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Review and analyses of IMEF bird surveys for Lachlan River valley
David Roshier and David M Watson
Institute for Land, Water and Society
Charles Sturt University
PO Box 789,
Albury NSW 2840
Review and analyses of IMEF bird surveys for Lachlan River valley
Summary
The data consist of a mixture of counts of varying precision. Moreover, there are
notable absences, unlikely occurrences and species that are underrepresented. In
addition single counts of one species at particular wetlands account for the majority of
individual birds recorded. For these reasons quantitative analyses and exploratory
modelling were no pursued as model outputs would be misleading. The survey
approach as written may be appropriate but only if implemented in a consistent
manner to ensure standardised data. Adding call-playback survey techiques,
considering detectability and expanding the survey area will ensure data are more
consistent, more representative of underlying patterns and more comparable.
1. Background
Water allocation is made on a whole-of-catchment basis by management agencies yet
the responses of individuals and populations of mobile species, such as birds and fish,
to changes in water regime are poorly known at the catchment scale. This lack of
knowledge is due, in part, to our inablity to reconcile local changes in abundance with
changes in the broader population and a limited understanding of the ecology of many
species. Nonetheless, targeted studies of particular species or functional groups offer
some insight into the responses of biodiversity to changes in water regime. For
instance, colonial-nesting waterbirds, such as ibis and spoonbills, are iconic species
whose population dynamics have been successfully used as a measure of the impacts
of water management (Kingsford & Johnson 1998; Leslie 2001, Driver 2004) and
engaged the community’s interest. Analyses of the response of other wetland bird
species to changes in river flow and wetland inundation point to significant impacts
due to river regulation (Kingsford et al. 2004, Briggs et al. 1997, Stapanian et al.
2004). Thus, there remains an imperative to develop surveys and methods to model
the responses of birds and others at the same catchment scale at which agencies
manage the resource.
The Department of Infrastructure, Planning and Natural Resources (DIPNR)
has developed the Integrated Monitoring of Environmental Flows (IMEF) program for
the Lachlan River valley and other catchments. As stated in DIPNR (2003), the
objectives of IMEF are:
1. to investigate relationships between water regimes, biodiversity and ecosystem
processes in the major regulated river systems of NSW (and the Barwon-Darling
River);
2. to assess responses in hydrology, habitats, biota and ecological processes
associated with specific flow events targeted by environmental flow rules; and
3. to use the resulting knowledge to estimate likely long-term effects of
environmental flow rules and provide information to assist in future adjustment of
rules.
Birds are one of several taxa monitored at 12 sites in the Mid and Lower
Lachlan. The monitoring is event-based and, since the commencement of monitoring
in 2000, there have been 20 inundation events of individual wetlands—mostly in the
first year. This monitoring program has produced data on 143 wetland and woodland
species from 111 individual surveys. We (Drs Roshier and Watson) undertook to
conduct preliminary analyses of the data, and model responses of wetland and
woodland birds to changes in river flow and wetland inundation. The agreed
analyses, outcomes and priorities (M-medium, H-high, VH-very high) follow:
Preliminary analyses.
1. Quantify changes in abundance and diversity of wetland and non-wetland bird
species over the survey period and in response to wetland inundation (VH for wetland
species, M for non-wetland species)
2. Examine species composition and diversity in response to flow and water
parameters (H)
3. Classify wetland species into functional groups and examine patterns within and
between groups (H)
4. Evaluate existing data for potential indicator species to enhance our understanding
of waterbird responses to environmental flows (VH)
Review of current bird survey techniques
5. Comparative evaluation of measures of waterbird responses: community based
versus functional groups versus indicator species (H)
6. Summarise advantages and disadvantages of alternative techniques for monitoring
waterbirds (M)
7. Assessment of suitability of response variables to desired management options
(ensuring the method informs management) (VH)
Outcomes
8. review of survey methods for waterbirds (M)
9. discussion of limitations and strengths in the interpretation of analyses using
current and alternative survey methods (H)
10. recommendations for alternative methods to enhance current surveys (M)
11. conceptual (non-mathematical) summary of patterns of abundance and species
richness in response to environmental flows and other factors (VH)
12. mathematical and/or statistical summaries of patterns of abundance and species
richness in response to environmental flows and other factors that can be linked to
current wetland flow models (VH)
13. evaluation of trends in abundance of functional groups of waterbirds (H)
14. identification of indicator species for targeted monitoring of waterbird responses
in the Lachlan River valley (H)
15. exploration of data requirements and modelling options based on specified
management scenarios (H)
2. Data quality
The survey data as originally supplied on 24/06/05 were incomplete with 36 of 109
survey dates with no corresponding bird data. These data included separate entries
with the same species name (plumed whistling-duck), species that were entered with
two different common names (superb fairy wren, sulphur-crested cockatoo), entries
with no scientific name and/or an indecipherable common name (black-eared
cuckoo). The data were corrected and returned on 8/11/05.
The final data set consisted of 1490 records of 143 species. The median and
maximum number of species seen on site surveys was 13 and 29, respectively. Both
these figures are lower than that expected of a comprehensive survey of wetland or
riparian habitats in this region and suggest there are issues with the either the time
allocated to complete the survey, the size of the area surveyed or species
identification.
Among the waterbirds and those that occupy the margins of aquatic habitats
there a number of notable absences (table 1). Also, based on the knowledge of the
authors there are a number of species that have been recorded at a lower frequency
than would be expected (table 2).
Table 1. Notable absences of waterbirds and species associated with aquatic habitats
from surveys of wetlands in the Lachlan River valley conducted from 1999 to 2003.
