The Use of Artificial Perches in the Restoration of a Degraded Coastal Environment in Southern Australia

Abstract

Artificial perches are a restoration tool used to accelerate the regeneration of degraded environments. They work by encouraging frugivorous birds to rest and defaecate seed in sites that lack vegetation. If these seeds can germinate and establish, then this may result in plant recruitment. This method was trialled for the first time in a degraded temperate coastal environment, which was located on the Younghusband Peninsula, South Australia. The potential effectiveness of artificial perches as a restoration tool was investigated by observing the frequency of perch use by seed-dispersing birds, by measuring seed deposition under perches and by determining the likelihood of subsequent plant recruitment under perches. The artificial perches were able to attract seed-dispersing birds. This was determined through direct observations and the use of remote cameras. In total, 24 bird species visited the perches, 9 of which were known to disperse seed. These seed-dispersers were not obligate frugivores but rather consumed fruit as part of their varied diets. During the peak fruiting period of summer and autumn, the spiny-cheeked honeyeater (Acanthagenys rufogularis) and the singing honeyeater (Lichenostomus virescens) were the species that most frequently visited the perches. These birds were important visitors, as they frequently consumed fruit and dispersed seed from a variety of plant species. The artificial perches effectively facilitated the dispersal of seed to the degraded site. Over 12 months, the quantities of seed collected beneath the perches were significantly greater than the quantities of seed that arrived in open areas of the degraded site (2161.2 ± 578.5 seeds/m2 compared to 0.32 ± 0.18 seeds/m2 [mean ± SE]). Most of this seed was deposited in summer and autumn, during the main period of fruit availability. On average, native plants accounted for 57.4% of the seeds received at the perches. To the benefit of restoration, the perches received the seeds from many native species (up to 13 species), including from the abundant and hardy shrubs Rhagodia candolleana, Myoporum insulare and Acacia sophorae. To the detriment of restoration, 42.4% of the seed deposited beneath the perches on average originated from the introduced shrub Lycium ferocissimum, which was likely due to its presence in the degraded site. This result indicated that perches have the potential to facilitate the spread of introduced fleshy-fruited species in degraded areas. While the artificial perches facilitated the deposition of many seeds, very few of these seeds were likely to recruit due to post-dispersal barriers. Recruitment potential was investigated for fleshy-fruited shrub species whose seeds were commonly deposited at the perches. Glasshouse and field experiments indicated that the establishment of these species was limited by recruitment barriers including poor germination and herbivory from grazing mammals. Recruitment may have also been limited by competition with introduced grasses. These factors combined would likely limit the recruitment of most species in the degraded areas of the Younghusband Peninsula. These findings suggest that if artificial perches are to be deployed to promote regeneration in the Younghusband Peninsula, then additional treatments will be required to help seedlings overcome post-dispersal recruitment barriers.