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Habitat Use and Survival of the Spotted Tinamou (Nothura maculosa) in Agroecosystems in the Province of Buenos Aires, Argentina

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Changes in the composition and configuration of agricultural landscapes stemming from grassland conver-sion and agricultural intensification have contributed to the global declines of many grassland and shrubland birds. In both North America and Europe there exists a large body of research on the effects of agriculture on populations of terrestrial gamebirds. However, little research exists for these species in Argentina or Latin America in general. In Argentina the most important gamebird species is the spotted tinamou (Nothura mac-ulosa). This species has become increasingly scarce in a significant portion of its range, possibly due to agricultural intensification over the last 15 years. Using radio telemetry, we examined habitat use, movements, and survival of spotted tinamous in 2 landscapes in the province of Buenos Aires, Argentina; one dominated by annual row crops and the other used for annual crops and grazing. During winter, individuals used in order of preference: fallow fields and areas with short herbaceous vegetation, followed by wetlands. Areas in winter wheat and field edges were used least in relation to their availabilty. Although birds generally maintained small home ranges, in some cases changes in cattle density and the structure of row crops caused birds to move considerable distances. Survival mid-winter to early spring was more than double in the mixed landscape s = 0.73, SE = 0.19) compared with the landscape dedicated to row crops s = 0.33, SE = 0.19). Considering how research in other parts of the world has demonstrated the effects of agricultural intensification on terrestrial gamebirds, these results are not unexpected and suggest a precarious future for the conservation of grassland and agroecosystem species in Argentina in light of present agricultural trends.
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Spotted Tinamou in Argentina
Habitat Use and Survival of the Spotted Tinamou (Nothura
maculosa) in Agroecosystems in the Province of Buenos
Aires, Argentina
Jeffrey J. Thompson1,2, John P. Carroll
Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602-2152 USA
Changes in the composition and configuration of agricultural landscapes stemming from grassland conver-
sion and agricultural intensification have contributed to the global declines of many grassland and shrubland
birds. In both North America and Europe there exists a large body of research on the effects of agriculture
on populations of terrestrial gamebirds. However, little research exists for these species in Argentina or Latin
America in general. In Argentina the most important gamebird species is the spotted tinamou (Nothura mac-
ulosa). This species has become increasingly scarce in a significant portion of its range, possibly due to
agricultural intensification over the last 15 years. Using radio telemetry, we examined habitat use, movements,
and survival of spotted tinamous in 2 landscapes in the province of Buenos Aires, Argentina; one dominated
by annual row crops and the other used for annual crops and grazing. During winter, individuals used in order
of preference: fallow fields and areas with short herbaceous vegetation, followed by wetlands. Areas in winter
wheat and field edges were used least in relation to their availabilty. Although birds generally maintained small
home ranges, in some cases changes in cattle density and the structure of row crops caused birds to move
considerable distances. Survival mid-winter to early spring was more than double in the mixed landscape (ˆs
= 0.73, SE = 0.19) compared with the landscape dedicated to row crops (ˆs= 0.33, SE = 0.19). Considering how
research in other parts of the world has demonstrated the effects of agricultural intensification on terrestrial
gamebirds, these results are not unexpected and suggest a precarious future for the conservation of grassland
and agroecosystem species in Argentina in light of present agricultural trends.
Citation: Thompson JJ, Carroll JP. 2009. Habitat use and survival of the spotted tinamou (Nothura maculosa) in agroecosystems in the province of
Buenos Aires, Argentina. Pages 111 - 119 in Cederbaum SB, Faircloth BC, Terhune TM, Thompson JJ, Carroll JP, eds. Gamebird 2006: Quail VI and
Perdix XII. 31 May - 4 June 2006. Warnell School of Forestry and Natural Resources, Athens, GA, USA.
Key words: agricultural intensification, conservation, Nothura maculosa, spotted tinamou, survival
Introduction
Globally, populations of grassland and shrub-
land birds have been declining due to habitat
conversion and agricultural intensification (Ask-
ins 2000, Goriup 1988, Murphy 2003, Pain and
Pienkowski 1997, Vickery and Herkert 1995). In
agroecosystems of austral South America habitat
loss and the intensification in management have
been extensive and rapid, particularly in the pam-
pas of Argentina starting in the early 1990’s, typified
by the increased use of external inputs, increased
yields, and a shift towards agricultural production
for export markets (Ferreyra 2001, Ghersa et al. 2002,
Hall et al. 2001, Solbrig and Vera 2001, Viglizzo et al.
