An Assessment of the Focal-Species Approach for Conserving Birds in Variegated Landscapes in.pdf

1364
Conservation Biology, Pages 1364–1373
Volume 15, No. 5, October 2001
An Assessment of the Focal-Species Approach for
Conserving Birds in Variegated Landscapes in
Southeastern Australia
JAMES WATSON,* DAVID FREUDENBERGER,†‡ AND DAVID PAULL*
*School of Geography and Oceanography, University College, University of New South Wales, Northcott Drive,
Canberra ACT 2600, Australia
†Commonwealth Scientific and Industrial Research Organization (CSIRO), Sustainable Ecosystems, GPO Box 284,
Canberra, ACT 2601, Australia, email d.freudenberger@dwe.csiro.au
Abstract: The temperate woodlands of the northern Australian Capital Territory and bordering the New
South Wales region of eastern Australia have been extensively disturbed by agriculture and urbanization.
Small patches of woodland are now embedded in a pastoral or suburban matrix. Birds within landscapes of
this region are threatened by a reduction in habitat area, increased isolation, and declining habitat condi-
tion. Within this setting, we assessed Lambeck’s (1997) “focal species” approach for its ability to identify the
minimum patch size, habitat structural complexity, and landscape connectivity required to accommodate ex-
isting woodland birds. Presence/absence data were gathered for 72 woodland remnants that varied in size,
isolation, and habitat structural complexity. The Hooded Robin ( Melanodryas cucullata) was identified as the
focal species for the threats of area and resource limitation because it had the most demanding requirements
for area (100 ha) and habitat complexity. The eastern Yellow Robin ( Eopsaltria australis) was the species
most threatened by isolation of remnants. A landscape designed to meet the habitat requirements of these
birds should encompass the requirements of all other woodland bird species that are sensitive to similar
threats. A revegetation scenario based on the requirements of these two focal species is not feasible because
the majority (95%) of woodland remnants within the study area are too small, too lacking in habitat struc-
tural complexity, and too isolated to meet the requirements of the focal species. If woodland management
guidelines concentrate on increasing small remnants to 10 ha in size and on ensuring that these remnants
have complex shrub and ground-layer vegetation and are not isolated by more than 1.5 km from neighbor-
ing remnants, the needs of at least 95% of the resident woodland bird species in the region should be accom-
modated. The focal-species approach was effective for rapidly developing planning guidelines for the conser-
vation of woodland birds in these variegated landscapes, and the approach is likely to be useful for guiding
landscape reconstruction in other environments.
Evaluación de la Aproximación de Especie Focal para la Conservación de Aves en Paisajes Variegados en el Sureste
de Australia
Resumen: Los bosques templados del norte del Territorio Australiano Capital y de la región circundante de
Australia oriental han sido perturbados extensivamente por la agricultura y la urbanización. Actualmente,
pequeños fragmentos de bosque están en medio en una matriz ganadera o suburbana. Las aves en los
paisajes de esta región están amenazadas por la reducción del área de su hábitat, incremento de aislamiento
y declinación de las condiciones del hábitat. En este contexto, evaluamos la aproximación “especie focal” de
Lambeck (1997) en su habilidad para identificar el tamaño mínimo del fragmento, la complejidad estruc-
tural del hábitat y la conectividad del paisaje requerida para albergar a las aves de bosque existentes. Se
recolectaron datos de presencia/ausencia en 72 remanentes de bosque que variaron en tamaño, aislamiento
‡Address correspondence to D. Freudenberger.
Paper submitted April 19, 2000; revised manuscript accepted November 11, 2000.

Conservation Biology
Watson et al. Focal-Species Approach for Conservation Planning 1365
Introduction
To prevent the further loss of species from landscapes
threatened by habitat loss, fragmentation, and habitat
degradation, it is necessary to determine the quantity,
configuration, and internal structure of habitats required
to meet the needs of those species still present. Lam-
beck (1997) presented a “focal-species” approach for
defining the landscape attributes required to meet the
needs of biota and the management regimes that should
be applied. Lambeck’s (1997) approach seeks to identify
a suite of sensitive species, each of which is used to de-
fine the configuration and composition of habitats that
must be present in the landscape. The species identified
as most sensitive to a threat in a particular landscape is
termed the focal species for that threat. For example,
the species that requires the largest area of habitat is
used to define the minimum area required for different
habitat patches, and the most dispersal-limited species
defines the configuration of patches and the characteris-
tics of connecting vegetation. It is assumed that a land-
scape designed and managed to meet the needs of the
most demanding species will encompass the require-
ments of all other species, although this assumption has
never been tested.
