Why some tits store food and others do not: evaluation of ecological factors

Abstract

Paridae are among the bird families benefiting from food storing. However, not all its members hoard food. Our objective was to clarify the role of ecological factors in occurrence of food storing. We reviewed the data on major ecological characteristics of the Paridae species and analysed their association with the presence/absence of food storing. Our statistical model revealed that geography (distribution in North America) and taxonomy (genus Poecile) are better predictors of food storing than any of the studied ecological traits. Nevertheless, food-storing Poecile species inhabit mixed or coniferous woodlands with seasonal richness of food, while non-storing species tend to prefer edge and open habitats, where alternative food sources are available. Sociality and territoriality outside breeding season coincides with food storing. The analysis performed within the Baeolophus–Lophophanes–Periparus–Poecile clade with ancestral food storing revealed no factor except continental climate that would explain the persistence of food storing. The phylogenetic analysis of ancestral states of the studied characters allowed us to propose a possible scenario for the emergence of food storing in Paridae. (1) Food storing is not ancestral in Paridae and appeared only once in the common ancestor of the Baeolophus–Lophophanes–Periparus–Poecile group. (2) According to estimation of molecular clock in Paridae, food storing appeared before their radiation in North America.