When presented with resources that differ in quantity, many animals use a numerosity system to discriminate between them. One taxonomically widespread system is the approximate number system. This is a numerosity system that allows the rapid evaluation of the number of objects in a group and which is regulated by Weber’s Law. Here we investigated whether wild, free-living rufous hummingbirds (Selasphorus rufus) possess an approximate number system. The hummingbirds were presented with two experiments. In the first we investigated whether hummingbirds spontaneously chose an array containing more flowers than an alternate array. In the second we asked whether the hummingbirds could learn to use numerosity as a cue to which of two arrays contained the better reward. The birds did not spontaneously prefer an array containing more flowers. After minimal training, however, they learned to choose the more numerous array and could differentiate between arrays of five and seven flowers. These data support the presence of an approximate number system in the rufous hummingbird. It seems plausible that having such a system would enable much more efficient foraging in this species.

当呈现数量不同的资源时，许多动物会使用数字系统来区分它们。一种在分类上广泛使用的系统是近似数系统。这是一个数字系统，可以快速评估组中对象的数量，并受韦伯定律的约束。在这里，我们调查了野生的，自由生活的红褐色蜂鸟（Selasphorus rufus）拥有一个近似数字系统。蜂鸟进行了两个实验。在第一个研究中，我们调查了蜂鸟是否自发选择了一个比其他阵列包含更多花的阵列。在第二个问题中，我们问蜂鸟是否可以学习使用数字作为线索来说明两个阵列中哪个包含更好的奖励。鸟类没有自发地喜欢包含更多花朵的花序。然而，经过最少的培训，他们学会了选择更多的花序，并可以区分五到七朵花的花序。这些数据支持在红褐色蜂鸟中存在一个近似数字系统。拥有这样一个系统似乎可以使该物种的觅食更加有效。