Sharon Mason, Accredited AABR Member
In May 2024, AABR hosted an excursion to Hurstbridge (Diamond Creek riparian zone near Ben Frilay oval).
Our Guide was Michael Smith, Naturalist and Educator with 14 people attending on an overcast morning.
Context
First, I will give a small bit of context of the area before I write about the walk and talk.
Hurstbridge town in the shire of Nillumbik is approximately 28 km to the North East of Melbourne CBD. It is a small urban area surrounded by Green Wedge i.e. it sits outside the Victorian Government’s Urban Growth Boundary – this means the private land outside Hurstbridge township is subject to restrictions on subdivision for now. This Green Wedge land consists of cleared land, horse paddocks, farmland, vineyards, hobby farms and bushland.
The below picture is a screen shot I took from the Victorian Government NatureKit website. In this picture the darker the green, the higher the relative biodiversity importance (this measurement takes into account the area’s importance for threatened flora, fauna, vegetation communities and vegetation condition). I have highlighted Hurstbridge in red with a red arrow. This picture shows the area surrounding Hurstbridge, which contains some exciting plants and animals and a reasonable degree of connectivity through the landscape.
The Excursion
Collecting data is the first step in a revegetation project Michael tells us. We set out listening and observing how animals are using the site. The idea is that one records information over time in this and other areas and builds up a knowledge of how animals use different plant species, configuration of species and structure of plants in the landscape. Then one can use this knowledge when creating habitat.
The setting: Diamond Creek flats have a scattering of old Manna gum trees (with hollows). We stand on a goat track, mown grass strip on either side, a created wetland on one side with oval beyond, a small bit of old revegetation the other, and the creek beyond. On the other side of the creek is bushland on private property. On the creek flats, there is a large amount of mown grass. The mown grass areas have a lot of potential to be transformed into more habitat and a much more interesting park.
We spent the majority of the time looking at the old revegetation (the plan was to look at more but time ran out). For birds, this area we looked at will only supply a part of their needs for food, shelter and mates. The bush block across the creek will be having a significant impact on the numbers and species and which species that can be seen on the public land. The amount of native vegetation and type across the broader landscape will also be affecting what is seen in this small patch.
Much discussion was had of behaviour and what different birds liked and didn’t like.
A few bird examples:
- Spinebills: midstory (Acacia dealbata) dives down to (Corea sp.) to feed on nectar and flies up into the eucalyptus canopy.
- Superb Fairy Wrens: likes the dense low vegetation (Lomandra longifolia, shrubs, exotic tussock grasses) and the abutting mown grass.
- Red-browed finch: will feed on the seed of the dense unmown exotic grass and seed in the mown lawn i.e. the exotic winter grass (Poa annua).
Photo: Jane Pammer
One section of the revegetation was not looking as good as the rest. A suggestion was made that it was missing shrubs and Acacia dealbata suckers due to the very thick layer of kikuyu grass (Cenchrus clandestinus). Spraying the kikuyu was suggested as a solution. It was then suggested spraying might kill the mycorrhizal fungi associated with the large eucalypt. (My thoughts: I presume the area was sprayed with glyphosate before the planting occurred, that the kikuyu is stopping a lot of water reaching the ground surface and its rhizomes are probably monopolising most of the water/nutrient/air supply in the top layer of soil. Thus, not helping the eucalypt or other existing plants and not providing any seed for insects/birds, i.e. is not great habitat and is expanding in area. Also, one way to encourage regeneration of existing plants or trigger germination of indigenous species in the soil bank is to create bare patches – spraying the kikuyu could be a step in this direction. I have no knowledge of the effects of herbicides on mycorrhizal fungi.)
