Isle of May NNR - Annual Report 2021

Bex Outram
David Steel
Published: 2023

1. Biological recording

1.1 Introduction to breeding seabirds

NatureScot monitors breeding seabird populations as part of its management of the National Nature Reserve as well as to report on the Special Protection Area (SPA) qualifying species.

Further seabird monitoring is carried out by the UK Centre for Ecology and Hydrology (UKCEH), under contract to the Joint Nature Conservation Committee (JNCC).  Data from this monitoring work is integral to JNCC’s national system of long-term monitoring for seabird populations, as the island is one of four strategic monitoring sites in Great Britain.  The other three sites are Skomer, Canna and Fair Isle. 

NatureScot carries out the population monitoring of the cliff-nesting seabirds, gulls, eiders and terns.  UKCEH monitors the breeding success, survival and food intake of the auks, shags, fulmar and kittiwakes.  UKCEH, along with the Isle of May Bird Observatory Trust (IOMBOT), provides numerous other pieces of data invaluable to this report, such as the dates of first eggs and chicks and sightings of migrant birds, cetaceans and lepidoptera.

1.2 Population monitoring of cliff-nesting seabirds

1.2.1 Sections and timings

The detailed AIC methodology for the five cliff-nesting bird species (guillemot, razorbill, kittiwake, fulmar and shag) is set out in the Isle of May Monitoring Handbook (NatureScot, 2001, revised 2002 and 2011).  The island is divided into the same standardised count sections as have been used in previous years.  All species are counted once during the first week in June to capture a snapshot of the populations.  2018 saw the addition of counts from the sea, to allow those birds nesting in caves and areas unseen from land to be included in the population counts.

The majority of the all-island count was carried out by Bex Outram from 4^th to 10^th June.  In sections that were sensitive, data was provided by Mark Newell of UKCEH to avoid additional disturbance.

1.2.2 Cornerstone plot counts

The counts of individual razorbill and guillemot during the AIC are converted to estimates of pair numbers.  The number of both razorbill and guillemot pairs breeding at the Cornerstone plot is monitored by UKCEH.  A count of each species was made at the Cornerstone plot at the beginning of every count session.

For each species, the number of pairs known to be breeding at Cornerstone was divided by the relevant Cornerstone count, for every count session.  This provided a “k” value which represents the difference between the number of individuals counted and the number of actual breeding pairs.  By multiplying this “k-value” with the number of individual birds counted during a session, the number of pairs can be estimated for that session.  Keeping raw counts to within a few hours of the Cornerstone plot count allows for the variation in attendance of adults on the cliffs.

1.3 Results of cliff-nesting seabirds

The overall 2021 counts for each of the five cliff-nesting species on the Isle of May are shown in Table 14.1.  Counts from previous years are also shown for comparison.  Table 14.3 shows the different section totals for each species.  A comparison from the previous year, percentage change, is seen in Table 14.2.  Breeding success and return rates are shown in Table 14.7 and Table 14.8 respectively.

1.3.1 Fulmar

The number of apparently occupied sites (AOS) was 321 pairs, three less than last season.

The first egg was seen on 16^th May, the first chick was seen on 2^nd July, with the first fledged bird seen in late August.  The breeding success was 0.49 (chicks per pairs monitored), above the long-term average.

1.3.2 Shag

The number of apparently occupied nests (AON) was 491, a decrease of 4 AON from last year.

The plots monitored by UKCEH showed the highest return rate (94.2%) of adults.  They also had a good breeding season, 2.04 chicks fledging per breeding pair, the second highest productivity figure.

The first shag egg was noted on 25^th March at Horse Hole and the first chick hatched on 27^th April from the same nest.

1.3.3 Kittiwake

Continuing the increase last year, the kittiwakes increased 5% to 5,193 AON, the highest count since 1997 (6,518 AON).

The kittiwakes experienced a higher than average return rate, 84.3%, from the plots monitored and went on to have a good breeding season with a productivity of 1.34, the second highest. 

The first egg was seen on 17^th May, with the first chick on 15^th June and first fledged chick seen taking flight on 20^th July.