Lambeck (1999) developed and applied this approach
to define minimum areas for revegetation in various re-
gions of the Western Australian wheat-sheep zone se-
verely affected by habitat fragmentation. We tested the
utility of the focal-species approach for conservation
planning in a markedly different landscape. We chose a
pastoral region of eastern Australia that retains eucalypt
woodland remnants dominated by a matrix of exotic
pastures, isolated eucalypt trees, and suburbia. We ex-
amined the effects of loss of habitat area, increased isola-
tion of habitats, and loss of habitat structure on wood-
land birds. The outcomes of the focal-species analysis
were used to develop spatially explicit and least-cost reveg-
etation guidelines for Greening Australia, a nongovern-
mental organization working with farmers committed to
landscape reconstruction (Freudenberger 1999).
Methods
Study Area
The study area is located in the northern Australian Cap-
ital Territory (ACT) and bordering areas of New South
Wales (NSW) (Fig. 1). The region has a temperate cli-
mate (mean minimum annual temperature 6.3 C, mean
maximum annual temperature 19.4 C) with a mean an-
nual rainfall of 631 mm with no seasonal pattern and an
elevation of 600–650 m above sea level (Bureau of Mete-
orology 1999). The city of Canberra (population 313,000)
is the major urban center within the region. The study
area consists of undulating hills and floodplains of the
Murrumbidgee and Molonglo Rivers. Before European
colonization in the early nineteenth century, grasslands
and woodlands comprised the dominant vegetation com-
munities (Burbidge Gray 1970). Large areas were cleared
for agriculture, and only 8% of the temperate woodlands
that occurred prior to European settlement are left within
the ACT (Environment ACT 1998). Although vegetation
clearance has now mostly halted, the remaining wood-
lands are being degraded by domestic livestock over-
grazing the shrubby and grassy understory, invasion of
weeds, removal of timber for firewood, and eucalypt
dieback (Landsberg et al. 1990; Australian Capital Terri-
tory Government 1999a).
Within the study area, two distinct landscapes exist.
The suburban landscape occurs where much of the nat-
ural vegetation has been replaced by native and exotic
vegetation in gardens, parks, and along roads. The re-
y complejidad estructural del hábitat. Melanodryas cucullata fue identificada como especie focal para las
amenazas de limitación de área y de recursos porque tuvo los requerimientos más demandantes de área
(100 ha) y de complejidad de hábitat. Eopsaltria australis fue la especie más amenazada por el aislamiento
de remanentes. Un paisaje diseñado para satisfacer los requerimientos de hábitat de estas aves debiera en-
globar los requerimientos de todas las demás especies de aves de bosque sensibles a amenazas similares. Un
escenario restaurado con base en los requerimientos de estas dos especies focales no es posible porque la
mayoría (95%) de los remanentes de bosque dentro del área de estudio son considerablemente más pe-
queños, tienen menor complejidad estructural del hábitat y están más aislados que los requerimientos de las
especies focales. Si los lineamientos de manejo de bosques se concentran en el incremento a 10 ha de los re-
manentes pequeños, procurando que estos remanentes tengan una compleja vegetación arbustiva y a nivel
de suelo, y que no estén aislados más de 1.5 km de los remanentes circundantes, se deberían satisfacer los re-
querimientos de por lo menos 95% de las especies residentes de la región. La aproximación de especie focal
fue efectiva para desarrollar lineamientos de planeación para la conservación de aves de bosque en estos
paisajes variegados rápidamente, y la aproximación es potencialmente aplicable para guiar la reconstruc-
ción en otros ambientes.

1366 Focal-Species Approach for Conservation Planning Watson et al.
mainder exists in remnant patches on hillsides surrounded
by the urban and suburban matrix. The rural landscape
is dominated by exotic pastures, pine plantations, tem-
perate woodland remnants, and native grassland rem-
nants. These two landscapes are not fragmented by in-
tensive cultivation and annual crops, but are modified by
grazing, urbanization, and selective clearing (e.g., fire-
wood removal). Using the framework of McIntyre and
Hobbs (1999), we classify these landscapes as “varie-
gated,” with a high degree of modification of the remain-
ing native vegetation.
