FINAL project 1.

School of Life Sciences

Research Proceedings

Honours project

© The School of Life Sciences [2015-2016] | 1

A Comparison of the Diversity and Distribution of Over-Wintering

Shorebirds on an Intertidal mudflat in the Firth of Forth, Scotland from

2013 to 2015.

Holly Brown

Bsc (hons) Marine Biology

Abstract

Intertidal flats provide a major feeding area for shorebirds. They are a predictable and rich source of food

due to cyclic tides and large numbers of benthic invertebrates. However, human interference has led to

the loss of a number of these habitats which in turn has led to a major decline in shorebird populations

globally. In order to conserve these important habitats, it is of great importance that the distribution and

use of these intertidal flats by shorebirds is well understood. This study looks at the abundance/ diversity

of shorebirds in relation to a number of environmental factors on an intertidal flat within the Firth of

Forth. This will allow for a better understanding of which areas on shore are preferred by shorebirds and

whether environmental factors such as temperature, salinity, benthic invertebrate distribution or sediment

structure have an effect on the distribution of these birds. The intertidal flat chosen was divided into three

zones and sampling/ bird observations were carried out during the winter of 2015/16. Eight different

shorebird species were chosen and their distribution on shore was noted across four observation days.

Sediment samples were collected to analyse the sediment structure and benthic invertebrate community to

determine if they are related to shorebird distribution. Other relevant environmental factors were also

recorded on these sampling days. Results of this study were also compared to a similar study done within

the same area on shore in 2013/14 to determine any changes in shorebird populations across the past 2

years.

Contents

1. Introduction

1.1. Shorebird background

1.2. Study Site

1.2.1. Forth Estuary

1.2.2. Cramond

1.3. Recent Shorebird population Structures

1.4. Birds of Interest

1.5. Aims

2. Materials and Methods

2.1. Bird Observation

2.2. Field sampling

2.3. Benthic Invertebrate Identification

2.4. Granulometric analysis

2.5. Organic matter analysis

2.6. Statistical Analysis

3. Results

3.1. Bird Observation

3.2. Environmental conditions

3.3. Benthic Invertebrate analysis

3.4. Granulometric Analysis

3.5. Results comparison with previous study

4. Discussion

5. Conclusion

6. Acknowledgements

7. References

8. Appendix

1. Introduction

Human interference with intertidal flats, including construction

work and tourism, has led to the loss and degradation of suitable

coastal habitats for overwintering migratory shorebirds

(VanDusen, Fegley et al., 2012). Due to cyclic tides, intertidal

flats provide predictable access to food resources, constituting a

major feeding area for shorebirds (Drouet, Turpin et al., 2015).

The loss of suitable coastal habitats for shorebird use, has led to

a decrease in shorebird populations (Granadeiro, Santos et al.,

2007). Flats are a major staging area for migratory and over-

wintering birds. Upon arriving at intertidal flats, migratory

shorebirds rebuild their fat stores rapidly, which have been

depleted after hours of flying, by feeding on the organisms found

on shore (Botton, Loveland et al., 1994). This allows birds to

regain enough energy to continue with their migration. Without

these vital ‘stop-over’ points many birds would not have the

resources to survive migration (Skagen & Knopf, 1994). It is

not only migratory birds which utilise these flats, overwintering

birds and permanent residents also take advantage of the

resources. Shorebirds are important to intertidal flats for a

number of reasons; they provide nutrients for invertebrates,


phytobenthos and microbes via their droppings and they are also

very good indicators of ecosystem health and productivity

(Chafer & Loyn, 2015).

In order to implement the correct management strategies to

conserve these important intertidal flats, it is important that there

is good understanding of bird distribution at both a local and

regional scale within the flats (Granadeiro et al., 2007). This is

possible with co-ordinated research.

1.1. Shorebird Background

The term Shorebird refers to any bird which carries out many of

its activities, such as feeding or resting, within the coastal area

(Baird, Evans et al., 1985). Not only are waders (Scolopacidae)

included in this term, but a variety of other birds which use

coastal habitats regularly i.e. Gulls (Laridae) and wildfowl

(Anatidae) are included also (Mendonça, Raffaelli et al., 2007).

Shorebirds obtain a large proportion of their daily energy

requirements (if not all) by feeding on intertidal areas

(Mendonça, Rafaelli et al., 2007) rich in small invertebrates.

The method in which shorebirds obtain their prey is seen to differ

between species, and indeed individuals, due to inter- and intra-

specific variation in bill length and shape (Nebel, Jackson et al.,

2005). The differentiations in bill morphology between different

shorebird species leads to alternative prey available to birds, thus

reducing inter-specific competition on the shore (Colwell,

2010). For example, long billed species mainly use touch to find

prey due to their touch sensitive bill tips which can detect prey

whilst probing, whereas short billed species generally use sight

(van de Kam, de Goeij et al., 2004). Differences in bill length

also allows access to prey at different depths within the sediment

(Chafer & Loyn, 2015).