1.3.4 Guillemot

The total number of individual guillemots has increased 12% to 26,134.  To calculate the number of breeding pairs, the ‘k’ value is used: to determine this factor, the number of breeding pairs at the Cornerstone plot is used.  This is provided by Mark Newell at UKCEH.  This year, the Cornerstone plot increased by 78 pairs to 335.

Table 1: Number of pairs of guillemot at the Cornerstone plot, 2007-2021

Year	No. of pairs at Cornerstone
2007	198
2008	191
2009	198
2010	201
2011	205
2012	195
2013	193
2014	194
2015	220
2016	229
2017	232
2018	228
2019	238
2020	257
2021	335

 

Using the ‘k’ value, the number of guillemot pairs has increased by 7.7% to 18,156 pairs.

The return rate of the marked individuals was 86.8%, lower than the long-term average.  The guillemot breeding season was average, with each monitored breeding pair producing 0.74 chicks.  

The first egg was seen on 26^th April, the first chick on 29^th May, and the first jumpling was noted leaving the cliffs on 17^th June.

1.3.5 Razorbill

The number of individual razorbills decreased slightly, down 1.7%.  However, when converted into breeding pairs using the ‘k’value, the number of breeding pairs increased 16.7% to 4,813 pairs. The ‘k’ value is determined by using the number of breeding pairs in the Cornerstone plot, provided by Mark Newell of UKCEH.  The breeding pairs in this plot have increased to 108 pairs, the highest figure on record: 4,813 breeding pairs of razorbills is the highest figure the Isle of May has recorded.

Table 2: Numbers of pairs of razorbill at the Cornerstone plot, 2007-2021

Year	No  of pairs at Cornerstone
2007	71
2008	64
2009	67
2020	62
2011	69
2012	72
2013	74
2014	72
2015	81
2016	79
2017	82
2018	87
2019	91
2020	92
2021	108

 

The return rate of colour-ringed individuals is 90%, which is above the long-term average.  Razorbills also had an average breeding season with a below-average productivity of 0.55.

The first egg was seen on 25^th April, the first chick on 30^th May and the first fledged chick on 19^th June.

1.3.6 Cormorants

Cormorants are easily disturbed birds, flighty in nature, and with this “colony” at the north-west end of Rona there were no visits to this area.  Observations were made from the North fog horn and from the boats.  This showed that 14 nests were occupied this season, up 10 nests from 2020.

1.4 Population monitoring of ground-nesting seabirds

1.4.1 Puffin

The first puffins carrying fish were seen on 26^th May; this indicates that the first chicks had hatched.  The last puffin carrying fish was seen in late August; however, the majority of the colony had left earlier in the month.

The return rate of colour-ringed puffins was 91.3%; this is above the long-term average.  The puffins had a good breeding success, with 0.8 chicks per pair, above average.

UKCEH undertook a puffin census in 2017, which resulted in a count of 39,200 occupied burrows with a 95% confidence level of between 32,200 – 46,300 occupied burrows.

1.4.2 Herring and lesser black-backed gull

The first incubating herring gull was seen on the 26^th April, the first chick was noted on 30^th May, with the first chick fledging on 4^th July.  The first lesser black-backed gull egg was recorded on 6^th May.

 

Table 3: Total apparently occupied herring and lesser black-backed gull nests, Isle of May, 1982-2021

Year	Total apparently occupied herring and lesser black-backed gull nests
1982	2850
1983	3963
1984	3718
1985	3198
1986	2625
1987	2651
1988	2274
1989	2272
1990	2169
1991	2235
1992	2213
1993	3318
1994	3392
1995	4189
1996	4610
1997	4396
1998	4133
1999	4634
2000	4329
2001	4048
2002	3565
2003	3605
2004	3649
2005	3414
2006	4583
2007	4519
2008	4905
2010	5563
2012	5633
2014	6247
2016	5723
2018	5082
2021	6907

Gull management

As part of the Isle of May management plan, designated gull-free zones were introduced in 1997 to increase tern productivity.  These areas are North Plateau South to Lochside, East and West Braes, Beacon, St Andrews Well, Cross Park and Tennis Courts.  Five nests were removed from the Lowlight to St Andrews well and 39 nests were removed from Kirkhaven.

