Seasonal variation in body mass and energy budget in Chinese bulbuls (pycnonotus sinensis)

Abstract

Background: Seasonal adjustments in body mass and energy budget are important for the survival of small birds in temperate zones. Seasonal changes in body mass, body temperature, gross energy intake (GEI), digestible energy intake (DEI), body fat content, as well as length and mass of the digestive tract, were measured in Chinese Bulbuls (Pycnonotus sinensis) caught in the wild at Wenzhou, China. Methods: Body mass was determined with a Sartorius balance. The caloric contents of the dried food and feces were then determined using a oxygen bomb calorimeter. Total fat was extracted from the dried carcasses by ether extraction in a Soxhlet apparatus. The digestive tract of each bird was measured and weighed, and was then dried to a constant mass. Results: Body mass showed a significant seasonal variation and was higher in spring and winter than in summer and autumn. Body fat was higher in winter than in other seasons. GEI and DEI were significantly higher in winter. The length and mass of the digestive tract were greatest in winter and the magnitude of both these parameters was positively correlated with body mass, GEI and DEI. Small passerines typically have higher daily energy expenditure in winter, necessitating increased food consumption. Conclusions: This general observation is consistent with the observed winter increase in gut volume and body mass in Chinese Bulbuls. These results suggest that Chinese Bulbuls adjust to winter conditions by increasing their body mass, body fat, GEI, DEI and digestive tract size.

Temperature and photoperiod as environmental cues affect body mass and thermoregulation in Chinese bulbulsPycnonotus sinensis

“…The ability to adjust energy intake to compensate for the energy expended in thermogenesis is essential for survival (Hegemann et al, 2012). Environmental temperature and photoperiod can, however, alter birds' energy intake (Kendeigh, 1945;Stokkan et al, 1986;Lou et al, 2013;Wu et al, 2014b). We found that Chinese bulbuls in the CS group had the highest M b and that this was consistent with changes in GEI and DEI.…”

“…Some small birds that live in seasonal environments increase their M b in winter (McKechnie, 2008;McKechnie and Swanson, 2010), by increasing their fat deposits and/or lean mass (Swanson, 1991a;Piersma et al, 1996). There is evidence to suggest that seasonal variation in the M b of Chinese bulbuls is due, at least in part, to seasonal variation in fat deposits and lean mass Wu et al, 2014a). Our results are consistent with those of previous reports on the response of Chinese bulbuls to seasonal change (Zheng et al, 2008a, and the M b of bulbuls was higher in cold groups than in warm groups, and in short photoperiod than in long photoperiod.…”

“…It has been demonstrated that a bird's M b , energy balance and RMR are all affected by temperature and photoperiod (McKechnie, 2008;McKechnie and Swanson, 2010;Wu et al, 2014b). Low ambient temperature can increase the RMR of some birds (Tieleman et al, 2003;McKechnie et al, 2007).…”

“…Temperature and photoperiod are considered to be the most important environmental factors influencing an animal's seasonal thermoregulation and driving the evolution of a suite of morphological, physiological and behavioral adaptations (Zheng et al, 2013a;Swanson et al, 2014;Zhou et al, 2016). Seasonal changes in temperature and photoperiod are important environmental cues that small birds use to adjust morphological and physiological parameters such as body mass (M b ), energy intake and thermogenic capacity (Swanson, 1990;Zheng et al, 2008a;Wu et al, 2014a). Winter is an energetically stressful period for birds living in temperate zones because the cost of thermoregulation increases while food quality and availability are reduced (Yuni and Rose, 2005;.…”

Daily variation in body mass and thermoregulation in male Hwamei (Garrulax canorus) at different seasons

“…Phenotypic flexibility refers to phenotypic changes that are reversible, temporary and repeatable, such as acclimation and acclimatization (Piersma and Drent 2003;Starck 2009;Liknes and Swanson 2011). The study on phenotypic plasticity has become a central topic in evolutionary ecology and resident endothermic animals in temperate climates provide for natural experiments in phenotypic flexibility (Liknes and Swanson 2011;Wu et al 2014).…”