Effect of LPS injection on a) mass-specific nightly metabolic rate, b) body temperature, c) relative mass loss during the night, d) absolute mass loss during the night, e) glucose concentration and f) ketone concentration of skylarks after 13 hours.

<p>Experimental birds were injected with LPS; control birds were un-injected. Black symbols represent experimental birds (LPS-injected), grey symbols control birds (un-injected). Bars represent the difference between these two groups. Means and standard errors are shown; numbers in bars represent sample sizes per group (control/experimental). The graphs show raw data without correcting for sex effects. There was never a significant treatment* annual cycle stage interaction (all P>0.084). See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036358#pone-0036358-t001" target="_blank">Table 1</a> for statistics.</p>