Specialist gulls that predated within the tern breeding colony were identified through tern watches and were removed; a NatureScot marksman shot one herring and one lesser black-backed gull at Kirkhaven on 9^th July.

1.4.3 Great black-backed gull

The first great black-backed gull egg was seen on 16^th April, the first chicks were seen on Rona on 18th May and the first fledged chick on 7^th July.

Nest count

The great black-backed gull population has increased to 116 pairs, the highest breeding count for the reserve.  The apparently occupied nests were recorded and mapped throughout the season.  The population on Rona was counted from the North Horn on 14^th May; nests were added through Sam Langlois-Lopez, PhD student, monitoring including the “mainland” population.

Productivity

Forty-six nests were monitored on Rona to establish a breeding productivity.  Numbered stakes were placed next to nests and with regular visits the number of eggs, chicks and fledged chicks was noted. The overall breeding success was low, 0.61, the lowest since the colour scheme was in place.

With the help of the IOMBOT and Mark Oksien we were able to continue with the colour-ringing scheme.  The yellow colour-rings were attached to the birds’ left leg whilst a metal BTO ring was attached to the right leg.  A total of 40 BTO rings were deployed and 26 colour-rings.

Table 4: Great black-backed gull, Rona

Figures for:	2019	2018	2017	2016	2015
Nests monitored	46	42	51	45	28
Breeding attempts	46	42	51	45	28
Number of eggs	120	117	140	124	75
Average clutch size	2.6	2.79	2.75	2.76	2.68
Hatched eggs	85	78	117	91	57
Hatching success	0.71	0.67	0.84	0.73	0.76
Number fledged	28	62	88	32	33
Productivity	0.61	1.48	1.73	0.71	1.18

 

1.4.4 Terns

For previous population counts, see Table 14.4, and for how 2020 counts relate to the previous season, see Table 14.5.

1.4.4.1 Roseate tern

Despite a pair summering on the island, there was no breeding attempt made.

1.4.4.2 Sandwich tern

Sandwich terns were seen throughout the season and ten pairs bred at the Beacon colony.  The first egg was discovered on 31^st May, the first chick on 25^th June, with the first chick fledging on 3^rd August.  Of the ten nests, each had one egg present and nine went on to successfully fledge chicks (productivity of 0.9).

1.4.4.3 Arctic and common tern

The first Arctic tern egg was laid on 22^nd May at the Jetty Triangle, and the first chick hatched on 16^th June, with the first fledged chick seen on 9^th July in the Mouse House field.

The first common tern egg was seen on 26^th May at the Beacon tern terrace, the first chick on 18^th June, with the first fledged chick seen on 12^th July.  The final chick departed the island on 1^st September.

Breeding pairs

Each year, around three weeks after the first egg-laying date, all tern nests on the island are counted to get a measure of total tern nest occupation.  On 18^th June, a whole colony count was completed with additional occupied nests added later in the season from monitored plots and extra counts of the Beacon terraces from the Beacon roof.  The count was completed by Bex Outram, David Steel, Chris Cachia-Zammit and Laura Kamp.  A total of 382 pairs of Arctic terns bred, 23 common terns (see Table 14.5).

Productivity

Four plots were chosen to monitor the breeding success of the Arctic terns this season.  Each nest was marked and the number of eggs, chicks and fledged chicks noted.  All chicks in these areas were ringed, helping keep track of the number of chicks that fledged from each plot.  This was then used to calculate a productivity figure.  The table below shows the different areas monitored and their productivity and the overall productivity figure: 0.55 chicks fledging per pair, an increase on last year’s figure of 0.03.

Table 5: Arctic tern breeding productivity, 2021

Figures for:	Mouse House Base	Jetty Triangle	Overall
Nests monitored	89	94	183
Breeding attempts	89	94	183
Eggs	129	167	296
Average clutch size	1.45	1.78	1.62
Number hatched eggs	108	78	186
Hatching success	0.84	0.47	0.63
Fledged	71	40	111
Productivity	0.80	0.43	0.61

Predation

As usual, the main tern watches were undertaken at the main Arctic tern colonies at Kirkhaven and the Beacon area of the island.  A total of 134 hours were completed at all stages of the breeding cycle from incubation to fledging stage.  The season proved very successful, with predation at a minimum, and only one specialist gull was identified and removed by a NatureScot marksman.  This, combined with protective measures such as tern nest boxes and the use of garden canes to help protect vulnerable young, proved effective in having a good tern season.

