were adults attending sites where they had bredthe previous summer and that the most frequently occupied sites were those where birds hadsuccessfully reared a chick and those with many neighbours (Harris & Wanless 1989, 1990b). Thusautumn attendance appeared to be due to competition for the best breeding sites and/or birdsreturning to maintain their pair bond (Plate 3).All these observations were made by observers present on the Isle of May for research on theseabirds or seals, or visitors to the Isle of May Bird Observatory. However, the advent of newtechnology has meant that it is now possible to monitor autumn attendance from the mainland.MethodsThe Scottish Seabird Centre, North Berwick, has live interactive cameras positioned at Pilgrim’sHaven on the Isle of May that are linked to the internet (www.seabird.org/wildlife/webcams/isle-of-may-cliff/). In spring and summer the cameras are mainly trained on Shags Phalacrocoraxaristotelis and Puffins Fratercula arctica while in the autumn and winter the main interest is the36:1 (2016)-10010203040506070Date (1=1 October) 19801950 1960 1970 201020001990Figure 1. The dates that Guillemots were first recorded ashore on the Isle of May, 1952–2015. Data are from Taylor& Reid (1981), Harris et al. (2006) and personal records.5Scottish Birds:  3–9The use of webcams to monitor autumn attendance of Guillemots on the Isle of May in 201536:1 (2016)Plate 3. Guillemots in winter plumage mating at a nest-site on the Isle of May, 21 October 1982. © Mike HarrisGrey Seals Halichoerus grypus and their pups. However, one camera includes views of twosections of the Guillemot colony and staff at the Scottish Seabird Centre arranged for these tobe monitored from first light until well into the day during autumn 2015. The images wererefreshed every few minutes and this allowed us to check if Guillemots were ashore eachmorning from 16 October until 20 December.A Guillemot in non-breeding plumage has a white throat and sides of the head which togetherwith its white underparts makes it stand out against the dark cliffs even in very poor light. Thesefeatures are particularly evident in the autumn when Guillemots are far less ‘relaxed’ than theyare in the summer with the result that they spend a considerable amount of time facing outwards(Plates 2, 4 & 5). Although the quality of some of the images downloaded from the internet waspoor, they were still adequate to identify when birds were ashore. Thus each morning from wellbefore dawn we checked the website every 15–20 minutes and saved the images. We latercounted the birds visible in the main area just to the north of Pilgrim’s Haven (Plate 4) usingPaint Shop Pro software. The counts of individual birds on the images were probably underes-timates since individuals facing towards the cliffs and those in dense groups may have beenoverlooked but we considered that the counts were adequate to provide a reliable index of thenumbers present. In 2014, some 200–400 pairs breed in this view. The other view showed justthe edge of a breeding group of c. 100 pairs and was used to determine when birds were presentwhen there were problems with the images of the main area.Checks were made throughout the day to determine when the birds finally departed. Although thecamera and the system for transmitting signals to the Scottish Seabird Centre are very robust,winter conditions can cause problems. Thus, during autumn 2015 occasional power and equipmentfailures resulted in a few breaks in transmission, spray from gale-driven waves reduced the clarityScottish Birds:  3–96The use of webcams to monitor autumn attendance of Guillemots on the Isle of May in 2015of the images and on a few days thickhaar prevented anything being seen.Fortuitously, staff from the Centre forEcology & Hydrology and ScottishNatural Heritage (SNH) and visitors tothe Isle of May Bird Observatory wereon the island when these problemsoccurred and were able to check ifGuillemots were ashore. However, onthese occasions we could not obtain anindex of the numbers present nor anestimate of when the birds departed.Observations ceased on 20 Decemberwhen the power supply on the islandfailed and there was nobody present tomake direct observations.Hourly meteorological data for Leuchars,30 km from the Isle of May (downloadedfrom www.ogimet.com/gsodc.phtml.en)were used to calculate the mean dailywind speed for the day of eachobservation and the previous day.Results and DiscussionGuillemots were first recorded ashoreon