The study area contains 203 woodland remnants of
0.5 ha in size (Fig. 1) (Watson 1999). These remnants
occur on farms, on grazed land leased from the ACT
Government, in rural nature reserves, and in urban parks.
Yellow box (Eucalyptus melliodora), Blakely’s red gum
(Eucalyptus blakelyi), and apple box (Eucalyptus bridges-
iana) are the dominant canopy species (Beard 1990).
Where intensive grazing is excluded, there occurs a
dense shrub layer of Eucalyptus regrowth, wattles (Aca-
cia sp.), bursaria (Bursaria spinosa), and exotic shrubs
such as sweetbriar (Rosa rubiginosa) and blackberry
(Rubus fruticosa). Ground-layer vegetation is generally
infested with exotic pasture species such as phalaris
(Phalaris aquatica), cocksfoot (Dactylis glomerata), and
perennial rye grass (Lolium perenne), but some native
grassy understory species persist (e.g., Danthonia sp.,
Themda australis, and Bothriochloa macra; Eddy et al.
1998).
Survey Sites
We collected data from 72 remnants (Fig. 1). This sam-
ple covered the range of sizes of all 203 woodland rem-
nants on an approximately logarithmic scale, so we sam-
pled more small than large remnants. We calculated the
Figure 1. The study area, showing
native vegetation remnants includ-
ing those surveyed for the presence
or absence of bird species in the
northern region of the Australian
Capital Territory and bordering
area of New South Wales.

area of remnant patches after screen-digitizing their out-
lines from a SPOT panchromatic satellite image captured
on 23 May 1997. Surveyed remnants ranged in size from
1.1 to 1617 ha, with a median size of 20 ha. We derived
an isolation index for each patch from the mean dis-
tance to its five nearest neighboring patches; it ranged
from 0.3 to 3.8 km, with a median isolation of 1.25 km.
About half the remnants were surrounded by suburbs
and the other half by pastures.
Habitat Structure
The canopy cover of a patch, the density of shrubs, and
the amount of litter and groundcover strongly influence
the diversity of bird species found on it (Recher 1969;
Wiens 1989; Ford Barrett 1995). We measured the
vegetation structural complexity of patches using a rapid
appraisal method first developed by Newsome and Catling
(1979) to explain the diversity of mammals found in a
wide range of habitats. At each remnant, we derived a
habitat complexity score, modified from the one de-
scribed by Catling and Burt (1995), on the basis of six
habitat attributes (Table 1). Each attribute was rated on
a scale of 0 to 3, and the scores for the six attributes
were totaled to give an overall score. A score below 5
represented an open canopy with sparse structure, no
understory shrubs, and little ground cover. A score be-
tween 5 and 9 represented a woodland with moderately
complex structure generally comprising 20% shrubs and
10–50% cover of ground herbage, logs, and litter. A score
of 10 described a structurally complex woodland. We
also recorded the dominant tree species at each remnant
and signs of recent disturbance such as fire and grazing.
We scored habitat complexity in quadrats of 100 100
m. A pilot survey determined that, to sample the varia-
tion in habitat complexity, one quadrat was required for
remnants of 2 ha in area, two quadrats for 2- to 10-ha
remnants, three quadrats for 10- to 50-ha remnants, four
quadrats for 50- to 100-ha remnants, and five quadrats
for remnants of 100 ha (Watson 1999). For remnants
where more than one quadrat was surveyed, a mean
habitat complexity score was calculated.
Bird Surveys
Presence/absence data were obtained for 72 woodland
remnants from a combination of sources. The majority of
remnants (57) were surveyed between February and April
1999 by J. W. and by M. Clayton. Additional presence/
absence data from January–March 1995 were obtained for
8 small woodland remnants from an unpublished data set
held by C. Davey. Data from 5 woodland remnants were
obtained from the Canberra Ornithologists Group and
were based on 20-minute surveys conducted concurrently
with our surveys. Data from 2 other remnants (1000 ha)
were obtained from the Canberra Ornithologists Group’s
database (data from January–March 1996–1998). Data from
3 remnants were obtained from Er (1995), who sampled
birds in yellow-box woodlands in the ACT on a regular
basis from January to May of 1995.