Common name
Scientific name
Status
Blue-billed duck
uncommon (Pizzey & Knight 2004)
Oxyura australis
Freckled duck
uncommon (authors) or rare (PK 2004)
Stictonetta naevosa
Hardhead
common (authors)
Aythya australis
Cattle egret
uncommon inland (authors)
Ardea ibis
Brolga
uncommon (Pizzey & Knight 2004)
Grus rubicunda
Buff-banded rail
Gallirallus philippensis common (authors)
Aust. spotted crake
common (Pizzey & Knight 2004)
Porzana fluminea
Latham’s snipe
uncommon (Pizzey & Knight 2004)
Gallinago hardwickii
Common greenshank
uncommon inland (Pizzey & Knight 2004)
Tringa nebularia
Marsh sandpiper
uncommon inland (Pizzey & Knight 2004)
Tringa stagnatilis
Wood sandpiper
uncommon (Pizzey & Knight 2004)
Tringa glareola
Sharp-tailed sandpiper
common (Pizzey & Knight 2004)
Calidris acuminata
Pectoral sandpiper
uncommon (Pizzey & Knight 2004)
Calidris melanotos
Curlew sandpiper
uncommon inland (authors)
Calidris ferruginea
Red-necked avocet
common (Pizzey & Knight 2004)
Recurvirostra
novaehollandiae
Red-capped dotterel
Charadrius ruficapillus common (authors)
Red-kneed dotterel
uncommon (authors)
Erythrogonys cinctus
Little bittern
uncommon (Pizzey & Knight 2004)
Ixobrychus minutus
Caspian tern
uncommon (authors)
Sterna caspia
White-winged black tern
Chlidonias leucopterus uncommon (authors)
Little grassbird
common (Pizzey & Knight 2004)
Megalurus gramineus
Golden-headed cisticola Cisticola exilis
common (Pizzey & Knight 2004)
Table 2. Waterbirds and species associated with aquatic habitats recorded at
frequencies less than expected in 111 individual surveys of wetlands in the Lachlan
River valley conducted from 1999 to 2003.
Common name
Scientific name
Total Status
Hoary-headed grebe Poliocephalis poliocephalus
4
common (Pizzey & Knight 2004)
Pink-eared duck
6
common (authors)
Malacorhynchus membranaceus
Musk duck
8
uncommon (authors)
Biziura lobata
Wood duck
178 abundant (authors)
Chenonetta jubata
Little egret
1
uncommon (Pizzey & Knight 2004)
Egretta garzetta
Baillon’s crake
6
uncommon (authors)
Porzana pusilla
Spotless crake
1
uncommon (Pizzey & Knight 2004)
Porzana tabuensis
Dusky moorhen
4
common (Pizzey & Knight 2004)
Gallinula tenebrosa
Purple swamphen
26 common (authors)
Porphyrio porphyrio
Improbable records
The Great-billed heron Ardea sumatrana recorded at Lignum Swamp on 11/01/00 is
an improbable record. This species is confined to coastal regions of the tropical north
of the continent, and has never been recorded in inland NSW. Given the time of year
and location, this record likely relates to a juvenile White-necked heron Ardea
pacifica, which is similar in overall size and plumage (although it has a markedly
smaller bill). We recommend that this record be deleted unless the observer has
corroborating evidence.
Other data issues
The figures reported for species abundance are a mixture of counts of individuals and
group estimates. While this is often a feature of survey data it is not articulated in the
sampling protocol at what level of abundance this change in counting method should
occur. Hence, some surveys simply report abundance as estimates of abundance to
the nearest 10 while others appear to be counts of individuals as high as 54.
The data are few and highly skewed with many zeros. The majority of
estimated abundances are less than 10 with a few records in the hundreds or
thousands. Of the 13,546 individual birds recorded, most records relate to a small
number of species on a single occasion at several sites. Among the 8,456 wetland
birds recorded, 3,500 are from two counts of ibis. Thus, in looking for responses of
wetland birds to changes in flow regime, it is likely that any significant relationship
will be due to the high degree of leverage of one or two points in the analysis. Indeed,
the data are largely the product of one flooding event in 2000. Earlier flooding events
for which data are available on other taxa do not include bird surveys at all stages of
the flood cycle.
It is possible to analyse data with many zeros using both parametric and nonparametric methods, but we do not think this appropriate at this stage. Alternative
approaches include basing the analysis on presence/absence or to combine data into
functional groups (see later). However, we believe it is premature to pursue such
analyses.
Based on the above concerns about data quality, we are unable to model
the responses of wetland birds to changes in river flow. At this stage, the
modelled outcomes from these data are likely to be unreliable. As a result it is
not possible to complete all components of tasks 1, 2, 3, 4, 11, 12, 13 and 15.
While issues of detectability and completeness are recognised in the written
protocol for bird surveys, IMEF Method 29 – Wetland waterbird survey (Driver et al.
2003), there is no explicit method in the protocol for correcting for biases and errors.
In the next section we review current approaches to bird survey and comment on the
protocol.
3. Synthesis of current approaches to bird survey
The basis of any analysis of biodiversity occurrence is the raw data—which species
were present at which locations at which time periods. Whether historic data,
opportunistically collected records or a systematically designed sampling protocol,
different kinds of data allow statements of varying precision, underpinning our
understanding of determinants of diversity and informing management and
meaningful conservation. Matching the scope of ecological inference and
management decisions to the resolution of the original data is the ultimate aim of
effective biodiversity sampling (Verner 1985, Mac Nally and Horrocks 2002, Watson
2003, 2004).
This preliminary review focuses on sampling waterbirds, a diverse and
prominent group associated with a range of habitats worldwide. This review covers
three main areas. Firstly, we highlight a suite of confounding factors that affect the
accuracy of waterbird surveys, focusing on ways to minimise or avoid them.
Secondly, we review the main methods used to sample waterbirds, both in Australia
and internationally—highlighting the inherent advantages and disadvantages of each.
Finally, we discuss some alternative approaches to sampling, demonstrating how a
sampling protocol can be designed to minimise the influence of confounding effects
while maximising the usefulness of the resultant data for informing management.