A number of bird species have adapted their bill shape/ length

to the predominant food type within the individual’s diet (Durell,

2000). For example birds may adapt the bill tip and bill width

to coincide with the prey they primarily seek out. Oystercatchers

are an example of this, and have the ability to alter bill

morphology periodically (Figure 1), throughout the year

allowing the birds to adapt to varying circumstances (Goss-

Custard, 1996). This ability to alter bill shape so readily,

mitigates intra-specific competition between birds within the

same feeding area.

The distribution of shorebirds has been seen to be related to

the distribution and abundance of their preferred prey, as seen

in a study by Norazlimi and Ramli (2014). The study was

conducted to determine the abundance and diversity of

shorebirds living in a mudflat of Jeram and Remis beach in

Malaysia. The study concluded that tidal stage and human

disturbance were two of the major factors affecting

shorebird distribution on mudflats. In the current study human

disturbance will be noted to determine any changes in shorebird

distribution.

Sediment grain size may also play a major, yet indirect, role

in shorebird distribution by directly affecting the densities of

invertebrates found across areas of the intertidal flat, as seen in

a previous study (VanDusen, Fegley et al., 2012). The study

highlights the importance of prey availability and abundance in

relation to shorebird communities on shore.

1.2 Study Site

1.2.1 Forth Estuary

The Firth of Forth is located on the East coast of Scotland and is

the second most important estuary for wintering shorebirds in

Scotland and the eleventh most important throughout the entire

UK (SNH, 2004). An abundance of invertebrate rich intertidal

flats are present throughout the Firth of Forth thus, providing key

feeding grounds for a number of migratory and

internationally/nationally important birds. An area covering

most of the Forth has been designated as a Special Protection

Area (SPA) and is therefore protected, for use by birds. The area

is also designated as a Site of Special Scientific Interest (SSSI)

(SNH, 2011). The entire Firth of Forth has been designated a

RAMSAR site due to its importance as a wetland (JNCC, 2015).

Historically, the Firth of Forth was used as an area for the

disposal of domestic, industrial and agricultural effluent leading

Figure 1: Morphology of three main bill-tip shapes of Oystercatchers.

Lateral, Frontal and Dorsal view (Goss-Custard, 1996).


to a depletion of water quality in the Forth (SNH, 2011)

However, within the last two decades pollution control by

regulatory authorities and the implementation of treatment

plants has led to drastic improvements in water quality (SNH,

2011). This led to the health of the Forth improving dramatically

allowing a number of shorebirds to re-establish within the Firth

of Forth (SNH, 2011). However, findings from 2011 show that

bird populations across the Forth were seen to be declining again

(SNH, 2011).

1.2.2 Cramond

Cramond is a small town situated on the south coast of the

Forth Estuary not far from Edinburgh. The area of tidal sands

extending from Hound point to Granton form an area known as

Drum Sands. The sands have been designated as a site of special

scientific interest (SSSI) and form part of the Firth of Forth’s

Special Protection Area (SPA) (Gittings, 2012).

A small island-‘Cramond Island’- sits within Drum Sands and

a causeway present allows pedestrian access to the island during

low water. The area is popular with dog walkers and families

however, only the East side is easily accessible and used for

recreational activities.

It is the ‘muddy’ West side of the causeway which is of

particular interest in this study. The sediment here is composed

of mainly shell fragments and mud. There are numerous rocky

outcrops present on the shore and a sparse covering of Fucus

vesiculosus and Fucus spiralis is present. The River Almond

which runs directly into the West side of Drum sands is a major

defining characteristic of this area.

Low water exposes the entire area of mudflats providing a major

feeding ground for hundreds of waders and waterfowl. Access

to the mudflats on the West side of Cramond is restricted which

limits the number of visitors to the area. This makes the mudflats

an ideal area for over-wintering shorebirds to feed on as

disturbance is minimal.

Figure 2: Map of Cramond. Approximate study site highlighted with black dotted line. Red square shows site in within

Scotland. Map created using ArcGIS pro software.


1.3 Recent shorebird Population Structures

Trends in shorebird populations have shown an overall decrease

in recent years (VanDusen , Fegley al., 2012). Table 1 shows

the general % change of the most abundant shorebird species

across sites throughout the UK during a 10 year period from

2002/3 to 2012/13. The decline in these populations is likely

due to harsh winters seen in recent years, however it has not been

proven that this is the definitive reason for such declines. (Holt,

Austin et al., 2015).

1.4 Birds of Interest

This study focused on eight species of bird known to be found at

Cramond. These species include: Curlew (Numenius arquata),

Oystercatcher (Haematopus ostralegus), Knot (Calidris

canutus), Turnstone (Arenaria interpres), Redshank (Tringa

tetanus), Bar-tailed Godwit (Limosa lapponica), Little stint

(Calidrus minuta) and Lapwing (Vanellus vanellus). Although

lapwings are not wading birds, they have been observed in large

numbers on the study site and are deemed ‘red status’ within the

UK (indicates the species has undergone severe breeding or

wintering population declines in the UK of more than

50% within the last 25 years (Woodward, Bray et al., 2015) and

so were included in this study.

