2.1 Site Specific Target Habitats
2.1.1
The
principal aim of the mitigation is the provision of suitable habitat for target
species, rather than the restoration of specific habitats of intrinsic
ecological value. Accordingly, the habitat target for the mitigation areas is
the enhancement, creation and maintenance of at least 27.1 ha of fishponds and
4.9 ha of marshland in Favourable Condition for target Species of Conservation
Importance.
2.1.2
It
is recognised that using only avifauna as the measure of success of the managed
wetland is unreliable because of the highly temporal nature of the species and
the uncertainty of the impact of external factors such as availability of food
sources, human disturbance and predator activity, on avifauna activity. In
addition to avifauna, other more stable targets (with less temporal variation)
have therefore been set, that reflect the habitat requirements of the target species.
Such targets include the increase in shallow feeding areas, benthic
composition, water quality, fish stocks and vegetation status and distribution.
These habitat related targets are described in Section 2.4.
2.1.3
The
definition of Favourable Condition of the habitat is dependent on the target
species for mitigation and their specific requirements. These are described
below.
2.2
Site Specific Target Species
2.2.1
Although
avifauna are not considered to be the most reliable indicator of success, it is
recognized that they are a key component of the ecosystem and need to be
monitored as such. A full list of species that are considered to be targets for
the mitigation measures and recommended measurable performance targets for each
are listed below in Table 2.1. Species are considered to be targets for the Lok
Ma Chau Station area mitigation area either if they are Species of Conservation
Importance occurring within the area to be impacted by the construction of the
Lok Ma Chau Station and the Spur Line within the Deep Bay Wetland Conservation
Area or are good indicators of overall wetland ecological value (e.g.
dragonflies and amphibians). Definition of Species of Conservation Importance
follows the EIA Report (BBV 2000) with the following exceptions. Eurasian Otter
which is restricted to the Deep Bay area in Hong Kong where it is rare (Reels
1996) has been added to the list as a consequence of a sighting made of this
species during baseline fieldwork during winter 2000-01. This species is
considered to be “Regionally Threatened” by Fellowes et al. (in press). Similarly, Chinese Bullfrog, which was recorded
during baseline fieldwork during 2000-01, has been included as a Target Species
in view of its Regionally Threatened status (Fellowes et al. in press) and its being an appropriate ecological indicator
species.
2.2.2
This
list of target species (and hence other aspects of the HCMP) will require
amendment in the light of any changes to the list of Species of Conservation
Importance that may be included in final EIA for the revised Spur Line
alignment.
2.2.3
Regularly
occurring wetland species that are either globally threatened, regionally
important or threatened in Hong Kong, because they have a restricted range
and/or are declining in numbers, are considered to be the main Target Species and are, therefore, the
principal focus for the wetland mitigation design and long-term management
requirements.
2.2.4
The
baseline survey showed that Greater Spotted Eagle did not occur regularly
within the Lok Ma Chau station area during 2000-01. Nevertheless it is
considered to be a key target species since it is globally threatened and its
Hong Kong population is restricted to the Deep Bay area and is regionally
important. Moreover, the baseline survey showed that its habitat requirements
could be accommodated within the proposed wetland mitigation area without
compromising objectives for other species.
2.2.5
As
described in the EIA report, large species of ardeid, such as Great Egret and
Little Egret, as well as Black-faced Spoonbills and the globally threatened
Imperial Eagle and Greater Spotted Eagle are likely to be most susceptible to
disturbance from the operation of the railway and station. Therefore, because
these species may not fully benefit from the mitigation measures being placed
alongside the station, mitigation within the more distant fish ponds will be
additionally targeted to these species.
2.2.6
In
contrast, many smaller species of birds, particularly reedbed passerines,
reptiles, amphibians and invertebrates are unlikely to be affected by disturbance
or the presence of the large railway station buildings. Mitigation alongside
the station complex will therefore focus on the creation of reedbed and other
marshland habitats that will benefit such species.
2.2.7
It
is considered that the provision of wetlands habitats that are suitable for the
wide range of target species listed below will also create suitable habitats
for a wide range of other taxa and contribute to the overall ecological and
biodiversity value and integrity of the Wetland Conservation area.
