1. MONITORING REQUIREMENTS
1.1 Section 6.2.5 of the approved EM&A Manual for the Project requires that potential work disturbance to inter-tidal bird communities is monitored during the construction phase. Appendix 1 shows the requirements and Event and Action Plan for monitoring works.
2. MONITORING EQUIPMENT
2.1 Equipment used for monitoring included a 20-60x spotting scope, 10x42 binoculars, and Hand-held GPS.
3. MONITORING LOCATIONS
3.1 Monitoring was conducted at two locations, Ngau Hom Shek (NHS) and Sheung Pak Nai (SPN), as shown in Figure 3.1. Monitoring at NHS was adjacent to the works area, and provides a record of potential construction phase disturbance. The SPN site is relatively distant from the works area, and was used as a control site.
4. MONITORING METHODOLOGY
Intertidal Mudflat Monitoring
4.1 Bird species and abundance within a 100m quadrat of exposed mudflat were recorded at low tide (>100m of mudflat exposed) on 19th July 2004. Records were made at both NHS and SPN (Figure 3.1).
4.2 Bird abundance and species composition were compared with baseline data recorded from September/October 2001 to May 2002, as presented in the Shenzhen Western Corridor EIA Report.
Tideline Monitoring
4.3 Surveys at NHS were conducted along a 10m wide belt transect centred along the tideline on 19th July, 2004. The transect extended 250m either side of the bridge alignment (Figure 3.1). The transect was divided into 50m sections, and bird density and species composition within each section was recorded. Surveys were conducted at low tide, when at least 100m of mudflat was exposed.
4.4 Surveys were also conducted at a 500m belt transect established at SPN (Fig. 3.1), on the same date using the same methodology adopted at NHS.
4.5 Bird density within the tideline transects at NHS and SPN was compared using the non-parametric Mann-Whitney test, where:
HO = There are no differences in bird densities along the tidelines at NHS and SPN.
4.6 Additionally, bird abundance and species composition were compared with baseline data recorded from September 2001 to May 2002, as presented in the Shenzhen Western Corridor EIA Report.
5.
RESULTS
Intertidal Mudflats
5.1
Densities
recorded on exposed mudflats were 2 birds/ha at NHS and 3 birds/ha at SPN. Two
species (Little Egret, Egretta garzetta, and Chinese Pond Heron, Ardeola
bacchus) were recorded at both sites, with an additional record of a single
White-breasted Kingfisher (Halcyon smyrnensis) from SPN (Figure 5.1).
5.2
At NHS, bird
densities recorded during recent surveys were similar to the mean value
presented in the EIA Report, with a mean of 1.5 birds/ha recorded in the EIA
Report, compared to 2 birds/ha recorded during monitoring conducted in July
2004. Bird densities recorded at SPN during recent monitoring were slightly
lower than those recorded in the EIA Report (3 birds/ha compared to 3.9
birds/ha). Species richness was higher at both sites than mean values presented
in the EIA Report. A mean of 0.9 species and 1.5 species were recorded in the
EIA Report at NHS and SPN respectively, compared to 2 species at NHS and 3
species at SPN recorded during monitoring conducted in July 2004.
Figure 5.1 – Comparison of Bird Abundance
and Species Composition on Exposed Mudflats: Ngau Hom Shek and Sheung Pak Nai,
July 2004
Tideline
5.3
Bird densities
recorded along tidelines were 36 birds/ha and 38 birds/ha at NHS and SPN
respectively, with 2 species recorded at NHS, and 3 species at SPN. Species
recorded at both sites comprised Little Egret (Egretta garzetta) and
Great Egret (Casmerodius albus), while Chinese Pond Heron (Ardeola
bacchus) were also recorded from SPN (Figure 5.2).
5.4
A Mann-Whitney
found no statistically significant difference between bird densities recorded
at NHS and SPN (P = 0.791).
5.5
At NHS, bird
density recorded during recent surveys was higher than the mean value presented
in the EIA Report (36 birds/ha compared to a mean of 23.2 birds/ha
respectively), and species richness was similar (2 species compared to a mean
of 1.8 species respectively). At SPN, bird densities recorded during recent
surveys (38 birds/ha) were lower than mean values recorded in the EIA Report
(58.2 birds/ha). Species richness was slightly higher, with 3 species recorded
during recent surveys, compared with a mean of 2.0 species recorded in the EIA
Report.
Figure 5.2 – Comparison of Bird Abundance
and Species Composition Along Tidelines: Ngau Hom Shek and Sheung Pak Nai, July
2004.
6.