For the 57 remnants surveyed specifically for this study,
we chose an area-search method because it is simple and
repeatable, an observer can efficiently cover a large area
and number of remnants in a short time, and it aims to de-
termine bird presence/absence within a particular rem-
nant (Howe 1984; Loyn 1986). A sampling effort of three
surveys per remnant, each lasting 20 minutes, was deemed
suitable for measuring the presence or absence of birds in
remnants in the study area (Watson 1999). We used calls
to locate birds and to aid identification. Only bird species
sighted within woodland remnants were recorded as
present. Birds seen flying above the canopy of remnants
were not recorded, except when they appeared to be
feeding in the air space overhead. We made three visits to
each remnant on consecutive days, unless bad weather
occurred. Surveys were confined to 0630–0900 hours and
1600–1830 hours and were conducted only on days with-
out rain or strong wind.
Analysis
Because we conducted the surveys in late summer and
early autumn, summer migratory species were leaving
the study area and winter migratory species were arriv-
ing. Consequently, following the classifications of Taylor
and Canberra Ornithologists Group (1992) and Robinson
and Traill (1996a), our analysis was restricted to wood-
land species that are generally resident in the study area
in all seasons and breed only in woodland habitat. Of the
101 bird species recorded during the surveys, 31 were
considered resident woodland species (Table 2).
We graphed the presence or absence of each resident
woodland bird species against the area, isolation, and
habitat complexity of each of the 72 remnants (e.g., Figs
2 3). From these graphs, we determined each species’
minimum requirement scores for area, isolation, and
habitat complexity by identifying the smallest, least
complex, or most isolated occurrence. No outliers were
identified. The most sensitive species—the species with
Table 1. The components of the habitat complexity score and
method of scoring in 1-ha quadrats in woodland remnants.*
Habitat complexity score (0–3)
Component 0 1 2 3
Canopy 0–10 10–20 20–50 50
Tall shrubs 0–10 10–20 20–50 50
Low shrubs 0–10 10–20 20–50 50
Ground herbage 0–10 10–40 40–70 70
Logs and fallen branches 0–10 10–40 40–70 70
Litter 0–10 10–40 40–70 70
*Values in the body of the table are the percent cover for the particu-
lar component. Canopy trees, 4 m high; tall shrubs, 2–4 m high;
low shrubs, 0.5–2 m high; ground herbage flora, 0.5 m.

the greatest requirement—for each parameter was de-
fined as the focal species for that parameter.
Presence/absence data for the woodland bird species
of interest were also modeled statistically to determine
the relationships between the occurrence of each spe-
cies and the size, isolation, and complexity of its habitat.
We modeled a binomial distribution with a logit-link func-
tion in a step-wise fashion using GENSTAT (GENSTAT 5
Committee 1995). The regression models were then used
to generate probability-of-occurrence functions at a range
of patch sizes and habitat complexity scores.
Results
There was a significant linear relationship (R2
0.56,
p 0.01) between habitat complexity and remnant area,
indicating that large remnants tended to have a more
structurally diverse habitat than small remnants. Habitat
complexity and remnant area were independent of rem-
nant isolation.
Remnant area explained a significant ( p 0.05) por-
tion of the deviance of the presence/absence data for 22
of the 31 resident woodland bird species (Table 2). The
mean habitat complexity score of each remnant ex-
plained a significant ( p 0.05) portion of the deviance
of presence/absence for 20 species. Remnant isolation
was not a significant variate in the model (Table 2).
Presence/absence thresholds for patch area, habitat
complexity, and isolation were assessed graphically. We
identified three broad groups of sensitivity among the
woodland bird species (Table 3). First, there were toler-
ant species that occurred in all remnant sizes and were
not sensitive to habitat complexity or isolation. Second,
there was a group of birds that were moderately sensi-
tive in that they were found only in remnants with a hab-
itat complexity score of 4. Isolation appeared to have a
variable effect on this second group of birds. The East-
ern Yellow Robin occurred only in remnants with an iso-
lation measure of 1.5 km (Fig. 2). Graphical analysis
for many of the other moderately sensitive birds also
showed that they were affected by an interaction be-
tween area and isolation. If they occurred in small rem-
nants of 10 ha in area, they had an isolation measure of
1.5 km. Third, there was a group of birds that were
highly demanding in their landscape requirements, found
Table 2. Mean deviance in individual logit-regression models for woodland bird species in relation to remnant area, habitat complexity,
and isolation.