Of these species, four are internationally important (Knot,

Bar-tailed godwit, Redshank and Turnstone) and two are

nationally important (Curlew and Oystercatcher) (SNH, 2004).

These birds therefore are of great conservation importance. A

number of the above species are known to be declining in

numbers throughout the UK (table 1) however the reasons for

these declines are unknown (SNH, 2011).

A similar study was conducted in 2013/14 at the same site

within the Firth of Forth by Dean Woodfin Jones (Jones, 2014).

The study compares two different shores, the West and East side

of Cramond, looking at environmental factors and human

disturbances which directly affect the diversity and distribution

of shorebirds at different areas on shore. Only the results from

the West side of Jones, 2014 study will be used for comparison

with the current study.

1.5 Aims

Primarily, to investigate effects of differences in

sediment particle size, benthic invertebrate species

composition and density and sediment organic matter

on shorebird abundance/ diversity between the upper,

mid and lower shore.

To compare findings with a previous study to

determine any changes in shorebird diversity (Jones,

2014).

To investigate the cause of any changes in shorebird

diversity from the previous study, i.e. any changes in

benthic invertebrate density or sediment granulometry

or organic matter presence.

2. Materials and Methods

2.1 Bird Observation

Prior to conducting the shorebird surveys, two preliminary visits

were carried out to the site chosen to find a suitable area to

survey the birds from and to compile a list of shorebird species

known to forage on the chosen site.

Shorebird surveys were conducted on 4 dates between the

15th of October and the 12th of December 2015 by a single

observer. All observations were conducted on days without

rainfall and average air temperatures of between 7°C and 15°

C. The area used by the observer to survey the birds was at

least 15m from the birds to prevent any disturbance to their

natural behaviour. All areas of the shore were visible from

this vantage point. Observations were conducted 2 hours

after low tide to ensure counts were not being made lower on

shore than any samples had been taken. A ‘new’ lower shore

was designated whilst field sampling. Counts were conducted

at 15 minute intervals until high tide was reached and all

birds had flown from the site. Counts were recorded on

paper, per species and later compiled to a spread sheet in excel.

In order to easily distinguish between lower, mid and upper

shore whilst surveying, wooden stakes already present on shore

were used in conjunction with prominent shore features such as

large rocks. As the entire shore was visible from the vantage

point it was possible to prevent double counting of birds which

moved from one area of the shore to the other: - only the final

position of the birds was counted during the time interval.

In order to identify the birds present on shore Centon, field

5.5°, 12x50mm binoculars were used. Any birds which were

unable to be identified on site were counted and their shore

position noted before taking a photograph to enable later

identification. If any disturbance to the birds occurred i.e.

dog barking or human presence on shore, counts were stopped

and birds were left to re-settle on the shore.

2.2 Field sampling

Field sampling took place over one day in October 2015 during

low water on the shore. Sediment samples were collected

for benthic invertebrate identification using box quadrats

(Width 32cm, Depth 29cm) and were placed into pre-

labelled 5L buckets. Three replicate samples were taken

randomly from each of the three shore sampling points (high,

mid and lower). Two samples were sieved on site using a

0.5mm mesh sieve and preserved with 70% ethanol, the third

was left as it would be used to give representative samples

for sediment analysis and organic matter. It was not possible

to sample down at the low water mark due the sediment being

unstable and therefore posing a safety risk. It was therefore

necessary to have an obvious marker for the new ‘lower shore

area’ which would also be used for bird observations. Areas

were distinguished using wooden stakes already present on

shore and surrounding prominent features such as rocks, to

ensure sample areas were the same areas in which the bird

surveys were being conducted.

Small water samples were taken, from the holes left by

the quadrats after invertebrate sample collection was done, to

later be analysed at the laboratory for salinity using a

refractometer.


A thermometer was used on site to determine water temperatures

at each sampling site.

Once back at the laboratory representative samples (200g)

were removed from the un-sieved buckets to be used for

granulometry and organic matter. The remaining sample was

sieved and 70% ethanol added. All samples were placed in cold

storage.

2.3 Benthic Invertebrate Identification

Samples containing the sieved sediment were analysed in the

laboratory by first carefully removing all benthic invertebrates

and placing them into petri dishes containing ethanol for further

preservation. The individual organisms were then identified

using a dissection microscope (Olympus 5230) and

identification literature (Fish & Fish, 2011). Where possible,

organisms were identified to species level, however, many

organisms were in poor condition after sieving, due to a number

of small pebbles present in samples disfiguring invertebrates. A

list of species and their corresponding sample site was compiled

and later analysed.

2.4 Granulometric Analysis

The three representative samples from each area on shore were

placed in separate porcelain dishes, weighed and then dried in an

oven for 48 hours until a constant weight was achieved. Each

sample was then covered with water and 20ml of sodium

hexametaphosphate was added to each. Each sample was stirred

for 10 minutes, left for 24 hours and then stirred for a further 10

minutes. The now disaggregated sediment was then wet sieved

using a 63 µm sieve to assess silt content.