3.1 Confounding factors
There is a large (and growing) literature on sampling birds, but most focuses
exclusively on terrestrial groups. While many recent advances have a direct bearing
on waterbirds, others have little relevance. Key reviews or discussions on these topics
are listed in the references section, with Verner (1985), Watson (2003, 2004), USFWS
(1999), Thompson (2002), Krzys et al (2002) and Conway and Gibbs (2005) being
most informative. Time of day, observer behaviour and experience, weather and
habitat complexity all have individual confounding influences, as well as interacting
to diminish accuracy of bird surveys (Recher 1998, Bibby et al. 1992, Craig and
Roberts 2001). Rather than discuss each of these individually, the effect of many of
these factors are discussed in terms of detectability. Observer effects are discussed
separately.
Detectability
There has been an increasing amount of research in the past five years on the effects
of detectability on the accuracy of bird surveys (Thompson 2002). Specifically, it is
clear that different species have different probabilities of being recorded under
otherwise similar conditions, and that the same species may differ in its likelihood of
detection at different times of the year, or in different habitats. Little work has been
conducted on detectability issues in waterbirds, and to-date, no research has examined
this topic in Australia. So, although no actual data can be brought to bear on the
importance of detectability differences to sampling Australian waterbirds, there are
several important issues that can be identified.
Habitat-based differences in detectability are the most common and can have
marked effects on datasets (Rosenstock et al. 2002). For example, Dusky moorhens
may be twice as likely to be seen and recorded in wetlands with no fringing
vegetation, compared with wetlands surrounded by reed beds. If detectability is not
taken into account, most survey methods would yield the result that moorhens avoid
wetlands with fringing vegetation. Typically, however, habitat-based differences in
detectability are less obvious, and so can be complex to identify, let alone correct for.
Thus, some calls are less audible in more open vegetation, some species are more
wary in open areas, and some species call less frequently away from cover—all
factors that would affect estimated densities or abundances, and undermine any crosssite comparisons.
Time-based differences in detectability relate to seasonal and resource-based
changes, whereby birds at one time of the year are more easily recorded than at
others. While typically measured as breeding/non-breeding in Northern Hemisphere
studies, this distinction is less clear-cut in Australian assemblages, where the
prevailing climate is irregular, and so seasonality and the timing of breeding vary
greatly from one year to the next. This stochasticity, coupled with the lack of obvious
breeding plumage for many Australian species makes it difficult to gauge breeding
status, and therefore evaluate any effect it may have on detectability.
While there are numerous schemes for estimating detectability of birds (e.g.,
measuring call frequency contemporaneously with the bird survey; Rosenstock et al.
2002), these issues can be largely avoided in sampling design. In regards to
estimating abundance, restricting sampling to presence/absence (or nominal estimates
like <10, >100) diminishes the influence of detectability differences between sites and
between time periods. As long as the sampling intensity is sufficient to detect a
species as present in the least detectable site at the least detectable time of year, these
issues will have little effect on the overall data-set.
Inter-specific detectability differences are more pervasive. While many
waterbirds are highly detectable—large bodied, travelling in groups, foraging in the
open and easily identified—other species are more secretive. Rails and bitterns are
two prominent groups that present significant difficulties for sampling—they are
rarely seen in the open, and when they are seen, have cryptic plumage and may be
difficult to positively identify to species. Painted Snipe are similarly wary, and it can
be difficult to distinguish true absences from a lack of presence data.
Implications for Lachlan Catchment data
In exploring the current data set, several species were notable for their absence, and
while no individuals of these species may have been present at any of the wetlands
during the study period, they may also have been present but not detected. Little
Grassbirds, Australasian Bittern and Buff-banded Rails are all reasonably common in
wetlands throughout this region, but were not recorded once. Rather than being a few
additional species that have little effect on the overall pattern, these species are
wetland specialists with strict habitat tolerances. As such they might be expected to
be highly sensitive to subtle differences in wetland structure and water regime, and so
should be targeted specifically (see playback surveys, below).
In sum, if comparisons between different seasons and different sites are to be
made, these can currently be made using presence/absence data with a low likelihood
of detectability differences affecting the comparison. If changes in relative abundance
are a priority, and need to be estimated, some measure of detectability should be
incorporated into the sampling design. Given that no procedure for Australian
waterbirds exists, a scheme like this would have to be carefully developed, using
variables such as call frequency, or time until first record to calibrate the data.
Finally, inter-specific differences in detectability will have confounding effects on
any inter-specific comparisons based on estimates of relative abundance. Even
though these can be minimised by restricting analysis to presence/absence, the current
sampling approach may not be recording all species, with several groups probably
requiring targeted sampling to confirm their presence.
Observer effects
While a range of observer-related effects are alluded to in the IMEF Method 29 –
Wetland waterbird survey (Driver et al. 2003), it is unclear how these issues were
guarded against. As discussed earlier, there are several dubious records and notable
absences—suggestive of inadequate observer training and/or inconsistent
interpretation of the prescribed sampling approach. Time of day and weather effects
are critical for many species, affecting both detectabilities and identification (Shields
1979, Craig and Roberts 2001).
While problematic with individual observers, these issues are further
compounded when there are multiple observers contributing data. Specifically, interobserver differences add another level of confounding effects—artefacts that can
outweigh any underlying differences between locations of time periods (Dawson
1981, Remsen 1994, Recher 1998). The only way to diminish inter-observer
differences is training, followed up by regular validation. Initially, observers must
have a minimum level of proficiency, in terms of identifying species using plumage,
behaviour and vocalizations; as well as estimating numbers. They must be trained to
ensure they are familiar with the survey procedures and how they should be applied.
Subsequent comparisons between observers are then needed to ensure comparable
levels of accuracy (USFWS 1999).
Implications for Lachlan Catchment data collection
Once the survey methods have been refined and established, all observers need to be
evaluated for competency, and trained to ensure consistency. In addition to applying
the established sampling protocol, more detailed guidelines need to be developed to
ensure the protocol is applied uniformly. Hence, colour of clothing and observer
behaviour (i.e., talking, walking speed, approach distance etc) should all be
standardized. Similarly, time of day (relative to sunrise and sunset) and weather
should be standardised, such that all samples are collected at similar times of the day
under comparable weather conditions.