2001).
The spotted tinamou (Nothura maculosa) is a com-
mon bird of grasslands and agroecosystems in east-
ern austral South America, one of the most impor-
tant terrestrial gamebirds in the region, and formerly
common in agricultural systems (Bucher and Nores
1988, Bump and Bump 1969, Cabot 1992, Davies
2002, Menegheti 1985). In recent years, within the
pampas of Argentina, the spotted tinamou has be-
come increasingly conspicuous by their absence ap-
parently stemming from the expansion and intensi-
fication of grazing and row crop practices.
All tinamous are relatively poorly studied; how-
ever, in austral South American grasslands the tina-
1Correspondence: jthompson@cnia.inta.gov.ar
2Present address: Instituto Nacional de Tecnolog´
ıa Agropecuaria (INTA), Instituto de Recursos Biol ´
ogicos, De los Reseros y las Caba˜
nas S/N, 1686
Hurlingham, Argentina
Gamebird 2006 |Athens, GA |USA 111 May 31 - June 4, 2006
Spotted Tinamou in Argentina
±
0 100 20050 km
Figure 1: Map showing the location of the district of San Miguel del Monte in the Province of Buenos Aires,
Argentina
mous replace the Galliformes and are their ecolog-
ical equivalent, which allows for inferences to be
drawn among the Galliformes and the Tinamiformes
in regard to tinamou ecology (Thompson 2004). We
used radio telemetry to investigate our theory of
ecological equivalence. Based upon the observed
effects of agricultural intensification on Galliformes
and existing knowledge of the spotted tinamou that
within pampean ecosystems we predicted that sur-
vival of spotted tinamous would be negatively cor-
related, and home range size positively correlated,
with increasing land use intensity while habitat se-
lection would favor areas most similar to natural
grassland in vegetative structure (Bump and Bump
1969, Thompson 2004).
Study Area
Our study sites were located in the district of San
Miguel del Monte in the province of Buenos Aires,
Argentina (Figure 1). San Miguel del Monte is lo-
cated in the flooding pampa, a regional subdivision
of the 760,000 km2R´
ıo de la Plata grassland system
that covers northeastern Argentina, Uruguay and
southeastern Brazil (Soriano et al. 1991). Tradition-
ally the flooding pampa has been used principally
for extensive livestock production (Hall et al. 1988),
however, since the early 1990’s row crop agriculture
has become an increasingly important land use.
We selected two study sites; one dedicated to
row crops and the other used for used for a mix
of row crops and grazing. The row crop site was
160 hectares, of which 85% was used for soybean,
corn, and winter wheat production, and the remain-
ing area comprised of wetlands or field borders. The
site with mixed row crop and grazing uses was 230
hectares, 50% of its area used for soybean, corn, and
winter wheat production, and the remainder, includ-
ing wetlands, used for cattle grazing.
May 31 - June 4, 2006 112 Gamebird 2006 |Athens, GA |USA
Spotted Tinamou in Argentina
Methods
During July 2003, we fitted 4 birds with pendant-
style transmitters (6.0 g, 2.2-2.3% of body mass)
equipped with an activity switch (Holohil Systems
Ltd., Ontario, Canada) at the row crop dominated
site and 14 birds in June 2004 at the mixed use site. In
2004, no birds were radio-tagged at the row crop site
because none were detected over a 2 month search
in the autumn of that year. All birds were captured
at night using spotlights and hand nets. Due to un-
certainties in sexing birds related to age (Bump and
Bump 1969), sexual differences were not included in
the study. In both years birds were located 3 times
per week from the date of capture until October 23
(mid-winter to early spring) dependent upon acces-
sibility to the sites.
Due to mortality, insufficient number of radio lo-
cations, radio failure, or radio loss we used 3 birds
from the row crop site and 8 from the mixed use site
in our analysis. Locations were entered into a geo-
graphic information system (GIS) for each site using
ArcGIS software (Environmental Systems Research
Institute, Inc.). Minimum convex polygons (MCP)
(Mohr 1947) were calculated for each individual us-
ing the Adehabitat Package Version 1.4 (Calenge
et al. 2006) in R 2.3.1 (R Development Core Team
2006) and the proportion of radio locations and MCP
in different habitat types determined using the GIS.
Within the row crop site we defined 6 habitat
types; winter wheat, fallow, wetlands, corn stub-
ble, tilled land, and field edges. For the mixed use
site we identified 5 habitat types; winter wheat, fal-
low, wetlands, mowed fallow, and grazed pasture.
