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SEPG 2245 - Date Awarded 2003
Sexual selection and the hihi: an investigation of population limitation in an endangered bird
Ewen, J.
Summary
Carotenoids are essential dietary components utilised not only in pigmentation but also as immuno-stimulants and antioxidants by animals. Reduced availability can have consequences on individual health and survival and this is likely exacerbated in sexually selected species that trade carotenoid use for health with signal quality. We used carotenoid profiles and plumage colour characteristics as indicators of habitat quality in an endangered passerine species in New Zealand characterised by proneness to pathogens, poor survival and failed reintroduction attempts. In addition this species is subject to strong sexual selection and males express a prominent carotenoid-based yellow plumage badge. There was a clear difference in the availability of carotenoids between the three populations of this species. Individuals of one reintroduced population were characterised by substantially higher concentrations of carotenoids circulating in the plasma and a brighter reflectance in the yellow and ultra-violet of yellow plumage. This population is also the only successful reintroduction of this species. Given the clear benefits carotenoids have, we suggest that our phenotypic approach is a valid and alternative method of assessing habitat quality. The large and significant variation between populations suggests either a lack of carotenoids and/or a variable pathogen load impacting on absorption and use of carotenoid resources. Our preliminary investigation into disease prevalence shows pathogens are indeed present and adds support to the variable pressures faced by these populations. Constraints on the availability of essential dietary components, such as carotenoids, need to be assessed as they potentially alter the dynamics and viability of small and endangered populations.
Full report: SEPG2245
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