3.2 Approaches to waterbird sampling
A wide range of techniques are used for sampling waterbirds and analysing patterns
of their occurrence (USFWS 1999, Conway and Gibbs 2005). These techniques may
relate to particular surveying techniques or specific variables used for analysis, and
will be discussed separately.
Visual versus auditory records—Visual cues (including plumage, overall size and
proportions as well as behaviour) are typically the main means of identifying birds.
With appropriate experience, this information is an accurate and reliable basis for
identifying birds to species and estimating abundances (Bibby et al. 1992, Stapanian
et al. 2002). While appropriate for many waterbirds (and many wetlands), visual cues
alone may be inappropriate in some situations. Heavily vegetated wetlands will
contain many species partially or completely obscured from view, either from landward or water-based perspectives. In contrast, auditory cues (both vocalizations and
splashing/rustling associated with bird activity) are less affected by intervening
vegetation. While many calls can be readily ascribed to particular species, others
(especially alarm calls) are not reliable for species-level identification. Moreover,
abundances can rarely be estimated from bird calls. Hence, rather than advocating
one source of data over the other, we strongly recommend using both visual and
auditory cues in concert.
Call playback—Even when bird calls are used, some species will consistently be
missed, and others will be disproportionately overlooked at certain times of the year
(many waterbirds are quiet after breeding). To redress this bias and minimise the
number of false absences, playing pre-recorded bird calls is a useful technique. A
recent review paper (Conway and Gibbs 2005) demonstrated that the addition of
playback surveys significantly increased the likelihood of detecting particular species
of rail and bittern in the USA and Canada. Despite being standard for waterbird
surveys in North America, call playback is not part of the standard complement of
techniques used in Australia. The reasons for this are unclear—call playback is
routinely used for nocturnal bird surveys throughout the country, and high quality
recordings are readily available for all species of interest.
Density and abundance—The advantage of limited area techniques is that abundance
estimates can be expressed in terms of density, which can then be extrapolated to the
area of interest. Verner (1985) discussed this topic in detail and identified a broad
range of artefacts, inherent biases and confounding factors associated with density
estimates (see also Dawson 1981). For waterbird surveys, two of the most serious of
these shortcomings relate to accuracy of counts (i.e., controlling for individuals
present but not detected), and the issue of representation (i.e. the degree to which a
detailed count within a subsample can be scaled up to reflect the overall site). While
density estimates can be a useful and sensitive complement to richness estimates,
Verner concluded that most sampling approaches are simply unable to generate
estimates that reflect underlying bird numbers. While this means absolute measures
are rarely possible, estimates of relative abundance (or scaled to generate relative
density estimates) may still be useful and reflect underlying differences (Dawson
1981). For relative measures, it is assumed that the various confounding factors and
biases are constant—occasionally possible, but rarely measurable. By controlling for
detectability (as mentioned previously), relative abundance measures can become
more robust and reliable.
Incidence—An alternative to abundance or density estimates (either in absolute or
relative terms) is incidence, or reporting rate (Wright 1991, Bibby et al. 1992, Watson
2003). This measure expresses the proportion of samples in which a species was
detected. As it is essentially a composite of multiple presence/absence samples, it is
not as finely resolved as direct estimates of abundance. While this means it will be
less sensitive to change, this also means that incidence is far more robust to changes
in detectability. Hence, in a given sample, a flock of 20 birds or a single individual
will both be denoted as “present”, and the records treated as equivalent. After ten
samples, the species may have been recorded as present in 8 of them, yielding an
incidence of 0.8. Rather than relating exclusively to abundance, incidence
incorporates site tenacity, territoriality, vagility and other autecological traits. As
such, comparing three species (A, B and C) with incidences of 0.8, 0.5 and 0.1
(respectively), the site could be considered most important for species A, of
intermediate value to species B, and of little importance for species C. Obviously,
incidence can be affected by differing ecologies and detectabilities, so comparisons
are best restricted to ecological similar taxa.
Total Richness—Most bird surveys collect data on all species encountered within the
sampling period, typically summarising these data as species richness (Herzog et al.
2002). While useful to quantify the range of species recorded, overall richness
estimates are typically too broad to be of analytical value. Instead, exotic species, non
target species and incidental records are typically removed, giving a woodland bird or
wetland bird richness estimates. This list of species may be further subdivided into
habitat specialists versus generalists, species that breed in the site, migrants or
seasonally restricted species. Of these, breeding species richness is one of the more
sensitive indices of site quality, and is frequently used in relation to terrestrial
avifaunae.
Breeding records—Those species breeding in a particular site are necessarily more
sensitive to within and between site variation, and can be a useful assay for site-based
differences. While some waterbird species are easily designated as breeding versus
non-breeding (e.g., colonially nesting egrets or pelicans), others are far more
secretive. Some species acquire distinctive nuptial plumage during breeding seasons,
enabling trained observes to distinguish not just breeding species from non breeders,
but also proportion of breeding vs non breeding individuals with a particular species.
Similarly, some species (bitterns, kingfishers, grebes) give distinctive vocalizations
during territory acquisition, courtship and incubation, although most species become
characteristically silent during chick rearing and fledging. Hence, distinguishing
breeding from non-breeding species within a particular site yields valuable data but
relies on detailed (and region-specific) knowledge and experience.
Functional groups—Another way to subdivide total richness estimates is to use the
overall ecology of the species to assign them to functional groups. Unlike total
richness, richness within a carefully defined functional group is far more likely to
elucidate subtle change or between-site differences. Functional groups should be
biologically real (i.e., corresponding to underlying biological similarities), and not just
defined relative to obvious differences like diet, but breeding strategies/nesting,
movement/migratory approaches and the like. Moreover, these groups should
correspond to groups that are sensitive to the key factors of interested. So, “cavity
nesting waterfowl” corresponds to a group of ecologically similar taxa, but may have
little explanatory value. Conversely, “reed-nesting residents” may include things as
varied as Little Grassbirds, Australasian Bittern and Purple Swamphen, but richness
of this group may be a highly sensitive indicator of flows, grazing and salinity. One
approach to classify birds in the Lachlan catchment is summarised in appendix 1.