We used compositional analysis (Aebischer et al.
1993), based upon radio locations and MCP, to eval-
uate habitat preferences. The compositional anal-
ysis was performed using BYCOMP.SAS (Ott and
Hoovey 1997) and, to obtain sufficient sample size,
we combined data from both sites and aggregated
habitat types into 5 categories; winter wheat, fallow,
wetlands, edge, and short herbaceous (corn stub-
ble, tilled land, mowed fallow, and grazed pasture).
Additionally, survival was estimated using Kaplan-
Meier staggered entry design (Kaplan and Meier
1958, Pollock et al. 1989). Standard errors were used
to determine statistically significance differences in
survival and mean home range size.
Results
The mean 100% MCP from the row crop site was
larger (19.0 ha, SE = 10.4 ha) than that from the
mixed use site (15.9 ha, SE = 7.3 ha), although dif-
ferences were not significant due to high variance.
Survival (ˆs= 0.73, SE = 0.19) was higher in the mixed
use site over 20 weeks compared to the row crop site
(ˆs= 0.33, SE = 0.19) over 15 weeks (Figure 2). Mor-
tality of the radio-tagged birds from both sites was
attributed mainly to predation (91%).
At the row crop site winter wheat, wetlands, and
field edges were used less, and corn stubble more,
than their availability based upon both the mean
proportions of MCP and radio locations within those
habitat types (Figure 3). In tilled land the mean pro-
portion of MCP and radio locations indicate approx-
imately equal use in relation to availability, while in
fallow, based on the mean MCP use was equal to
availability, but considerably higher than its avail-
ability based upon the mean proportion of radio lo-
cations (Figure 3). As at the row crop site about half
of the area of the mixed use site was in winter wheat,
which was utilized less than its availability (Figure
3). Fallow, mowed fallow, and wetlands were all
used more than their availability, while based upon
the mean proportion of MCP, grazed pasture was
used equal to its availability, and less than its avail-
ability based upon the mean proportion of radio lo-
cations (Figure 3).
The compositional analysis using the aggregated
data from both sites, and based upon MCP, ranked
short herbaceous habitat as the most utilized habitat
in relation to availability, with fallow, winter wheat,
and edge ranked equally as second, followed by
wetlands (Table 1a). No habitats were used signif-
icantly more than others (P= 0.05) but fallow and
short herbaceous habitat were preferred over wheat,
fallow over wetlands, short herbaceous over fallow,
and wetlands over short herbaceous (Table 1a).
Gamebird 2006 |Athens, GA |USA 113 May 31 - June 4, 2006
Spotted Tinamou in Argentina
Row crop
Proportion
0.0
0.2
0.4
0.6
0.8
1.0
Grazing/Row crop
Proportion
0.0
0.2
0.4
0.6
0.8
1.0
June
July August September October July August September October
AB
Figure 2: Estimated survival and standard error for spotted tinamous in the A) site dominated by row crops (n= 3) and B) the mixed grazing
and row crop site (n= 8)
May 31 - June 4, 2006 114 Gamebird 2006 |Athens, GA |USA
Spotted Tinamou in Argentina
Row Crop
Wheat
Wetland
Fallow
Edge
Corn Stubble
Tilled
Proportion
0.0
0.2
0.4
0.6
0.8
Habitat
MCP mean
Points mean
Grazing/row crop
Wheat
Wetland
Fallow
Mowed
Grazed
Propotion
0.0
0.2
0.4
0.6
0.8
AB
Figure 3: Proportional habitat use by spotted tinamous based on mean area of minimum convex polygon (MCP) and mean number of ra-
dio locations (Points) in relation to proportional availability of habitat types for A) the row crop site and B) the mixed use site. Error bars
represent standard error.
Gamebird 2006 |Athens, GA |USA 115 May 31 - June 4, 2006
Spotted Tinamou in Argentina
Table 1: Results of compositional analysis based on a) minimum convex polygon (MCP) home ranges and
b) radio locations. Higher ranking indicates greater use compared to availability. Within the matrix, (+)
signifies that the row habitat is preferred over the column habitat, whereas a (-) signifies the opposite.