Table 2.1
Wetland mitigation performance targets for target species in the
Lok Ma Chau / San Tin Station area
|
Species |
Target |
Notes |
|
SPECIES OF CONSERVATION IMPORTANCE |
||
|
Globally Threatened Species |
||
|
Black-faced Spoonbill |
Doubling of baseline.* |
Regular occurrence during winter 2000-01 but not previously. |
|
Greater Spotted Eagle |
Recorded. |
Not at present a regularly occurring species but included as a
target species (c.f. para. 2.2.2). |
|
Imperial Eagle |
Recorded. |
|
|
Japanese Yellow Bunting |
Recorded at least one year in four. |
Not a regularly occurring species in the area. Irregular
occurrence in Hong Kong. |
|
Regionally Important Species |
||
|
Eurasian Otter |
Recorded on average once per 12 month period. |
Target reviewed if additional fieldwork shows that it is of regular
occurrence in the area. |
|
Black-winged Stilt |
Doubling of baseline.* |
|
|
Common Teal |
Doubling of baseline.* |
|
|
Eurasian Coot |
Doubling of baseline.* |
Not regular in the area to be impacted by the station or the
mitigation area, though regular in the Lok Ma Chau area. |
|
Great Cormorant |
Doubling of baseline.* |
|
|
Chinese Pond Heron |
Doubling of baseline.* |
|
|
Great Egret |
Doubling of baseline.* |
|
|
Grey
Heron |
Doubling
of baseline.* |
|
|
Little Egret |
Doubling of baseline.* |
|
|
Red-billed Starling |
Doubling of baseline.* |
|
|
Chinese Bullfrog |
Doubling of baseline.* |
|
|
Locally Important Species |
||
|
Common Snipe |
Doubling of baseline.* |
|
|
Common Stonechat |
Doubling of number of birds recorded in other commercially
operated fishponds in the area. |
|
|
Pallas’s Grasshopper Warbler |
Doubling of number of birds recorded in other commercially
operated fishponds in the area. |
Not regular in the area. |
|
Pintail Snipe |
Doubling of number of birds recorded in other commercially
operated fishponds in the area. |
Species not separable in the field. |
|
Swinhoe’s Snipe |
||
|
Zitting Cisticola |
Doubling of number of birds recorded in other commercially
operated fishponds in the area. |
|
|
ECOLOGICAL INDICATOR SPECIES |
||
|
Dragonflies |
||
|
Agriocnemis spp. Onychargia
atrocyana Ischnura
senegalensis Ceriagrion
auranticum Anaciaeschna
jaspidea Nannophya
pygmaea Nannophyopsis
clara Brachydiplax
chalybea Brachythemis
contaminata Orthetrum
luzonicum Neurothemis
tullia Neurothemis
fulvia Palpopleura
sexmaculata Rhodothemis
rufa Rhyothemis
variegata Urothemis
signata |
30% of species present and breeding after 2 years and 60% of
species present and breeding after 5 years. |
Indicator species for freshwater marsh. |
|
Anax
guttatus Anax
parthenope Ictinogomphus
pertinax Sinictinogomphus
clavatus Epopthalmia
elegans |
60% of species
present and breeding after 5 years. |
Species of large ponds with permanently high water levels
(unable to tolerate seasonal drain down due to larval stage of more than one
year). |
|
Amphibians |
||
|
Bufo
melanostictus Kalophrynus
interlineatus Microhyla
ornata Microhyla
pulchra Polypedates
megacephalus Rana
guentheri Rana
limnocharis Rana
macrodactyla Rana
taipehensis |
50% of species present and breeding after 2 years; 75% of
species present and breeding after 5 years. |
Indicator species for freshwater marsh habitat. Note that Rana rugulosa is treated separately as
a Key Target Species. |
Note: Black-naped Oriole, Richard’s Pipit and
Japanese Quail are not included as target species as these do not use the
target wetland habitats.
* Baseline
considered to be taken from waterfowl counts in HK BWS Ramsar Site Waterbird
Monitoring Programme. Control sites will be selected for monitoring and the
data collected during the monitoring will be used, in addition to the baseline
data, for comparison of bird usage in the enhanced fish ponds.