The contents of the sieve were placed back into porcelain

dishes and dried, again to a constant weight. The new weight was

recorded and the difference between this and the initial weight

was assumed to be the 63 µm portion of the sample.

The remaining dried sediment was then passed through a

sieve stack (mesh sizes were: 4000µm, 2000µm, 1000µm,

500µm, 250µm, 125µm, 63µm, <63µm) using a sieve shaker

(Octagon digital 200 sieve shaker). The contents of each sieve

were weighed and recorded. Median Phi values were obtained

to determine the sediment type and calculations were done to

determine skewness and sorting of sediment particles. The

following equations were used to determine skewness and

sorting, respectively:

2.5 Organic matter analysis

A small portion (20g) of sediment was removed from the

samples used for granulometry (prior to drying) to carry out

organic matter content analysis. The samples were placed in

small porcelain dishes, weighed and then placed in a muffle

furnace at 500°C for 24 hours and then at 600°C for a further 24

hours. Once cooled, the samples were reweighed and the weight

loss recorded. The percentage of organic matter was then

calculated.

2.6 Data Analysis

Multivariate data analyses were carried out using PRIMER 6 to

analyse bird observation data, including cluster analysis,

ANOSIM and SIMPER tests. Bray Curtis similarity index and

log transformed data were used. Log transformed data were used

for multivariate analyses to reduce the influence of dominant

species on the results. Diversity indices were also calculated

from the raw data using PRIMER 6 (Pielou’s evenness and

Shannon Wiener diversity). Univariate statistical analysis was

carried out using IBM SPSS statistics 22 to determine if there

were any significant differences in shorebird abundance/

diversity between sample sites. One way ANOVA was used to

investigate bird abundance due to the normal distribution of data

and Kruskal-Wallis tests were used for bird diversity (although

data were normally distributed, results of Levene’s test were

<0.05 and therefore ANOVA results were not valid- Kruskal

Wallis analysis was used as alternative). Post-hoc Tukey tests

were carried out on any significantly different data after one-way

ANOVA was carried out.

In order to analyse the invertebrate count data, cluster analysis,

ANOSIM and SIMPER testing (with Bray Curtis similarity

index and log transformed data) were carried out. PRIMER 6

was used to conduct this analysis. PRIMER 6 was also used to

calculate diversity indices (Shannon Wiener diversity and

Pielou’s evenness) using raw data. One way ANOVA was

carried out to determine any differences in invertebrate

diversity between sites. Post-hoc Tukey tests were carried out

on significant data. Differences in invertebrate abundance

between sites were tested using a Kruskal-Wallis test due to the

non-parametric nature of the data. Tests were carried out using

IBM SPSS statistics 22.

Environmental conditions (temperature, salinity and organic

carbon content) were analysed by conducting Kruskal Wallis

tests (due to non- normally distributed data), using IBM SPSS

statistics 22, to determine any significant differences between

sites. Mann-Whitney U tests were used with Bonferroni

correction on any non-parametric data which was significantly

different to determine which sites were different from each

other. All significances were accepted as P≤0.05. All tables

and figures were produced using Microsoft Excel 2013.

3. Results

3.1 Bird Observations

The average abundance (Figure 3) of individual shore birds was

highest at low shore (LS) whilst species diversity (Figure 4) was


highest on the high shore (HS) according to results of Shannon

Wiener Diversity (Table 2). Pielou’s evenness values for each

area on shore showed a relatively even spread of abundance

across the species present (Table 2). There was no significant

difference, however, between the abundance or diversity of

shorebirds when comparing all three areas of the shore (high,

mid and low). There was also no significant difference between

the abundance of birds across the four observation days

(P>0.05).

Figure 3: Average shorebird abundance across three sample sites (LS=

low shore, MS= mid shore, HS= high shore). Total number of

replicates for each site was 24, six replicate counts were conducted

each day over a total of 4 days. Data sharing a letter are not

significantly different to each other (P≥0.05). Data not sharing a letter

are significantly different to each other (P≤0.05). Data shown are mean

± standard error of the mean (SEM).

Figure 4: Average shorebird diversity across three sample sites (LS=

low shore, MS= mid shore, HS=high shore). Total number of species

=8. Data sharing a letter are not significantly different to each other

(P≥0.05). Data not sharing a letter are significantly different to each

other (P≤0.05). Data are mean values ± standard error of the mean

(SEM).

Figure 5: Average shorebird abundance by species across three sample

sites (LS= low shore, MS= mid shore, HS= high shore). Total number

of shorebird species present = 8. Data shown are mean ± standard error

of the mean (SEM).


It is clear that the two most dominant species present on shore

were Redshanks and Curlews (figure 5), with Redshanks having

a predominantly higher abundance on the lower shore.

