Despite the appealing hypothesis that carotenoid-based colouration signals oxidative status, evidence supporting the antioxidant function of these pigments is scarce. Recent studies have shown that lutein, the most common carotenoid used by birds, can enhance the expression of non-visual traits, such as birdsong. Nevertheless, the underlying physiological mechanisms remain unclear. In this study we hypothesized that male European starlings (Sturnus vulgaris) fed extra lutein increase their song rate as a consequence of an improved oxidative status. Although birdsong may be especially sensitive to the redox status, this has, to the best of our knowledge, never been tested. Together with the determination of circulating oxidative damage (ROMs, reactive oxygen metabolites), we quantified uric acid, albumin, total proteins, cholesterol, and testosterone, which are physiological parameters potentially sensitive to oxidation and/or related to both carotenoid functions and birdsong expression. We found that the birds fed extra lutein sang more frequently than control birds and showed an increase of albumin and cholesterol together with a decrease of oxidative damage. Moreover, we could show that song rate was associated with high levels of albumin and cholesterol and low levels of oxidative damage, independently from testosterone levels. Our study shows for the first time that song rate honestly signals the oxidative status of males and that dietary lutein is associated with the circulation of albumin and cholesterol in birds, providing a novel insight to the theoretical framework related to the honest signalling of carotenoid-based traits.

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Life history theory predicts that individuals have to trade-off resources between diverse energy-demanding activ- ities, such as mounting an immune response and performing advertisement behaviour. The availability of immunomodula- tory micronutrients can affect this trade-off. Carotenoids can upregulate both the humoral and cell-mediated immune re- sponse, but little is known about their effect on behavioural traits during the sickness phase induced by a common inflam- mation. To investigate whether dietary carotenoids can miti- gate the severity of the sickness syndrome and promote fitness-related traits, we studied how the song rate of captive male European starlings (Sturnus vulgaris, Linnaeus 1758) receiving dietary carotenoids and coping with a challenge (li- popolysaccharide, LPS) mimicking a bacterial infection var- ied during the sickness phase and the subsequent recovery phase. We found that birds not provisioned with carotenoids and injected with LPS sang less than control birds during the sickness phase, but not during the recovery phase.Conversely, birds provided access to a carotenoid-enriched diet never de- creased their song rate. Our results show that immune- challenged birds have to trade-off between mounting an im- mune response and advertising only when their access to die- tary carotenoids is limited. No differences in song rate were observed between treatments during the recovery phase. Our study is the first to investigate the role of dietary carotenoids Communicated by K.McGraw * Stefania Casagrande scasagrande@orn.mpg.de 1 Department of Biology, Ethology Group, University of Antwerp, Antwerp, Belgium 2 Institute for Education and Information Sciences, Research Unit Didactica, University of Antwerp, Antwerp, Belgium on a behavioural syndrome-like sickness and to show that providing a carotenoid-rich diet can alleviate the social costs associate

Study Objectives In this study, we (1) describe sleep behaviour and architecture, and (2) explore how sleep is regulated in dusky antechinus (Antechinus swainsonii), a small insectivorous marsupial. Our aim is to provide the first investigation into sleep homeostasis in a marsupial. Methods Wild-caught male dusky antechinus (n = 4) were individually housed in large indoor cages under a natural photoperiod of 10.5 h light / 13.5 h dark. Continuous recordings of EEG, EMG, and tri-axial accelerometry were performed under baseline conditions and following 4-h of extended wakefulness. Results Antechinus engage in SWS and REM sleep. Some aspects of these states are mammal-like, including a high amount (23%) of REM sleep, but other features are reminiscent of birds, notably, hundreds of short sleep episodes (SWS mean: 34 s; REM sleep: 10 s). Antechinus are cathemeral and sleep equally during the night and day. Immediately after the sleep deprivation ended, the animals engaged in more SWS, longer SWS episodes, and greater SWS SWA. The animals did not recover lost REM sleep. Conclusions Sleep architecture in dusky antechinus was broadly similar to that observed in eutherian and marsupial mammals, but with interesting peculiarities. We also provided the first evidence of SWS homeostasis in a marsupial mammal.

Song is a sexually selected trait that is thought to be an honest signal of the health condition of an individual in many bird species. For species that breed opportunistically, the quantity of food may be a determinant of singing activity. However, it is not yet known whether the quality of food plays an important role in this respect. The aim of the present study was to experimentally investigate the role of two calorie-free nutrients (lutein and cholesterol) in determining the expression of a sexually selected behavior (song rate) and other behaviors (locomotor activity, self-maintenance activity, eating and resting) in male zebra finches (Taeniopygia guttata). We predicted that males supplemented with lutein and cholesterol would sing at higher rates than controls because both lutein and cholesterol have important health-related physiological functions in birds and birdsong mirrors individual condition. To control for testosterone secretion that may upregulate birdsong, birds were exposed to a decreasing photoperiod. Our results showed that control males down-regulated testosterone in response to a decreasing photoperiod, while birds treated with lutein or cholesterol maintained a constant singing activity. Both lutein- and cholesterol-supplemented groups sang more than control groups by the end of the experiment, indicating that the quality of food can affect undirected song irrespective of circulating testosterone concentrations. None of the other measured behaviors were affected by the treatment, suggesting that, when individuals have full availability of food, sexually selected song traits are more sensitive to the effect of food quality than other behavioral traits. Overall the results support our prediction that undirected song produced by male zebra finches signals access to high-quality food.