Indicator species—An alternative to richness-based measures is to select a particular
species that reflects overall change (Brooker 2002). There has been considerable
interest (both internationally and within Australia) to identify these indicator species.
While a well chosen indicator species can be an efficient and repeatable means of
measuring response to treatments, or variation across space and time, choosing the
right species is critical. The species must be highly detectable—i.e., need to
maximise likelihood that a lack of records corresponds to an actual absence.
Identification needs to be straightforward, both to minimize chances of
misidentification and to allow ease of sampling by a range of observers. In order to
be an accurate indicator, variation in the chosen species should reflect overall change
in the group of interest. Finally, and most importantly, the species should respond to
factors of interest. Selecting an effective indicator species is generally a three step
process. Firstly, collect a large, broad-based data-set incorporating all the species of
interest across the breadth of sites/treatments available. Secondly, identify a species
that reflects overall change in the data set (and is appropriately detectable and
distinctive). Thirdly, evaluate change in a complementary data set to determine
whether changes in the indicator species reflect broad-based change.
4. Appraisal of current sampling approach
The current approach to sampling waterbirds involves four surveys of 12 wetlands
each year: pre-flow counts in March/April followed by counts 14, 60 and 90 days
after wetland inundation. On any reach, survey area is a 100m section for full width
of billabong, including any birds flying in vicinity within 100m.
The current protocol is based on a fixed effort and community scale abundance
estimates. The main benefit of this approach is its breadth—it gives a broad overview
of occurrence patterns of a large number of wetland dependent species across the
catchment. Accordingly, it yields useful baseline data on which species occur where,
times at which particular species are abundant within the catchment, and highlights
particular localities that support high diversities. Other than these broad statements,
however, many of the confounding factors discussed earlier prevent more detailed
statements, and preclude explicit comparisons across space and time.
The sampling effort used is constant, which assumes that the fixed effort is
equally representative of large, complex sites supporting high diversities and small,
simplistic sites supporting relatively low diversities. This high inter-site variability
coupled with known behaviours of waterbirds confounds between-site comparisons.
Species rich sites may be relatively under-sampled, while species-poor sites may be
relatively over-sampled, diminishing actual differences between the sites.
As discussed briefly earlier, there are several notable absences from the
overall dataset, and several notable inclusions. This raises questions about the
experience of the observers collecting the data, their training, their familiarity with
waterbird species in the region, and their ability to identify species by visual, auditory
and/or behavioural cues. This is especially the case with rails, bitterns and other
cryptic groups—rarely picked up during routine surveys. Even with experienced
observers, however, these species are often overlooked, and call playback is now
routinely used in North America when conducting wetland surveys.
Aside from issues of comparability and representation, the fixed sampling
effort represents a small to very small sub-sample of the overall wetland (USFWS
1999). Hence, for a typical billabong 50 m wide, the survey area for wetland birds is
a ~0.5 ha section of billabong 1-5 km in length. Regardless of where the sample is
located, the resultant survey cannot be considered representative of the overall
wetland. Just as with transect counts in terrestrial systems, the resultant data maybe
an accurate indication of which species occurred within the sampling area, but these
data cannot be extrapolated to the wetland scale, diminishing the utility and relevance
of the data for management decisions (decisions that operate at the wetland and
whole-of-catchment scale).
A strong argument for continuing with the existing sampling protocol is to
make the most of work already in hand, making temporal comparisons across the
catchment. The alternative is to evaluate how well the current decisions are being
informed and supported by the resultant data. So, if long-term temporal comparisons
are the priority (i.e., how have bird distribution patterns changed over time),
continuing with the existing sampling approach is reasonable. Alternatively, if
meaningful and accurate statements about the timing, magnitude and value of
differing flow regimes are to be formulated, at the scale of individual wetlands,
subregions or the overall catchment, it may be appropriate to consider changing the
sampling regime.
5. Suggested alternative sampling approaches
Patch-scale sampling
In terms of overall sampling design, patch-scale sampling is a priority. In addition to
avoiding problems of unequal representation among samples, this approach also
yields data at the wetland scale. Using fixed-area approaches, explicit comparisons
can be made between samples (Merikallio 1958), yet statements about the waterbird
diversity of the overall wetland cannot be made (Watson 2003, 2004). Hence, using
the overall wetland as the scale of sampling allows data of comparable representation
to be collected, and can be used to make statements at the wetland scale.
If sampling is conducted at the wetland scale, careful consideration is needed
to determine when samples are complete. This can be done a posteriori with the data
in hand using rarefaction, but this assumes data have been collected in a cumulative
way, and necessarily involves removing data points in order to bring all inventories to
the same levels of completeness. For subsequent data collection, however,
application of a well-selected results-based stopping rule is recommended (Peterson
and Slade 1998). Rather than using an arbitrary effort-based stopping rule, based on
either time or area sampled, results-based stopping rules use the data to determine
when sampling is complete. As discussed in detail in Watson (2002, 2003), stopping
rules should be designed with data comparability, logistical efficiency and practical
applicability in mind. Hence, stop sampling once all species are seen in at least two
sampling periods would yield data of high completeness that are comparable across
sites and times, yet would be prohibitively time-intensive to collect. we would
advocate tailoring a stopping rule that generates data of at least 75% completeness—
any less, and representation becomes an issue. Note, that this need not involve
exhaustive surveying efforts—three-to-five back to back half hour surveys would
readily satisfy many stopping rules for the vast majority of wetlands.
Sampling methods
Once scale of sampling, stopping rules and sampling frequency have been selected,
survey methods require consideration. Passive observation, even complementing
visual based observations with auditory cues, will consistently miss some species, and
under-represent several key groups (Conway and Gibbs 2005). To address this
shortcoming, we would recommend complementing observation-based sampling with
the use of call play-back. Rather than for all species, this would be for a predetermined subset of species: species considered possible in the region, and unlikely
to be detected from observation alone. Playback location, timing, intensity and
response times would all need to be determined, balancing time required with data
yielded. As with survey timing and frequency, these decisions are best made on the
basis of a small scale, representative pilot study, rather than arbitrarily, or with
reference to research conducted elsewhere. Rather than being directly comparable to
records of species gathered passively, these proactive detections could only be used to
confirm presence or support putative absences—they would not yield incidence or
abundance estimates (even in relative terms).
