2. Introduction
The first survey of the productivity of the Common Guillemot Uria aalge population at St.
Abbs Head National Nature Reserve (NNR) was completed in 2014, making this year’s
survey only the second of its kind. Common guillemots are by far the most numerous
breeding seabird at St. Abbs Head NNR with the most recent whole colony count in 2013
estimating a population of 32,990 birds (Cole 2013).
The productivity of the Razorbill Alca torda population was completed alongside the common
guillemot productivity survey in 2014 but had also been conducted in isolation on occasional
years. The most recent whole colony count of the razorbills in 2013 estimated a population
of 1,820 birds (Cole 2013).
Both common guillemots and razorbills are member of the Auk family and share many
behavioural traits: they both form monogamous pair-bonds which are maintained from year
to year; they form gregarious nesting colonies during the breeding season; and the pair
shares all breeding duties: incubation, brooding, feeding and defence of nest-area territory.
Furthermore, in both species a maximum of one chick is successfully fledged per season
(Cramp & Simmons 2004).
As such both species productivity are surveyed in much the same way, and so visits to
common guillemot and razorbill plots can be made simultaneously. As both common
guillemots and razorbills build no nests it makes it difficult to assess which birds breed and
which chicks fledge. This means monitoring the productivity of this species requires
intensive effort with daily or near-daily visits to the survey plots (Wash et al. 1995).
Methodology
The methodology used was based on the common guillemot productivity-monitoring method
and razorbill productivity-monitoring method 1 in the Seabird Monitoring Handbook (Wash et
al. 1995).
In 2014, five common guillemot plots were monitored on 13 visits between the 25/05/15 and
the 01/07/15. The mean productivity on the colony was calculated as 0.46 ± 0.12 (Common,
2014a). In addition, four razorbill plots were monitored on 13 visits between the 21/05/15
and the 05/07/15. The mean productivity on the colony was calculated as 0.43 ± 0.029
(Common 2014b).
After the 2014 reports were distributed, Mike Harris, one of the authors of the Seabird
Monitoring Handbook, gave feedback that the common guillemot productivity was lower than
he expected. He suggested that the number of plots monitored was reduced, the monitoring
period lengthened and the frequency of visits increased. These suggestions were
implemented for both the common guillemot and razorbill productivity-monitoring in 2015.
The plots monitored in 2014 were revisited and from these three common guillemot plots
and two razorbill plots were selected to be included in the 2015 survey. The common
guillemot plots were Cleaver Rock, Downie’s Goat and Headland Point, and the razorbill
plots were Cleaver Rock and Hope’s Heugh. The plots selected could be surveyed from a
closer position and a better viewing angle, so that observations of site contents would be
more likely to be made and with more confidence.
Crummack, C. 2014
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3. The photographs taken of the plots in 2014 lacked contrast and brightness, which made it
difficult for the observer to re-located the nests that were surveyed. For this reason, new
photographs were taken. The annotated plot photographs and maps showing the location of
the observer in relation to the plot are included in the appendices.
As recommended in the methodologies from the Seabird Monitoring Handbook each plot
was visited three times and the location of active sites were recorded. Then 50 sites at each
of the common guillemot plots that had been recorded as active on all three occasions were
selected for monitoring. Similarly, 25 sites at each of the razorbill plots were selected for
monitoring. The sites were selected on the basis that the contents of the site was visible and
the site was located near features on the cliff that would help the observer locate it on
subsequent visits.
Productivity-monitoring of the common guillemots began on the 02/05/15 and productivity-
monitoring of the razorbills began on the 20/05/15. Visits were made on 5 days of every
week, unless the weather conditions were considered to be unsafe. There were more days
of very high-winds than was expected during the season, with visits deemed unsafe on 20
days during the common guillemot productivity-monitoring period and 13 days during the
razorbill productivity-monitoring period.
The common guillemot plots were surveyed before the razorbill plots. On the 28/05/15,
30/05/15 and 03/06/15 unsafe weather conditions stopped work, so the common guillemot
plots were surveyed but the razorbill plots were not. Table 1 gives an analysis of the time,
length and frequency of the survey period by the different plots.
Once daily visits of the common guillemot plots had commenced it became apparent the
amount of effort which was required was not sustainable, so the common guillemot plot at
Headland Point was purged from the survey. Thus two plots of common guillemots
containing a total of 100 sites and two plots of razorbill containing a total of 50 sites were
monitored for the duration of the 2015 season.
From the 02/07/15 common guillemots plots where no adult or one adult was observed on
the previous visit ceased to be monitored, similarly this occurred on the 03/07/15 at the
TABLE 1: ANALYSIS OF TIME, LENGTH AND FREQUENCY OF SURVEY PERIOD
Plot
No.
