Whitebellied sunbirds (Nectarinia talatala, Nectariniidae) do not prefer artificial nectar containing amino acids

Amino acids are the most abundant class of compounds in nectar after sugars. Like its sugar concentration, the amino acid concentration of nectar has been linked to pollinator type, and it has been suggested that amino acid concentrations are high in the floral nectars of plant species pollinated by passerine birds compared to those pollinated by hummingbirds. We investigated the feeding response of whitebellied sunbirds (Nectarinia talatala) to the inclusion of amino acids in artificial nectar (0.63 M sucrose solution). The response to asparagine, glutamine, phenylalanine, proline, serine and valine, amino acids commonly found in floral nectars, was tested individually and using a mixture of all six amino acids, at two different concentrations (2 and 15 mM). Sunbirds showed no significant preference for amino acids in nectar, or avoided them, especially at the higher concentration. We discuss these findings in the light of the nitrogen requirements of nectarivorous birds and data on amino acids in floral nectars.