Body mass loss amongst moulting Pochard Aythya ferina and Tufted Duck A. fuligula at Abberton Reservoir, South East England

Abstract

We assessed the contribution of endogenous fat stores to meeting energetic needs during the flightless moult period in Pochard and Tufted Duck by regressing mass on the progression of wing moult, as measured by primary length. Pochard lost between 22.1% (males) and 24.2% (females) of body mass and female Tufted Duck 12.2% during wing moult at Abberton Reservoir, Essex. Based on a 27-day flightless period, Pochard lost on average 8.3-8.4 g per day and Tufted Duck 3.2-3.4 g per day, presumably due to fat expenditure. Assuming the daily energy expenditure (DEE) to be 1.79 the basal metabolic rate (BMR), the contribution from burning endogenous fat equated to 37-40% of Pochard and 19-20% of Tufted Duck DEE during remiges moult. One frequently re-trapped female Pochard expended fat stores that almost fulfilled her entire energetic requirements during moult if she rested and did not feed for most of the moult. These results confirm that Pochard and Tufted Duck accumulate fat stores that help to meet energetic needs during the flightless wing moult period. This endogenous source of energy may free them to exploit habitats that are safe from predation but which may not fully supply the energetic needs of moulting ducks from exogenous sources.

Do Seaducks Minimise the Flightless Period?: Inter- and Intra-Specific Comparisons of Remigial Moult

“…In other words, the decrease of body mass of phase II corresponds to the steep slope of feather growth models, hence a period of high energy demand. Similar observations of body mass loss during remigial moult were recorded for different species of waterfowl in both captive and wild situations [10], [17], [64], [73], [74]. However, the SUSC and WWSC male scoters did not show any significant variation of body mass in our study, as observed for Common Scoters ( Melanitta nigra ) [39].…”

Molts and Plumages of Ducks (Anatinae): An Evaluation of Pyle (2005)

“…There is increasing evidence that the complete prebasic molt in birds involves more than just feather replacement but is accompanied by a whole restoration of body tissues affiliated with increases in metabolic rate, increases in whole body protein synthesis, osteoporosis, loss of body fat, and suppression of the immune system as regulated in part by thyroidal activity (Voitkevich 1966;Murphy 1996;Kuenzel 2003). Similar metabolic processes also appear to occur during ecdysis and/or molt in fish, reptiles, and mammals (King 1972) as well as during the complete prebasic molt (sensu Pyle 2005) of ducks (e.g., Fox and King 2012), suggesting that the prebasic molt may be part of a restoration process ancestral to most or all vertebrates. Such substantive physiological processes may not occur contemporaneously with partial inserted molts, which may have originally evolved in birds simply to replace worn feathers (Pyle and Kayhart 2010;Wolfe and Pyle 2011).…”

Variation in body mass and foraging effort of Barrow’s Goldeneyes (Bucephala islandica) during remigial molt

“…Some waterfowl meet nutritional requirements of remigial molt through exogenous resources, increasing foraging effort and maintaining or gaining mass during molt (Ankney 1979, Young and Boag 1982, Fox et al 2008. Other species deplete endogenous (somatic) resources during molt and lose body mass as a result (Panek and Majewski 1990, Hohman 1993, Brown and Saunders 1998, Fox and Kahlert 2005, Portugal et al 2007, Fox and King 2011. Other species rely on both strategies to meet nutritional demands during different stages of remigial molt (Owen and Ogilvie 1979, Bailey 1985, Moorman et al 1993, Thompson and Drobney 1996, Fox et al 2009).…”

“…For example, birds that are losing mass (i.e., depleting somatic resources) and foraging little may be adaptively losing mass, possibly to enhance predator evasion (Panek and Majewski 1990, Brown and Saunders 1998, Zimmer et al 2010. Birds that are losing mass and foraging laboriously may be nutritionally limited (Fox and Kalhert 2005, Portugal et al 2007, Fox and King 2011, whereas birds that maintain or gain mass and forage little are likely able to acquire exogenous nutrients easily during remigial molt.…”