Significant difference between habitats (P<0.05) is indicated by (+++) or (– – –).
a
Habitat wheat wetlands edge fallow short herbaceous rank
wheat . . . – 2
wetlands . . . – + 1
edge . . . . . 2
fallow + + . . 2
short herbaceous + - . + - 3
b
Habitat wheat wetlands edge fallow short herbaceous rank
wheat . . – – – 0
wetlands + . . – 1
edge . . . . . 0
fallow +++ + . . + 3
short herbaceous + + . . 2
Note: Because of low or no use a P-value for edge habitat could not be computed.
The same analysis using radio locations ranked
fallow and short herbaceous habitats as the first and
second most utilized habitats, respectively, in re-
lation to availability, followed by wetlands (Table
1b). Winter wheat and edge were equally the least
used in relation to availability (Table 1b). Fallow
was utilized significantly more than wheat (P= 0.05)
while fallow, short herbaceous, and wetlands were
preferred over wheat, fallow and short herbaceous
were preferred over wetlands, and fallow over short
herbaceous (Table 1b).
Discussion
The mean range size of spotted tinamous at both
sites was affected by movements related to chang-
ing habitat amounts and characteristics and cattle
disturbance. At the row crop site as winter wheat
reached 10cm in height birds began to utilize those
areas, often exclusively and as the wheat matured to
25cm in height those areas were abandoned for ar-
eas with shorter vegetation. Within the mixed use
site the largest movements by birds were related to
disturbance by cattle.
The lower surival in the row crop dominated
site is consistent with observations of Pinheiro and
L´
opez (1999) who found lower abundances of spot-
ted tinamous in agricultural land in southern Brazil
compared to natural grasslands. Additionally, for
the Galliformes there are multiple cases where in-
creased intensification in land use has led to lower
survival and declining populations (e.g. Berner
1988, Hill and Robertson 1988, Jansen et al. 2000,
Malan and Benn 1999, Potts 1986). Based upon this,
the observed differences in survival between the two
sites are expected if the spotted tinamou is viewed as
an ecological equivalent to the Galliformes. Admit-
tedly, sample sizes are small, particularly for the row
crop site; however, the rarity of spotted tinamous at
the row crop site in 2003 and their absence from the
site in 2004 suggest a real process rather than a sta-
tistical artefact.
Habitat preferences by the spotted tinamou, and
the closely related Darwin’s Tinamou (Nothura dar-
winii), within both natural and agricultural habi-
May 31 - June 4, 2006 116 Gamebird 2006 |Athens, GA |USA
Spotted Tinamou in Argentina
tats, favour areas with relatively low (10-30 cm) and
sparse vegetation (J.J.Thompson pers. obs., Bump
and Bump 1969, Isacch and Martinez 2001, Leveau
and Leveau 2004, Mosa 2004) and explains the pat-
tern of habitat use at both sites. For example, use
of winter wheat was most frequent when plants
were 10-25 cm tall. Although wheat was generally
avoided once it reached >25cm in height, birds then
used it as escape cover.
The most preferred habitats; fallow, mowed fal-
low, and corn stubble all shared in common a well
developed ground cover of herbaceous vegetation,
both living and dead, that was not in excess of 50
cm and with little or no emergent vegetation above
that level. Tilled land was used more as it was colo-
nized by herbaceous vegetation, particularly clover
(Trifolium spp.), and vegetative cover increased.
Spotted tinamous are often common in pasture-
land (J.J.Thompson pers. obs., Bump and Bump
1969, Menegheti 1985, Pinheiro and L´
opez 1999),
as are Darwin’s tinamou (J.J.Thompson pers. obs.,
Bump and Bump 1969, Mosa 2004), due to the
low vegetative structure that is maintained through
moderate grazing. At the mixed use site, however,
pastureland was overgrazed so that ground vegeta-
tion was cropped near to ground level, which ex-
plains a lower than expected preference for grazed
areas. The preference for relatively short vegetation
also explains the avoidance of field edges in the row
crop site. Field edges consisted of tall (>1m) and
dense grass and also contained woody vegetation,
which were avoided by the birds.
The difference in the use of wetlands among the
sites appeared to be a function of the water levels
within wetlands at each site. At the row crop site
wetlands contained water and were avoided, where
as at the mixed use site, wetlands were dry and con-
tained suitable herbaceous cover along their perime-
ter that was utilized by the birds. It should be noted
that although wetlands were not used by individ-
uals at the row crop site, much of the fallow areas
were not put into production due to their proximity
to wetlands, subsequently wetlands were indirectly
responsible for the availability of preferred habitats.