1.4.5 Eider

The first sitting female was seen on 20^th April, with the first brood of duckling seen on Rona on 9^th May.

Nest count

No nest count was conducted this year.

Eider management

No management specific to eiders was undertaken this year.  Visitors were warned during their introductory talk that females would be nesting close to the path network and of the potential risk of coming across a female taking her ducklings to water, and advised to give them a wide berth.  Some ducklings were found paralysed from nettle stings; these were kept in a box for an hour or so until they had recovered and then put with females and ducklings on the Loch, who took them into their crèche.

1.5 Other breeding birds

These are observations of numbers from around the island from NatureScot staff and volunteers, UKCEH and members of the Isle of May Bird Observatory.

Manx Shearwater (Puffinus puffinus)

Work by David and Margaret Thorne and Harry Urquhart, IOMBOT, identified nest activity on the island and identified one occupied burrow.  The same male and a female were seen and recorded regularly at the burrow until mid-August but no breeding attempt was made.

Shelduck (Tadorna tadorna)

During the early season there appeared to be just two pairs around the island.  Only one female was seen with ducklings this year: on 10^th June, a female and nine duckling were seen leaving East Tarbet.

Table 6: Number of pairs of shelduck, 2007-2021

Year	No. of pairs
2007	3 - 4
2008	5
2009	6
2010	6
2011	4 – 8
2012	6
2013	4
2014	3-4
2015	3-4
2016	4
2017	3-4
2018	3
2019	4
2020	No count
2021	2

 

Mallard (Anas platyrhynchos)

One pair of mallard were seen regularly on the loch.  On 22^nd June, a female and five ducklings were seen on the loch.  On 29^th June, a female and three small ducklings were seen on Rona, most probably a different female.

Table 7: Number of pairs of mallard, 2007-2021

Year	No. of pairs
2007	2
2008	0
2009	0
2010	0
2011	0
2012	0
2013	2
2014	3
2015	0
2016	0
2017	0
2018	0
2019	1
2020	No count
2021	2

Oystercatcher (Haematopus ostralegus)

This year, a total of 17 nests were identified.  Although no monitoring of the nests was undertaken, several pairs successfully fledged chicks.

Table 8: Number of pairs of oystercatcher, 2007-2021

Year	No. of pairs
2007	19
2008	19
2009	17
2010	17
2011	14
2012	16
2013	9
2014	20
2015	19
2016	24
2017	13
2018	20
2019	25
2020	No count
2021	17

Feral pigeon (Columba livia (domest.))

No specific counts were made of feral pigeons on the island.  They nest on the island in burrows and rock crevices.

Swallow (Hirundo rustica)

Three pairs bred on the island; a pair in the coal shed, a pair in the artificial nest cups at the visitor centre and another whose nest location was not found. All had fledged two broods, with the last of the family party remaining until the end of September.

Table 9: Number of pairs of swallow, 2007-2021

Year	No. of pairs
2007	0
2008	0
2009	0
2010	0
2011	0
2012	2
2013	3
2014	3
2015	6
2016	4
2017	4
2018	4
2019	1
2020	4
2021	3

Rock pipit (Anthus petrosus)

The first rock pipit with nesting material was noted on 19^th April, the first chick on 15^th May.  Breeding territories were plotted on a map, with twenty four being noted through the season.

Table 10: Number of pairs of rock pipit, 2007-2021

Year	No. of pairs
2007	8-9
2008	9-10
2009	12-14
2010	15
2011	13
2012	23
2013	18
2014	24
2015	24
2016	20
2017	15
2018	23
2019	No count
2020	No count
2021	24

Pied wagtail (Motacilla alba)

Pied wagtail territories were plotted on a map throughout the season and approximately sixteen pairs bred.

Table 11: Number of pairs of pied wagtail, 2007-2021

Year	No. of pairs
2007	8
2008	9
2009	11
2010	12
2011	13
2012	18
2013	14
2014	13
2015	12
2016	12
2017	9
2018	10
2019	No count
2020	No count
2021	16

Carrion crow (Corvus corone)

One pair was noted for much of the year, “Patch” and partner (Patch named after a white patch on the chest, making this individual easily identifiable), the same individual as in previous years.  This pair were joined by four others, possibly the young from last year, for the early part of the season.  None made an attempt to breed on the island.