Bird name Area (ha) Habitat complexity Isolation (m)
Crested Pigeon, Ocyphaps lophotes 5.56a
2.68 0.08
Crimson Rosella, Platycercus elegans 0.12 5.08a
0.15
Eastern Rosella, Platycercus eximius 12.32b
6.51a
0.33
Varied Sittella, Daphoenositta chrysoptera 11.2b
10.56b
3.46
White-throated Treecreeper, Cormobates leucophaeus 28.56b
23.1b
0.40
Brown Treecreeper, Climacteris affinis 16.92b
13.91b
0.08
Superb Fairy-Wren, Malurus splendins 13.2b
23.63b
0.25
Spotted Pardalote, Pardalotus punctatus 16.53b
24.26b
1.03
White-browed Scrubwren, Sericornis frontalis 7.44b
6.31a
0.11
Speckled Warbler, Chthonicola sagittata 18.28b
24.34b
1.09
Weebill, Smicrornis brevirostris 18.05b
10.72b
0.02
Brown Thornbill, Acanthiza pusilla 12.89b
33.27b
0.27
Yellow Thornbill, Acanthiza nana 4.58a
7.18b
0.01
Striated Thornbill, Acanthiza lineata 10.27b
19.62b
0
Buff-rumped Thornbill, Acanthiza reguloides 17.81b
24.21b
2.2
Yellow-rumped Thornbill, Acanthiza chrysorrhoa 0.13 0.18 0.02
Southern Whiteface, Aphelocephala leucopsis 3.97 0.03 1.15
Noisy Miner, Manorina melanocephala 13.74b
0.9 0.66
Scarlet Robin, Petroica multicolor 13.23b
19.3b
0.24
Hooded Robin, Melanodryas cucullata 13.63b
16.57b
0.55
Eastern Yellow Robin, Eopsaltria australis 6.10a
2.57 2.56
Jacky Winter, Microeca fascinans 3.15 3.09 0.01
Grey Shrike-Thrush, Colluricincla harmonica 24.7b
18.26b
0.23
Rufous Whistler, Pachycephala rufiventris 28.26b
19.6b
3.33
Grey Fantail, Rhipidura fuliginosa 14.11b
16.78b
1.09
Willie Wagtail, Rhipidura leucophrys 0.15 0.01 3.89
Restless Flycatcher, Myiagra inquieta 0.11 3.69 0.32
White-winged Chough, Corcorax melanorhamphos 23.1b
9.94b
0
Double-barred Finch, Taeniopygia bichenovii 0 0.16 0.18
Red-browed Finch, Neochmia temporelis 0.43 3.8 0.57
Diamond Firetail, Stagonopleura guttata 0 0.03 0.08
a
p 0.05.
b
p 0.01.

only in areas of 100 ha and with a habitat complexity
score of 8. The Hooded Robin is an example of this
highly sensitive group (Fig. 3).
Based on the thresholds shown in Table 3, the Hooded
Robin was identified as the focal species for both rem-
nant area and habitat complexity (Fig. 3). This bird was
found only in woodland remnants that were 100 ha
and with a habitat complexity score of 13 (Fig. 3). Iso-
lation was not a statistically significant factor, but we be-
lieve that the graphical data for the Eastern Yellow
Robin (Fig. 2) were sufficient to consider it as the candi-
date focal species for isolation, as it did not occur in
remnants of 1.5 km from the mean distance to the
nearest five remnants.
Cumulative probability functions were developed for
each resident woodland species (Table 4). Remnants of
10 ha and with a mean habitat complexity score of 8
had a 20% chance of containing half of the 31 species
of resident woodland birds. There was a clear graphical
interaction between area and habitat complexity in the
probability of occurrence curves for many of the species
of resident woodland birds. For example, the Brown
Treecreeper had a low probability of occurring in patches
with a low habitat complexity score regardless of patch
area, and a high probability of occurring if the patch was
both large and complex (Fig. 4).
Cumulative probability curves for remnant area and
isolation also were derived for each sensitive and moder-
ately sensitive bird. Many of these birds had a uniformly
low probability of occurring in small remnants and a uni-
formly high probability of occurring in large remnants.
Within intermediate-sized remnants, many birds had an
increased probability of occurring when the mean dis-
tance to the nearest five remnants was 200–1000 m.
Figure 2. Presence or absence of the Eastern Yellow
Robin ( Eopsaltria australis) in the northern region of
the Australian Capital Territory and bordering area of
New South Wales (see Table 1 for definition of the hab-
itat complexity score).
Figure 3. Presence or absence of the Hooded Robin
( Melanodryas cucullata) in the northern region of the
Australian Capital Territory and bordering area of
New South Wales (see Table 1 for definition of the hab-
itat complexity score).