The preferences and differences in habitat use
within and between sites are consistent with the re-
sults of the compositional analysis since fallow areas
and the habitats comprising the short herbaceous
category, while more variable, are the habitats most
similar in structure to natural grasslands. Similarly,
the quality of wetlands varies annually dependent
upon precipitation, reducing interannual use, while
row crop fields and edge were avoided or used con-
siderably less in relation to their availability.
The preferences in habitat, size of home ranges,
and survival that we observed were consistent with
our expectations based upon existing knowledge of
tinamou ecology, and the response of Galliformes
and other bird species to the intensification of agri-
cultural land use (Thompson 2004). From this study
and others (Canavelli et al. 2003, Bellis et al. 2004,
Demar´
ıa et al. 2002, Fernandez et al. 2003) it is ap-
parent that the intensification of agriculture that has
occurred in Argentina has resulted in similar nega-
tive ecological effects as observed in other regions.
The continued expansion and intensification of
agriculture in Argentina suggests that pampean
agroecosystems will continue to be degraded, with
the most ecologically valuable systems being main-
tained in areas only suitable for extensive livestock
production. Moreover, within intensively managed
systems, fallow and areas unsuitable for production
(i.e. wetlands) will increasingly become critical for
biodiversity conservation.
Acknowledgments
This work was facilitated by a Fulbright Student
Grant to Argentina, research scholarships from the
American Pheasant and Waterfowl Society and the
Leslie E. Tassell Avicultural Foundation, and sup-
port from the University of Georgia (Latin Amer-
ica and Caribbean Studies Institute, The Gradate
School, Warnell School of Forestry and Natural Re-
sources) to JJT. C. Villalba, A. Iturralde, J. Tangerini,
M. Dominguez, H. Mega, and M. Conroy provided
assistance in the field.
Gamebird 2006 |Athens, GA |USA 117 May 31 - June 4, 2006
Spotted Tinamou in Argentina
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dos, Z. Roberto, and H. Del Valle. 2001. Ecolog-
ical lessons and applications from one century of
low external-input farming in the pampas of Ar-
gentina. Agriculture, Ecosystem and Environment
83:65–81.
Gamebird 2006 |Athens, GA |USA 119 May 31 - June 4, 2006
... The home ranges reported varied from 0.1 ha in the Highland Tinamou (Nothocercus bonapartei) (Schäfer 1954) to 24 ha in the Brushland Tinamou (Nothoprocta cinerascens; Lancaster 1964a). To date, only one study on home range has used the radio-tracking technique and reported mean home range sizes of 16 and 19 ha for the Spotted Nothura (Nothura maculosa; Thompson and Carroll 2009). In general, tinamous are considered resident, non-migratory species, with the probable exception of the genus Tinamotis (Cabot 1992, Davies 2002. ...
... selected 12 g necklace tags (R1-2D model, Holohil System, Carp, Ontario, Canada) with a 24-month lifespan that represent 2.7% of the minimum adult body weight reported for this species (Davies 2002). Necklaces are the most common tagging system used for game birds (e.g., Novoa et al. 2002, Oakley et al. 2002, Pérez et al. 2004, Watson et al. 2007) that have the same size and ground-dwelling habits as the Ornate Tinamou, and were used successfully with the Spotted Nothura in a study by Thompson and Carroll (2009). Necklaces are recommended for bird species that do not fly frequently (Marcström et al. 1989, Kenward 2001. ...
... The loss of 42% of the tagged birds (probably because of predation) is lower than other studies on ground-dwelling birds (which are common target species of several predators): 88% in adultreintroduced Northern Bobwhites (Colinus virginianus; Oakley et al. 2002), 81% in Red-legged Partridge chicks (Alectoris rufa; Pérez et al. 2004) and 91% for the wild Spotted Nothura (Thompson and Carroll 2009). ...
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Very little is known about the home range and movement patterns of tinamous. The Ornate Tinamou (Nothoprocta ornata), a species of the central Andes that is important for cynegetic and biomonitoring purposes, was previously reported to have a very small territory (2.43 ha). This was based solely on field observations. In order to gain a better understanding of the movement patterns, home range size, and home range overlap of this species, we radio tracked 12 adult individuals in an Andean agro-ecosystem for a full year. The birds remained within their home ranges all year; 100% MCP (minimum convex polygon) home ranges were 43.8 ± 21.6 ha (22–85 ha), 95% kernel home ranges were 58.8 ± 31.9 ha (25–118 ha) and 50% kernel core areas were 15.3 ± 8.9 ha (6–33 ha). Only two birds, probably sub-adults, showed extensive movement patterns before their death. Individuals overlapped their home ranges extensively (from 30–98% with 2–3 tagged individuals), but these values were probably higher because a small proportion of the population was tagged. No sexual differences were detected in home range size or overlap. Our results support the usefulness of Ornate Tinamou as a sentinel species in biomonitoring studies and highlight the need for further research into the philopatric and dispersion behavior of juveniles before planning cynegetic strategies.