Peregrine falcon (Falco peregrinus)

No breeding attempt was made this year.  Individuals were present on the island for the majority of the spring, which included a male and young female.  These were often seen at ‘Peregrine’s Nest’, where in the past others have bred; it appeared this pair were just feeding.

Wood pigeon (Columba palumbus)

Two pairs have bred this season.  The nests of the first attempts were not found; however, two fledglings were noted on 24^th June and then a further one fledging in July, indicating two different pairs.  On 5^th September, when undertaking a wader count, a nest was found on the ground within a clump of red goosefoot along the east side of the island containing two eggs.  A further nest with two eggs was identified in elders at the low Light on 6^th September, confirming two pairs breeding on the island.

1.6 Wader counts

Wader counts were undertaken weekly from the end of July onwards, once the breeding seabirds had departed from breeding sites.  See Table 15 for the peak counts per month.

1.7 Mammals

1.7.1 Grey seal

The number of adult seals started to increase throughout September and the first seal pup was born on 30^th September at Mill Door. 

1.7.2 Cetaceans

The report is a combination of observer effort from the residents of Fluke Street and the Isle of May Bird Observatory as well as the staff who work on the various visitor boats.  Overall, it was a reasonable year for whales and dolphins, with three species recorded in May waters, which included a good showing of Minke Whales during the autumn months.  More interestingly, a potential Sei Whale was spotted in early October.

Harbour porpoise (Phocoena phocoena)

A scattering of sightings in the spring included two on 31^st March, a single on 25^th April, and two on 27^th May.  It was not until July that the species started to be reported on a regular basis, with 1-3 on four July dates, with four on 10^th July, whilst August produced 1-3 on seven dates, with a peak of four on 22^nd August.  As usual, autumn produced the bulk of records, with 1-5 on four September and eight October dates, with peaks of six on 25^th September and 9^th October, and seven on 7^th September.  The last records of the year occurred in early November, with 1-2 on six dates between 2^nd and 10^th November, with a peak of three on 8^th November.  

Bottle-nosed dolphin (Tursiops truncatus)

As usual, there were regular reports from visitor boats of small numbers hugging the coast along Fife and Lothian, but the species is scarce further out in island waters.  A single on 22^nd June was the only spring sighting.  Other records included 18 on 25^th September, 1-5 on four October dates, with peaks of 15 on 26^th October, and 12 on 27^th-28^th October.

Minke whale (Balaenoptera acutorostrata)

It proved to be a productive year for this baleen whale, with the first record of the year not until midsummer (which is the norm) with a single off the west side on 8th July.  Thereafter, records started to increase, with singles on seven dates from 16^th-29^th August and 1-2 daily between 3^rdand 8^th September.  The most productive month of the year was October, with 1-2 seen around the island on 10 dates, with a series of sightings early in the month being noteworthy.  These included four on 7^th October, an impressive eight on 8^th October and five still on 9^th October.  These animals were feeding off all parts of the island, taking advantage of migratory fish, and on occasions could be detected on calm days by the sound of their breathing.  A late individual was seen off the north end of the island on 4^th-5^th November.

Whale spp.

One of the most intriguing and interesting reports concerned a whale sp. off the east side of the island on 1^st October, which was potentially a Sei Whale.  The animal surfaced twice and the large ‘blow’ was noted at some distance, but not enough was captured to confirm the sighting.  A few weeks later, during the week of 11^th October, a similar event occurred, with a large whale blow off the east side.  This followed the record of a long staying Sei Whale in the upper Forth which was also seen in St. Andrews Bay in late September.

1.8 Lepidoptera

1.8.1 Butterfly

Records of butterflies were made by informal observations from members of Fluke Street and the IOMBOT residents throughout the season.  The first butterfly record was a single peacock on 17^th March.  A transect walk was established in 2020, in conjunction with UK Butterfly Monitoring Scheme (UKBMS), and continued for a full season this year.  A transect is walked once a week by NatureScot staff/volunteers and all butterflies are recorded within 5 metres of the transect line.  Specific weather conditions have to be met for a transect walk to take place, which can limit the number of walks per season (1^st April – 30^th September).  In total, 17 survey walks were conducted: see the results below in Figure 10.

