1.1               The intertidal bird surveys were conducted on 10 March 2009.  The weather was fine but overcast.  The temperature was 16.9 oC - 19.4oC and the humidity was 63% - 84%.

 

Intertidal Mudflat Monitoring

 

1.2               Graph 4.1 shows the number and species of shorebirds recorded at the 100 m x 100 m mudflat quadrats at NHS and SPN.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Graph 4.1      Abundance and Species Composition of Shorebirds on the Exposed Mudflats (100 m x 100 m Quadrat) at Ngau Hom Shek and Sheung Pak Nai – 10 March 2009

 

 

 

 

1.3              At the NHS impact monitoring site, 4 species (Little Egret Egretta garzetta, Chinese Pond Heron Ardeola bacchus, Great Egret Egretta alba, and Eurasian Curlew Numenius arquata) of 28 individuals were recorded; whereas at the SPN control site, 4 species (Little Egret Egretta garzetta, Chinese Pond Heron Ardeola bacchus, Great Egret Egretta alba, and Grey Heron Ardea cinerea) of 13 individuals were recorded during the survey.  While higher abundance was recorded at the NHS impact monitoring site, and species diversity was the same at both sites, there was no evidence to suggest any adverse impacts from SWC operation on shorebird communities during the survey.

1.4               Table 4.1 compares the density and number of shorebird species recorded during the EIA and the recent survey.

 

Table 4.1       Density and Number of Shorebird Species Recorded during the Previous EIA and the Survey on 10 March 2009 on the Exposed Mudflats (100 m x 100 m Quadrat) at Ngau Hom Shek and Sheung Pak Nai

 

 

Density of Shorebirds (Birds/Ha)

No. of species

 

Ngau Hom Shek

Sheung Pak Nai

Ngau Hom Shek

Sheung Pak Nai

Current Survey

28

13

4

4

Previous EIA

2.3

4.2

1.3

1.8

 

1.5               The shorebird density and diversity at NHS recorded during this survey were higher than the numbers recorded during EIA.  These results suggest that the operation of HK-SWC had no effect on the shorebird communities during this survey.

1.6               The abundance and diversity of shorebirds recorded at NHS during this survey (4 species of 28 individuals) were similar to the previous monitoring survey conducted in January 2009 (4 species of 23 individuals).  

 

 

 

 

 

 

Tideline Monitoring

 

1.7               Graph 4.2 presents the abundance and species composition of shorebirds recorded on the 500 m x 10 m tideline transects at NHS and SPN.

 

Graph 4.2      Abundance and Species Composition of Shorebirds along the Tidelines (500 m x 10 m transect) at Ngau Hom Shek and Sheung Pak Nai – 10 March 2009

 

 

1.8               At the NHS impact monitoring site, 2 species of 47 individuals of shorebirds (Great Egret Egretta alba, and Little Egret Egretta garzetta) were recorded; whereas at the SPN control site, 5 species of 55 individuals of shorebirds (Little Egret Egretta garzetta,  Grey Heron Ardea cinerea, Eurasian Curlew Numenius arquata, Little Ringed Plover Charadrius dubius, and Osprey Pandion haliaetus) were recorded.

1.9               The tideline transect at the NHS impact monitoring site recorded approximately the same bird abundance as, and slightly lower species diversity than, the SPN control site.  There was no significant evidence to suggest adverse impacts on shorebird communities from the operation of the HK-SWC during the survey.

1.10           A parametric t-test found no statistically significant difference between the bird abundance along the tidelines at NHS and SPN (P=0.626).  The result suggests that no adverse impact on shorebird communities was observed during the operation of the HK-SWC during the survey.

1.11           Table 4.2 compares the density and number of shorebird species recorded during the EIA and the recent survey.

 

Table 4.2       Density and Number of Shorebird Species Recorded during the Previous EIA and the Survey on 10 March 2009 along the Tidelines (500 m x 10 m transect) at Ngau Hom Shek and Sheung Pak Nai

 

 

Density of shorebird (birds/ha)

No. of species

 

Ngau Hom Shek

Sheung Pak Nai

Ngau Hom Shek

Sheung Pak Nai

Current survey

94

110

2

5

Previous EIA

23.2

58.2

1.8

2

 

1.12           During this survey, the shorebird density and diversity at the NHS impact monitoring site and SPN control site were both higher than that recorded during the previous EIA.  The results of this survey suggest that the operation of HK-SWC had no adverse effect on the shorebird communities during this survey.

1.13           When compare the recent survey with the previous survey conducted in January 2009, the density and species diversity of shorebirds recorded during this survey (94 birds/ha of 2 species) were lower than the previous survey (324 birds/ha of 6 species) at NHS.  While for SPN, both surveys recorded approximately the same densities and abundance (this survey – 110 birds/ha of 5 species; previous survey – 92 birds/ha of 6 species).

 

Monitoring of Effects of Shade

 

1.14           During the survey, only two sets of data, ‘Under Bridge’ and ‘On Exposed Mudflat’, were collected, as the shade was right under the bridge.

1.15           Graph 4.3 presents the results recorded during the survey for effects of shade on the strips of mudflat (250 m x 40 m) at the NHS impact monitoring site.

 

Graph 4.3      Abundance and Species Composition of Shorebirds on the Strips of Mudflats (250 m x 40 m) “Under Bridge” and “On Exposed Mudflat” at Ngau Hom Shek – 10 March 2009

 

               

On Exposed Mudflat
 

Under Bridge
 

 

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1.16          At the strip of mudflat right under the HK-SWC (Under Bridge), 1 species (Little Egret Egretta garzetta) of 6 individuals of shorebirds were recorded during the monitoring survey; whereas 2 species (Little Egret Egretta garzetta and White-breasted Kingfisher Halcyon chloris) of 5 individuals were recorded on the exposed mudflat.

1.17           The recent monitoring survey show that bird abundance and diversity were similar on the strips of mudflat “Under Bridge” and “On Exposed Mudflat”.  Moreover, a statistical Mann-Whitney Rank Sum test found no statistically significant difference between the bird abundance within the two strips of mudflat  (P=0.222).  This result suggests that the physical existence of the HK-SWC and its shade has no adverse impact on the shorebird communities at NHS during the recent survey.

1.18           As discussed in the operation monitoring report dated November 2007, distribution of shorebirds may be affected by a number of abiotic or biotic factors apart from the operation of the HK-SWC, and they are listed below:

l            Early-staged establishment of benthos communities in the mudflat under bridge after the construction phase provide less food resource for shorebirds, which may account for the lower number of shorebirds recorded under the bridge.  However, benthos communities in mudflat under the bridge are expected to build up gradually in long-term and such factor should be diminished in the future.

l            The curve-shaped tideline at some locations may provide less feeding area and feeding opportunities for shorebirds, which may affect their distribution at NHS.

l            The uneven and patchy distribution of shorebirds in nature means that it may cause bias in statistical analysis.

l            A succession of oyster farms was found located on the mudflat approximately 50 m away from both sides of the alignment of HK-SWC.  The oyster areas were observed to be a popular feeding ground for shorebirds and were frequently visited.  The abundant food resource in these areas may have a positive effect on the abundance and diversity of intertidal shorebirds on the strip of exposed mudflat at NHS.