More on Currawongs or: "Attack of the Killer Malurus"
The material in this post was sent to me in an email from Denis Wilson (another member of COG) . It is too lengthy to be attached to my post as a comment and "off topic" for Denis's blog. However I thought the comments expressed were both interesting and helpful in understanding the biology of the Currawong so with Denis's agreement I have posted it here. It is under (a slightly modified version of) his original title, the reason for which is made clear at the end!
Martin
Hi Martin.
Thanks for the supportive comments re my attempt at establishing an "ethically neutral" view of Currawongs.
Re your statistical analysis, I am not blessed with a statistical approach to life. I am more of an empiricist.
Let me take you back a bit (before my time). The National Library has an excellent set of photos of early Canberra, which shows the central basin of Canberra (especially near "old" Parliament House, which was much photographed, of course). Circa 1927 the area was nearly bare.
One of the first grand parkland plantings was Telopea Park - where tall Eucalypt species were chosen. The other even earlier planting was Haig Park - but it was built specifically as a windbreak for the early settlement around Civic and Braddon. They chose dense conifers for that line of trees.
Since then, millions of trees, handed out free by Yarralumla Nursery, and Street Trees planted by "Parks and Gardens" workers, have matured all across Canberra.
There is now a suitable tall tree habitat for Currawongs, so they no longer need to travel to the tall forests of the Brindabella Ranges and Tidbinbilla to find suitable nesting sites.
Now to some personal history. I came to Canberra in September 1959. I went to school with a Kid who boasted of having collected the "First Currawong Eggs in Canberra" - from the tallest Eucalypt trees in Canberra at the time - in Telopea Park. That was circa 1962 or 1963.
However, I would say that the main change to Currawong presence in Canberra occurred between the years 1965 and 1980 (approximately). That was the time during which a sufficient stock of suitable breeding sites (tall Eucalypts mostly) developed.
.
Presumably even Currawong populations will reach what I would call "saturation" levels, when the demand for tall tree is satisfied. So the absence of suitable nest sites no longer limits the breeding season population.
Hence, there is no longer a need to be "vertical migrants" - as this seasonal variation was referred to, in the COG literature. Birds which feed in Canberra over winter no longer need to leave to find nest suites.
Obviously these comments pre-date the calamitous bushfires of January 2003.
There was of course, a much earlier change to Currawong populations, when the City Fathers promoted planting fruit trees and Berry-bushes, notably Pyracantha and Hawthorns and Cotoneaster to provide "winter colour". They inadvertently provided huge quantities of winter feed for Currawongs. (Also work for Bush Care volunteers).
One other factor to note is the adult Currawong diet is heavily based upon fruit, whereas the chicks require near-total high protein diet - worms, grubs, insects and baby birds.
So, my comment about the Botanic Gardens becomes relevant here.
Currawong predation of the much studied Superb Fairy Wren (Malurus cyaneus) population there (by ANU Biology Dept students) was very high, in the late 1990s. Some females would lay as many as 4 clutches in a season, before getting a single fledgling out of the nest.
When my father banded there in the 1960s, Currawongs would seldom be seen in warmer months, the season when the Wrens were breeding. So, that is another change I can testify to, personally.
While my memory predates your Statistics considerably, I would point out that there is the photographic record from even earlier, to demonstrate the radical change to the habitat of Canberra.
We have moved a long way from the ethical debate.
I feel sure, it really is a "faux-debate" about sentimentality, whereas, in Tennyson's phrase, "Nature, red in tooth and claw" ought not be concerned with advantaging one species over another.
Certainly I cannot support a "cull" based upon a human view of what's "nice" and what's not. Yes, Pigeons and Wrens are cute.
But just imagine for a moment, Martin, that you are the size of an aphid. We would all have a different view of which species are nice, and which are not, then. "Attack of the Killer Malurus" would be the top-selling Horror Movie.
Cheers
Denis
.
Martin
Hi Martin.
Thanks for the supportive comments re my attempt at establishing an "ethically neutral" view of Currawongs.
Re your statistical analysis, I am not blessed with a statistical approach to life. I am more of an empiricist.
Let me take you back a bit (before my time). The National Library has an excellent set of photos of early Canberra, which shows the central basin of Canberra (especially near "old" Parliament House, which was much photographed, of course). Circa 1927 the area was nearly bare.
One of the first grand parkland plantings was Telopea Park - where tall Eucalypt species were chosen. The other even earlier planting was Haig Park - but it was built specifically as a windbreak for the early settlement around Civic and Braddon. They chose dense conifers for that line of trees.