2.3
Specific Requirements for Target
Species
2.3.1
All
target species are freshwater specialists, or wetland specialists. Some of
these have more specific habitat requirements, and although the design caters
for such species the range of micro-habitats, water levels, and vegetation
types will provide foraging or roosting habitat for all target species (see
Table 2.3).
Table 2.3
Summary of Habitat Requirements of Target Species of Conservation Importance
Key: habitat important for F = Foraging;
R = Roosting; B = Breeding.
|
Species |
Deep
water |
Shallow
water |
Muddy
vegetation free margins |
Reedbeds |
Other
emergent / marsh vegetation |
Bare
or sparsely vegetated bunds |
|
Amphibians |
|
F,B |
F,B |
F,B |
F,B |
|
|
Reptiles |
|
F |
F |
F |
F |
F,B |
|
Eurasian Otter |
F |
F |
F |
F |
F |
|
|
Black-faced
Spoonbill |
|
F |
F |
|
|
R |
|
Greater
Spotted Eagle |
|
F |
|
|
F |
F |
|
Imperial
Eagle |
|
F |
|
|
F |
F |
|
Japanese
Yellow Bunting |
|
|
|
F,R |
F,R |
F |
|
Red-billed
Starling |
|
|
F |
|
F |
F |
|
Great
Cormorant |
F |
|
|
|
|
|
|
Chinese
Pond Heron |
|
F |
|
F,R |
F |
|
|
Great
Egret |
|
F |
|
|
F,R |
|
|
Little
Egret |
|
F |
|
|
F |
|
|
Common Teal |
F |
F |
|
F,R |
|
|
|
Eurasian Coot |
F |
F |
|
|
|
|
|
Black-winged Stilt |
|
F |
F |
|
|
|
|
Grey Heron |
|
F |
|
|
F |
|
|
Northern Hobby |
|
|
|
|
|
|
|
Pheasant-tailed Jacana |
|
F |
|
|
F |
|
|
Common Snipe |
|
|
F |
|
F,R |
|
|
Pintail Snipe |
|
|
F |
|
F,R |
|
|
Swinhoe's Snipe |
|
|
F |
|
F,R |
|
|
Richard's Pipit |
|
|
F |
|
|
F |
|
Bluethroat |
|
|
F |
F,R |
F,R |
|
|
Common Stonechat |
|
|
|
F,R |
F,R |
F |
|
Zitting Cisticola |
|
|
|
F,R |
F,R |
|
|
Chestnut Bittern |
|
F |
|
|
F,R |
|
|
Pallas's Grasshopper
Warbler |
|
|
|
F,R |
F,R |
|
2.3.2
Detailed
accounts of the habitat requirements of main Target Species are provided below.
Black-faced
Spoonbill
2.3.3
Black-faced
Spoonbills have been subject of a number of studies in Hong Kong (notably Anon.
(1999), Melville et al. (1999), Anon
(in prep.a), Anon (in prep.b)). In addition, when it was discovered during
baseline fieldwork that Black-faced Spoonbills were utilising drained
ponds at Lok Ma Chau during winter
2000-01, their use of this area was subject to additional specific survey
efforts (BBV 2001a, BBV in prep.).
2.3.4
Black-faced
Spoonbills are tactile feeders. Feeding takes place in turbid water bodies with
a flat or gradually sloping fine sediment bottom with water depths from 5 – 23
cm. (Yu and Swennen 2001). In Hong Kong these requirements are met in the
intertidal mudflats in Deep Bay, as well as in fish ponds and gei wai. The relative importance of
intertidal areas and fish ponds and gei
wai is influenced by tidal regime and pond management, with the latter
habitats being particularly important during adverse weather and when ponds are
drained for harvesting (Anon in prep.a, Yu and Swennen 2001). Black-faced Spoonbills
largely feed on small prey items, especially shrimps Palaemonetus sp. and Mosquito Fish Gambusia affinis, but larger prey items such as Tilapia Oreochromis mossambicus are also eaten,
especially when these are readily available in partially drained ponds (Leader
1998, Yu and Swennen 2001).
2.3.5
Black-faced
Spoonbills will be major beneficiaries of the rotational drain down of ponds
and, since these will provide areas free of disturbance, with turbid water of
an appropriate depth for foraging and plentiful food. Together with Ardeids,
the detailed design and management of ponds will be specifically targeted at
the requirements of this species.