Redshank distribution decreased with distance from the

water’s edge. Curlews on the other hand appeared to prefer mid

shore (MS) and although their abundance decreases towards

high shore, they were still present in higher numbers at high

shore than Redshanks. Oystercatchers were observed on all

three areas of the shore, however, their abundance decreased

dramatically at high shore. It can be seen in Figure 5 that the

abundance of Oystercatchers on the lower shore was in fact

slightly higher than that observed of Curlews, although the

presence of Oystercatchers at high shore was next to none.

Lapwings were predominantly observed at high shore with

very few birds seen feeding on the lower shore. Little stints on

the other hand, were observed mainly on the lower shore.

Turnstone were observed on only one observation day and

were seen only on the mid shore. Knots were only observed on

the mid and high shore with no presence seen on the lower

shore. Bar-tailed godwits were not observed on any area of

the shore across any of the observation days.

Results from the cluster analysis carried out on bird data

(Figure 6) highlight almost 100% similarity between

sample sites LS1 and LS2 (Lower shore sample site 1 and 2).

There is little distinct grouping throughout the rest of

the sites highlighting no distinct differences between the

sample sites.

However, it can be seen that HS4 (high shore sample site 4) has

Figure 6: Cluster analysis of shorebird abundance across the three sample sites with Bray Curtis similarity. Six replicates were taken

at each zone across 4 observation days (LS= low shore, MS=mid shore, HS= high shore).

Figure 7: Average temperature across sample sites (LS= low shore,

MS= mid shore, HS= high shore). Data shown are mean ±

standard error of the mean (SEM).

Figure 8: Average salinity (ppt) across sample sites (LS=low shore,

MS= mid shore, HS= high shore). Data shown are mean ±



a dissimilarity of around 55% when comparing it to all other

sample sites. Results of the ANOSIM give an R value of 0.269

and a P value of 3.6%. This shows there is no significant

differences in species composition between sites. When looking

at which species contribute to the differences between each site,

results of SIMPER analysis show that Oystercatchers contribute

the most to differences between species composition on lower

shore and high/mid shore. Lapwings are seen to contribute the

most to the differences seen between mid and high shore.

All birds, with the exception of Knot, Turnstone and Bar-

tailed Godwit were present in all areas of the shore to some

extent. Bar-tailed Godwits were not observed on shore

throughout any of the observation days which was contrary to a

previous study carried out in the same location (Jones, 2014).

Oystercatchers generally were not present on the upper shore

and it became clear that upon departure from the site, the birds

were flying across to the Shore of Cramond Island. Many of the

birds preferred feeding when there was a film of water over the

sediment- which explains the high abundance on the low shore.

Disturbance on shore was minimal due to access to the West

side of Cramond being difficult. Throughout the observation

period only one pedestrian was seen on shore collecting mussels.

Pedestrian presence was moderate on the East side with dogs

barking occasionally. A large proportion of birds flew from the

site upon hearing dog barks. The site was under a flight path for

Edinburgh airport however, the presence of planes low in the sky

did not appear to affect birds on shore in any way. The presence

of pedestrians crossing the causeway to Cramond Island was

also moderate however, again did not cause any disturbance to

the birds.

3.2 Environmental Conditions

The highest temperature (Figure 7) was recorded on the upper

shore with an average of 10.1°C obtained, whereas the lowest

temperature was recorded on the Lower shore with an average

temperature of 7.8°C obtained. After analysing the results using

a Kruskal Wallis test it is clear that there is a significant

difference in temperature between each site with results of the

statistical analysis giving a P value of 0.048. Mann- Whitney U

tests did not distinguish which sites the significant difference lies

between, as all pairwise comparisons showed no significant

difference. The differences may lie between lower shore and

high shore, and mid shore and high shore, which can be seen in

Figure 7.

Salinity on shore (Figure 8) was analysed using the same

statistical test and indicated significant differences between each

site (P= 0.025). However, after conducting Mann- Whitney U

analysis to determine any significant differences between sites,

it is unclear where these differences lie. When looking at figure

8, it may be that the difference is between lower shore and high

shore as salinity can be seen to be higher on lower shore than

that of the high shore. Salinity varied greatly from lower shore

to high shore with an average of 33.3 seen on the lower shore

and an average of 21.3 seen on the high shore.

Results of organic carbon content analysis showed no significant

difference (just) between study sites after a P value of 0.051 was

obtained. The lower shore showed the highest percentage of

organic carbon content with an average of 4.87% and the upper

shore showed the lowest organic carbon content with a 2.25%

average (Figure 9).

3.3 Benthic invertebrate analysis

Average invertebrate abundance was highest at high shore and

was much lower on low and mid shore. The majority of

invertebrates found overall were crustaceans (e.g. Corophium

spp.) however, these were only present on the high shore.

Molluscs were the next most abundant group with presence on

all three sites- the highest abundance again was observed on the

high shore. Polychaetes were also seen on all areas of the shore.

There was no significant difference in abundance of individuals

across the shore (Figure 10) with a P value of 0.057 obtained,

although Figure 10 suggests quite a difference between low/mid

shore and high shore.

