A Comparative Analysis of the Nutritional Quality of Mixed and Exclusive Fruit Diets for Yellow-Vented Bulbuls

Abstract

Yellow-vented Bulbuls (Pycnonotus xanthopygos) were fed a mixed diet of four fruit species (Rhamnus alaternus, Lonicera etrusca, Rubia tenuifolia, Ephedra aphylla) and diets containing each of these four fruits separately. A mixed-fruit diet proved no more nutritious than a single-fruit diet, and all the birds lost weight at the same rate regardless of diet. Birds fed a mixed-fruit diet assimilated less protein than those fed exclusively on Rubia and Rhamnus fruits, and assimilated more energy than those fed exclusively on Ephedra fruits. The apparent metabolizable energy (AME) in bulbuls fed a mixed diet (0.73) was higher than in those fed on Rubia and Ephedra (0.69 and 0.61, respectively) but lower than in those fed on Rhamnus (0.82). Protein content alone does not explain loss of body mass. However, lack of specific amino acids, or high potassium to sodium ratios, may cause mass loss. In addition, a mixed diet of four fruit species may not prevent the accumulation of secondary compounds to a damaging level resulting in low protein assimilation.

The integration of energy and nitrogen balance in the hummingbirdSephanoides sephaniodes

“…to be correlated with food habits, as similar low values have been observed in nectarivorous honeyeaters and sunbirds (Paton, 1982;Bradshaw and Bradshaw, 2001;Roxburgh and Pinshow, 2000) as well as in frugivorous birds and small mammals (Howell, 1974;Smith and Green, 1987;Izahaki, 1992;van Tets and Nicolson, 2000;Roxburgh and Pinshow, 2000).…”

Estimating multiple benefits from vegetation in mediterranean ecosystems

“…Mediterranean vegetation includes many species producing fleshy fruits that serve as food for many bird species (Izhaki et al 1991;Izhaki 1992;Herrera 1998;Greenberg et al 2007). We estimated the density of energy in fleshy fruits as an indicator of potential habitat value for birds.…”

“…Energy content per fruit was calculated from data on fruit size and nutritive composition by species (Izhaki 1992(Izhaki , 1998(Izhaki , 2002. Energy content per fruit varies in a fivefold range, between Phillyrea latifolia (lowest) and Rhamnus alaternus (highest).…”

Digestive efficiency of Knysna and purple-crested turacos fed varying concentrations of equicaloric and equimolar artificial fruit

“…Avian frugivores, in contrast to avian nectarivores, have been poorly studied with regards to the effects that different fruit sugar types, concentrations and molarities have on their digestive efficiency (Levey and Martínez del Rio, 1999;Levey and Martínez del Rio, 2001;Lotz and Schondube, 2006). Although fruit choice by avian frugivores may be influenced by a number of non-nutritive factors such as fruit colour, size and secondary compounds (Murphy, 1994), the bird's digestive ability and the fruit's nutritional value are considered to be important factors (Martínez del Rio and Restrepo, 1993;Johnson et al, 1985;Izhaki, 1992;Fuentes, 1994). Indeed, Worthington suggested that digestion is likely to be the most important restriction placed on avian frugivores (Worthington, 1989).…”