Inferring regional, habitat and phylogenetic patterns in caliochory from bird nests in a museum collection

Abstract

Coevolution of plants and animals may lead to features or behaviour that are mutually beneficial. This is exemplified by plant adaptations for seed dispersal, including caliochory, which is the dispersal of seeds by birds in nest materials. Caliochory is a recently identified seed dispersal mechanism and to date there has been no detailed analysis of characteristics that make seeds suitable for caliochory. Moreover, the distribution of this syndrome across regions, habitats, plant taxa or bird taxa has never been investigated. To test the hypotheses that the probability of seeds being incorporated in nest construction is influenced by bird phylogeny, habitat, region, plant morphology or plant olfactory properties, we examined plant materials in bird nests at the Natural History Museum (UK). Despite the age of this international collection (80–120 years) we were able to identify most of the plant materials to the level of family, genus or in some cases to species. We found that selection of material for construction and lining of nests varies among bird taxa but is also influenced by region and vegetation type. Linings of fluffy seeds were more frequently used in arid than mesic climates. Possible adaptation for caliochory among angiosperms appears more frequent in open, arid and disturbed vegetation than in closed and mesic habitats.