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Abstract. Burrow-nesting seabirds, such as the wedge-tailed shearwater (Puffinus pacificus (Gmelin)) physically and chemically engineer the soil of their colonies in a manner that is likely to affect plant growth and ecology. We examined this functional interaction by measuring the diversity, vertical structure and productivity of vegetation in shearwater colonies on Rottnest Island, Western Australia, and by comparing these with those in the adjacent, non-colonised heath. The colony supported a distinct, less diverse vegetation community and was dominated by short-lived, succulent exotics. An ecotone was present between the two communities. Across all species, vegetation was shorter and denser in the colony and individual species that co-occurred in both locations were stunted in the colony. The percentage of bare soil in the colony was double that of the heath. The productivity of a phytometer (Rhagodia baccata) was significantly higher in colony soil than in heath soil. In a glasshouse experiment, cuttings grown in colony soil had 337% of the root mass and 537% of the foliage mass of plants grown in heath soil. Field measurements demonstrated increased leaf set and foliage extension in colony plants. Seed germination from the colony soil (2674 seedlings m −2 ) greatly exceeded that of the heath (59 seedlings m −2 ). Dense, productive and species-poor colony vegetation supports the assemblage-level thinning hypothesis as the mechanism for vegetation change, but we argue that prominent colony species are simply better adapted to high nutrient loads and frequent disturbance. A model of vegetation succession is also proposed.

Invasive plant pathogens have impacted forest and woodland systems globally and can negatively impact biodiversity. The soil-borne plant pathogen Phytophthora cinnamomi is listed as one of the world's worst invasive species and alters plant community composition and habitat structure. Few studies have examined how these Phytophthora-induced habitat changes affect faunal communities.We examined bird communities in Banksia woodland with, and without, Phytophthora dieback in a biodiversity hotspot, southwestern Australia. Seven sites along dieback fronts, with paired 1-ha plots in diseased and healthy vegetation, were surveyed monthly for birds over seven months. Vegetation assessments showed that diseased sites had reduced plant species richness, litter, shrub, tree and canopy cover, high bare ground and significantly lower flowering scores, than healthy sites. Bird community composition differed significantly between diseased and healthy sites, although total bird abundance, total species richness and foraging guilds, did not. Average species richness of birds per survey and the abundance of brown honeyeaters, western spinebills and silvereyes was lower in diseased than healthy sites. The tawny-crowned honeyeater had higher abundances in diseased sites.Similarity matrices of habitat structure, flowering scores and bird assemblages were congruent, indicating that habitat structural differences were influencing bird community composition. Our results suggest that this pathogen is potentially a serious threat to avian biodiversity and especially for nectarivores, and populations in fragmented landscapes. Since elimination of the pathogen is not currently possible, management should focus on methods of preventing its spread until techniques to eliminate the pathogen are developed.

Summary 1.Studies of ecosystem engineering may use burrow volume and soil displacement rate to quantify the impact of burrowing vertebrates. Calculations of burrow volume from morphometric measurements have previously treated burrows as rectangular or elliptical prisms. 2. Here we use burrows of the Wedge-Tailed Shearwater (Puffinus pacificus Gmelin, 1789) to demonstrate a new method for collecting morphometric data, and for mathematically modelling burrow shape used to calculate burrow volume. 3. Our method improves on previous estimates by better estimating the cross-sectional burrow shape, and by accounting for some of the variation in burrow width and height. 4. Wedge-Tailed Shearwater burrows were parabolic in cross-section, averaged 1·99 ± 0·04SE m in length and had a mean volume of 0·06 ± 0·00SE m 3 . The shearwaters excavate at a rate of 7·75 m 3 ha −1 year −1 (10·51 t ha −1 year −1 ) which ranks them above many geomorphic mammals. We suggest that this warrants further investigation into the role of burrowing seabirds as ecosystem engineers.