Presence, absence and incidence
Ideally, survey data should give a range of responses, not simply present or absent;
yes or no. One way to achieve this, without significant increases in survey effort, is to
record presence/absence data in sequential sampling periods (as advocated previously,
and discussed in depth in Watson 2003). This allows incidence estimates to be
calculated: the proportion of sampled in which a particular species was recorded.
Although lacking the sensitivity of true abundance estimates, incidence is far more
robust to changes in detectability, and so is far more likely to yield reliable estimates.
While related to abundance, incidence is also affected by site tenacity, territoriality,
social structure and home range size of particular species. Hence, it yields a broad
index of how important a particular site is for a given species or suite of species. Duck
species a, b and c may have been recorded with incidences of 0.1, 0.4 and 0.9,
respectively. Regardless of differences in actual or estimated number, this translates
to this particular site being most important for species c, (being recorded 9 out of 10
times), and of least importance for species a. This provides a more fine-grained set of
responses, allowing the resultant datsa-set to be more sensitive to detect subtle
differences between treatments/sites/times.
Beyond presence/absence
While compiling multiple presence/absence records can yield greater resolution than a
simple binary variable, further details may be needed. What are the effects of altered
flow regimes on the breeding response of a particular species or group of species?
Incidence data would not address this question—additional data are required. For
many species of waterbird, external characteristics (typically, plumage pattern,
occasionally size and behaviour) can be used to distinguish adults from immatures,
females from males, and breeding adults from those not in breeding condition. While
not practicable (or even possible) for all species, collecting these supplemental data
for selected species would augment the occurrence data, and give far more finely
resolved information to inform management. Hence, for a particular species, a range
of possible responses are possible. Present—yes or no? If present, breeding—yes or
no? If present and breeding, was breeding successful—yes or no. Additional data
would yield even greater resolution: number of breeding attempts, number of chicks
fledged etc.
One potential sampling approach
As a worked example, I’ve selected spoonbills. There is more than one species (in
this case, two); easily identified to species with minimal training; adults can be readily
distinguished from immatures/juveniles; breeding adults can be readily distinguished
from non-breeding adults; and nests are relatively easy to locate. These procedural
differences reflect underlying ecological differences between the two species—they
utilise habitats differently (for foraging, roosting and nesting), they feed on different
prey (large invertebrates, compared with small fish). Taking this ecological
information into account, a sampling protocol is designed. Standardised searches will
be conducted before and after altered flow regimes, using the overall wetland as the
sampling scale, and conducting targeted observations coupled with call playback for
rails and bitterns at least once. Spoonbill data will be collected separately, noting
maximum number of individuals seen, and approximate ratio of adults to immatures,
non-breeding adults to breeding adults. Using a conservative stopping rule of 75%
completeness, a survey will be deemed completed after (typically) 3 to five 15 minute
sampling periods—i.e., a total effort of between 45 minutes and 75 minutes. These
will be conducted twice, before and after the event. Resultant data will comprise
richness estimates (of known completeness) for all waterbirds before and after the
event (including cryptic species), standardised incidence estimates for all species
detected, plus detailed demographic indices for two congeneric species of divergent
ecologies. As Yellow-billed Spoonbills feed primarily on small waterborne inverts
which in turn, respond directly (and rapidly) to water conditions, their presence,
numbers and population composition give a sensitive, accurate and broad-based
measure of overall water quality and biodiversity value. Given that some flows lead
to short-term benefits whereas others entrain longer-term effects, a subset of wetlands
may require a third survey (just for spoonbills). This would take less than one hour
per wetland, and would focus on the other species, Royal Spoonbill. Unlike its
congener, this species is primarily piscivorous, with fish taking longer to respond to
changes in flow than small invertebrates. Hence, a flow that yields breeding in both
species of spoonbills likely represents a more significant event for a broad range of
other species than a flow that stimulates breeding in only Yellow-billed Spoonbills.
This approach combines many of the specific recommendations made earlier.
¾ Observers are trained
¾ Sampling is timed relative to events of biological significance and
management relevance
¾ Sampling is conducted at the patch scale
¾ Sample completeness is standardised, allowing explicit comparisons between
surveys
¾ Call play-back is incorporated to enhance sampling resolution for cryptic
groups
¾ Indicator species are chosen, reflecting their ecology and sensitivity to key
underlying processes
¾ Focal species that can be readily identified, aged, and scored for breeding
status are incorporated.
Herons and cormorants could also be used as focal groups, but both would yield
differing information—herons being more sensitive to water depth and reeds,
cormorants more sensitive to water temperature and presence of dead trees.
Moreover, as both groups are primarily piscivorous, their numbers would reflect
water changes over a longer period than spoonbills. While the richness of duck
species is greater still, their ecological requirements (particularly feeding preferences,
habitat preferences for breeding) are less clearly demarcated, making interpretation
and management response less straightforward.
