Nov. 7th : Oti's outline
Lab meeting 11/07/2005
Ideas and plans for the coming field-season
1. Does testosterone affect the investment into the mating effort and parental care at penduline tits?
There is trade-off between mating and parental effort.
Monogamous species: males T level show peak in the early breeding season than maintain much lower T level.
- mating effort (courtship, singing, territoriality, mate guarding) high T level
- parental care (incubation, feeding, nest defense) low T level T level decline when eggs or young are present
Treatment with T could induce polygyny in monogamous males (Wingfield 1984), also could decrease or inhibit incubation behavior at males (Ridder et al. 2000).
Polygynous species: maintain high level of T during the whole breeding season.
Polygamous PT???
Male incubation and parental care occur more often during the late breeding season.
Questions:
1. Whether natural plasma T level is higher at the beginning of the breeding season than later?
2. After controlling to the effects of the breeding season, whether deserting males possess higher T level than incubating males?
3. Whether T influences the song quality or activity?
Experimentally elevated T level resulted in increased song activity at many monogamous bird species, for example at starlings (Ridder et al. 2000), house finches (Stoehr and Hill 2000).
2. Bird song might evolve to reveal the health status of the male
- male resistance and sexually selected traits might covary: good genes for parasite resistance (Hamilton and Zuk 1982)
Hematozoan parasites had effect on repertoire size at sedge warblers (Buchanan et al. 1999)
Testosterone might cause immunsupression ICH hypothesis (Folstad and Karter1992): increased risk of parasitism. This hypothesis is much debated recently.
Question:
Whether the hematozoan parasitic infection affects the song duration or elaboration?
3. Testing female mate-guarding hypothesis (Petrie et al. 1992) on a polygamous species
At monogamous starlings female copulate repeatedly with his mate to prevent polygyny. (Eens and Pinxten 1996): female mate-guarding hypothesis.
Personal observations: Females respond to males song with solicitation copulation behavior.
Playback experiment: to play female call at the nest to test whether it is modify the copulation rate.
Hypothesis: increased number of free females in the population might generate increased solicitation-copulation behavior as a response to prevent male desertion and keep the male at the nest.
To exclude that the increased solicitation rate is due to the increased singing activity of the male, first it is necessary to investigate whether is there any correlation between female solicitation rate and male song activity.
4. Comparative study between two relative species
A South - African Anthoscopus species is closely relative to Euroasian penduline tit, however this species is cooperative breeder with biparental care. Comparative study would reveal the differences between two species regarding sexual advertisements.
My hypothesis assumes that the Anthoscopus species possesses less elaborated song due the stronger selection effects on penduline tit.
Our future plan is to get permission to investigate the hormonal differences in the brain of the two species.
Thesis work for an undergrad student:
1. territory quality:
At polygamous species without male parental care the territory quality might be of greater importance to nestling females than the repertoire size (Hasselquist 1998)
2. Comparison of song parameters between deserted and new mates:
the proportion of EPC is very low at PTs (around 4%), desertion is instead of EPC?
3. Song matching
3.1. Song repertoire matching between neighboring males
3.2. Matching ability and reproductive success
Playback experiment:
Better matching with larger repertoire size
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