Figure 9: Average organic carbon content across sample sites (LS= low

shore, MS= mid shore, HS= high shore). Data shown are mean ±

standard error of the mean. Data sharing a letter are not significantly

different (P≥0.05). Data not sharing a letter are significantly different

(P≤0.05).


Figure 10: Mean number of invertebrate individuals across the three

sites on shore (LS= low shore, MS= mid shore, HS= high shore). Total

number of samples = 9, three replicates from each sample site. Data

sharing a letter are not significantly different (P≥0.05). Data not

sharing a letter are significantly different (P≤0.05). Data shown are

mean values ± standard error of the mean (SEM).

Figure 11: Mean number of invertebrate species across the shore from

the three sites on shore (LS= low shore, MS= mid shore, HS= high

shore). Total number of species present = 6. Data sharing a letter are

not significantly different (P≥0.05). Data not sharing a letter are

significantly different (P≤0.05). Data shown are mean values ±


Figure 12: Cluster analysis of Invertebrate abundance across the three sample sites with Bray Curtis similarity. Nine samples were taken across

the shore, 3 replicates at each sample site (LS= low shore, MS= mid shore, HS= high shore).


Average species diversity was highest on the high shore

according to Shannon Wiener diversity (Table 3). Lowest

diversity was seen mid shore (Figure 11). There was no

significant difference in diversity between low shore and mid

shore or high shore, however a significant difference in species

diversity was observed between mid-shore and high shore.

Cluster analysis shows three distinct groups, with high shore

being dissimilar to lower and mid shore with a similarity of less

than 40%. Low shore and mid shore are relatively similar with

similarity of around 70% (Figure 12). All three high shore sites,

although are dissimilar have a similarity of around 90%.

ANOSIM tests gave an R value of 0.621 and a P value of 3.6%,

showing that there was a significant difference between sites,

however the high P value shows that this difference is not a large

one. The main difference in species composition between lower

and high shore was crustaceans shown from the results of

SIMPER analysis. Polychaetes contributed the most to the

difference in composition between low and mid shore and

crustaceans contributed the biggest difference in species

composition between mid and high shore.

3.4 Granulometric analysis

The granulometric composition of the shore varied slightly from

lower and high shore in comparison to mid shore. Graphical

median particle size analysis showed median phi values lying

between 3-3.75 for low and high shore giving a composition of

mainly muddy sediment. On the other hand, the median phi

value obtained for mid shore was 2.5 showing a composition

mainly of muddy sand (Table 4).

Low shore was mostly very poorly sorted, with sediment

comprising mainly of shell fragments and pebbles. Mid shore

and high shore were poorly sorted, however with distance up the

shore, a reduction in shell fragments and pebbles within the

sediment was seen possibly explaining the invertebrate

abundance pattern seen on shore.

3.5 Results comparison with the previous study

The previous study (Jones, 2014) was conducted over 4

observation days with one additional day included for sample

collection. Invertebrate samples in study 1 were collected using

box cores (length: 32cm, width: 32cm and depth: 29cm) and

sediment samples were collected using tube cores (Depth 29cm

and diameter: 4cm). Temperature was taken on site, and small

water samples were taken from each area of the shore (from the

same hole that sediment samples were taken from) to be later

analysed for salinity in the laboratory.

When comparing the current study with the previous study

(study 1) in terms of bird observations, it is clear that the current

study has an overall higher abundance of birds across all three

study sites on all observation days. However, Lower shore still

has the highest abundance of birds in each study. Redshanks

were observed to be most dominant at mid shore in study 1,

however, they appeared to prefer the lower shore in the current

study. Although their numbers were lower at high shore in study

1, they were still the most dominant species present at high

shore. This differs from the current study as redshanks are co-

dominant with curlews on the high shore. Oystercatchers were

Figure 13: Sediment particle size analysis. Average % Cumulative

mass across three sites (HS= high shore, MS= mid shore, LS= lower

shore). Three replicates were taken at each site. Phi values represent

–log2 sieve diameter.


seen to prefer low shore with their numbers decreasing up the

shore further from the water line- a pattern similar to both

studies. Bar-tailed Godwits and knots were present on all three

sites in small numbers in study 1, however in the current study

bar-tailed godwits were not observed on any areas of the shore

across all days. Knots showed a similar pattern in both studies

with small presence on each area of the shore with the exception

of mid shore- no knots were observed on mid shore in the current

study. Curlews were observed in large numbers on the low shore

in study 1 and their presence decreased with distance from the

low shore. A dissimilar pattern was observed in the current

study with curlew abundance being most dominant on mid shore.

It is obvious that curlew numbers are much higher in the current

study. Dunlin were observed on low shore and mid shore during

study 1 however, were not observed during the current study on

any site.

Shorebird diversity was seen to be highest on the lower shore

in the previous study however appears to be highest on the high

shore in the current study. There were three species observed on

shore in the current study that were not included in study 1:

Little stint, turnstone and lapwing. Lapwings were most

dominant on high shore while the other two species were seen

present on all areas of the shore in small numbers.