DISCUSSION AND
CONCLUSION
Intertidal Mudflats
6.1 Bird density was similar and species richness slightly higher on exposed mudflats at both NHS and SPN than mean values given in the EIA Report.
6.2 During surveys conducted in July 2004, bird densities and species richness recorded at both SPN and NHS were very similar. As such, there was no apparent construction phase disturbance to avifauna feeding on mudflats at NHS.
Tideline
6.3 At NHS, bird densities recorded along the tideline in July 2004 were higher than mean values given in the EIA Report. Bird tideline densities recorded at SPN were lower than mean values given in the EIA Report.
6.4 Tideline densities recorded in July 2004 at SPN were lower than records from the same site during the winter season. For example, the density recorded in February 2004 was 262 birds/ha, compared with 38 birds/ha in July 2004. The decline in bird densities at SPN can be attributed to a fall in the number of Curlews recorded at the site. 118 Curlews were recorded from SPN on 13th February 2004, whereas none have been recorded from the site since April 2004. This decline is consistent with general abundance patterns of Curlews in Hong Kong. Curlews are common winter and early spring visitors to Hong Kong, with peak numbers generally occurring in the first two weeks of February (Carey et al, 2001). Records of this species decline through late February and March as much of the population migrates to the north (ibid.).
6.5 During surveys conducted in July 2004, no statistically significant difference in tideline densities at NHS and SPN was observed, and there was no evidence of construction phase disturbance at NHS, the potential impact site.
References
Carey, G.J., Chalmers, M.L., Diskin, D.A., Kennerley, P.R., Leader, P.J., Leven, M.R., Lewthwaite, R.W., Melville, D.S., Turnbull, M., and Young, L. (2001): The Avifauna of Hong Kong. Hong Kong Bird Watching Society, Hong Kong.
Appendix 1 – Requirements
and Event and Action Plan for that potential work disturbance to inter-tidal
bird communities monitoring works.
Work disturbance on inter-tidal bird
communities:
Distribution of feeding shorebirds on inter-tidal mudflats near construction
sites of the alignment will be studied. Distances of feeding birds on mudflat
within 500m of both sides of the construction site will be recorded. Birds
feeding on exposed mudflats and tidelines will be recorded separately. Survey
will be carried out when more than 100m mudflat is exposed, as in the EIA
study. A graph showing the distribution pattern of feeding birds around the
construction site will be plotted. A control site will be set up on mudflats at
Sheung Pak Nai. Distribution pattern of feeding birds on both sides of a strip
of mudflat of equal width as the construction sites will be studied in the same
way as in the construction site. Distribution patterns of birds at the
construction site and control site will be compared using statistical test.
Bird abundance and species richness in the construction site and the control
site will also be compared with the baseline data of these two locations
collected during the field surveys for the EIA study (Table 3.10 & 3.11 in
Appendix 9A of the EIA report). The data from the control site will provide
information on the bird density and composition in the outer Deep Bay area,
while the data from the construction site can reflect the potential effect of
construction works on birds. Any changes of bird density recorded in the
construction site will be adjusted by the changes of bird density in the
control site. Discussion on any changes of species composition recorded in the
construction site will also make reference to the results from the control
site. Sampling frequency will be once per month throughout the construction
phase. If a 30% net reduction (after adjustment) of bird density was recorded
in the construction site, the ET and the on-site engineer will be alerted to
any non-compliance of mitigation measures or site practices. The monitoring
frequency will also be increased to once per week (Table 6.2) until the
recorded bird density stores and complies with the 30% allowance of Trigger
level. If the net reduction continues and exceeds 50% (allowance of Action
level, see Table 6.2), disturbance mitigation measures such as erection of
disturbance barrier will be applied. The weekly monitoring frequency will be
maintained until the recorded bird density stores and complies with the 30%
allowance of Trigger level.
Table 6.2 Trigger
and Action levels for Bird density
|
Parameters |
Trigger level |
Action |
Action level |
Action |
|
Bird density (No./ha) |
30% net reduction of bird density in construction site
in comparison with baseline data in construction site from EIA filed surveys
(Table 3.10 & 3.11 in Appendix 9A of the EIA report) and the change of bird density in
control site. |
Alert the ET and on-site engineer. Increase the
monitoring frequency to weekly. |
50% net reduction of bird density in construction site
in comparison with baseline data in construction site from EIA filed surveys
(Table 3.10 & 3.11 in Appendix 9A of the EIA report) and the change of bird density in
control site. |
Disturbance mitigation measures such as erection of
disturbance barrier.
|