Plot
Name
Species Average
Start
Time
Earliest
Start
Time
Latest
Start
Time
Start
Date
End
Date
Survey
Length
Visits Days of
Bad
Weather
Days
-off
1 Cleaver
Rock
Common
Gullemot
11:08 07:45 15:35 2-May 16-Jul 75d 34 20 22
2 Downie’s
Goat
Common
Gullemot
12:06 08:30 17:00 2-May 16-Jul 75d 34 20 22
3 Cleaver
Rock
Razorbill 12:52 08:00 17:35 20-May 3-Jul 44d 21 19 22
4 Hope’s
Heugh
Razorbill 13:01 08:45 17:35 20-May 9-Jul 50d 24 19 21
Crummack, C. 2014
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4. razorbill plots. The remaining nests were monitored until no adult or one adult was observed
at the nest.
Observations were made using a spotting scope and recorded in a field notebook. The date
of each visit was recorded along with the survey start time at each plot. Then one of the
observation codes were used to define the contents at each site, see table 2 below.
At the beginning of the common guillemot productivity-monitoring the observer realised that
when they recorded the nest contents as “Incubating Adult” the bird may just be sitting and
the site could be inactive. As the codes form a series which progresses through the breeding
stages, this code was also used when there was an apparent pair with one of the birds
incubating. An apparent pair with one of the birds incubating is more indicative of an active
site than a single bird possibly incubating or sitting, so the observer included the “Incubating
Pair” code at the beginning of the razorbill productivity-monitoring to help establish whether
a site was active or not.
The content codes are taken from the Breeding success checklist (A). The brood code
definitions used in this survey are simplified from Table Gm.1: Guide to ageing guillemot
from the Seabird Monitoring Handbook and combines some of the age classes. Breeding
success checklist (A) is included in the appendices.
The observations were then copied on the observers return to the office onto the Breeding
success checklist (A), as recommended in the Seabird Monitoring Handbook, and provided
as an appendix. A notebook was much more convenient to use in the field, particularly in
high-winds and this method also ensured there was a copy of the results.
TABLE 2: SITE CONTENT CODES AND DEFINITIONS
Code Defintion
0 No Adult
1 One Adult
2 Two Adults
P Apparent Pair
IP Incubating Pair*
I Incubating Adult
C Clutch
BS Brood Small - chick covered in downy feathers
BM Brood Medium - dark ‘mask’ on eye
BL Brood Large - clean-looking black and white plumage
*Only used in razorbill productivity-monitoring
Crummack, C. 2014
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5. Results
At St. Abbs Head NNR in 2015, a total of 62 common guillemot broods fledged from 85
active sites across two plots. The productivity of the common guillemot colony is calculated
as 0.67 ± 0.03. In addition a total of 16 razorbill broods fledged from 43 active sites across
two plots. The productivity of the razorbill colony is calculated as 0.32 ± 0.07. Table 3 gives
these results by the individual plots. The productivity for each plot is the mean of the
‘Fledged/Active + Regular Sites’ and ‘Fledged/Active Sites’ and standard error is calculated
using the same values. The colony productivity and standard error is the mean the
productivity and standard error values for plots of the given species.
Sites were included as active if a clutch and/or a brood was observed. A site was included as
regular if an ‘apparent pair,' ‘incubating pair’ and/or ‘incubating adult’ were frequently
observed but a clutch or brood was not. Sites where none of these conditions were meet
were deemed inactive.
Table 3 and Chart 1 shows the outcome of the sites surveyed in five categories, and
includes the number of inactive and regular sites at each plot. Sites where the ‘brood
fledged’ or ‘brood failed’ or ‘clutch failed’ are active sites with respect to the productivity
calculations. A site was categorised as ‘clutch failed’ if a clutch was observed but a brood
was not.
In alignment with the definition in the Seabird Monitoring Handbook a brood was considered
fledged if it was observed 15 days after the initial observation of a brood at the site. Although
there were 9 sites where a brood was categorised as fledged without meeting this criteria.
There were 3 sites where the brood was categorised as medium or large on it’s first
observation, 2 of these were defined as large on their last observation of and categorised as
‘brood fledged’ and 1 was defined as medium on their last observation and was categorised
as ‘brood failed’.