... Previous analyses found a negative but variable relationship between annual crops and raptors [27], which can be explained by the variability in the responses of different species. As predicted, ground omnivores and insectivores were affected by soybean and corn, most likely because their primary habitat (i.e., ground) is highly modified, affecting the availability of food and nesting grounds [72,73]. Despite being affected by row crops, species such as the Firewood-gatherer and Spotted Nothura are widely distributed, which could indicate that they find suitable habitats within the agricultural matrix not captured by our analyses, such as isolated trees for the first one, and other crops, natural grasslands or fallows for the latter [72]. ...
... As predicted, ground omnivores and insectivores were affected by soybean and corn, most likely because their primary habitat (i.e., ground) is highly modified, affecting the availability of food and nesting grounds [72,73]. Despite being affected by row crops, species such as the Firewood-gatherer and Spotted Nothura are widely distributed, which could indicate that they find suitable habitats within the agricultural matrix not captured by our analyses, such as isolated trees for the first one, and other crops, natural grasslands or fallows for the latter [72]. On the other hand, most insectivore gleaners seemed unaffected by crops, contrary to our prediction. ...
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Rapid expansion and intensification of agriculture create challenges for the conservation of biodiversity and associated ecosystem services. In Argentina, the total row crop planted area has increased in recent decades with the expansion of soybean cultivation, homogenizing the landscape. In 2003 we started the first long-term, large-scale bird monitoring program in agroecosystems of central Argentina, in portions of the Pampas and Espinal ecoregions. Using data from this program, we evaluated the effect of land use and cover extent on birds between 2003-2012, accounting for imperfect detection probabilities using a Bayesian hierarchical, multi-species and multi-season occupancy model. We tested predictions that species diversity is positively related to habitat heterogeneity, which in intensified agroecosystems is thought to be mediated by food availability; thus the extent of land use and cover is predicted to affect foraging guilds differently. We also infer about ecosystem services provisioning and inform management recommendations for conservation of birds. Overall our results support the predictions. Although many species within each guild responded differently to land use and native forest cover, we identified generalities for most trophic guilds. For example, granivorous gleaners, ground insectivores and omnivores responded negatively to high proportions of soybean, while insectivore gleaners and aerial foragers seemed more tolerant. Habitat heterogeneity would likely benefit most species in an intensified agroecosystem, and can be achieved with a diversity of crops, pastures, and natural areas within the landscape. Although most studied species are insectivores, potentially beneficial for pest control, some guilds such as ground insectivores are poorly represented, suggesting that agricultural intensification reduces ecological functions, which may be recovered through management. Continuation of the bird monitoring program will allow us to continue to inform for conservation of birds in agroecosystems, identify research needed to reduce key uncertainties, and anticipate the effects of changes in agriculture in central Argentina.
... forestry is increasing (Bilenca and Miñarro 2004, Viglizzo et al. 2005, Martino and Methol 2008). Over the past 15 years, conversion of grasslands to cropland has resulted in loss of habitat for many grassland birds (Vickery et al. 2003, Gabelli et al. 2004, Sarasola et al. 2007, Thompson and Carroll 2009, Codesido et al. 2011). These activities usually result in the total replacement of native vegetation that can trigger changes in bird species richness, composition, and abundance (Filloy and Bellocq 2007, Pedrana et al. 2008). ...
... In the West Inland Pampa, moderate grazing of native grasslands can increase structural heterogeneity and plant species richness relative to undisturbed grasslands, resulting in greater bird species richness and abundance (Isacch et al. 2003). Apart from the effects of grazing on habitat quality, livestock can also affect bird populations through direct disturbance of individuals (Thompson and Carroll 2009) and nest trampling (Azpiroz 2000, Zalba and Cozzani 2004, A. Di Giacomo, unpubl. data). ...
