Male satin bowerbird painting and female choice Jef Akst, Christy Bergeon, and Emily Chester.

Male satin bowerbird painting and female choiceJef Akst, Christy Bergeon,

and Emily Chester

Sexual Selection Theory

• Within a species, one sex acts as a limiting resource for the other

• Intrasexual selection - Competition between individuals of the same sex for access to mates

• Intersexual selection – Mate-choice exhibited by the limiting sex

exaggerated phenotypic characteristicsSexual selection depends on the success of certain individuals over others of the same sex, in relation to the propagation of the species; while natural selection depends on the success of both sexes, at all ages, in relation to the general conditions of life. --Charles Darwin, 1871.

Sex Roles

• Traditional sex roles– Male-biased OSR, females are limiting sex– Male: high competition, elaborate

ornamentation– Female: high PI, more choosy

Competition between males for access to females

Mate-choice exhibited by females

Bowerbirds (Ptilonorhynchidae)• Found in Australia & Indonesia

• 19 species – Catbirds - no bower, monogamous– Maypole/hut builders– Avenue builders

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Regent’s bowerbird Great bowerbird Satin bowerbird





Bowers• Place for copulation• Built of sticks• Maypoles, huts, avenues• Associated with well-

decorated display courts– Colorful natural and artificial

objects used for decorations

• Important role in mate attraction

• Attended year-round

Bowers

Uy & Borgia 2000

Satin bowerbirds(Ptilonorhynchus violaceus)

• Found in rainforest of Eastern Australia• Polygynous• Create avenue bowers• Long-lived

– Males acquire adult plumage at 7 years







Females are choosy!

• Visitations to bowers influenced by– Male size– Display rate– Number of decorations

• Copulations influenced by

– Male size

– Painting rate

• Male masticates plant material• Spreads mixture on inside walls of bower• Painting accounts for 24% of bower

maintenance time• Females nibble at painted twigs

Painting

Proposed research

Painting rate is positively correlated with male mating success (Robson et al., 2005).

• Objectives:– What aspects of painting rate influence female

mate choice?

• Approaches:– Behavioral observations

– Visual and chemical characterization

Study Site

• Bunya Mountains (26°51’54”S, 151°35’15’’E)

• 160 km north-west of Brisbane, Australia

Methods

• Motion-sensitive cameras will be directed at male bowers with a wide enough view to capture the platform and entire bower area.

• We will measure:– Time spent painting– Total paint signal

• Percentage of bower paint cover• Average thickness of paint

– Paint freshness = latency to female visitation following male painting

– Rates of female nibbling = # nibbles/time in bower

Methods

• And look for correlations with:– Male fitness = frequency of copulation =

number of copulations/time spent at bower

• Controlling for:– Number of visits to bower by females– Bower volume– Number of decorations surrounding the

bower

Methods – Chemical ProfilesStir bar sorptive extraction methodMeasure both fresh paint and samples dried

for 24 hoursGas chromatography – mass spectrometry

J.Z. Zhang et al. (2005)

Stir bar

Roller device

Methods – Visual SpectraFull spectrum reflection spectrometer

Measure both fresh paint and samples dried for 24 hours under uniform light conditions

Principle Components Analysis

S. M. Doucet et al (2006)

Potential Outcomes

• Visual spectra– Correlation with chemical profile?

• Chemical profiles– Quality - different compounds identified– Quantity - variable strength of volatiles

• Male painting rate (Robson 2005)• Amount of paint (area, thickness)• Female nibbling rate• Freshness

Conclusion

• Identifying characteristics of paint that may be used in female choice

• Future directions:– Manipulations of paint

may demonstrate causal relationships

– Measuring strength of selection of female choice may elucidate mechanisms of bower divergence

Male satin bowerbird painting and female choice Jef Akst, Christy Bergeon, and Emily Chester.

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