Greater Spotted Eagle
2.3.6
Habitat
utilisation in the Deep Bay area was studied during winter 2000-01 (BBV 2001b).
Greater Spotted Eagles are a winter visitor to Hong Kong and are present from
late October to early April. Their distribution in Hong Kong is restricted to
the Deep Bay area, with the notable exception that they roost at night in hills
to the south; with most birds apparently roosting in the Castle Peak area
during winter 2000-01 (Carey et al.
2001, BBV 2001b). As with Imperial Eagle, observations during winter 2000-01
showed that the most important area for this species was Mai Po, with secondary
foci at Tsim Bei Tsui and Nam Sang Wai. Together these areas
accounted for 86% of records (BBV 2001b). In contrast to the distribution of
Imperial Eagles, during this study there were no records from Lok Ma Chau;
indeed there were very few records from east of Mai Po. This species is scarcer in Hong Kong than Imperial
Eagle (Carey et al. 2001); the
frequency of sightings during winter 2000-01 was approximately half that of
Imperial Eagle (BBV 2001b).
2.3.7
The
pattern of occurrence was related to the presence of abundant waterbirds on
ponds (especially wild ducks). Despite the presence of large numbers of
waterbirds (including ducks) the intertidal zone is not utilised. Trees are
required for daytime loafing or hunting perches and the study in winter 2000-01
suggested that, in comparison with Imperial Eagle, this species is less likely
to occur in extensive open active fish pond areas
2.3.8
Greater
Spotted Eagles do not, technically, meet the criterion of regular occurrence in
the Lok Ma Chau area required for inclusion on the list of Key Target Species
as this species was not recorded regularly there during winter 2000-01 (BBV
2001a, BBV 2001b). However, it is proposed that this species be included as a
Key Target Species for the reason that it is Globally Threatened (BirdLife International
2000)n and has habitat requirements which can be accommodated within the
mitigation area without compromising any other mitigation objectives (in fact
the mitigation proposals are identical to those required for Imperial Eagle).
2.3.9
Greater Spotted Eagles
will be attracted to concentrations of waterbirds, especially ducks, which
will provide a source of food. They are likely to avoid areas adjacent to
the LMC Station as well as the eastern part of the mitigation area where human
activities associated with the presence of the Spur Line and the Boundary
Crossing point will deter use. Accordingly, it is proposed to maintain ponds
1 and 2 (shown in Figure 4.1 in the Design Section,
these ponds are those most remote from the station) with shallow to moderate
water levels throughout the winter to provide suitable feeding and loafing
habitat for ducks; thus providing a potential food source for Greater Spotted
Eagles in an undisturbed area.
2.3.10
Habitat
utilisation in the Deep Bay area was studied during winter 2000-01 (BBV 2001b).
Imperial Eagles are a winter visitor to Hong Kong and are present from late
October to early April. Their distribution in Hong Kong is restricted to the
Deep Bay area, with the notable exception that they roost at night in hills to
the south; with most birds apparently roosting in the Castle Peak area during
winter 2000-01 (Carey et al. 2001, BBV 2001b). Observations during winter
2000-01 showed that the most important area for Imperial Eagles is Mai Po
Nature Reserve, with Ma Tso Lung being the second most important area.
Together, these two areas accounted for 66% of sightings during the study. Tsim
Bei Tsui, Nam Sang Wai and Lok Ma Chau were sites of similar secondary
importance, with Lok Ma Chau accounting for 8% of sightings.
2.3.11
The
pattern of occurrence was related to the presence of abundant waterbirds on
ponds (especially wild ducks), with a secondary factor being an avoidance of
developed and disturbed areas. Despite the presence of large numbers of
waterbirds (including ducks) the intertidal zone is not utilised. Trees are
required for daytime loafing or hunting perches, but ponds surrounded by
continuous large trees (as at parts of Nam Sang Wai) are avoided.