the Isle of May in autumn 2015 on20 October when three individualswere visible via the camera at 06:30GMT. Numbers peaked at 10individuals at 06:35 but the ledgeswere empty by 06:42, 11 minutesbefore official sunrise at Edinburgh, 30km to the west of the Isle of May. Wecannot discount the possibility that afew birds had been ashore on the Isle ofMay before this date but none wasreported by observers present on theisland. On 21 October five birds werepresent at 06:30 and these remaineduntil 07:45. The following day wasstormy with driving rain, rough seasand local wind speeds reached 82km/hr. Viewing conditions weretherefore extremely difficult, but nobirds appeared to be ashore. However,birds were definitely present thefollowing day and the colony wasoccupied every day until 20 Decemberwhen the camera ceased to function(Figure 2). Comparing the frequency ofGuillemot attendance in autumn 201536:1 (2016)Plate 4. Guillemots ashore in the area monitored by the ScottishSeabird Centre’s webcam at 06:55 hr on 29 October 2015.© Maggie Sheddan.Plate 6. Guillemots at the secondary monitoring site as seen via thewebcam on the Isle of May at 10:00 hr on 8 December 2015.© Scottish Seabird Centre.Plate 5. Guillemots still ashore on the Isle of May at 08:10 hr on 31October 2015. © Maggie Sheddan.7Scottish Birds:  3–9The use of webcams to monitor autumn attendance of Guillemots on the Isle of May in 201536:1 (2016)(A)1 = 1 October Hours after dawn012345(B)1 = 1 OctoberMaximum count 0204060801001201401608070605040302080706050403020Figure 2. Guillemot attendance on the Isle of May in autumn 2015 as monitored by the Scottish Seabird Centre’swebcams. (a) The length of time after dawn that birds were present on the ledges; open circles indicate days whendeparture times were not known. (b) Maximum counts of birds in the field of view of one camera; diamonds indicatedays when birds were present but not counted.Scottish Birds:  3–98The use of webcams to monitor autumn attendance of Guillemots on the Isle of May in 2015with other records indicates that the presence of birds on 59 consecutive mornings is unprece-dented. Staff from SMRU are usually present on the Isle of May throughout November. Theiropportunistic records indicate that overall Guillemots were ashore on 19 of 57 (33.3%) of earlymorning checks in November in 1995, 2008 and 2011. In 1981–83, we deployed time-lapsecameras at the Guillemot colony at Fowlsheugh (85 km north of the Isle of May) and recordedbirds ashore on 16 of 72 (22%) of days in November.Data from the webcam indicated that the more Guillemots that were ashore, the later in the daythey remained on the ledges. Thus by the last week in November when over 100 birds were presentin the area covered by the camera, birds were sometimes ashore for almost four hours. The timespent ashore then declined somewhat but overall there was a highly significant positivecorrelation between the maximum number of Guillemots counted in a day and the length of timebirds were ashore (r = 0.38, P = 0.008, n = 47 days). The relationship was apparent despite thefact that in some instances Guillemot numbers suddenly declined and a Herring Gull Larusargentatus or Great Black-backed Gull L. marinus could be seen standing in the area. In othercases where birds stayed for much shorter periods than anticipated, they could well have beendisturbed by researchers or birdwatchers or by fishing boats close in under the cliffs. Using hide-based observations in the 1980s we had previously found a similar positive correlation betweenmaximum numbers and length of time ashore when attendance levels were lower.A previous study in Caithness in the 1980s suggested that periods of attendance in autumn alwaysstarted when wind speed was low or declining (Mudge et al. 1987). However, conditions on theIsle of May in autumn 2015 were not unusually calm, indeed on the day prior to Guillemotsstarting to come ashore every day, local wind speeds reached 82 km/hr. Furthermore, during thesustained period of attendance there was no significant correlation between the maximum countand either mean wind speed on the current or previous day (r = - 0.15, P = 0.43, and r = 0.093,P = 0.62, respectively, n = 62). Similarly, data from Fowlsheugh over the 1980/81 winter foundno evidence of a direct link with weather (Harris 1984).Favourable local feeding conditions have also been suggested to be associated with autumnattendance. Thus in California, in years when food availability was high or average