TABLE 3: PRODUCTIVITY RESULTS
Plot No. Plot Name Species Fledged/Active +
Regular Sites
Fledged/Active
Sites
Productivity Standard
Error
1 Cleaver Rock Common Gullemot 0.71 0.74 0.73 0.02
2 Downie’s Goat Common Gullemot 0.60 0.64 0.62 0.03
3 Cleaver Rock Razorbill 0.22 0.32 0.27 0.07
4 Hope’s Heugh Razorbill 0.32 0.42 0.37 0.07
TABLE 4: OUTCOME OF SITES
Plot No. Plot Name Species Inactive Regular Clutch failed Brood failed Brood Fledged
1 Cleaver Rock Common Gullemot 7 2 3 6 32
2 Downie’s Goat Common Gullemot 3 3 4 10 30
3 Cleaver Rock Razorbill 6 7 4 2 6
4 Hope’s Heugh Razorbill 1 7 4 3 10
Crummack, C. 2014
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6. There were also 7 sites where a brood was defined as small on the first observation and
large on the last observation, these broods reached an estimated age of 13 to 14 days, and
so were also categorised as ‘brood fledged’.
Also note, that there were 5 sites where the brood meet the criteria for categorisation of
‘brood fledged’ by reaching at estimated age of 15 days but they were defined as medium on
the last observation.
CHART 1: OUTCOME OF SITES
There were 39 sites where brood was observed but a clutch was not. At 11 of these sites the
‘brood failed’ and at 28 of these site the ‘brood fledged’. Table 5 gives the number of these
instances by plot.
The first observation of a common guillemot clutch was on the 02/05/15 and the last
observation of a common guillemot brood was on the 14/07/15, this indicates a breeding
season of 73 days. The first observation of a razorbill clutch was on the 20/05/15 and the
last observation of a razorbill brood was on the 07/07/15, this indicates a breeding season of
48 days.
TABLE 5: MISSED CLUTCHES
Plot No. Plot Name Species No. of Sites Brood Failed Brood Fledged
1 Cleaver Rock Common Gullemot 16 6 10
2 Downie’s Goat Common Gullemot 11 2 9
3 Cleaver Rock Razorbill 5 2 3
4 Hope’s Heugh Razorbill 7 1 6
Crummack, C. 2014
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Plots
1
2
3
4 40%
24%
60%
64%
12%
8%
20%
12%
16%
16%
8%
6%
28%
28%
6%
4%
4%
24%
6%
14%
Inactive Regular Clutch failed Brood failed Fledged
7. Discussion
The productivity of the common guillemot colony has increase from 0.46 ± 0.12 in 2014 to
0.67 ± 0.03 in 2015. Monitoring commenced on the 02/05/2015 and 34 visits to each plot
were made, this was 23 days earlier than 2014 and 23 more visits. Moreover, the number of
plots monitored went from 5 in 2014 to 2 in 2015. The scale of increase in productivity in
2015 compared to 2014 would suggest that the productivity in 2014 was underestimated and
that by implementing the suggestions given by Mike Harris the accuracy of the productivity
figure increased.
However, the productivity of the razorbill colony is low at 0.32 ± 0.07, compared to 0.43 ±
0.029 in 2014. Monitoring commenced on the 20/05/2015 and an average of 22.5 visits to
each plot were made, this was 1 day earlier than 2014 and an average of 9.5 more visits.
Moreover, the number of plots monitored went from 4 in 2014 to 2 in 2015. The productivity
is possibly an underestimate as due to the sample size not being sufficient. Or, as the 2014
and 2015 values are quite similar, it could be a reflection of the state of the razorbill colony at
St. Abbs Head NNR. This would suggest that continued productivity-monitoring and colony
counts of this population are important to establish in the colony is undergoing a significant
decline.
In order to establish if these low productivity values are not an underestimate, it would be
recommended that the number of razorbill plots are increased back to four and the number
of sites to approximately 100, next season. This would bring the sample size in line with the
common guillemots whose productivity result appears to be accurate.
Since completion of the productivity-monitoring and after rereading the methodologies given
in the Seabird Monitoring Handbook it has become apparent that their were two
misinterpretations during the 2015 season.
Firstly, the observer plotted exactly 50 sites at each guillemot plot and 25 at each razorbill
plot. The methodology states that plots should contain approximately 50 sites and 25 sites
respectively. It also states to plot the position of all active sites on the plot photograph.
Secondly, the observer did not add any new active sites at any of the plots.
After completion of the productivity-monitoring the observer contacted Mike Harris to confirm
if the productivity-monitoring methodologies from the Seabird Monitoring Handbook had
been misinterpreted and what impact this would have on the results. He confirmed that
these were misinterpretations but said that this would not have an impact on the results.
Even if these misinterpretations did not have an impact on the results, for the purposes of
repeatability of the auk productivity-monitoring at St. Abbs Head NNR, it would be
recommended that in future seasons the observer plots all active sites on the plot
photographs.
The deviations from the methodology are more pronounced at the common guillemot plots,
as the plot photographs used this season contain a very large number of sites. The observer
plotted sites that they believed they could relocated easily and which they would be able to
see the contents. That meant that only some active sites within the plot photographs were
Crummack, C. 2014
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8. monitored. So for future seasons, the plot photographs require an area to be delimited within
them so that they contain approximately 50 sites.