Discussion
Revegetation Guidelines
Following the focal-species approach of Lambeck (1997),
we identified the Hooded Robin as the species most sen-
sitive to habitat area and complexity. We propose the
Eastern Yellow Robin as the candidate focal species for
isolation, although there were insufficient occurrences
to detect a statistically significant effect of isolation. If
the spatial and compositional requirements of these two
species could be met, then the requirements of other
bird species, limited by similar threats, should also be
met. The conservation planning guidelines we derived
from these two focal species were (1) conserve or create
remnants at least 100 ha in size; (2) conserve or create a
diverse vegetation structure (with a habitat complexity
score of at least 12); and (3) conserve or establish wood-
land patches that are within a mean of 1.5 km of five
neighboring patches.
We conducted this study for a revegetation project
on public and privately held land (Freudenberger 1999;
Watson 1999). The creation of 100-ha patches is beyond
the scope of most private landholders who have rela-
tively small farms in the region. Therefore, a less strin-
gent set of guidelines was required by the landholders
and groups involved in this project. Given that manage-
ment criteria for woodland remnant revegetation had to
be achievable and cost-effective, we devised the follow-
ing revegetation guidelines based on the requirements
of moderately sensitive species (Table 3): (1) revegeta-
tion should increase the area of each remnant to at least
10 ha; (2) remnants should have a mean habitat com-
plexity score of at least 6 (created by reducing grazing
sufficiently to establish a native understory); (3) if rem-
nants are 1.5 km from one another, intervening patches
should be created; and (4) conservation of existing
remnants of 100 ha should be a priority, and if these
remnants have a poor habitat structure, they should be
Table 3. Thresholds for minimum remnant size, habitat complexity, and isolation for resident woodland birds.
Bird category and name Area (ha) Habitat complexity score Isolation (m)
No. of patches occupied
(maximum 72)
Toleranta
Crested Pigeon 6 3 400 23
Crimson Rosella 2 3 400 69
Eastern Rosella 2 3 300 45
Weebill 2 3 400 38
Willie Wagtail 3 2 400 45
Yellow-rumped Thornbill 3 3 400 56
Buff-rumped Thornbill 4 3 500 41
Superb Fairy-Wren 2 3 400 52
Grey Fantail 3 3 400 57
Moderately sensitiveb
Varied Sittella 9 8 2700 10
White-throated Treecreeper 6 6 400 34
Brown Treecreeper 8 8 400 13
Spotted Pardalote 6 6 400 27
White-browed Scrubwren 6 6 300 15
Brown Thornbill 4 6 400 29
Yellow Thornbill 12 8 500 9
Striated Thornbill 5 4 400 31
Southern Whiteface 3 6 2300 10
Noisy Miner 7 4 400 17
Scarlet Robin 5 6 300 28
Eastern Yellow Robin 4 5 1500 7
Jacky Winter 9 6 400 6
Grey Shrike-Thrush 5 5 400 20
Restless Flycatcher 2 6 400 11
Rufous Whistler 9 6 300 30
White-winged Chough 5 5 300 3
Double-barred Finch 11 6 2000 7
Red-browed Finch 3 4 3100 18
Diamond Firetail 3 6 3000 8
Sensitivec
Hooded Robin 100 13 500 5
Speckled Warbler 10 8 400 12
a
Occupied remnants including those 6 ha in size and with a habitat complexity score of 3.
b
Only occupied remnants with a habitat complexity score of 4.
c
Only occupied remnants of 100 ha and with a habitat complexity score of 8.

enhanced by planting native grasses and shrubs within
them.
These less demanding guidelines were more accept-
able to landholders and other stakeholders in the proj-
ect, in part because they built on the skeleton of small
remnants in the landscapes. Nearly 70% of the 203 rem-
nants in the study area are smaller than 20 ha (Watson
1999). For those on-farm remnants larger than 10 ha, pri-
ority should be given to controlling livestock by fencing
and planting of native understory shrubs and grasses.
Many other remnants need to be enlarged to a minimum
of 10 ha and enhanced with understory plantings.
These guidelines, which focus on enhancing small but
numerous remnants, should significantly enhance the
probability of retaining most resident woodland birds in
this region, although the probability of occurrence is
low for some bird species in remnants of 10 ha (Table
4). The survival of any given species depends on the
scale of implementation of our guidelines. Some species
may still be lost from this region if an insufficient num-
ber of 10-ha patches are retained, created, or en-
hanced. We can only claim that creation of structurally
complex 10-ha patches should provide occupiable habi-
tat and contribute significantly to regionally viable popu-
lations. Some form of metapopulation analysis is needed
to determine the spatial extent over which these guide-
lines should be implemented.