2.3.12
Imperial Eagles will
benefit from the reduction in human disturbance arising from the management
of the mitigation area. They will also be attracted to concentrations of waterbirds,
especially ducks, which will provide a source of food. However, Imperial Eagles
are likely to avoid areas adjacent to the LMC Station as well as the eastern
part of the mitigation area where human activities associated with the presence
of the Spur Line and the Boundary Crossing point will deter use. Accordingly,
it is proposed to maintain ponds 1 and 2 (see Figure
4.1) with shallow to moderate water levels throughout the winter to provide
suitable feeding and loafing habitat for ducks; thus providing a potential
food source for Imperial Eagles in an undisturbed area.
Black-winged
Stilt
2.3.13
The
following is based on non-systematic observation in Hong Kong including
observations at Lok Ma Chau during winter 2000-01 (BBV 2001a). In Hong Kong,
Black-winged Stilts are restricted to fresh or brackish water habitats,
favouring large disused fish ponds in the Deep Bay area and bloodworm ponds in
Long Valley. Black-winged Stilts are recorded in Hong Kong throughout the year,
but have not been known to breed; the small numbers present in summer
presumably being non-breeding individuals or early returning migrants (Carey et al. 2001). Distribution on the Deep
Bay area is somewhat erratic with flocks opportunistically utilising ponds
which are of a suitable depth for feeding (c. 5 – 15 cm water depth) as this
species rarely forages whilst swimming (Cramp and Simmons 1983). There is also
some evidence that birds may move several kilometres between feeding and
roosting areas in Hong Kong, with birds which roost in the Deep Bay area during
the day flying to Long Valley to feed at night (BBV 2001c).
2.3.14
Black-winged
Stilts feed predominantly on aquatic invertebrates, especially insects. Food is
taken by wading in open water and invertebrates are taken from on and below the
water surface and from aquatic vegetation (Cramp and Simmons 1983).
Black-winged Stilts will benefit from shallow open water areas overlying soft
mud with aquatic vegetation sparse or absent.
Common
Teal
2.3.15
The
following is based on non-systematic observation in Hong Kong including
observations at Lok Ma Chau during winter 2000-01 (BBV 2001a). Common Teal are
winter visitors to Hong Kong and are present between September and April.
Though there are occasional records from other wetland sites; the majority of
Common Teal are found in Deep Bay. Within Deep Bay favoured habitats are
intertidal creeks amongst mangroves, gei
wai and well-vegetated ponds, especially those with abundant growth of the
facultative wetland grass Paspalum
distichum. A common denominator in these preferences is the presence of mud
or shallow water feeding areas in proximity to cover. More open wetland
habitats such as active fish ponds, intertidal mudflats and Deep Bay itself are
less favoured by Common Teal than most other duck species in Hong Kong – it is
probably not co-incidence that this species is a frequent prey item for raptors
including Greater Spotted and Imperial Eagles.
2.3.16
Diet
of Common Teal has not been studied in Hong Kong; however elsewhere in its
range it is considered to be omnivorous, filtering invertebrates and seeds from
water or soft mud whilst either walking or swimming. Seeds are often
particularly important in winter (Cramp and Simmons 1977).
2.3.17
Common Teal will benefit
from the provision of suitable feeding and loafing areas at ponds 1 and 2
in Figure 4.1 (where water levels at shallow
to moderate levels and Paspalum distichum
will be established to provide food and cover) and the freshwater marsh areas.
2.3.18
The
following is based on casual observation in Hong Kong. Eurasian Coots are
primarily winter visitors to Hong Kong, but a few individuals are usually seen
in summer and breeding has been recorded. In Hong Kong, Eurasian Coots are
largely restricted to the Deep Bay area, where the largest numbers are present
in the open waters of the bay itself. Small numbers are found on brackish and
freshwater ponds and gei wai where
these have extensive marginal and emergent vegetation, especially reeds Phragmites spp.
2.3.19
Diet
has not been systematically studied in Hong Kong, but elsewhere in its range
this species is omnivorous with plant matter (vegetative parts and seeds of
aquatic plants) predominating (Cramp and Simmons 1980). In Hong Kong, Eurasian
Coots are regularly attracted to grain provided for waterfall at Mai Po NR.
2.3.20
This
species will benefit from the provision of feeding areas and shelter in the
freshwater marsh. The diversity of marginal and emergent vegetation and
management of water levels will maintain suitable conditions for this species
throughout the year and may encourage more individuals to remain in summer and
perhaps to breed.