Conversely the razorbill plot photographs do contain approximately 25 sites so most active
sites within the plots were monitored. These plot photographs could be used in future
seasons without the need to delimit an area within them.
Plotting the positions of active sites on the plot photographs is the most challenging aspect
of the common guillemot productivity-monitoring. Due to the size and density of the colony, it
was very hard for the observer to be confident that nests were being accurately relocated on
each visit during this stage.
As nest sites remain virtually unchanged, if all active sites in the delimited plot photographs
were plotted, monitored sites could also remain virtually unchanged and be monitored from
year to year. For new observers undertaking the auk productivity-monitoring at St. Abbs
Head NNR for the first time, this would make the initial and most challenging aspect of the
survey much more manageable. Presumably, it would also have a positive effect on the
accuracy on the results.
The observer was concerned at the common guillemot plots that in areas where the birds
were densely packed they would not be able to observe the contents of the nests. As noted
in the results section there were 39 sites where a brood was observed but a clutch was not.
This was despite the observer selecting sites which they believed observations of clutches
would occur. In hindsight, this was not something that needed to be of concern, as although
the observer did not observe some clutches they were confident that all broods were
observed.
At the beginning of the season it is difficult to tell whether the birds are incubating or if they
are resting on the cliffs. Only when they lift their chests off the cliffs to preen themselves is
there a chance of observing a clutch. Most of the time they appear to be sleeping and do not
move at all during the period of observation. This results in many recordings of ‘incubating
adult’ at the sites in the early part of the season.
However, there is a distinct change in the birds behaviour once the clutch has hatched. In
many instances when a small brood was observed for the first time, it was noticed that both
parents were present at the site shielding the chick in a ‘tent-like’ manner with their wings.
Furthermore, the adults appeared to interrupt incubating more frequently to preen
themselves and the chicks, thus allowing the brood to be observed. As the broods grow, they
become more active and are more likely to be observed. They also reach a point where they
become too large to be incubated against the brood-patch and instead are held under the
adults wing; when they reach this stage their presence cannot be missed.
Despite the two misinterpretations of the common guillemot and razorbill productivity-
monitoring methods from the Seabird Monitoring Handbook the results for the common
guillemots appear to have improved from last year and lessons were learned which can be
applied in the next season.
Crummack, C. 2014
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9. These are the key recommendations for next seasons survey:
A. Delimit the common guillemot plot photographs so that they contain approximately 50
pairs.
B. Increase the number of razorbill plots to 4 so that approximately 100 pairs are monitored.
C. Plot all active sites onto the plot photographs, record the site contents at this stage as it
will help establish if it is an active site. This will require a lot of effort.
D. Use the incubating pair code when plotting active sites of both the common guillemot
and razorbill and continue to use it throughout the productivity-monitoring.
E. Add new active site as they appear.
F. Focus effort on recording small broods as soon as they appear, once the first one is
observed visits should occur daily in order to get accurate age estimates.
Crummack, C. 2014
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10. References
Cole, L. 2013. St Abb’s Head National Nature Reserve Seabird Report for 2013.
Unpublished, available from the National Trust for Scotland, St. Abbs Head NNR.
Common, J. 2014a. The breeding success of Guillemots (Uria aalge) at St. Abbs Head
National Nature Reserve during 2014. Unpublished, available from the National Trust for
Scotland, St. Abbs Head NNR.
Common, J. 2014b. The breeding success of Razorbills (Alca torda) at St. Abbs Head
National Nature Reserve during 2014. Unpublished, available from the National Trust for
Scotland, St. Abbs Head NNR.
Cramp, S. & Simmons, K. E. L. (eds.) 2004. BWPi: The Birds of the Western Palearctic
Interactive. DVD-ROM. Sheffield: BirdGuides Ltd.
Walsh, P.M., Halley, D.J., Harris, M.P., del Nevo, A., Sim, I.M.W., & Tasker, M.L. 1995.
Seabird monitoring handbook for Britain and Ireland. Published by JNCC / RSPB / ITE /
Seabird Group, Peterborough.
Appendices
1. 2015 Auk Productivity-Monitoring Plots - Location Map.pdf
2. 2015 Common Guillemot Productivity-Monitoring Plot - Cleaver Rock.pdf
3. 2015 Common Guillemot Productivity-Monitoring Plot - Downie's Goat.pdf
4. 2015 Razorbill Productivity-Monitoring Plot - Cleaver Rock.pdf
5. 2015 Razorbill Productivity-Monitoring Plot - Hope's Hugh.pdf
6. Breeding success check-sheet (A) from the Seabird monitoring handbook.pdf
Crummack, C. 2014
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