Sunday, 24 September 2017

Warped weather extremes

It usual to focus on weather which is the obvious extreme of the variable being considered.  By this I mean the highest maximum temperature or the lowest minimum temperature.  However today I have looked at variations on this theme with highest minimum temperature and lowest maximum temperature.

The catalyst for this was the overnight minimum this morning (24 September) being 12.4o C, which is the highest minimum temperature recorded for Carwoola in September since records started in 1993.  (There are of course issues about day-minima vs overnight minima, and it is possible the temperature will drop below 12,4 by midnight thus reducing my recorded minimum for the day, but it is still notable.  I shall return to this point below)  This follows the maximum on 23 September of 28.4o C which was definitely a new high temperature (or maximum maximum) for the month.  So at least there is some consistency.

This chart shows the maximum minimum for each month for all years over the period and for the last two years.  (I have assumed that things will return to more normal levels after today.)  I have added an arrow to point to the September 2017 value
 I restricted that chart to the long term (ie since 1993) average and the last two years.  I did also look at a scatterplot of maximum minimum (maximin) x year to see if there was a trend (anything that might give me an excuse to rubbish soon-to-be-former Senator Malcolm Roberts must be explored).  Despite the 4 warmest years being 2017 and 2011-13 the value of r2 was pretty miserable at 0.2614, so there is no significant trend.

Having looked at warping in that direction I thought I should in all fairness check the opposite, minimum maximum (minimax), temperature for September.
For both the last two years the line for minimax is well above the long term average.  I would like to say "Cop that, soon-to-be-former Senator Malcolm Roberts!" but unfortunately there is no significant trend in those data and of the last three years 2015 ranks 12th highest out of 26 readings, 2016 ranks 13th and 2017 is 21st. The value of r2 was 0.0009, which is about the lowest level of that statistic I have seen!  So no trend (which doesn't mean that the soon-to-be-former Senator Malcolm Roberts is not full of it).

In undertaking this unnatural analysis I did come across a few errors in the data which I have fixed up, so there might be some small changes in series compared to what I have used in the past.  This doesn't really prove Trewin's Law (any interesting statistic is probably a processing error) since some of the other interesting values turned out to be correct.

On the subject of Trewin's Law it is possible that the starting point for this post is a great example thereof, in that the overnight minimum might not be the minimum for the day (as explained earlier).  I have tried to look at overnight minima by only looking at the time period earlier than 9am.  For various reasons I only have 2 Septembers (2014 and 2015) with times recorded as well as dates and temperatures.  In 2014 the minimum daily temperature recorded was 7.2o C while the overnight low was 11.4o C.  Thus it is possible that there was a high, but unrecorded, overnight minimum in years such as 2004 and 2010, both of which recorded a daily maximum of 27o C.  (Being optimistic, the previous recorder has advised that his minima were calculated for a day starting at 7:00am so it is likely that high overnight minima were captured for the day following.  He does also note "...had some curious minima not necessarily during the night. I think one day last month when it snowed we had a minimum of 1.2 degrees at 11.30.am.")

Saturday, 23 September 2017

It must be Spring!

In the past week I have added 6 species to my Garden Bird Chart for the year.  Some of them are migrants while others are just birds getting noisy and thus more visible.

However the point of this post is the growth that is happening with many of the plants we were given as assistance to regenerate the garden after the fire.  Thank you so much to the people and businesses which donated the plants: it is really pleasing to see things coming to life, especially after the appallingly dry weather we have experienced since March.

Here are some pix (I may add to this later, but had to expedite matters this morning).

The label on this tree has faded but it starts with 'Zelk' so I think it may be a Zelkova: if so it is going to need some pruning in later years as they get to 20m!
It is possibly unpromising to put an unknown-species tree early in the post but this is just beginning to get swelling the buds.
 A couple of snaps of what I think is a maple.  I like the hairiness of the buds.

 This is definitely a maple.
 Lowerdown this is a Sedum ....
 .... followed by Agastache ...
 ... and finally Rehmannia.
The last 3 species should all flower nicely and will be snapped when they do so.

Friday, 22 September 2017

Tawny Frogmouth update

The pair of Tawny Frogmouths which roost (most of the year) in our garden have yet again built a nest in the Big Yellow Box - Eucalyptus meliodora, not something from Playschool.