2.3.21
Great
Cormorants are winter visitors to Hong Kong and are economically important as
the numbers of this fish-eating species which occur in Deep Bay are perceived
to have a significant impact on the profitability of commercial fish farming.
Studies of the wintering ecology of Great Cormorants in Hong Kong, their impact
on fisheries and possible preventative measures are in progress but have not
been published.
2.3.22
Great
Cormorants in Hong Kong roost communally. There are currently two roosts in the
Deep Bay area: at Mai Po NR and at Nam Sang Wai. Cormorants disperse to feed;
either in Deep Bay itself or on fish ponds. They use both active and inactive
ponds, but avoid small ponds, especially those surrounded by trees or adjacent
to sources of human activity. They readily take advantage of fish
concentrations, including the provision of “trash fish” (Tilapia) in ponds at Mai Po NR to divert feeding pressure from
commercial ponds.
2.3.23
Great
Cormorants will benefit considerably from the provision of ponds stocked with
“trash” fish when the water level is high. Management of ponds for this species
will, thus, accord with that proposed for Black-faced Spoonbills and Ardeids:
cormorants will utilise ponds when they are full, whilst the other species will
largely benefit when they are drained. A subsidiary benefit of encouraging
cormorants to use stocked ponds in the mitigation area is that they will be
diverted from commercial ponds thus reducing conflict with fish farmers and
avoiding the need for more drastic deterrence measures.
2.3.24
Chinese
Pond Herons are found in Hong Kong throughout the year. Habitat utilisation has
been studied in Hong Kong by Young (1994) who showed that birds breeding at the
Mai Po Village egretry fed mainly around fish ponds. Individuals typically
forage solitarily along the edges of open water areas or areas within sparse or
short vegetation. They utilise open areas such as intertidal mudflats or
drained down ponds less than larger Ardeid species in Hong Kong. Chinese Pond
Herons breed colonially, either on their own or with other Ardeid species.
Nests are often placed in bamboos Bambusa
spp. Breeding adults largely forage within 3 km of their colonies (Young and
Cha 1995).
2.3.25
Chinese
Pond Herons will benefit from the provision of shallow open water areas or
shallow water areas with partial vegetation cover up to around 300 mm in
height. As such, they are likely to utilise all edge areas so long as
vegetation is not too dense or water too deep to prevent successful foraging.
Currently the closest egretry to Lok Ma Chau is at Mai Po Village, a distance
of 2 km. Whilst this is within the foraging range of breeding Chinese Pond
Herons, it is possible that the provision of suitable breeding habitat at Lok
Ma Chau would benefit this species (a former egretry at Lok Ma Chau was
abandoned in 1993 possibly due to increased disturbance from the vehicle
Boundary Crossing Point (Young and Cha 1995)). Accordingly, it is proposed to
plant of clumps of Bambusa vulgaris
(which will also fulfill a screening function) along the northern fringe of the
mitigation area.
2.3.26
Great
Egrets are one of the scarcer breeding Ardeids in Hong Kong, but numbers are
much greater in winter (Young and Cha 1995). Habitat utilisation has been
studied in Hong Kong by Young (1994) who showed that whilst this species feeds
on drained ponds and gei wai,
intertidal mudflats are significantly more important as feeding habitat.
Despite these habitat preferences, Great Egrets will benefit to some extent
from the provision of shallow water feeding areas on stocked ponds and will
take advantage of drained ponds.
Grey
Heron
2.3.27
Grey
Herons have bred in Hong Kong, but this species is primarily a winter visitor
(Young and Cha 1995). Habitat utilisation has been studied in Hong Kong by
Young (1994) who noted that this species is predominantly a crepuscular feeder
in Hong Kong and primarily uses gei wai
as a daytime roost; but also utilises fish ponds for feeding. Grey Herons will
benefit from the provision of shallow water feeding areas on stocked ponds and will
take advantage of drained ponds. They are also likely to benefit from areas
free of human disturbance, which will be suitable as daytime roost sites.
