Effects of Body Condition on Molting in Mallards

Abstract

The effects of high and low protein food on molting in penned, wild-strain Mallards (Anus plutyrhynchos) from southwestern Sweden were studied in 1979, 1980, and 1985. Body condition, as indicated primarily by lipid deposits, declined during the flightless period. This decline was probably more the result of a strategy to recover flight capability rapidly than the result of stress. By metabolizing stored lipids, birds may be able to seek refuge in habitats offering protection from predators, even if food in such habitats is scarce. During the flightless period, food quality did not affect the growth rate of the primary feathers. But when exposed to low protein food, even after recovering flight capability, birds, especially males, developed shorter wing feathers; this feather shortening may reduce their condition capacity, i.e., their capacity to increase body condition without reducing their flight capacity in late autumn. A lowered condition capacity could lead to decreased survival of the ducks when exposed to severe winter conditions. Female Mallards demonstrated a higher condition capacity than males, which may contribute to the more rapid recovery of female primaries. Since the final length of the primaries is affected by food quality during molting, wing length is probably not a variable suitable for use in a condition index.

Annual changes in body mass and resting metabolism in captive barnacle geese (Branta leucopsis): the importance of wing moult

“…Therefore, birds were not able to compensate for the increased energetic demands during moult by increasing their food intake. They noted that mallards with only 1-3 flight regimes missing still continued to exhibit what they described as 'secretive behaviour', and still continued to lose body mass, indicating that the birds were aware of their vulnerability to predation whilst flightless (Pehrsson, 1987;Adams et al, 2000). The captive geese showed a marked difference in behaviour during the flightless period of the wing moult, S. J. Portugal, J.…”

“…In the wild, this period of flightlessness could present several problems for the geese, such as restricting their normal capacity to forage and escape predation. Therefore, it is apparent that shortening of the flightless period has a selective value (Douthwaite, 1976;Owen and Ogilvie, 1979;DuBowy, 1985;Pehrsson, 1987;Fox and Kahlert, 2005).…”

“…Mass loss during wing moult has been documented in several waterfowl species, including the Russian breeding population of barnacle geese (van der Jeugd, 2003), Barrow's goldeneye Bucephala islandica (Van de Wetering and Cooke, 2000), greylag geese Anser anser (Fox and Kahlert, 2005), mallard Anas platyrhynchos (Pehrsson, 1987), Eurasian teal Anas crecca (Sjöberg, 1986) and South African shelduck Tadorna cana (Geldenhuys, 1983).…”

Energetics and Nutrition of Molt

“…Milder forms of malnutrition may result in shortening of the final length and (or) mass of a feather, but this response is not consistently observed either (cf. Pehrsson 1987;King 1991b with Berthold 1976;Hegsted et al 1941). Alatalo et al (1983) wisely cautioned against interpreting the shorter wings in first-year birds of many passerine species as evidence of nutritional constraints and suggest that a shorter wing length improves maneuverability in these birds.…”

Plasticity in moult speed and timing in an arctic‐nesting goose species

“…Poor body condition and subsequent energetic limitation can aff ect the moult process. Pehrsson (1987) showed in Mallards that moult is preceded by an increase in stored nutrient level, which can be used during the fl ightless period (Portugal et al 2007).…”