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Bird rarity in terra-firme forest: Bird rarity in terra-firme forest: reality or imperfect detection?reality or imperfect detection?
Marconi Campos CerqueiraMarconi Campos CerqueiraGonçalo Ferraz, Claudeir Vargas, Christian Borges, Thiago Gonçalo Ferraz, Claudeir Vargas, Christian Borges, Thiago Vernucci, Angela Midori, Marcelo Santos, Monica Ribas, Vernucci, Angela Midori, Marcelo Santos, Monica Ribas,
Mario Conh-HaftMario Conh-Haft
Fotos:Erik Johnson
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“Rare species play such a central role in conservation biology that Rare species play such a central role in conservation biology that the discipline has been defined as the science of scarcity and the discipline has been defined as the science of scarcity and diversity “Soulé, 1986diversity “Soulé, 1986
Hypothesis:Hypothesis: - The ornithologist`s perception of commonness and rarity - The ornithologist`s perception of commonness and rarity
reflect the truth about forest patch occupancy by birds. reflect the truth about forest patch occupancy by birds.
Conservation implications: Conservation implications: - some common species may be mistakenly classified as - some common species may be mistakenly classified as
rarerare..
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Rarity as occupancy :Rarity as occupancy :
- Proportion of occupied sites, or occupancy, instead of abundance.Proportion of occupied sites, or occupancy, instead of abundance.- Positive interspecific correlation between occupancy and abundance – not only Positive interspecific correlation between occupancy and abundance – not only
obvious but well documented (Gaston and Blackburn 1999)obvious but well documented (Gaston and Blackburn 1999)
- Locally abundant species tend to occupy more places than rare ones.Locally abundant species tend to occupy more places than rare ones.
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Fiuí fiu fiitri
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???? ??
Detectio
n is not perf
ect
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Trogons
Puffbirds Jacamars
Ovenbirds
Woodcreepers
77
Antthrushes
Wrens
Vireos
Antwrens
Antshrikes
88
Study areaStudy area
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2 weeks of survey:
1st week – Ten trained researches make 3-minute point counts in ten different trails simultaneously.
660 point counts660 point counts
1980 min of observation1980 min of observation
330 km collective walk330 km collective walk
2nd week- playback of 16 species` songs in one more visit per point by one observer.
Methodology
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Improve and measure observer skillsImprove and measure observer skills
Prior training in the fieldPrior training in the field Memory training with ‘electronic flashcards’Memory training with ‘electronic flashcards’ Memory retention test -> observer scoreMemory retention test -> observer score Observer score as covariate of detection Observer score as covariate of detection
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AnalysisAnalysis
Parameter estimation(Occupancy and detection)Parameter estimation(Occupancy and detection)
Maximum likelihoodMaximum likelihood
Hypothesis testingHypothesis testing
Models selection AICModels selection AIC the model with lowest AIC value provides the most the model with lowest AIC value provides the most
parsimonious and best approximation of information parsimonious and best approximation of information contained in the datacontained in the data 1
1(Burnham e Anderson 1998)
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Detection probabilitiesDetection probabilities
Example: Example: Bucco tamatiaBucco tamatia
Model Δ AIC
Ψ(.) p(playback+time) 0
Ψ(.) p(playback+time+score) 2
Ψ(.) p(playback) 31.2
Ψ(.) p(playback+score) 33.2
Ψ(.) p(time) 37.2
Ψ(.) p(time+score) 37.69
Ψ(.) p(.) 51.17
Ψ(.) p(score) 51.22 p(playback+time)
Naive estimate = 0,25
Estimated occupancy = 0,38 ± 0.09
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Time of the day Time of the day ×× detection (given presence) detection (given presence)
Observer score Observer score ×× detection (given presence) detection (given presence)
Playback Playback ×× detection (given presence)detection (given presence)
Occupancy for 20 species – final estimateOccupancy for 20 species – final estimate
00.10.20.30.40.50.60.70.80.9
1
sp1 sp2
Species
Occupancy
00.10.20.30.40.50.60.70.80.9
1
sp1 sp2
Species
Occupancy
0
0.2
0.4
0.6
0.8
1
sp1 sp2
Species
Occupancy
So… are the birders getting it?So… are the birders getting it?
00.10.20.30.40.50.60.70.80.9
1
1 2
Species
Occupancy
So… are the birders getting it?So… are the birders getting it?
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Rarity team
Sure they are
getting it!