2.3.28
Little
Egrets are found in Hong Kong throughout the year. Habitat utilisation has been
studied in Hong Kong by Young (1994) and Cornish (1996). These studies showed
that Little Egrets in Hong Kong feed primarily in fish pond and intertidal
mudflat areas. Little Egrets feed opportunistically on fish remaining when
ponds are drained and are often the most abundant Ardeid species in such
feeding concentrations. Breeding birds typically forage within 3 km of
egretries (Young 1994), which may be situated either in bamboos or a variety of
tree species.
2.3.29
Little
Egrets feed by wading and will benefit from the provision of shallow water
feeding areas in ponds and shallow water areas in the marsh so long as
vegetation is not too dense. In addition Little Egrets are likely to be one of
the main beneficiaries of the proposed management regime for the ponds as they
will readily take advantage of the availability of fish as ponds are drained.
Like Chinese Pond Herons, Little Egrets may benefit from the provision of
bamboo clumps along the northern boundary of the mitigation area, which will
provide suitable breeding sites.
Red-billed
Starling
2.3.30
Red-billed
Starling is a winter visitor to Hong Kong, occurring in large flocks in the
northwest New Territories. The wintering population in Hong Kong is considered
probably to be of international importance for this species (Carey et al. 2001). Red-billed Starlings are
omnivores and feed around fish ponds, wet agricultural areas (especially where
these are contaminated by effluent from pig farms), edges of reedbeds and both
natural and artificial drainage channels. They readily take advantage of
spilled food provided for fish or ducks. Much food is obtained on the ground
but they also frequently feed in trees where they consume insects and fruit
(though their gape size is too small to permit them to take most fruits of Melia azedarach, the most frequent
fruiting tree around fish ponds).
2.3.31
This
species will benefit from sparely vegetated fringes to ponds and marsh areas,
especially where these are close to tree and shrub areas adjacent to the
drainage channels and the station perimeter. It will also benefit from the
proposed tree and shrub planting which will provide fruit and invertebrate food
and shelter.
Chinese
Bullfrog
2.3.32
This
large frog species is thought to be in marked decline locally and drastic
decline regionally, and has therefore been rated as of Potential Regional
Concern by Fellowes et al. (in
press). It is commonly sold in food markets in Hong Kong and in southern China.
It is a species closely associated with areas of wet agriculture, and breeds in
ponds and marshes. The species is present but not common at Lok Ma Chau.
2.3.33
Chinese
Bullfrogs feed on insects and small frogs and rodents (Karsen et al., 1998). They will benefit from
provision of permanent and, particularly, seasonal marsh habitat (from which
predatory fish are absent), with good development of emergent and/or edge
vegetation and variable, but generally shallow, depth. Presence of prey items
such as odonate larvae and other frog species will also encourage establishment
of this species.
2.4.1
As
described in the EIA Report (BBV 2000) it is considered that the most
appropriate form of wetland mitigation in the San Tin / Lok Ma Chau area is the
enhancement of fish ponds over the majority of the mitigation area. Currently
the large biogeographically important populations of herons and egrets that use
fishponds in the Deep Bay area primarily feed on the abundant small
non-commercial fish and invertebrates (termed ‘trash fish’) that thrive as a
by-product of the highly productive commercial fish-farming systems. These
include Gambusia affinis (Mosquito
Fish), Macrobrachium nipponense (a
prawn) and Oreochromis mossambicus (a
species of Tilapia).
2.4.2
However,
these food resources are generally only readily available to birds when the ponds
are drained down for fish harvesting during the winter. Furthermore, only a
small proportion of fish ponds are drained at one time and only for short
periods. The spatial distribution of birds feeding on ponds is therefore highly
dynamic and variable as birds move between fish ponds as they are drained. When
recently drained, such fish ponds may contain many hundreds of feeding egrets,
herons and other waterbirds. Consequently, a large area of fish ponds is
required to support the bird populations and avoid ‘feeding bottlenecks’.
2.4.3
When
ponds are full, their use by birds is severely limited due to their relatively
steep sides, deep water and their frequent lack of marginal vegetation. These
characteristics also limit their biodiversity interest for other taxa groups.
The main objective of enhancing fish ponds would therefore be to:
• Increase the value of fish ponds to Black-faced Spoonbills, herons and egrets outside harvesting periods (i.e. draw-down), by increasing food resources and food availability and by reducing disturbance effects. Enhancement of the value of fish ponds to such birds outside harvest periods could reduce the potential for ‘feeding bottlenecks’ thereby possibly reducing the area of fish ponds needed to support the population.