The guidelines derived from our focal-species analysis
may be underestimates of the landscape elements and
configurations needed by the extant birds in the region.
We assumed that the occurrence of birds in the sur-
veyed remnants had reached equilibrium after periods of
extensive clearing that essentially ceased in the 1950s.
But this region is still subject to urban encroachment,
eucalypt dieback, weed invasion, and continuous live-
stock grazing. There is evidence that bird species are
still declining in distribution and abundance in the re-
gion (Wilson 1999). Some of the occupied remnants
may in fact be suboptimal sinks contributing little to the
maintenance of viable populations. Recommendations
derived from a focal-species analysis should be seen as
spatially explicit hypotheses that need to be tested
through adaptive management. Our recommendations
may well be inadequate, but we will find out only
through long-term monitoring of revegetated patches of
woodland.
Our revegetation guidelines are derived from the land-
scape requirements of moderately sensitive species, rather
than those of the most sensitive ones. This triage ap-
proach, in which efforts are put into the species that can
feasibly be saved rather than targeting the most sensitive
species, is supported by Robinson and Traill (1996b)
and Reid (1999). They suggest the need for pragmatism
in the development of revegetation guidelines. Our guide-
Table 4. Percent probability of resident birds occurring in
woodland remnants of differing size and habitat complexity score
(HCS; see Table 1).
Bird
5 ha,
HCS 4
10 ha,
HCS 8
100 ha,
HCS 12
Crested Pigeon 19 27 56
Crimson Rosella 89 98 99
Eastern Rosella 39 55 91
Varied Sittella 0 3 56
White-throated Treecreeper 1 43 83
Brown Treecreeper 2 3 68
Superb Fairy-Wren 25 68 98
Spotted Pardalote 2 17 88
White-browed Scrubwren 6 10 53
Speckled Warbler 0 8 78
Weebill 23 33 90
Brown Thornbill 3 22 84
Yellow Thornbill 2 6 32
Striated Thornbill 8 30 81
Buff-rumped Thornbill 6 41 97
Yellow-rumped Thornbill 73 78 98
Southern Whiteface 5 20 1
Noisy Miner 8 9 67
Scarlet Robin 8 22 78
Hooded Robin 0 0 46
Eastern Yellow Robin 0 3 36
Jacky Winter 0 1 13
Grey Shrike-Thrush 2 10 82
Rufous Whistler 0 42 95
Grey Fantail 41 75 99
Willie Wagtail 62 64 58
Restless Flycatcher 3 15 95
White-winged Chough 4 5 82
Double-barred Finch 2 9 9
Red-browed Finch 6 23 32
Diamond Firetail 6 11 12
Figure 4. Cumulative probabilities of the occurrence
of the Brown Treecreeper (Climacteris picumnus)
based on remnant area and habitat complexity in the
northern region of the Australian Capital Territory
and bordering area of New South Wales (see Table 1
for the definition of the habitat complexity score).

lines should provide occupiable habitat for about 95% of
woodland birds within the study area.
Highly sensitive woodland bird species will be con-
served only if remnants of 100 ha are conserved and
long-term enhancement programs occur within and around
them. Our guidelines are not designed to conserve all
the woodland birds declared threatened in the ACT
(Swift Parrot [Lathamis discolor], Superb Parrot (Poly-
telis swainsonnii), Painted Honeyeater [Grantiella picta],
Regent Honeyeater [Xanthomyza phrygia], Brown Tree-
creeper and Hooded Robin [Australian Capital Territory
Government 1999b]). These endangered parrots and hon-
eyeaters are highly mobile species, either rare in the re-
gion or habitat specialists, and were not detected during
our surveys. The needs of the Brown Treecreeper (Ta-
ble 3) are likely to be met by our reduced guidelines, but
the needs of the Hooded Robin will be met only if all of
the focal-species guidelines are implemented. In addi-
tion, our revegetation guidelines are expected to pro-
vide habitat for taxa other than birds because we assume
that revegetation within remnants provides resources and
niches for a wide range of biota, although this assump-
tion needs to be tested.
Generality of the Focal-Species Guidelines
It is not known how far focal-species conservation guide-
lines can be extended into other habitats and regions.
