Abstract:
The use of fungal rhizomorphs of marasmioid fungi (horsehair fungi) as nesting material, especially by tropical bird species, is a widespread but poorly documented phenomenon. I show in this first experimental examination of the physical properties of horsehair fungi, that the fungal rhizomorphs utilized by Icterus pustulatus have a significantly higher tensile strength and reduced water uptake than alternative fibres used to build nests. These results suggest an adaptive advantage for the use of marasmioid fungi in nest construction.