• The
management regime proposed is expected to benefit other species of conservation
importance that currently use fishpond habitats. For example, the managed
wetlands, at Mai Po which include areas of former fishponds have been shown to
support significantly higher densities of Greater Spotted and Imperial Eagles
than occur in commercial fishponds (ref baseline report). Both are globally
threatened. In addition, the provision of a less homogonous wetland area and
the resultant increase in habitat diversity within the Lok Ma Chau fishponds
will provide habitat for other species that are generally rare within
commercial fishponds. The areas of reeds and marsh will be more suitable for
small migrant passerines that the habitats available at present. For
example, Pallas’s Grasshopper Warbler, a species that prefers dense rank
vegetation and avoids open and
sparse habitats would benefit.
• Increase
their overall biodiversity value and suitability for other non-bird Species of
Conservation Importance, such as some mammals including Eurasian Otter,
amphibians and reptiles, whilst maintaining their current important functions
for herons, egrets and other water birds.
2.4.4
Figure
1.2 indicates the location of the proposed area of enhanced fishponds.
These will be placed away from the buildings to minimise disturbance impacts
from the railway station and others sources such as the Lok Ma Chau border
crossing. They would also be contiguous with the main area of fishponds in
the WCA and Ramsar site as a whole. Maintaining a contiguous area for compensation
which is linked with an existing area of recognised conservation importance
is of significant ecological value.
2.4.5
The
specific fish pond habitat targets for the mitigation area are:
• Enhancement
and maintenance of a total of 27.1 ha of fishponds (including essential
structures, e.g. water control structures, and other habitats e.g. bunds).
• >
20% of the fish pond area (excluding bunds and ponds that are dry for
maintenance) consists of shallow water (i.e. < 10cm depth).
• Target
plant species (see below) comprise >50% cover on > 20% of the area of
fish pond bunds and islands.
• Undesirable
invasive species and exotic species are < 10% of vegetation cover.
• Plant
cover is <5% on > 75% of the area of fish pond bunds and islands.
• 70-80%
of the fish pond area (excluding bunds and ponds that are dry for maintenance)
is under traditional polyculture fish pond management systems (see below for
fish farming operation specifications).
• 10
- 30% of the fish pond area (excluding bunds ponds that are dry for
maintenance) is set-aside from fish farming and is under specific conservation
management (see below for specifications).
2.4.6
The fishpond enhancement
measures will be supported by the creation of some areas of reedbed and marshland
habitat alongside the station buildings (Figure 1.2).
These habitats will be established alongside the station complex to function
as a barrier to disturbance and as shelter/cover for smaller herons, crakes,
passerines, amphibians, reptiles and mammals. This marshland habitat will
also have a high carrying capacity for several such target Species of Conservation
Importance as well as providing habitat for some that at present occur in
the area only in small numbers (see Table 1.2).
2.4.7
The
specific marshland targets for the mitigation area are:
• Creation and
maintenance of a total of 4.9 ha of marshland habitat (including essential
structures, e.g. water control structures, and other habitats e.g. bunds) in
Favourable Condition. Marshland habitats are defined as wetlands (i.e. where
wetland hydrological conditions or wetland soils are present or where wetland
plants are dominant) with shallow water (average < 1m) and wetland plant
species cover greater than 30% of the area.
• Wetland
plant species (as defined in monitoring SOPs; see EM & A Manual) comprise
over >90% of established
vegetation.
• Undesirable
invasive species and exotic species are < 10% of vegetation cover.
• The
average depth of water (outside drawn down periods for maintenance) is 20 – 50
cm.
• The
percentage of open water (i.e. unvegetated water) is 5 - 30%.
• Exposed
soils are wet and soft (with penetrability of less than 6 kg F), outside drawn
down periods for maintenance, over 75% of the area.
2.4.8
An
additional area of reedbed will also be created alongside the station for water
clean-up purposes. This habitat will provide additional habitat for reedbed
species, potentially including smaller herons, bitterns and various passerines,
but is not part of the specific mitigation measure documented in this HCMP.