They were the latest starting of any year since I started recording full details in 2010.  There are a range of observational snafus (I found that link really helpful) for several years:

  1. I was actually aware of the nest in 2008, but the male was already in situ by that time.  
  2. For 2009 I noticed the skinny platform of twigs before a cloaca was placed upon it, but as brooding started 3 days later I had clearly missed the commencement. of the process.  
  3. 2011 marked a shift to a different tree.  I only realised this when the male went AWOL and I found him sitting on a nest about 40m away.
  4. In 2014 they were back in the old tree and I thought twigs started to be gathered very early.  However brooding started "on time" so I think the early start was just some windblown twigs falling into the designated fork.
So of the last 10 years I actually have 6 observations of the date of starting nest building which I regard as reliable.  I have been able to come up with some estimates of dates of starting nest building for the missing years as explained below, but don't regard them as anything more reliable than anecdotes.
  • I have looked at the set of dates for 2008 and the chicks didn't leave the nest until 27 November, far later (approximately 3 weeks) than any subsequent year except 2016 when fledging seems to have been delayed by the very wet Winter (which was still 9 days earlier than 2008).  Counting back from that 2008 date it  would seem likely that the male started brooding about 27 September 2008 which is even later than this year's record.  
  • Looking at 2009, 2011 and 2014  and counting back from the commencement of brooding gives possible dates for commencing nesting in those years in the 'normal range' of mid-late August.   
In contemplating what might be causing variations in the date of starting nest building, rainfall seems to be an obvious contender since it affects the supply of food.  I have looked at two measures of rainfall: total rainfall year to date (YTD); and Winter (June -August) falls.  The outcome is summarised in this chart (where Day of the Year is number of days since 1 January in that year).
I was a tad surprised at the poor performance of the Winter rainfall series.  It appears that an interpretation is that the record-breaking sogginess of 2016 didn't delay the start of nest building as much as could be expected.  (Just for fun I changed the 2016 Winter rainfall to see what happened: reducing it from 291mm to 210mm raised the value of R2 to that of the YTD series.  That way lies insanity.)

There are many other possible measures of triggering rainfall (eg: June plus July; May to July etc etc) but I don''t have the time to invent and test every combination. I also have a niggle that the variation in rainfall is relatively great compared to the variation in starting date which implies that something else (eg some measure of temperature) might also be involved.  Excel isn't up to that.

The next milestone in the breeding cycle comes when the male "assumes the position" on the nest,
... ending the nest building phase.  This next graph shows the dates of starting the two activities measured from the start of the year.

For the previous years for which I have good records nest building averages to about 18 days.  This year they took 14 days, equal to 2012. (That year the nest was not as visible since it was in the different tree so it is possible I missed one or two days with little material in the nest.)

Thus I have 5 reliable observations of the start and finish of nest building (2010, 2013 2015-17).  Again, I wondered if the various lengths of the nest building phase correlated with rainfall for those years.  Looking at total rainfall for the year to date the correlation with number of days to build the nest is strong at 0.76.  Restricting the rainfall to June - August gives an even stronger relationship at 0.94.  (Of course 5 observations isn't really enough to make any big calls.)  Adding in the least dubious value for 2014 improves the correlation with year to end August rainfall to 0.84 but reduces that with Winter precipitation to 0.88.  (If I assume I only missed the first day of nest building in 2014 the correlations rise to 0.91 and 0.95 respectively: but making changes like that leads to wearing a wrap-round jacket!).  I have summarised this in a graph (including 2014).
I have no idea why the values of R2 appear somewhat inconsistent with the correlation coefficients cited in the text, but do note the small number of observations.  The key point is that there appears to be a pretty good correlation between the length of the nest building exercise and the amount of Winter rainfall.

This is really an exercise in getting a baseline for looking at the timing of nesting behaviour of the birds.  5 - 6 observations isn't much data.  Inshallah I'll add to the data next year and or other folk who regularly monitor individual nests will be able to do their own analyses.

Following my posting a link to this post on Facebook a friend asked if I had looked at the effect of temperatures on these dates.  I hadn't done so but have now looked at a few correlations.  I decided that I would look at average maximum and average minimum temperatures (for June and July) against day of starting and length of nest building.  Of these the only correlation coefficient greater than +0.2 was average maximum temperature against length of nest building.  The coefficient was -0.39 which is not great, but does suggest that nest takes longer when the maximum is lower.

My data isn't robust enough to try to muck about with multiple regressions involving rain and temperature.

Thursday, 21 September 2017

Botanical reflections on "poetry"

In the days of my youth I played Coarse Rugby in England.  A consequence of this was that I was occasionally forced to visit establishments which engaged in commerce, with particular reference to beer.

As one of my team-mates (actually the vicar's son) said "You don't buy beer, you just rent it."  When visiting the return location (which in the case of a Watney House was possibly directly plumbed to the spigots) one was often regaled with witty ditties, many of which have been collected by the English broadcaster Nigel Rees.  One that has stuck in my mind was
"A poets ambition must be small,
to write his verse on an outhouse wall" 
(or words to that effect).

That reminiscence has been generated by a visit to the Glossodia site on our block today.  After looking at about 50 leaves I finally got my reward.  Two of the leaves in one area were accompanied by buds!
To rephrase the admonitory doggerel above:
A botanists life must be blighted
If stuff like that gets them excited!
My guess is that it will be another week at least before this proves it isn't a Caladenia.  I revisited the site 3 days later and found another 3 buds of this species WHICH ISN'T A CALADENIA!
Going to another site, quite close to the Glossodias I found some Microtis leaves.
At least one can justify excitement about Glossodia with the flowers being very attractive.  With Microtis - which as far as I understand is one of the few genera not even taxonomists have tried to merge into Caladenia (Saguaro are probably under threat) - the flowers are minute and pale green.