Community
approach
Functional groups
Call playback
Limited-area
samples
Patch-scale
samples
Incidence
Approach
/Method
Abundance
Most meaningful measure, fine
grained and sensitive
Estimated in either absolute or
relative terms, this is a
measure of how many
individuals of a particular
species were detected
Also called reporting rate, this
is the proportion of samples in
which a species was recorded
Using pre-existing biological
features to define the sampling
area (ie, the lake, the woodland
remnant, the catchment)
Typically rectangular
(transects) or circular (point
counts) areas of fixed
dimensions, used to subsample
larger areas
Playing a pre-recorded
vocalization of a particular
species to elicit a response—
typically a territorial call
Rather than examining species,
using ecological similarities
(typically feeding, habitat use,
nest site preference) to group
similar species together
Picks up subtle factors unclear with
species-specific analyses, maximises
sensitivity to variables of concern—ie
match underlying variables to
particular groups most liely to show
signal
Inclusive approach to sampling Includes all species, so ideal for longbiodiversity, incorporating all
term studies, useful for comparisons
Essential for determining whether
cryptic species are present, efficient
Can yield density estimates; best
when samples are internally
homogeneous and subsampled area is
large and consistent subset of whole
Yields data at patch scale, ideal when
management/treatment is also applied
at patch scale
Less affected by flocking birds, easily
calculated,
Advantages
Description
Requires excellent identification skills,
lots of noise, so overall patterns rarely
Inaccurate when sites vary in area, or
when sites exhibit high within-site
heterogeneity; yield data at the sample
scale—often not the most meaningful
scale for inference or management
Unable to give definitive data on
absences, less accurate than count data
for estimating numbers of individuals,
ethic concerns during breeding season
Assumes functional groups are well
defined, simplistic and may not be
comparable between regions
Fairly coarse grained measure unable
to distinguish subtle changes in
numbers
Can only be used in inherently patchy
systems—ie where area of interest is
biologically defined
Issues of detectability, both between
species and observers and also sites
and times of year
Disadvantages
Indicator species
species within a class (all
between regions
birds), or within an ecological
subgroup of that
class(waterbirds)
Rather than examining all
Most efficient approach
species (either individually or
collectively), using one species
as an assay for wider patterns
May miss other factors, and assumes
species have been chosen correctly
conclusive
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Appendix 1: A Functional classification scheme for birds in the Lachlan catchment
For management the two flow parameters most easily adjusted are duration of inundation
and water depth. Birds will respond to these both directly and indirectly. For colonialnesting species there is a direct response to duration of inundation and water depth that
results in initiation of breeding activity (Kingsford and Johnstone 1996; Leslie 2001). For
others, changes in water depth alters access to food resources and/or the availability of
prey items. Indirect effects of duration of inundation and water depth include the
presence or not of fringing vegetation and the extent of exposed shoreline. These provide
protection from predators and disturbance and/or feeding habitat for some species. The
survey data were divided into functional groups based on feeding habit and responses to
flow parameters. One possible scheme for dividing the wetland birds of the Lachlan
River valley follows;
Dabblers and probers—feed in the shallow margins of wetlands and include stilts, rednecked avocet, migratory shorebirds and most of the ducks.
Colonial-nesting waders—this group are long-legged waders that either dabble in shallow
water or probe for food. They distinguish themselves from other dabblers and probers by
forming nesting colonies when conditions are suitable—ibis and spoonbills.
Deep-water foragers—only occur on the deeper wetlands where water depth is ~1m or
more. This group includes the black swan, Eurasion coot, musk duck, blue-billed duck
and hardhead.
Reed-nesting birds—rely on fringing vegetation for protection from predation and
disturbance. This group includes the bitterns, crakes, rails, swamphen and several small
passerines that occur exclusively in these habitats.
Piscivores—fish eating species. This group includes grebes, terns, gulls, white-bellied
sea-eagle and azure kingfisher.
Colonial-nesting Piscivores—Piscivores that distinguish themselves from other
piscivores by forming nesting colonies when conditions are suitable—cormorants, most
herons and the Australian pelican
Shoreline foragers—feed mostly on the exposed shore of retreating wetlands and their
shallow margins. This disparate group includes Australian wood duck, Australian
shellduck, plumed whistle-duck and dotterels.
Woodland birds—all species not primarily dependent of aquatic habitats.
Other—this group has two species not readily classified with any of the above groups
because they occur in a broader range of habitats. These are the masked lapwing and the
magpie goose.
Table 3. Proposed functional groups for birds observed in the Lachlan River valley.
Common Name
Emu
Peaceful Dove
Diamond Dove
Common Bronzewing
Crested Pigeon
Baillon's Crake
Spotless Crake
Black-tailed Native-hen
Dusky Moorhen
Purple Swamphen
Eurasian Coot
Great Crested Grebe
Australasian Grebe
Hoary-headed Grebe
Great Cormorant
Little Black Cormorant
Pied Cormorant
Little Pied Cormorant
Darter
Australian Pelican
Marsh Tern
Gull Billed Tern
Silver Gull
Masked Lapwing
Black Fronted Dotterel
Black-winged Stilt
Banded Stilts
Common Sandpiper
Painted Snipe
Glossy Ibis
