Nectar Characteristics and food selection by hummingbirds.

Hummingbirds selected food in choice experiments based primarily on sugar concentration and secondarily on rate of intake and position. Sugar compositions had little effect on food choice, but the preferred sugar compositions appear to be the most common in nectars of plants visited by hummingbirds. Most amino acids in sugar water were not detected at concentrations found in nectars. Higher amino acid concentrations generally resulted in rejection. Hummingbirds did not necessarily select food in the laboratory to maximize feeding efficiency, but under natural circumstances similar choices could result in optimal feeding efficiencies. The determinants of food choice by hummingbirds provide a rationale for viewing factors important in plant competition for pollinator visits.