Study 1 observed overall lower average temperatures with the

highest temperature observed at 7.1°C on the lower shore and

the lowest temperature observed on the upper shore at 6.8°C- a

whole 4°C lower than that of the current study.

Study 1 showed salinity to be highest at mid shore with an

average value of 29.9 low shore was seen to have the lowest

salinity at 28.5. Salinity decreases with distance from low shore

in the current study with a maximum average salinity of 33.3

seen on low shore- 5 lower than observed on low shore in study

1. Salinity in study 1 is 8 higher on high shore than the current

study.

The previous study conducted showed an overall higher

average abundance of invertebrates found at each sample site

with the exception of high shore. High shore in the current study

had an overall higher average abundance of invertebrates than

study 1.

Crustaceans appeared to be the most dominant taxa found in

study 1 with the highest abundance found on the low shore,

followed by mid shore. The current study also shows an overall

dominance of crustaceans, however only on high shore which is

very different in comparison to study 1 in which crustaceans are

present in very small numbers on high shore. Polychaetes were

found on all areas of the shore in study 1, with the highest

abundance observed on the high shore. Polychaetes were only

found on high shore in the current study. Molluscs too were

found on all three areas of the shore with the highest abundance

observed on mid shore in study 1. A similar pattern was

observed in the current study however the highest abundance

was seen on high shore.

3. Discussion

The optimal foraging theory considers the optimum food intake

in relation to energy expenditure (Macarthur & Pianka, 1966).

It is to the bird’s advantage to consume more energy than it is

using. The simplest optimal foraging model, known as Ideal

Free Distribution (IFD), is used to predict the equilibrium of

organisms amongst patch resources/ habitats (Kennedy & Gray,

1993). It works on the assumption that birds are able to use prior

knowledge of the area to determine patch quality (where a patch

is a cluster of invertebrates within sediment) to reduce energy

loss (van Gils, Schenk et al., 2003). Due to many birds always

returning to the same site to feed (Coleman & Milton, 2012), this

becomes possible as shorebirds begin to recognise the patches

with the highest energy available, and so waste less energy

moving between patches of lower energy intake, reducing

overall energy expenditure (van Gils et al., 2003). This is

important in conserving energy, allowing the birds to build up

their fat stores.

Intertidal flats are the most productive in the world (Masero,

2003) and provide high numbers of prey with minimum

disturbance for shorebirds. Shorebirds use areas such as the

intertidal flat in this study to build up energy reserves. Birds

require energy to maintain body temperature, to fly to and from

feeding grounds and to gather food (Evans, 1976). They are

faced with the conflicting problems of predation and surviving

cold weather. It is advantageous to the birds to increase their fat

reserves to overcome the cold weather, however it is also

advantageous to remain lean to avoid predation (Rehfisch, Insley

et al., 2003). It is therefore essential that intertidal flats become

the forefront of conservation efforts, before shorebird numbers

deplete further due to the loss of suitable feeding grounds. In

order to do so, it is first necessary to understand the use of these

habitats by shorebirds to implement appropriate management

strategies (Gill & Handel, 1990).

The results of this study aim to help understand the use of

intertidal flats by shorebirds, by observing the distribution of

shorebirds across the shore, whilst also taking environmental

factors into account. The highest abundance of birds in this

study was observed on the lower shore which may be explained

according to a number of factors. The sediment on the lower

shore was very poorly sorted, which leads to the assumption that

the sediment here has poor porosity, leading to a film of water

forming on the surface of the sediment (Nelson, 1994). This film

of water leads to increased availability of invertebrates within

the sediment (VanDusen, Fegley et al., 2012) and therefore bird

abundance on this area of the shore also increases. This did not

significantly affect the spread of birds across all areas of the

shore and it remains that the birds did not prefer one area of the

shore significantly more than another area.

The low numbers of invertebrates collected during this study

may have been a consequence of a number of factors. Possibly

more care should have been taken when sampling i.e. reducing

noise and vibrations when collecting samples to prevent scaring

invertebrates deeper into the ground. Due to time restraints

replicates were kept to a maximum of two when sampling,


The increase in birds observed may be due to construction of

Queensferry crossing. Construction work causes an increase in

disturbance, which may lead to birds leaving their

current feeding sites (Smit & Visser, 1993) in order to find sites

which are less disturbed. Due to the site of interest in this

study being far enough from the bridge construction to avoid

disturbance it is possible that the birds usually found on

intertidal areas by the new Forth Bridge have been forced to

move to the current study site to feed.

There was a number of individual species observed in study

1 which were not present in the current study; Dunlin, Bar-

tailed godwit and grey plover were not observed on any

of the observation days carried out during this study.

This may possibly be due to a decrease in invertebrate

abundance throughout the study site leaving birds with a

lack of prey available.

The increase in bird abundance seen may not be a continuing

trend due to their most likely being slight differences in

conditions and disturbance on observation days between the

two studies. The differences in invertebrate abundance may

also be down to slightly altering sample sites.