Article
ABSTRACT The grasslands of southeastern South America (SESA), comprising one of the most extensive grassland ecosystems in the Neotropics, have been negatively impacted by the development of the livestock industry, arable agriculture, and forestry. SESA grasslands have a rich avifauna that includes 22 globally threatened and near-threatened species, and many other species have suffered local population extinctions and range reductions. In addition to habitat loss and fragmentation, grassland birds in SESA are threatened by improper use of agrochemicals, unfavorable fire management regimes, pollution, and illegal capture and hunting. Studies to date have provided information about the distribution of grassland birds, the threats populations face, and the habitat requirements of some threatened species, but more information is needed concerning dispersal and migration patterns, genetics, and factors that influence habitat use and species survival in both natural and agricultural landscapes. There are few public protected areas in the region (1% of original grasslands), and many populations of threatened grassland birds are found on private lands. Therefore, efforts to preserve grassland habitat must reconcile the interests of land owners and conservationists. Current conservation efforts include establishment of public and private reserves, promotion of agricultural activities that reconcile production with biodiversity conservation, development of multilateral conservation projects across countries, and elaboration of action plans. Measures that result in significant losses to private land owners should include economic compensation, and use of economic incentives to promote agriculture and forestry in native grassland areas should be discouraged, especially in priority areas for grassland birds. Although more studies are needed, some actions, particularly habitat protection and improved management of public and private lands, should be taken immediately to improve the conservation status of grassland birds in SESA. Los pastizales del sureste de Sudamérica (SESA), que conforman uno de los mayores ecosistemas de pastizales en el Neotrópico, han sufrido transformaciones importantes debido al desarrollo de la industria ganadera, la agricultura y la forestación. Los pastizales del SESA tienen una rica avifauna que incluye 22 especies amenazadas o casi amenazadas y muchas otras han sufrido extinciones poblacionales locales y reducciones muy sustanciales de sus rangos de distribución. Además de la pérdida de hábitat y la fragmentación, las aves de pastizal del SESA están amenazadas por el uso inapropiado de agroquímicos, regímenes desfavorables de manejo del fuego, contaminación, captura y caza ilegales. Los estudios al día de hoy han generado información sobre la distribución de aves de pastizal, las amenazas que sus poblaciones enfrentan y de los requerimientos de hábitat de algunas especies amenazadas, pero aun es necesaria más información sobre patrones de dispersión y migración, genética y los factores que afectan los patrones de uso de hábitat y la sobrevivencia de especies en paisajes naturales y agrícolas. Hay muy pocas áreas protegidas públicas en la región (1% de los pastizales originales) y muchas poblaciones de aves de pastizal amenazadas se encuentran en tierras privadas. Por ende, los esfuerzos que buscan preservar características de hábitat similares a las de los pastizales naturales deben reconciliar los intereses de productores y conservacionistas. Los actuales esfuerzos de conservación, incluyen, el establecimiento de reservas privadas y públicas, la promoción de prácticas agrícolas que reconcilien producción y conservación, el desarrollo de proyectos multilaterales de conservación entre varios países, y la elaboración de planes de acción. Las medidas que resultan en pérdidas significativas para los productores privados deberían incluir compensaciones económicas, y el empleo de incentivos económicos para fomentar la agricultura y forestación en pastizales nativos deberían ser desalentado, especialmente en el caso de áreas de prioridad para aves amenazadas. A pesar de que todavía se necesitan mas estudios, algunas medidas, en particular la protección y manejo de hábitat tanto en tierras públicas como privadas deberían aplicarse inmediatamente para mejorar el estado de conservación de las aves de pastizal en el SESA.
... Moreover, Milvago chimango increased with increasing habitat conversion and the presence of another species (Circus buffoni) increased in grassland-dominated landscapes (Carrete et al., 2009; Pedrana et al., 2008). Other examples include decreasing population and distribution of the Pampas meadowlark (Sturnella defilippii) associated with grassland conversion and overgrazing (Fernández et al., 2003), and greater survival of the spotted tinamou (Nothura maculosa ) in agroecosystems in the province of Buenos Aires in a mixed landscape of pasture and agriculture compared to an agriculture-dominated landscape (Thompson and Carroll, 2009). ...