Photo:Cathy Willis
Bioregions, Ecological Vegetation Classes (EVC’s), and NatureKit were all mentioned briefly. This Victorian Government information is useful. However, finding some good remnants of similar EVC is, I think, much more useful. This site is in Highlands Southern Fall Bioregion, the EVC is 18: Riparian Forest. In NatureKit the mapping is fairly broad scale, so you cannot rely on the exact location of your site being the particular vegetation class/s it is mapped as. If one decides ‘yes, I agree this is Riparian Forest’, one cannot then decide that the list of species provided is what is most appropriate to use for your site. When I read the list of ‘species typical of at least part of EVC range’ (quote from web site) Riparian Forest in Southern fall bioregion, many of the plants listed I would not expect to survive on this Hurstbridge site now. Note the word ‘part’ in the quoted words. Also, these lists only mention some of the species you may find. Michael says ‘it never floods here; it is not a proper Riparian Forest’. (My post talk thoughts: part of the description of Riparian Forest says ‘regularly inundated and permanently moist’, – this description no longer describes the Hurstbridge site. The site in the past would have been wetter, the creek is now very eroded and incised. If the bottom of the creek was less deep the site would be moister. As well, before colonisation the catchment of the creek would have absorbed much more of the water that falls, and this water would have slowly seeped through the landscape to the creek flats. Creeks that once ran all year round now do not, e.g. Smiths Creek, a tributary of Diamond creek, stopped running in summer in the 1940’s. Now the catchment is full of hard surfaces, gutters, drains, roads and roofs, with overgrazed and compacted land, so water that falls moves very fast across ground, gutters etc. into Diamond Creek and on to the Yarra. Also, the trend for this area, at present, is that rainfall is decreasing and the temperature is increasing.
Michael thinks the council should be planting to provide more habitat for some iconic butterfly species and also to do some interpretation on these species.
Some examples of interesting butterfly species:
Imperial hairstreak /Imperial blue (Jalmenus evagoras). The larvae feed on Acacia sp. such as immature (a few metres high) black wattle (Acacia mearnsii) and blackwood (Acacia melanoxylon). It is easy to see adults, larva, pupae and attending ants (Iridomyrmex sp.) all on the one plant. Adults feed on flowers of sweet bursaria (Bursaria spinosa). Late flying adults will feed on flowers of wetland plants such as purple loosestrife (Lythrum salicaria) and Australian gypsywort (Lycopus australis) when bursaria has finished flowering.
Moonlight jewel (Hypochrysops delicia delicia). The larvae use borer holes in Acacia sp. such as blackwood (A. melanoxylon), silver wattle (A. dealbata), and black wattle (A. mearnsii) to shelter in during the day and to pupate in. The attendant ants (Crematogaster sp.) also live in the borer holes. It is important for this species that acacias are left to mature and senesce. Adults feed on sweet bursaria flowers.
Two-spotted line blue (Nacaduba biocellata). ( Right) The larvae feed on lightwood (Acacia implexa) flower buds. Adults feed on sweet bursaria flowers.
Michael mentioned that in a block in suburbia with little connection to a larger natural landscape it can be hard to attract birds, but one can have an insect garden.
Michael created insect habitat in his backyard in suburban Reservoir. Some of the plants he used to attract insects were cut-leaf daisy (Brachyscome multifida), common everlasting (Chrysocephalum apiculatum), Pelargonium sp., Dianella sp., hop goodenia (Goodenia ovata) and a range of indigenous grasses – Poa sp, kangaroo grass (Themeda triandra), wallaby grasses (Rytidosperma sp.). This small planted area attracted native bee species, wasps and common butterflies.
Thanks to all the people who came and asked questions and joined the conversations. I think you made the day work well. Thanks to Michael – his passion and enthusiasm I have not captured in the words above. I loved that Michael could point out hollows and what had nested there and where the baby powerful owls had called from, and on and on about so many animals.
We found a rain moth, and Michael said ‘that’s djeri’ (the grub which is found in or near the tree Wurun, Manna Gum). The Wurundjeri are the Manna Gum people.
Someone asked “is there any material they can read?”.
Michael has made 2 videos
Wildlife of the Nillumbik Shire (covers many animal groups including insects)
Nillumbik Pollinators: Bees, Flies and Butterflies.’(strictly insects)
Books
Habitat Management for Invertebrates – a practical handbook by Peter Kirby – this is a British book, but a lot of the logic holds for Australia.
Butterflies -Identification and life history by Ross P. Field – this book covers Victorian butterflies and gives distribution, habitat, life cycle, larval food plants in Victoria.
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