Nine species were recorded throughout the year.  The most frequently recorded species was the small tortoiseshell, noted in almost all months from March to October, and the most numerous was the red admiral.  August was the month with the highest count of butterflies.  Wall was recorded on six days, with a peak of two individuals; this is a species that is becoming more common on the Isle of May, along with speckled wood, recorded on one day in 2021.  See Table 16 for full details of the records.

1.8.2 Moth

Moth trapping at Fluke Street was undertaken by NatureScot staff and volunteers from March through to October.  The MV light trap was set up in the garden outside the principal keeper’s cottage; the trap could be moved into the outdoor shelter during adverse weather and when puffins were leaving their burrows (to prevent them from being drawn towards the light).  A second trap was available to those at the IOMBO, who had the trap running by the Low Light bushes.  Trapping was carried out from 28^th March until the end of the season, with the last trap of the year on 20^th October.

Trapping was conducted on a total of 54 nights, with a total of 92 different macro species being recorded along with 14 micro moths.

Four new species were first records for the Isle of May: figure of eighty, grass rivulet, grey pine carpet and brindled pug.  Centre-barred sallow, copper underwing and gold spot were recorded for the second time.

The most numerous moth caught was bright-line brown-eye.  It was regularly caught throughout the season, on a total of 28 nights, and 104 individuals were caught on 7^th June.

2. VISITOR REVIEW

It proved to be an interesting but successful visitor season despite the Covid restrictions.  The start of the season was delayed from the usual 1^st April opening, with the first boats sailing from 26th April.  Even then, all boats were restricted and not running at capacity throughout the summer until all restrictions were lifted on 9th August.  Despite this, with a combination of staycation and popularity, the island still attracted over 10,000 visitors, which was impressive considering the restrictions in place.

As usual, boats departing from Anstruther brought the majority of visitors, with the May Princess bringing 7,981 whilst the fast RIB Osprey carried a further 1,280.  During the season, boats travelled from the Lothian side of the Firth of Forth, with the Seabird Centre RIB bringing 1,043 and BlueWild a further 98.  Small private leisure craft and kayaks carried a further 152 visitors, bringing the annual total to 10,544.

Table 12: Visitor numbers on individual boats, 2021

Month	May Princess	Osprey RIB	Seabird RIB	Bluewild	Others	Total
April	128	37	16	0	21	202
May	1,219	225	208	0	14	1,666
June	1,586	239	218	26	8	2,077
July	1,987	336	326	42	53	2,744
August	2,249	288	172	23	52	2,784
Sept	812	155	103	7	4	1,081
Total	7,981	1,280	1,043	98	152	10,554

 

Table 13: Annual totals for each individual boat operator, 2015-2021

Year	May Princess	Osprey RIB	Seabird RIB	Others
2021	7,981	1,280	1,043	152
2020	-	-	-	-
2019	11,551	1,474	984	239
2018	11,112	1,373	1,029	221
2017	10,385	1,349	798	251
2016	9,830	1,327	743	164
2015	8,803	1,219	669	238

3. VOLUNTEER REVIEW

Due to Covid restrictions applying to accommodation use, the volunteering scheme did not return to normal (which is usually two volunteers for the summer months).  Last year was similar and as a result the island staffing levels were below normal.  However, once restrictions allowed, one recruit was taken on, Christopher Cachia-Zammit, who was on the island from 7th June-8th September.  Chris was another good appointment and helped in all aspects of the island from visitor work to seabird monitoring.  

As well as our long-term volunteer, NatureScot students and seasonal staff, Maisie, Julie, Esther, Ellie, Ian and Andrew from Tentsmuir NNR, Loch Leven and the Stirling reserves helped for a week in September.  All six volunteers were resident on the island from Monday 13th-Friday 17th September and various island tasks were completed, including clearing timber off Rona, tern terrace construction and various painting jobs, amongst others.  Other help during the year came from short-term volunteers who helped on a day-to-day basis.

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