Birdwing butterflies again

I posted a photo of a male Cairns Birdwing a couple of weeks ago with the comment that they are so common that “I rarely bother pointing a camera at them.” As usually happens in such cases, I proved myself wrong soon afterwards.

The occasion was my sighting of a female which I thought might be of the Northern species, the New Guinea Birdwing (Ornithoptera priamus), which shouldn’t be seen in Townsville according to the books. I then wanted to check that the local males weren’t (also?) New Guinea Birdwings but that meant getting a good look at the upper surface of the wings, which is not at all easy.

Birdwings and Ulysses on any rack of tourist-trap postcards lie around with their wings gaudily spread but in real life they do nothing of the sort. The wings slam shut as soon as they perch, presenting their much more discreet undersides to the gaze of predatory birds. Almost the only way of getting a photo of the upper sides from a wild swallowtail is to take a burst of shots of a hovering butterfly and throw away most of them. That’s how I got this one.

Cairns Birdwing
Male Birdwing butterfly

There are a few points of interest:

  • Getting a really sharp, clear photo by this technique is a fluky business. You need lots of light so the shutter speed can stay high enough to freeze the movement (I didn’t have that luxury), and enough shots that at least one of them is well composed.
  • It is definitely a Cairns Birdwing, not the northerner, because the large central black area has no green streak through it. That’s a little disappointing but not surprising.
  • The wings are catching the light at very different angles and show the same kind of apparent colour-change as the Eggfly. In this case, the bright yellow-green of the wing becomes bluish-purple when seen at an acute angle; it can look even more purple in flight, depending on the angle of the sun.
  • And this is an old, battered individual. The trailing edge of the left fore-wing is ragged, and the coloured areas have scratches where scales have been scraped off. This sort of damage is why I noted that the Lurcher (click here and scroll down) was rather elderly.

Harbingers of the Wet

Honeyeater
Juvenile Blue-faced Honeyeater feeding in the Poplar Gum

Birds have been visiting us in greater numbers than usual thanks to the simultaneous flowering of all our biggest trees, the poplar gum, paperbark and mango. Rainbow Lorikeets have joined our resident friarbirds and honeyeaters (the Yellow Honeyeaters are still around, by the way) taking advantage of the abundance.

In the last week or so I have heard (but not seen) both a Koel and a Torres Strait Pigeon (aka PIP) in my garden. Both are Wet season visitors and both are here earlier than usual, if only by a few weeks. Of course, our weather has not been following ‘normal’ patterns. (Nor has the weather anywhere else, and climate change is largely to blame.) So far we’ve had a warmer and wetter Dry season than usual (120mm in June-July-August, more than offsetting a dry April and May), although not wet enough to relieve our water restrictions.

Rainbow Lorikeet
Rainbow Lorikeet looking for his share

Home solar update

The 1.5 KW solar system on our roof has just passed a good round number in its total output – 12 000 kWh, or 12 MWh – and that’s a good enough excuse for another update.

We installed the system in May 2011 so it has produced an average of 6.26 kWh per day for five years. That’s a useful percentage of a household’s consumption: according to Ergon’s figures on the back of our power bill, the average consumption for a household like ours is about 20 kWh per day, so our panels are producing nearly a third as much as we use.

Of course, we use some of our solar power during the day and export the rest of it, and then use Ergon’s power all night, so our net benefit doesn’t quite reflect those numbers. I did the sums a year after the installation and came up with a figure of $700 p.a., with the expectation that that would increase if power prices increased. Using the same logic now for the five year period, we find:

  • Total produced = 12 000 kWh (6.26 kWh/day)
  • Total exported to grid ~ 5200 kWh, for ~ $2300 income
  • Total PV power used at home ~ 6800 kWh, for ~ $1700 savings
  • Total benefit ~ $4000

In 2011 I said:

All in all, making the best guesses I can for the unknowns, pay-back time for the whole project (PV system and switchboard) looks like being in the 5 – 8 year range. That’s perfectly acceptable … Of course, if the electricity tariff rises (hands up everyone who thinks it is going to fall? No, my hand didn’t go up either), pay-back time will drop accordingly.

The cost for the system was $3500. Even if my new figures on exports and savings are on the optimistic side, it looks like our system has paid for itself, just a few months ahead of the earliest date I anticipated.

That’s pleasing, of course. The thought that it will continue to  bring us that $800 p.a. benefit indefinitely is even more pleasing. So is the thought that we have done our little bit to reduce CO2 emissions, and that it has basically cost us nothing to do so.

Was there any downside?  Maintenance costs? Repair costs after the cyclone? None at all. It just sits there quietly on the roof, collecting photons and turning them into useable electricity, day after day.

For the record, the general tariff was 19.4 c/kWh when we installed the system five years ago, had risen to 30.8 c/kWh by July 2014 and has now (surprisingly) dropped back to 22.3 c/kWh. In May 2011 the “service fee” or “daily supply charge” was only $23 per quarter, whereas by May 2014 it had risen to 55 cents per day ($49 per quarter). It has continued to rise and is now $1.07 per day, closing in on $100 per quarter. The supplier is simply trying to maintain revenue in the face of flat or falling demand and the service fee is a favoured strategy – but that’s a topic for another day.