科研之友
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摘要
Restored wetlands are commonly assessed as avian breeding habitat using surveys, but data on reproductive parameters are needed to better understand how restoration affects wetland-dependent bird populations. A novel way to assess differences in breeding habitat quality is to compare the maternal allocation of carotenoids (i.e., biologically active yellow, orange and red pigments) to egg yolks, which is both diet and habitat dependent. We compared yolk carotenoid concentrations of red-winged (Agelaius phoeniceus) and yellow-headed blackbirds (Xanthocephalus xanthocephalus) that bred in natural, recently restored (i.e., restored a parts per thousand currency signaEuro parts per thousand 6 yrs ago) and restored (i.e., restored 9-16 yrs ago) wetlands to determine if restored wetlands provided critical reproductive resources at levels similar to natural sites. We also measured emerging insect abundances, water chemistry, and landscape-level parameters for study wetlands and related these variables to yolk carotenoid concentrations. Moreover, to understand the importance of damselflies to the diet of blackbirds, we measured the carotenoid content of damselflies and compared this to the yolk carotenoid content found in blackbird eggs. Bird abundances were also measured at each wetland to compare the traditional method of assessing breeding habitat to our novel yolk-carotenoid approach. In 2008, red-winged blackbirds in natural wetlands had higher carotenoid concentrations than birds in recently restored wetlands, suggesting that natural wetlands provided better breeding habitats. In 2009 there was a severe drought and we found contrasting results, with red-winged blackbirds in restored wetlands having higher carotenoid concentrations. Adult damselflies contained five carotenoids commonly found in avian tissues, suggesting they are likely an important source of carotenoids for wetland-breeding blackbirds. In contrast to yolk carotenoids, neither avian species richness nor abundance was significantly related to wetland type. Based on model selection results for water chemistry parameters, variation in concentrations of yolk carotenoids in red-winged blackbirds was best explained by conductivity, whereas variation in avian abundance was explained by total nitrogen, and avian species richness by chlorophyll-a concentration. Model selection results for landscape-level parameters revealed that variation in concentrations of red-winged blackbird yolk carotenoids was best explained by percent water in a 500 m buffer and variation in both avian abundance and avian species richness by wetland surface area. Our novel yolk carotenoid approach allowed us to identify differences in breeding bird habitat quality across wetland types, which we failed to detect with traditional bird survey data; our results highlight the need for additional studies comparing methods for assessing wetlands as breeding habitat for wetland-dependent birds.
- 出版日期2013-6