Guillemotsreturned to the cliffs in October whereas when feeding conditions were less good and/or winterswere especially stormy as a result of El Niño, arrival was delayed until the spring (Boekelheide etal. 1990, Ainley et al. 2002). We have no information on feeding conditions for Guillemots aroundthe Isle of May in autumn 2015 but the birds’ behaviour suggests that they must have had accessto a plentiful supply of food within commuting distance of the colony to enable them to visit theirbreeding sites when foraging time was limited due to relatively short days.The Scottish Seabird Centre webcam did not allow us to follow individual birds to determine whatfactors influenced individual-level attendance because none of the birds in the viewing area werecolour-ringed and in any case the quality of images would not have been good enough tofacilitate this. However, breeding success of Guillemots on the Isle of May in 2015 (0.79 chicksfledged per pair laying) was very similar to the mean value for 1982–87 (0.78 ± SE 0.01) whenhide-based observations indicated that the sites which were occupied most frequently were thosewhere breeding success was higher (Harris & Wanless 1989).Data from the webcam therefore indicated that Guillemots on the Isle of May in autumn 2015returned when we expected but the frequency of colony attendance was the highest recordedat this colony, or indeed at any other colony in Scotland. Breeding success in 2015 was notexceptionally high nor were autumn weather conditions exceptionally benign, so the mostlikely reason why Guillemots were ashore so much is that local feeding conditions must havebeen extremely favourable.36:1 (2016)9Scottish Birds:  3–9The use of webcams to monitor autumn attendance of Guillemots on the Isle of May in 2015Webcams are increasingly being used to record biological data and our observations highlight theirpotential to record colony attendance outside the breeding season. Although our interest wasinitially simple curiosity, plans for offshore wind and tidal energy generation mean that how muchtime pelagic seabirds spend close to the colony is highly relevant to marine spatial planning.AcknowledgementsWe thank Alexander Turnbull, Nigel Ward, Claudia Gehrig and Caroline Vevers at the ScottishSeabird Centre for their help and perseverance in keeping the webcams functioning, DavidSteel (SNH), Mick Marquiss and Maggie Sheddan for reporting on the attendance of Guillemotswhen there were problems with the cameras and Simon Moss, Paula Redman and othermembers of SMRU for checking the colonies in previous years. Norman Elkins extracted andinterpreted the relevant wind data.ReferencesAinley, D.G., Nettleship, D.N., Carter, H.R. & Storey, A.E. 2002. Common Murre (Uria aalge). In: Poole, A, & Gill, F. (eds) The Birds of North America. The Birds of North America, Inc.,Philadelphia, PA.Boekelheide, R.J., Ainley, D.G., Morrell, S.H., Huber, H.R. & Lewis, T.J. 1990. Common Murre. In: Ainley, D.G. & Boekelheide, R.J. (eds) Seabirds of the Farallon Islands. Stanford UniversityPress, Stanford.Harris, M.P. 1984. Monitoring winter attendance of guillemots at breeding colonies. Annual Report Institute of Terrestrial Ecology 1984: 73–74.Harris, M.P. & Wanless, S. 1989. Fall colony attendance and breeding success in the Common Murre. Condor 91: 139–146.Harris, M.P. & Wanless, S. 1990a. Moult and autumn colony attendance of auks. British Birds83: 55–66.Harris, M.P. & Wanless, S. 1990b. Breeding status and sex of common murres (Uria aalge) at a colony in autumn. Auk 107: 603–605.Harris, M.P., Heubeck, M., Shaw, D.N. & Okill, J.D. 2006. Dramatic changes in the return date ofCommon Guillemots Uria aalge to colonies in Shetland, 1962–2005. Bird Study 53: 247–252.Mudge, G.P., Aspinall, S.J. & Crooke, C.H. 1987. A photographic study of seabird attendance at Moray Firth colonies outside the breeding season. Bird Study 34: 28–36.Taylor, K. & Reid, J.B. 1981. Earlier colony attendance by Guillemots and Razorbills. Scottish Birds 11: 173–180.Mike P. Harris & Sarah Wanless, Centre for Ecology & Hydrology, Bush Estate,Penicuik, Midlothian EH26 0QBEmail: mph@ceh.ac.ukRevised ms accepted January 201636:1 (2016)

The use of webcams to monitor the prolonged autumn attendance of guillemots on the Isle of May in 2015

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The use of webcams to monitor the prolonged autumn attendance of guillemots on the Isle of May in 2015

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