Use of spider silk for nest building by the Regent Honeyeater Anthochaera phrygia and the Helmeted Honeyeater Lichenostomus melanops cassidix

The Regent Honeyeater Anthochaera phrygia and Helmeted Honeyeater Lichenostomus melanops cassidix have both suffered a dramatic decline in number and reduction in range as a result of extensive habitat clearance. As part of recovery plans aimed toward reintroduction to the wild, both species are part of an intensive captive breeding program being conducted at a number of institutions, including Taronga Zoo, Sydney. These honeyeaters incorporate arthropod silk into their nests, as has been reported for other small passerines. However, little is known about how birds choose and use the silk that they collect during nest building. We presented breeding pairs with cribellate silk from the Black House Spider Badumna sp. and ecribellate silk from the Golden Orb-weaver Nephila plumipes or ‘clean/fresh’ and ‘dirty/old’ Badumna sp. silk and observed which were taken by the birds. Lichenostomus melanops cassidix showed a preference for the cribellate silk of Badumna sp., always selecting this silk type first. Nevertheless, the ecribellate silk of N. plumipes was also taken occasionally. Anthochaera phrygia, on the other hand, showed no clear preference for the silk of either Badumna sp. or N. plumipes, though they did display a preference for clean/fresh Badumna sp. silk, which was selected more often than dirty/old Badumna sp. silk. Dissection of an A. phrygia nest indicated that silk is used within the nest to help bind the other nest materials. These observations suggest that passerines may select silk non-randomly for use within their nests, possibly preferring clean/fresh cribellate silk.