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Revista chilena de historia natural

Print version ISSN 0716-078X

Abstract

CARLOS, BOSQUE  and  PACHECO, M. ANDREINA. Dietary nitrogen as a limiting nutrient in frugivorous birds. Rev. chil. hist. nat. [online]. 2000, vol.73, n.3, pp.441-450. ISSN 0716-078X.  http://dx.doi.org/10.4067/S0716-078X2000000300007.

Fruit pulp is considered nutritionally inadequate for frugivorous birds because of its low protein content. Consequently, frugivores are expected to minimize their nitrogen losses as an adaptation to frugivory . In this review we examine properties of fruit and physiological traits of frugivores that affect their ability to subsist on fruit diets. Most tropical and temperate fruit seem to contain enough nitrogen to satisfy bird’s requirements if their food intake was adjusted to meet their energy needs, but requirements depend on body mass. Birds of larger body size should require foods having a higher ratio of nitrogen to energy than smaller species. However, digestible nitrogen may in fact be limiting because fruit pulp seems to contain considerable amounts of nonproteinaceous nitrogen and an amino acid composition that deviates from that required by birds. Both of these characteristics of fruit pulps should augment nitrogen losses of frugivores and consequently their needs when consuming natural diets. In terms of their physiology, we expect frugivores to maximize their nitrogen extraction efficiency from the diet and hint the possibility that low urinary nitrogen losses of frugivores might be related to a low metabolic rate. Minimization of endogenous fecal losses could be the most important adaptation of frugivores to subsist on nitrogen poor diets. It is not evident how specialized frugivores can have lower than expected nitrogen requirements when compared to birds of other dietary groups. We suggest several areas of research that should improve our understanding of the complex interactions involved in the regulation of protein needs of frugivorous birds

Keywords : frugivory; frugivorous birds; fruit composition; nitrogen requirements; nitrogen; protein.

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