Sex-specific mass loss in chick-rearing South Polar skuas Stercorarius maccormicki- stress induced or adaptive?

Published source details Ritz M.S. (2006) Sex-specific mass loss in chick-rearing South Polar skuas Stercorarius maccormicki- stress induced or adaptive?. Ibis, 149, 156-165.
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This study is summarised as evidence for the following.

	Action	Category
	Provide supplementary food for gulls, terns and skuas to increase adult survival Action Link
	Provide supplementary food for gulls, terns and skuas to increase reproductive success Action Link

Provide supplementary food for gulls, terns and skuas to increase adult survival

A randomised, replicated and controlled trial on King George Island, Antarctic Peninsula, in the boreal summer of 2000-1 (Ritz 2006) found that female south polar skuas Catharacta maccormicki (also Stercorarius maccormicki) that were fed when raising two chicks lost significantly more weight than control (unfed) females (average loss of 7.9% of body weight for fed pairs vs. 4.6% for controls). There was no such effect in male skuas (average loss of 2.1% of body weight for 27 fed males vs. 5.5% for 27 controls) or if females raising single chicks were included in results (loss of 6.9% of body weight for 27 fed pairs vs. 4.5% for 27 controls). Supplementary food consisted of 25-100 g of fish provided to adults every other day, corresponding to approximately 20% of a chick’s daily energy needs. This study also includes the impact of feeding on chick growth and survival, see ‘Provide supplementary food to increase reproductive success’.
Provide supplementary food for gulls, terns and skuas to increase reproductive success

A randomised, replicated and controlled trial on King George Island, Antarctic Peninsula, in the boreal summer of 2000-1 (Ritz 2006) (as part of the same study as Ritz et al. 2005) found that male south polar skuas Catharacta maccormicki (also known as Stercorarius maccormicki) from 27 pairs provided with supplementary food were present at nests more often than males from 27 control (unfed) pairs (males present for 83% of observations when chicks were 7-50 days old for fed pairs vs. 74% for controls, a total of 955 observations). There was no difference in female attendance (81% attendance for fed pairs vs. 80% for controls, 955 observations). Chicks from fed pairs were not significantly larger than chicks from control (unfed) pairs, although wing growth was slightly faster in fed chicks (there were no changes in mass, head size or tarsus growth rates). Supplementary food consisted of 25 g of fish provided to adults every other day when chicks were 6-35 days old and 100 g of fish when 35-55 days old. This corresponds to approximately 20% of a chick’s daily energy needs. This study also investigated the impact of feeding on adult condition, discussed in ‘Provide supplementary food to increase adult survival’.