After abandoning our initial plan of Duggan Park due to high winds and the potential of falling branches, it was decided to head to a more sheltered site nearby, which proved to be a brilliant decision.
We surveyed four 2 ha plots along the escarpment, south of Picnic Point, between Tabletop Drive and Stevenson Street (Bridle Trail).
The site is primarily eucalypt open-forest consisting of grey gum, forest red gum, yellow box, brush box and narrow leafed ironbark. There are also patches of casuarinas and acacias. The understory has patches of shrubs, including lantana, and grasses. The area was very green and lush following recent rain.
Despite the windy day we observed a total of 34 species, all of which were fairly typical for the area this time of year.
The most abundant birds on the day were the yellow-faced honeyeaters (19).
The next most common were the red-backed fairy-wrens (13), the males looking stunning with their red and black plumage contrasting against a green backdrop.
Of note was the sighting of a collared sparrowhawk.
The adult bird conveniently perched in a tree near the car park. The bird’s notched tail and staring eye were able to be seen clearly, enabling it to be identified as a sparrowhawk rather than brown goshawk, a very similar looking bird also found in the area.
A striated thornbill was also sighted. These cryptic little birds forage high in the canopy and are easily overlooked
Contributed by Sharon Warne
Here’s the complete list for the day:
|Australian Brush-turkey||Alectura lathami|
|Brown Thornbill||Acanthiza pusilla|
|Cattle Egret||Bubulcus ibis|
|Collared Sparrowhawk||Accipiter cirrocephalus|
|Double-barred Finch||Taeniopygia bichenovii|
|Eastern Whipbird||Psophodes olivaceus|
|Eastern Yellow Robin||Eopsaltria australis|
|Golden Whistler||Pachycephala pectoralis|
|Grey Butcherbird||Cracticus torquatus|
|Grey Fantail||Rhipidura fuliginosa|
|Leaden Flycatcher||Myiagra rubecula|
|Lewin’s Honeyeater||Meliphaga lewinii|
|Little Lorikeet||Glossopsitta pusilla|
|Olive-backed Oriole||Oriolus sagittatus|
|Rainbow Lorikeet||Trichoglossus moluccanus|
|Red-backed Fairy-wren||Malurus melanocephalus|
|Red-browed Finch||Neochmia temporalis|
|Rufous Fantail||Rhipidura rufifrons|
|Rufous Whistler||Pachycephala rufiventris|
|Sacred Kingfisher||Todiramphus sanctus|
|Scaly-breasted Lorikeet||Trichoglossus chlorolepidotus|
|Specked Warbler||Pyrrholaemus sagittatus|
|Spotted Pardalote||Pardalotus punctatus|
|Striated Thornbill||Acanthiza lineata|
|Torresian Crow||Corvus orru|
|Variegated Fairy-wren||Malurus lamberti|
|White-browed Scrubwren||Sericornis frontalis|
|White-napped Honeyeater||Melithreptus lunatus|
|White-throated Treecreeper||Cormobates leucophaea|
|Yellow-faced Honeyeater||Caligavis chrysops|
The similarities between Brown goshawks and Collared sparrow hawks caused some discussion at the cafe afterwards, and so subsequently Scot wrote this:
What’s going on with these birds is an example of sympatric speciation. This is where you have one species and a segment within that species starts going its own way genetically. This can occur for a number of reasons but it’s not due to the population being separated by a geological event – that’s allopatric speciation.
A great example of that is in New Zealand. Originally there was what’s called proto-Kakas, which were the forebear of both the Keas and Kakas there now. When the mountains formed in the South Island (about 5 millions years ago) it split the proto-Kaka population and eventually gave rise to the Kea and Kaka that we know today. But this is allopatric speciation, the Collared sparrow hawks and Brown goshawks are sympatric speciation.
They both occur throughout Australia across a variety of habitats – there is no natural barrier separating the populations. Without reading any genetic studies, because the Collared sparrow hawk has slightly more specialised feeding habits, and because there are 3 subspecies of Brown goshawk recognised, but none for the Collared sparrowhawk, I would suggest that the Brown goshawks are basal and that the Collared sparrowhawks are an offshoot from them, rather than the other way round.
What constitutes something being different enough to be its own species is always up for debate. The more you drill into the biological species concept the less it stands up. ie one species can’t interbreed with another one and produce viable young. There are exceptions to this, and there may also be instances where populations believed to be different species could in fact interbreed and produce viable young but we don’t know because the populations are so far apart (and this could be in time as well as space), so the usefulness of this definition breaks down. It is interesting to consider that since many people have some Neanderthal DNA in them – Homo sapiens and Homo neanderthalensis can’t be different species under the biological species concept.
This leaves what is called the phylogenetic species definition – which is a combination of the morphological and evolutionary ones. The morphological species definition is based on morphological and biomechanical similarities; and the evolutionary one is based on genetic similarities and the likelihood of common ancestors. These can both be used to determine how similar or different animals can be; and then these definitions can be combined to give us the phylogenetic species definition. This tells us where a species sits in its evolution and classification in relation to others. Hence phylogenetic trees.
The morphological differences between the Collared sparrow hawk and Brown goshawk are enough to define them as different species under the morphological species definition, although they are obviously extremely closely related. Hence a recent speciation event I believe, and the main reason why there are no subspecies of the Collared sparrowhawk ie there hasn’t been enough time for them to evolve yet, but there has been with the Brown goshawk. It is also logical then that Collared sparrow hawks are the descendants of the first subspecies of Brown goshawks to evolve, and that they continued their own evolution far enough to eventually to be distinct enough to be their own species.
The habits and behaviours of these birds are now enough to keep the populations separated as well, and I’ve found no records of them hybridising, though I have with the Brown and Grey goshawks.