It should be noted that none of the trends seen in this report

can be assumed as ongoing due to its small scale.

Further research should be carried out to help understand or

predict the effects of anthropogenic activities on

intertidal areas (Granadeiro, Santos et al., 2007). This will

then help determine why there are a number of fluctuating

shorebird populations and why these alterations are happening

as currently data on trends of shorebird populations are poor

or non-existent (Simmons, Kolberg et al., 2015). This

will help implement further management strategies to the

site to help prevent further declines in populations.

4. Conclusion

however in future studies, increasing the number of replicates at

each sample site would be advantageous.

The observed abundance of shorebirds in relation to

invertebrates across the sample sites in the current study does not

portray the relationship expected. In relation to the Ideal Free

Distribution model, the area of the shore containing the highest

abundance of invertebrates, in theory, should have had the

highest abundance of shorebirds present. This was not the case

in this study as the lowest abundance of shorebirds was observed

on the area of the shore with the highest abundance of

invertebrates. This may be due to the human disturbance of the

East side of Cramond being closer to the high shore, on the West

side, than any other area of the shore. It has been seen that

shorebirds change their feeding behaviour when humans are

present to reduce any risks perceived (Thomas, Kvitek et al.,

2003).

Sedimentary analysis appears to have had no effect on the

abundance/diversity of birds on any area of the shore. The very

poorly sorted sediment on lower shore may explain the lack of

invertebrates present on this area of shore- however, does not

explain why the abundance of birds was not highest on this area

of the shore. The sediment becomes less poorly sorted on mid/

high shore which may explain the slight increase in invertebrate

abundance/diversity. This does not explain the substantial

increase in invertebrate abundance present on high shore

however.

Upon comparison there are a number of dissimilarities

between the current study and study 1 which was carried out

during the winter months of 2013/14. In a report by Scottish

Natural Heritage (SNH, 2011) it was observed that the number

of Curlews present within the Firth of Forth Site of Special

Scientific Interest (SSSI) had almost doubled in numbers since

2000. This runs parallel with the results obtained in this study

which show a dramatic increase in the number of Curlew present

across the shore in comparison to Study 1, highlighting an

obvious trend in increasing curlew populations. It is not only

Curlews which can be seen increasing in population, the overall

abundance of birds seen in 2015/16 is much higher than was seen

in 2013/14. Results of invertebrate counts do not coincide with

the increase in bird population observed as overall there was a

decrease in invertebrate abundance across all areas of the shore

from 2015/16 in comparison to 2013/14.

Organic carbon content in the study carried out this year was

a lot lower than that seen in study 1, this may explain the large

decrease in invertebrate abundance seen in the current study

compared to study 1. This decrease in organic carbon content

observed may be a result of increased overall temperatures seen

across the shore in the present study. The increase

in temperature makes it possible for microbial organisms to

breakdown organic matter quicker- thus reducing its presence (Kaiser, Attril et al., 2011). However, this does not give explanation as to why shorebird abundance was much higher in the present study.

Overall, due to the highest abundance of birds seen on

lower shore, in both studies, it may be concluded that

shorebirds prefer this area of shore. Possibly due to its

very poorly sorted sediment, which leads to the assumption

that the sediment has poor porosity, therefore allowing a film

of water to form. This increases the availability of

invertebrates for birds to feed on. However, results from

the current study reveal very few invertebrates were

present on the lower shore, which does not account for the

increase in bird abundance. Results of this 2015/16 study

show an increase in bird populations which, when compared to the study done in 2013/14 (Jones, 2014) and trends seen in local bird populations from 2002/3-2012/13 (Table 1), appears to be a solitary occurrence since the site was last seen designated as a RAMSAR site and a special protected area in 2001 (JNCC, 2015). This indicates that the bird populations are beginning to increase, which highlights the need for the area to remain a RAMSAR site and special protected area. This will


give bird populations the chance to increase more substantially over the next few years without being disturbed. The reason for the increase in bird abundance/diversity in this study when compared to the previous study is unclear. The reduced carbon

content seen in this study in comparison to study 1 is most

likely due to the increased temperatures seen on shore in this

study. The higher temperatures are likely to lead to a faster

depletion in carbon content. However, the reduced abundance/

diversity of benthic invertebrates seen in this study when

compared to study 1 are un-explained and should not have led

to an increase in bird populations when taking the Ideal Free

distribution into account. Further studies should be carried out

to determine if the increase in bird populations seen in this

study is an on-going trend or isolated to this study only.

6. Acknowledgements

I would like to thank my project mentor Teresa Fernandes for all

her help and encouragement during my final year project. Also

a huge thank you to Hugh Barras for helping me with my field

sampling, equipment and lab techniques throughout my project

and for keeping me positive when things got tough. Also a big

thanks to the lab technicians at Heriot Watt for helping me find

any equipment I required.


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8. Appendix

Raw data, previous study data and statistcal justification available on

request.

FINAL project 1.

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