The area behind the Glossodia patch is rather heathy, on a particularly stony ridge.  To my great pleasure and surprise some of the Leucopogon fletcheri was in nice flower.

Nearby one of the most pathetic of the local wattles, Acacia gunnii was still in flower.  It is usually one of the first to come into blossom: perhaps when you are only 30cm high and sparsely flowered you start early to try to get a heads start on the big boys?
In the matter of "quite unexciting" Luzula densiflora could be considered a contender if looked at from a distance.  However i think getting a close up takes it into the "interestingly complex" category.
There were quite a lot of meat ants charging about on secret ant business.  Pleasingly they kept away from me.  When I got back home I found that a Chrysomelid Leaf Beetle had hitched a ride.  As they don't bite me I carefully put it out in the garden to do  its thing.
On the return visit I found a couple of buds of Microseris lanceolata (Yam Daisy).


Monday, 18 September 2017

Some garden flowers

Having given the wattles a run a couple of days ago I thought I'd put up some snaps of some of the plants flowering in ur garden at present.   Despite the almost total lack of rain and high winds.

The daffodils (and relatives) have been giving good service for several weeks but are changing a bit as the varieties bloom at different times.  As was intended when Frances bought them).

These are the relatives: two pale versions of jonquil.  Apart from looking quite attractive, if Perfumed Garden is your thing, these can be smelt for several metres (and if brought into the house can be overwhelming)..

 Small blue bulbous flowers - looking back I find my friend Alison suggested in the past this is Triteleia.
I'll note in passing that these flowers were being visited by hoverflies.  I saw my first butterfly for the season also (a Cabbage White, but they all count!)

A couple of fruiting plum trees appear to have survived, in part at least.
 So have a couple of flowering plums.  This one was getting some action from a honeybee ...
...  and looking very spiffy when backed by an unfortunately cloudless sky.

Saturday, 16 September 2017

Acacia Day - a little late

I didn't get out to take photos of the flowering wattles for the official Wattle Day so have decided that 16 September will be Acacia Day.  I have tried to find some photos of African What-used-to-be-Acacias (but following the taxonomic stoush of the Century (so far) have been renamed Vachellia and Senegalia) but all my snaps from Tanzania are ungood.  So we'll stick with the victorious Ocker Wattles.

To my surprise quite a few have survived the fire and are flowering nicely at the moment.

As is nearly always the case this season it was blowing a gale outside but hopefully these images will give the idea.  I have usually done close up first then a shot of a larger area of shrub/tree.

Acacia rubida: many of these bit the dust but this one is doing well.

 Quite a number of Acacia dealbata survived well.

 The most lurid survivors are Acacia mearnsii from the direct seeding.
 At a distance the very bright flowers stand out well against the relatively dark foliage.
 Not the best photo of Acacia pravissima but this is about the only one which survived.
The next day I found - OK noticed - a couple more of these, and as the wind was less intense was able to get some better images.


Tuesday, 12 September 2017

Winter Weather summary

I recently received a comment on my August Weather report (sorry, can't remember who) to which I replied that I would compile a summary of Winter in total.  I have finally got around to that.

For reasons I have described in an earlier post I define Winter as being July and August.  (In this area June seems to have more in common, both meteorologically and through observed natural history, with March and April than July and August.)

Rainfall

 As would be expected it was a relatively dry year, being well below average rainfall.  However it wasn't extreme.

Temperatures

My data series is missing reports of temperatures for most Winter days in 2001 and 2004 so those years are omitted from the series.  I - or at least Excel - calculated trend lines for the two series but neither of them shown a significant trend.  (The minimum series was closer to significance than the maximums.)

The maximum temperatures were very close to average.  The average minimum in 2017 was also close to the average average minimum (convoluted term shown deliberately to highlight depth of manipulation involved).  I think it interesting that the past 8 years have all been above the longer term average.

The most interesting attribute of Winter temperatures is whether there is a frost or not.  As explained elsewhere a temperature at screen height of 2oC indicates a temperature of 0oC at ground level.  I thus use 3 measures of frost:

  • A light frost (which my Dad used to call a ground frost) with a minimum between +2oC and 0oC;
  • A hard frost (which my Dad used to call an air frost) with a minimum equal to or less than 0oC; and
  • Total frosts ( the sum of the above).

In analysing the data this became complicated by the days on which it was apparent that values were missing (and had been replaced by 0).  I decided that days on which both maximum and minimum temperatures were  0oC were "missing values" while a minimum of that level was dinkum.  As a consequence the number of days per Winter became variable and I have decided to illustrate the 5 of recording days with a frost.
With due allowance for the impact of my messing around as described above, and noting the shape of some non-significant trend lines, I think that what this shows is the impact of the dry years from about 2001 to 2010 in giving a high proportion of hard frosts and the wetter period from 2010 to 2016 giving a higher rate of light frosts.  I shall see what Excel can do in the way of a regression of percentage of frosts against rainfall and update this post with the result.