Do mothers bias offspring sex ratios in carotenoid-rich environments?

2nd hihi paper for 2016 out @ Behavioral Ecology!

Kirsty J. MacLeod, Patricia Brekke, Wenfei Tong, John G. Ewen, Rose Thorogood

Behavioral Ecology (2016) 28 (1): 131-137.

Here we've proved that non-significant results can be published!  As part of a wider supplementation experiment investigating the effects of carotenoids (a dietary biochemical responsible for birds' pigmentation and implicated in their immune systems) on hihi, we determined the sex of as many eggs laid as possible.  By following these nests closely in the field, (including hunting tirelessly for dead nestlings thrown from the nest by tidy parents!) we managed to collect a dataset to test whether mothers invest more in sons when these are likely to become sexier adults relative to daughters.  There is some evidence that hihi males with greater access to carotenoids when young achieve greater reproductive success in adulthood (see nice work by Leila Walker during her PhD here and here).  Therefore, we surmised that mothers better able to provision sons with carotenoids might invest in producing more of them to improve their fitness.  Data from two field seasons however failed to find any evidence for this, and provides more evidence that sex-ratio manipulation by mothers is difficult to detect.

Read more about this paper, and Kirsty's companion paper on how mothers manipulate hatching asynchrony, in this nice blog post on her site.