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In Argentina, the rapid expansion and intensification of row crop production that has occurred during the last 20 years has resulted in the loss of habitat and spatial heterogeneity in agroecosystems. One of the principal effects of industrialized row crop production is the loss of avian diversity and associated ecosystem services that benefit crop production. To better understand the response of bird species to the intensification and expansion of row crop agriculture in Argentina, and the potential effects on the provision of ecosystems services, we analyzed the relationship between short- and long-term changes in agricultural land use on the densities of six bird species (Milvago chimango, Caracara plancus, Tyrannus savana, Zenaida auriculata, Molothrus bonariensis, and Sturnella supercilliaris) using data from a large-scale, long-term avian monitoring program in central Argentina. Species densities responded individually to long-term landuse changes; T. savana and M. chimango densities were positively related to an increase in the annual cropping area, whereas C. plancus and S. supercilliaris were positively related to the area of non-plowed fields. M. bonariensis and Z. auriculata (considered crop pests) showed a weak relationship with land use. None of the species exhibited response to short-term changes in land-use. Although generalist species can apparently adapt to a diversity of open habitats, species that provide pest control services were also related to semi-natural habitats and thus likely to suffer from land transformation associated with intensive agricultural management. Our results, as well as those found in similar systems, denote strong inferential evidence that the disappearance of remnants of natural and semi-natural habitats in heavily transformed agricultural landscapes will have a substantial negative effect on the provision of pest control services provided by avian abundance and diversity.
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https://cdnsciencepub.com/eprint/JS8GEVNTGVJJNMJPMZMM/full _______________________________________________________________________ Grassland degradation and fragmentation produced by land use have globally impacted biodiversity. In the Neotropics, the Pampas Grasslands have been greatly altered by agriculture and the introduction of exotic trees. To evaluate the effects of changing habitat features on native grassland fauna, we studied a breeding population of a ground nesting bird, the Spotted Nothura Nothura maculosa (Temminck, 1985) in a natural grassland under cattle-grazing in central-east Argentina. We estimated daily nest survival rate (DSR) and modeled it as a function of habitat (distance to habitat edges, cattle density and nest concealment) and temporal factors. Of the 80 nests found, 64 (80 %) failed, predation being the principal cause of failure. DSR was 0.874, estimating a cumulative survival of only 6.8 % throughout egg laying and incubation. DSR increased with distance to continuous forests and decreased with nest age. Nests located near forest edges could have increased predation risk because they are potentially exposed to forest dwelling predators in addition to grassland dependent ones. Considering the low success found and the ongoing invasion of exotic trees in the region, we encourage governments to protect large areas of grassland that ensure adequate nest success for tinamous and other ground nesting birds.
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Abstract During the past century, the Pampas meadowlark Sturnella defilippii underwent a severe population drop and now, it is confined mostly to southern,Pampas,grasslands. We analyzed,the habitat and landscape,characteristics associated to the presence of repro- ductive groups of Pampas meadowlarks in this area. During the 1999 breeding season, we surveyed 89 randomly stratified selected points where,we noted the presence/absence of Pampas,meadowlarks.,For each point we estimated seven habitat variables related to vegetation cover and six landscape variables derived from different maps. We found 11 groups of displaying males, nine of them on natural grassland plots. Multivariate analyses indicate that field type and vegetation cover are the main factors associated to the presence of Pampas,meadowlark.,Reproductive,groups,were found,preferentially at natural grasslands with high vegetation cover. Habitat loss and,intensive grazing of fields appear,to be the main,factors associated to their sharp population,decline and distri- bution retraction. # 2003 Elsevier Ltd. All rights reserved. Keywords: Pampas,meadowlark;,Sturnella defilippii; Pampas grasslands; Population decline; Habitat transformation
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Land-use practices can impact on bird populations. This study set out to explain why the helmeted guineafowl, Numida meleagris (Linnaeus 1766; Aves: Numididae) declined in the Midlands of KwaZulu-Natal, South Africa, an agricultural area where these birds were once abundant in savannas mixed with cultivation. Within the Midlands, the potential roles of land-use practices and pesticides were investigated. Using a grid cell approach, the distribution of 11 land-uses was mapped for 19 farms with different levels of guineafowl abundance. The edge distance between extensive and intensive agriculture was significantly associated with the presence of guineafowl. The presence of guineafowl was associated with greater land-use diversity, showing this species' preference for a mosaic of land-uses. Extensive agricultural areas were used for cover and intensive ones for food, but the adjacency of these land-uses affected access to these resources. Larger flocks (≥100 birds) were associated with pastures free of agro-chemicals, while smaller flocks (
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We present results on the estimation of survival distributions for an important problem in animal ecology. The problem involves estimation of survival distributions using radio-tagged animals. It requires allowance for censored observations due to radio failure, emigration from the study area, and animals surviving past the end of the study period. We show that survival analysis techniques already used in medical and engineering studies may be applied to this problem. Emphasis is placed on the model assumptions and the need for further research. An example to illustrate the strengths and weakness of this approach is presented.