Peel Inlet from Murray-Serpentine delta— Photo:The Department of Water and Environmental Regulation
The Naturalists Club has a cottage on Cooleenup Island on the eastern edge of the Murray River Delta Islands of the Peel Inlet. Club members erected the building in 1983 and it is still decorated in a charming 1970’s style. Members have kept records over the years of birds, animals and plants sighted on the island and in the surrounding waters. The YNO (Yunderup Nature Observatory) has not been very well used for quite a few years now. The club had its own boat to get to the island but due to this downturn and ongoing maintenance costs of the boat, it was retired in 2014. The current caretakers, Roman and Lucy Mandyczewsky, ferried us to and from the island with their boat.
It was obviously time to do some more surveys so a small party under the leadership of Jolanda Keeble spent a very enjoyable weekend doing just that. We saw 41 species of bird, dolphins, nine species of mosses, lichen and fungi and also did a plant survey in which they compared what was present with a survey done in 1997-2000 (see Yunderup Excursion Species List for full list of species seen on the latest excursion.)
Unfortunately the island environment has been severely degraded over the last 15 years. This is thought to be in large part due to the Dawseville cut. This was constructed 20 years ago to flush the algal blooms – caused by phosphates from farming – out of the inlet. It has been successful in doing that but “the Dawesville Cut has had a profound influence on the hydrodynamics and water chemistry of the Peel – Harvey Inlet by increasing exchange of the waters of the inlet with the ocean thus magnifying tidal effects and changing the inlet from seasonally fresh to brackish system to a predominantly marine salinity system” ♦. This has resulted in many tree deaths and a reduction in the orchids and other wildflowers on the island. Because of the recent heavy rain the Murray river was flowing quite strongly and it was reasonably fresh. There was a lovely view of Kitchen Lake from the north window of the house kitchen. However all the old swamp paperbarks –Melaleuca rhaphiophylla– in the view were dead – they cannot grow in continuously salty surroundings. There are saltwater paperbarks on the island – M. cuticularis – and these are doing very well.
There are about 27 buildings on the island and this of course has caused weeds to proliferate. A book on weeds would have been much more useful to us than one on wildflowers! We went for two walks on each day and recorded 38 species of birds, 68 plants (of which 32 are weeds) and a few lizards and insects. The bull-ants Myrmecia gulosa are very common on the island and have distinctive volcano-shaped mounds, some up to 60cm high, to protect the nest from flooding.
There is not a lot of bush left on the island so we only saw a few wildflowers. Only one orchid out of a possible 23 and that was the yellow cowslip – Caladenia flava. There were lots of little orange drosera – Drosera glanduligera – flowering and a few purple tassels – Sowerbaea laxiflora. Hardenbergia creeper was seen in a couple of places.
We had lovely sunny weather so there were lots of birds around. Dozens of blue wrens everywhere, honeyeaters, spoonbills and many different types of ducks. There is a large osprey’s nest in the top of a flooded gum. The highlight for me was seeing a Horsfield’s Bronze cuckoo and a pine tree with over 20 Nankeen Night Herons roosting in it.
It was a delightful weekend with good food and good company. All residents on the island have been told that they will need to be off the island in 20 years time due to rising water. We hope to go again and would encourage other members to go and enjoy the field station before we lose the use of it.
Jonica Foss