Since then, millions of trees, handed out free by Yarralumla Nursery, and Street Trees planted by "Parks and Gardens" workers, have matured all across Canberra.
There is now a suitable tall tree habitat for Currawongs, so they no longer need to travel to the tall forests of the Brindabella Ranges and Tidbinbilla to find suitable nesting sites.
Now to some personal history. I came to Canberra in September 1959. I went to school with a Kid who boasted of having collected the "First Currawong Eggs in Canberra" - from the tallest Eucalypt trees in Canberra at the time - in Telopea Park. That was circa 1962 or 1963.
However, I would say that the main change to Currawong presence in Canberra occurred between the years 1965 and 1980 (approximately). That was the time during which a sufficient stock of suitable breeding sites (tall Eucalypts mostly) developed.
.
Presumably even Currawong populations will reach what I would call "saturation" levels, when the demand for tall tree is satisfied. So the absence of suitable nest sites no longer limits the breeding season population.
Hence, there is no longer a need to be "vertical migrants" - as this seasonal variation was referred to, in the COG literature. Birds which feed in Canberra over winter no longer need to leave to find nest suites.
Obviously these comments pre-date the calamitous bushfires of January 2003.
There was of course, a much earlier change to Currawong populations, when the City Fathers promoted planting fruit trees and Berry-bushes, notably Pyracantha and Hawthorns and Cotoneaster to provide "winter colour". They inadvertently provided huge quantities of winter feed for Currawongs. (Also work for Bush Care volunteers).
One other factor to note is the adult Currawong diet is heavily based upon fruit, whereas the chicks require near-total high protein diet - worms, grubs, insects and baby birds.
So, my comment about the Botanic Gardens becomes relevant here.
Currawong predation of the much studied Superb Fairy Wren (Malurus cyaneus) population there (by ANU Biology Dept students) was very high, in the late 1990s. Some females would lay as many as 4 clutches in a season, before getting a single fledgling out of the nest.
When my father banded there in the 1960s, Currawongs would seldom be seen in warmer months, the season when the Wrens were breeding. So, that is another change I can testify to, personally.
While my memory predates your Statistics considerably, I would point out that there is the photographic record from even earlier, to demonstrate the radical change to the habitat of Canberra.
We have moved a long way from the ethical debate.
I feel sure, it really is a "faux-debate" about sentimentality, whereas, in Tennyson's phrase, "Nature, red in tooth and claw" ought not be concerned with advantaging one species over another.
Certainly I cannot support a "cull" based upon a human view of what's "nice" and what's not. Yes, Pigeons and Wrens are cute.
But just imagine for a moment, Martin, that you are the size of an aphid. We would all have a different view of which species are nice, and which are not, then. "Attack of the Killer Malurus" would be the top-selling Horror Movie.
Cheers
Denis
.
Comments
I just read the stuff on your blog re the Currawongs. We have been chasing one recently which was attacking our crested pigeons. It was quite brutal and persistent. My daughter is now very anti-Currawong, but we did have a bit of a discussion about the ethics of intervention.
A couple of observations.
Dennis Wilson’s reference to photos only goes back to 1927. My understanding is that at this time this area had been cleared of eucalypts for sheep farming. The habitat had in fact already been modified by the homos. Perhaps Currawongs were here and had been reduced in number due to habitat destruction? I doubt you could source anything now to see what the situation was say in 1850.
We have often had discussions on ‘good evolution’ and ‘bad evolution’
In most things, diversification is good, but should we support ‘weak’ species?
What is the natural environment?
To many of us, it is the one we first see or are used to. Hence the fact that many around Canberra ‘pine’ for the old forests that burnt down….
Back in early 80’s we were in Tasmania. The Franklin Dam was a hot issue. Besides doing a tour down the Gordon river, we also went to Strathgordon to have a look at the hydro works and the Lake Pedder dam. I recollect that we did some group tour through the power plant with hydro Tasmania and were taken to various lookouts. Of course, the topic of the Franklin dam was raised and discussed. There we were standing on the dam wall, looking over Lake Pedder and having a discussion of the merits or otherwise of hydro power and high conservation areas. One woman listened intently to the conversation, taking in the view before saying something along the lines of ‘oh well, I hope they never do anything to spoil this beautiful place’. My wife stamped on my foot to shut me up as my eyeballs rolled so far I saw the back of my skull.
I would also add that I like Dennis’s view on things depending on your point of view – A lion hunt is a magnificent thing to behold – unless you are a wildebeest.