Experimental evidence for the influence of food availability on incubation attendance and hatching asynchrony in the Australian reed warbler

Published source details Eikenaar C., Berg M.L. & Komdeur J. (2003) Experimental evidence for the influence of food availability on incubation attendance and hatching asynchrony in the Australian reed warbler. Journal of Avian Biology (formerly Ornis Scandinavica 1970-1993), 34, 419-427.
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This study is summarised as evidence for the following.

	Action	Category
	Provide supplementary food for songbirds to increase reproductive success Action Link

Provide supplementary food for songbirds to increase reproductive success

A randomised, replicated and controlled study in a 10 ha Australian reed Phragmites australis wetland in southern Australia, over two breeding seasons (September to January) in 1999-2001 (Eikenaar et al. 2003), found that Australian reed warbler Acrocephalus australis females provided with supplementary food spent longer incubating eggs than control (unfed) females (12 fed females spent approximately 57% of time incubating vs. 51% for ten controls). There was also a significant difference between days when food was provided and those when it was not (on fed days, 59% of time spent incubating vs. 52% of time on unfed days, seven tested). There were no differences between other measures of incubation attendance, such as start and end times of incubation bouts or the average length of bouts. However, broods from fed territories had larger hatching asynchronies (calculated as the difference in size, at one to three days old, between the first- and last-hatched chicks, divided by the mean size of all nestlings) than control pairs (tarsus length asynchrony of approximately 0.15 and weight asynchrony of approximately 0.35 for ten fed broods vs. 0.10 and 0.20 for 19 controls). The effect of feeding on fitness of chicks or parents was not reported. Supplementary food consisted of 30 g of blowfly maggots (over 150% of daily energetic requirements of an adult reed warbler) provided every other day whilst eggs were incubated, but stopped before eggs hatched.