Context: 15.4km2 of steep river valley, remnant Eucalyptus woodland, degraded ex-farmland infested with introduced European Olive, and revegetation sites. Numerous recreational walking tracks and lookouts over the valley and down to the river. Includes Hardy’s Scrub on the the south side of Chapel Hill Road.
Final stop on the first City Nature Challenge day was a loop through Onkaparinga River National Park, starting at Gate 11 on Piggott Range Rd, following the fire track along the ridge and back along Sundew Ridge Hike.
Finding Bird species during the CNC is very much dependent on luck. I missed out on the Black Swan at Onkaparinga River Recreation Park, but added four species within the first few minutes on this hike. A female Crescent Honeyeater (Phylidonyris pyrrhopterus), which is quite common, a Yellow-faced Honeyeater (Caligavis chrysops), far less common, a Striated Thornbill (Acanthiza lineata), common but hard to get clear enough photos to ID on an overcast day, and finally an unexpected Collared Sparrowhawk (Accipiter cirrocephalus).
Through this section of the park there are few understory Plant species. Considering the density of vegetation higher up the river along the Echidna Hike, it seems likely this is due to historic farming usage, or an excess of Western Grey Kangaroos. Aside from the Eucalypts, the area is a repeating patchwork of Varnish Wattle (Acacia verniciflua), Sticky Hop-Bush (Dodonaea viscosa), Rock Wattle (Acacia rupicola), Kangaroo Thorn (Acacia paradoxa). A few Prickly Guinea-Flowers (Hibbertia exutiacies) are still present. The absence of understory allows large numbers of Bridal Creeper (Asparagus asparagoides) to proliferate. The occasional flowering Twiggy Daisy-Bush (Olearia ramulosa) adds some colour this time of year.
Even in this section of the park the Mosses cover much of the ground this time of year giving it a yellow-green colour. Like the other Plant species, these are mostly a few common species, repeating. I found at least 8 species without much effort on this hike, including Barbula calycina, Leptodontium paradoxum, Triquetrella papillata, Polytrichum juniperinum, and a Rosulabryum sp.
Breaking from the fire track and heading back along the Sundew Ridge Hike, the track runs along the side of a denuded hillside with views directly down to the Onkaparinga River.
Further along this track the vegetation density increases. On the high side of the track I spotted a Koala (Phascolarctos cinereus). These don’t seem particularly common in this park. This is only the 2nd one I’ve located over the last few years. Under the trees near the track I found a large patch of Slender Velvet-Bush (Lasiopetalum baueri). These only seem to grow in the area between this track and down to the river, always is large patches rather than individuals.
Along the track I found a great example showing the size range of two local Ant species. A relatively large Pony Ant (Genus Rhytidoponera) with a tiny Big-headed Ant (Genus Pheidole) chewing on its antenna.
Last of all, a species I was hoping to find, a small cluster of Early Sundews (Drosera praefolia). This particular carnivorous Plant puts up its flowers in April, which then senesce before its leaves emerge. It’s possible this is an adaptation that helps to prevent pollinators becoming ensnared.