Provide supplementary food for wildfowl to increase adult survival
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
Background information and definitions
Well-fed animals are likely to be in better physical condition than those with too little food: having greater muscle mass and larger fat supplies to help them survive lean periods. However, it is worth noting that species that forage in groups can have dominance hierarchies, which alter the relationship between weight and fitness. For example Gentle and Gosler (2001) found that, amongst great tits Parus major in Oxfordshire, England, more dominant birds had a lower mass than subdominants, particularly when perceived predation risk was high. Birds with lower masses are better able to take off and therefore escape predators than heavier birds (Krams 2002). However, because of their dominance, they were able to usurp other birds from food resources when hungry. Care should therefore be taken when interpreting results which do not directly examine survival.
Krams, I. (2002) Mass-dependent take-off ability in wintering great tits (Parus major): comparison of top-ranked adult males and subordinate juvenile females. Behavioral Ecology and Sociobiology, 51, 345–349.
Gentle, L.K. & Gosler, A.G. (2001) Fat reserves and perceived predation risk in the great tit, Parus major. Proceedings of the Royal Society of London. Series B: Biological Sciences, 268, 487.
Supporting evidence from individual studies
A randomised, replicated and controlled trial at Karrak Lake in Northwest Territories, Canada, (Gloutney et al. 1999) found that female lesser snow geese Chen caerulescens caerulescens and Ross’s geese C. rossii used supplementary food to different extents during incubation and showed different physiological responses to food. However, both males and females of both species were either heavier, had heavier hearts, more body fat or larger flight muscles when fed, compared to unfed controls. Differences were apparent both after laying and at the end of incubation. Between 250 g and 400 g of cracked and whole corn, durum wheat or shelled rice was provided each day.Study and other actions tested
A study in a wetland reserve in Northern Ireland (McGeehan 2005) found that mallards Anas platyrhynchos were attracted to, and ate, ‘Wildbird Mix’ seeds provided. However, they dominated and excluded other species, so the mix was replaced with white millet seed. This was too small for mallard to eat, and so other species such as wigeon A. penelope and teal A. crecca were able to feed. The reaction of waders to the same feeding activity is discussed in ‘Provide supplementary food to increase adult survival – Waders’.Study and other actions tested