Forest birds in landscape mosaics:

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Forest birds in landscape mosaics theory and
empirical evidence
Cristián F. Estades
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Theory of Island Biogeography
(MacArthur Wilson 1963, 1967)
Importance of Island size Isolation
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Metapopulations
(Levins 1969, 1970 Gilpin Hanski 1991)
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Ideal Free Distribution
(Fretwell and Lucas 1970)
Density dependent habitat selection
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Source - sink dynamics
(Pulliam 1988)
Sources (R gt M, E gt I) subsidize Sinks
(RltM, E lt I)
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Birds in habitat islands - agricultural landscapes
Birds in Illinois forest fragments (Blake Karr
1984)
Incidence function of Red-eyed Vireo (Robbins et
al. 1989)
Species richness
Probability
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Birds in forest fragments in Southern Chile
Bird species richness (spp/plot)
p 0.001
p 0.07
Forest fragment area (ha)
Forest fragment area (ha)
Matrix agricultural fields (Willson et al. 1994)
Matrix pine plantations (Estades Temple 1999)
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Extended foraging area
d
d
d
d
d maximum distance of foraging trip
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Mosaic approach
(Wiens 1995)
General theoretical framework (but is it really
workable?) Landscape Mosaics are too
Idiosyncratic
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Mosaic approach
Habitat mosaic
Quality Suitability Fitness etc...
Resource mosaic
Cover
Nest sites
Food
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1. The effect of breeding-habitat patch size on
bird population density
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Individual based model
Goal Explore the effect of relative distribution
of food and nest sites on the relationship
between breeding habitat patch size and bird
density.
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Simulation model results
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Effect of flight distance
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General model
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Conclusions
The effect of breeding-habitat patch size on bird
population density depends on the relative
location of food and nesting sites in the
landscape. Management of the matrix may affect
the suitability of fragmented landscapes for
breeding birds The effect of additional foraging
resources in the matrix on birds in fragmented
habitat-patches depends on the species? maximum
flight distance and perceived foraging risk.
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2. Spatial dynamics of bird communities in a
forest landscape mosaic
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Problem
The distributions of most forest bird species in
the fragmented landscape of the Maule region are
not adequately predicted by the size and/or
isolation of forest patches (Estades and Temple,
1999).
Hypotheses
The distribution of bird species in a landscape
can be modeled by looking at the distribution of
food and nest sites. The distribution of birds
in the landscape changes over time in accordance
to the distribution of the limiting resources.
During the breeding season the best predictor of
the distribution of birds is the product of the
local abundance of nest sites and food resources
and during the non breeding season the best
predictor is the abundance of food resources.
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Study area
Maule Region, Chile
Pine plantations 80
Native forests 10
Open areas 7
Others 3
10,000 ha
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Dominant species Nothofagus dombeyi
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Dominant species Nothofagus glauca
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Dominant species Pinus radiata
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Studied species
Tufted Tit-tyrant Open-cup nester Understory
Des Murs? Wiretail Open-cup nester Understory
White-crested Elaenia Open-cup nester Understory
and canopy
Thorn-tailed Rayadito Cavity nester
Fire-eyed Diucon Open-cup nester Understory and
canopy
White throated Treerunner Cavity nester
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Sampling
120 point count stations (variable radius point
counts with correction for detectability) Field
seasons Winter (June) 1999 Spring (Oct-Nov)
1999 Summer (February) 2000 Winter (June)
2000 Spring (Oct-Nov) 2000 Summer (February)
2001
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Model
Breeding season Bird abundance f(Nest sites
Food abundance) Non-breeding Bird abundance
f(Food abundance) Generalized linear model,
negative binomial distribution
Nest sites
Food abundance
0 50 100
200m
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Diet
Analysis of droppings
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Food abundance
Foliage shaking
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Food abundance
Aristotelia chilensis
Fruit sampling
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Nest sites
Abundance of cavities
Density of understory
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Conclusions
Most studied birds changed their distributions in
the landscape between seasons and many of these
changes matched the changes in the distribution
of key resources. Although factors such as
competition, predation and parasitism may
influence the distribution of birds in a
landscape mosaic, the ?resource mosaic? model
represents a parsimonious approach to
understanding the distribution of birds in a
patchy landscape where the matrix surrounding
patches of preferred habitat is not completely
useless
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3. Nest success of the Thorn-tailed Rayadito in a
forest landscape mosaic
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Problem
Thorn-tailed Rayaditos in the Maule region have
higher densities in smaller forest fragments
because these birds can forage in the surrounding
pine plantations (Estades and Temple, 1999). But
is the breeding success of birds that include
pine plantations in their home ranges equal to
the breeding success of birds that forage
entirely in native forest?
Hypothesis
The breeding success of Thorn-tailed Rayaditos is
positively associated with the amount of native
vegetation around the nest because of the effect
of reduced food concentration and a potentially
higher level of predation in the artificial
forests
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Upland forest Riparian forest Pine
plantations
native vegetation 100 25.5 0
50m
1.34 1.13 1.0 relative arthropod
ab.
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Nest success of Thorn-tailed Rayaditos
Most failures were due to predation No evidence
of an effect of food density
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Thylamis elegans
House Wren
Rodent
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Nest predators
Thylamis elegans
Phylodrias chammisonis
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Predators of fledglings and adults
Accipiter chilensis
Glaucidium nanum
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Competitors
Liolaemus tenuis
Picoides lignarius
Pygarrichas albogularis
Troglodytes aedon
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Conclusions
Concentration of food resources did not limit
breeding performance of Thorn-tailed
Rayaditos Small riparian forest fragments
surrounded by pine plantations not only harbor
higher rayadito densities than large upland
forest patches (Estades and Temple, 1999), but
they also provide a safer place to breed for this
species. Differences in breeding success between
habitat types were probably due to differences in
concentration of predators and competitors and
average nest height.
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Ongoing work
Nest success and nesting density of open-cup
nesters in different parts of the landscape
Movements of individual birds in the landscape
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Acknowledgements
? Fondecyt (Chile) grants 1990786 and 7990027 ?
Zoological Society of Milwaukee County ?
Association of Field Ornithologists ? Dept.
Wildlife Ecology. University of Wisconsin -
Madison ? School of Forest Sciences. Universidad
de Chile (Santiago) ? Committee Stanley Temple,
Nancy Mathews, Christine Ribic, Tony Ives,
Tim Moermond ? All the field assistants ? Friends
here and there ? Paula and Josefa