The Tamarugo conebill (Conirostrum tamarugense) is a rare bird, endemic of the desert of northern Chile and southern Peril. information about its basic natural history, including its distribution and behavior is isolated and scarce. The objective of this work was to study the food preferences and habitat selection of C. tamarugense, during the breeding period. The study was conducted at the ''Pampa del Tamarugal'' National Reserve in the Tarapaca province, Chile. Diet, apparent digestibility and daily food requirements are described. Food availability and bird density were also studied in five zones within the reserve. Tamarugo conebill Is insectivorous and specialist, consuming preferentially larvae of Leptotes trigemmatus (Lycaenidae). Based on allometric relationships, we found that daily food requirement was similar to the expected value for a 10 g passerine. The five recognized forest zones present significant differences in foliage volume, leptotes's larvae abundance and bird. Birds preferred more profitable zones, with mature and unmanaged trees, probably because food resources are more abundant and starch costs are low. Apparently, population dynamics of C. tamarugense is associated with the Tamarugo forest history. We pointed that the conservation status of this species depends on the Tamarugo forests and associated insects.