Barrett et al. (1994) established a patch-area threshold of
6–20 ha based on extensive bird surveys in the Northern
Tablelands of New South Wales, which is consistent
with our results. Similarly, Loyn (1987) reported that bird
abundance did not increase with area above 10–30 ha in
fragmented forest patches in southeastern Victoria, Aus-
tralia. Both Barrett et al. (1994) and Loyn (1987) found
that patches smaller than 6–10 ha tend to suffer from eu-
calypt dieback and are colonized by Noisy Miners, which
generally exclude smaller resident woodland birds such
as those identified as moderately sensitive in our study
(Table 3). In contrast, an area threshold of 20 ha has
been detected in Western Australia (Lambeck 1999) in
agricultural regions that are drier and more intensively
cultivated than our study region.
The general applicability of our revegetation guidelines
may be constrained by the fact that we surveyed birds
during only one season, so only the requirements of resi-
dent woodland species could be analyzed. These species
were not breeding during the survey, so they may have
had different requirements for woodland area and habi-
tat complexity during the breeding season. This could
affect the thresholds identified in our analysis. Studies by
Recher et al. (1980) and Ford et al. (1996) show that the
most appropriate procedure for surveying bird occur-
rence is to sample during all seasons of a year for at least
3 years in a row, which would overcome interannual
variation in species composition within remnants and give
access to migratory and resident species. We recognize
these concerns, but revegetation guidelines were needed
within months, not years.
Usefulness of the Focal-Species Approach
The purpose of our study was to test the utility of the fo-
cal-species approach (Lambeck 1997) for conservation
planning in a landscape different from the one in which
it was developed. We have demonstrated that the ap-
proach is a rapid and cost-effective means of developing
spatially explicit conservation and revegetation guidelines
for birds in variegated landscapes comprising remnant
patches in a matrix of exotic pasture and isolated native
trees or remnants in a suburban matrix. This extends the
usefulness of the focal-species approach already demon-
strated in areas of the Western Australian wheat-sheep
zone (Lambeck 1999).
Our study is only a partial assessment of Lambeck’s
(1997) focal-species approach because it did not mea-
sure the threats of fragmentation to all biota within the
study area. Birds may not be the taxa most sensitive to
threats of habitat loss, isolation, and loss of habitat struc-
ture. Even though birds are high in the food chain and
therefore represent the needs of numerous taxa, there
are limitations to their use as focal species. Birds are
highly mobile and therefore presumably respond to the
threat of habitat isolation differently from less mobile
fauna. Birds may also respond to the threats of area limi-
tation and resource limitation differently from other
taxa. Our results show that Lambeck’s (1997) focal-spe-
cies approach can be used to identify minimum spatial
thresholds for birds still present in highly modified land-
scapes. These thresholds may not meet the needs of all
biota present in landscapes, however, because other
biota and threatening processes such as predation were
not included in our study.
Conclusions
We concur with Lambeck (1999) that guidelines derived
from the focal-species approach are more useful to land
managers and conservation planners than are general en-
hancement principles that essentially state that large and
proximate remnants are better than small and isolated
remnants. The focal-species approach allows explicit
recommendations to be developed that should improve
the probability of retaining a wide range of species in
fragmented landscapes. The focal-species approach is
likely to be useful in the development of conservation
guidelines in other highly modified landscapes in Austra-
lia and elsewhere. Finally, recommendations derived from
the focal-species approach are eminently testable. The
usefulness of our guidelines should be tested by moni-
toring the occurrence of moderately sensitive birds in

remnants enhanced to 10 ha in size, planted with a di-
verse understory, and situated within 1.5 km of other
suitable habitat.
Acknowledgments
Funding for this project was provided in part by the Nat-
ural Heritage Trust through Greening Australia, ACT SE
NSW, Inc. We thank P. Fennell (Canberra Ornithologists
Group), C. Davey, and M. Clayton for providing or ob-
taining bird survey data. B. Forrester and N. Nicholls pro-
vided statistical advice. R. Palmer provided assistance in
generating the many graphs required for the focal-spe-
cies analysis, and I. McCredie provided cartography ser-
vices. The School of Geography and Oceanography, Uni-
versity College, University of New South Wales, shared
in the cost of the SPOT satellite image. J. Reid, S. Briggs,
and R. Lambeck provided comments on preliminary drafts
of this paper. A. Elvin of Greening Australia was invalu-
able in supporting this project and helping obtain access
to remnants on privately held land.
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