Sacred (Aust. White) Ibis
Straw necked ibis
Royal Spoonbill
Yellow Spoonbill
Great Billed Heron
Little Egret
Intermediate Egret
Great Egret
White-Faced heron
White-Necked Heron
Nankeen (Rufous) Night Heron
Australiasian Bittern
Magpie Goose
Australian Wood (Maned) Duck
Black Swan
Plumed Whistling-Duck
Australian Shelduck
Pacific Black duck
Chestnut Teal
Grey teal
Australiasian Shoveler
Pink Eared Duck
Musk Duck
Swamp Harrier
White Goshawk
Scientific Name
Dromaius novaehollandiae
Geopelia striata
Geopelia cuneata
Phaps chalcoptera
Ocyphaps lophotes
Porzana pusilla
Porzana tabuensis
Gallinula ventralis
Gallinula tenebrosa
Porphyrio porphyrio
Fulica atra
Podiceps cristatus
Tachybaptus novaehollandiae
Poliocephalus poliocephalus
Phalacrocorax carbo
Phalacrocorax sulcirostris
Phalacrocorax varius
Phalacrocorax melanoleucos
Anhinga melanogaster
Pelecanus conspicillatus
Chlidonias hybridus
Sterna nilotica
Larus novaehollandiae
Vanellus miles
Elesyornis melanops
Himantopus himantopus
Cladorhynchus leucocephalus
Actitis hypoleucos
Rostratula benghalensis
Plegadis falcinellus
Threskiornis molucca
Threskiornis spinicollis
Platalea regia
Platalea flavipes
Ardea sumatrana
Egretta garzetta
Ardea intermedia
Ardea alba
Egretta novaehollandiae
Ardea pacifica
Nycticorax caledonicus
Botaurus poiciloptilus
Anseranas semipalmata
Chenonetta jubata
Cygnus atratus
Dendrocygna eytoni
Tadorna tadornoides
Anas superciliosa
Anas castanea
Anas gracilis
Anas rhynchotis
Malacorhynchus membranaceus
Biziura lobata
Circus approximans
Accipiter novaehollandiae
Functional group
woodland
woodland
woodland
woodland
woodland
reed-nesting
reed-nesting
reed-nesting
reed-nesting
reed-nesting
deep-water forager
piscivore
deep-water forager
deep-water forager
colonial-nesting piscivore
colonial-nesting piscivore
colonial-nesting piscivore
colonial-nesting piscivore
piscivore
colonial-nesting piscivore
piscivore
piscivore
piscivore
other
shoreline forager
dabblers and probers
dabblers and probers
dabblers and probers
reed-nesting
colonial-nesting wader
colonial-nesting wader
colonial-nesting wader
colonial-nesting wader
colonial-nesting wader
piscivore
colonial-nesting piscivore
colonial-nesting piscivore
colonial-nesting piscivore
piscivore
piscivore
colonial-nesting piscivore
reed-nesting
other
shoreline forager
deep-water forager
shoreline forager
shoreline forager
dabblers and probers
dabblers and probers
dabblers and probers
dabblers and probers
dabblers and probers
deep-water forager
woodland
woodland
Wedged Tail Eagle
Little Eagle
White Bellied Sea Eagle
Whistling Kite
Black (fork-tailed) Kite
Square-tail Kite
Black Shouldered Kite
Letter Winged Kite
Grey Falcon
Brown Falcon
Nankeen Kestrel
Sulfur crested cockatoo
Little Corella
Galah
Cockatiel
Crimson Rosella
Yellow Rosella
Eastern Rosella
Australian Ringneck
Red Rumped Parrot
Blue Bonnet
Blue-winged Parrot
Azure Kingfisher
Laughing kookaburra
Sacred kingfisher
Fork-tailed Swift
Pallid cuckoo
Black eared cuckoo
Welcome Swallow
Tree Martin
Fairy Martin
Willie Wagtail
Jacky Winter
Red Capped Robin
Hooded Robin
Eastern Yellow Robin
Rufous Whistler
Gilberts Whistler
Grey Shrike-Thrush
Magpie Lark
Black Faced Cuckoo Shrike
Grey Crowned Babbler
White Browed Babbler
Western Gerygone (Warbler)
Weebill
Southern Whiteface
Yellow (Little) Thornbill
Western Thornbill
Inland Thornbill
Yellow Rumped Thornbill
Brown Songlark
Rufous Songlark
Clamorous Reed-Warbler
Golden-headed Cisticola
Superb Fairy (Blue) Wren
Variegated Fairy Wren
Black Faced Woodswallow
Brown Treecreeper
Aquila audax
Hieraaetus morphnoides
Haliaeetus leucogaster
Haliastur sphenurus
Milvus migrans
Lophoictinia isura
Elanus axillaris
Elanus scriptus
Falco hypoleucos
Falco berigora
Falco cenchroides
Cacatua galerita
Cacatua sanguinea
Cacatua roseicapillus
Nymphicus hollandicus
Platycercus elegans, race elegans
Platycercus elegans, race flaveolus
Platycercus eximius
Barnardius zonarius
Psephotus haematonotus
Northiella haematogaster
Neophema chrysostoma
Alcedo azurea
Dacelo novaeguineae
Todiramphus sanctus
Apus pacificus
Cuculus pallidus
Chrysococcy) osculans
Hirundo neoxena
Hirundo nigricans
Hirundo ariel
Rhipidura leucophrys
Microeca fascinans
Petroica goodenovii
Melanodryas cucullata
Eopsaltria australis
Pachycephala rufiventris
Pachycephala inornata
Colluricincla harmonica
Grallina cyanoleuca
Coracina novaehollandiae
Pomatostomus temporalis
Pomatostomus superciliosus
Gerygone fusca
Smicrornis brevirostris
Aphelocephala leucopsis
Acanthiza nana
Acanthiza inornata
Acanthiza ewingii
Acanthiza chrysorrhoa
Cincloramphus cruralis
Cincloramphus mathewsi
Acrocephalus stentoreus
Cisticola exilis
Malurus cyaneus
Malurus lamberti
Artamus cinereus
Climateris picumnus
woodland
woodland
piscivore
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
piscivore
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
Mistletoe Bird
Silvereye
Striped Honeyeater
Pied Honeyeater
White Plumed honeyeater
Noisy Miner
Yellow Throated Miner
Blue Faced Honeyeater
Noisy Friarbird
Little Friarbird
Diamond Firetail Finch
Double-barred finch
Apostle Bird
White winged chough
Pied Currawong
Pied Butcher Bird
Grey Butcher Bird
Australian Magpie
Little Wattlebird
Grey Fantail
Restless Flycatcher
Australian Raven
Little Raven
Striated Pardalote
European Goldfinch
Common Myna
Common Starling
Dicaeum hirundinaceum
Zosterops lateralis
Plectorhyncha lanceolata
Certhionyx variegatus
Lichenostomus penicillatus
Manorina melanocephala
Manorina flavigula
Entomyzon cyanotis
Philemon corniculatus
Philemon citreogularis
Stagonopleura guttata
Taeniopygia bichenovii
Struthidea cinerea
Corcorax melanorhamphos
Strepera graculina
Cracticus nigrogularis
Cracticus torquatus
Gymnorhina tibicen
Anthochaera chrysoptera
Rhipidura fuliginosa
Myiagra inquieta
Corvus coronoides
Corvus mellori
Pardalotus striatus
Carduelis carduelis
Acridotheres tristis
Sturnus vulgaris
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland
woodland