Nightbirds of the SE Corner

 After compiling a post about the Nightbirds of Gippsland I recalled that I had a set of data from Birdata covering my Mallacoota District and Bega Valley Shire.  I will label this area the "SE Corner".  The following snip from Google Earth shows the approximate boundaries of East Gippsland Shire (green boundary), Bega Valley Shire (pink boundary) and Mallacoota District (red boundary).  The Shires also extend into the sea but the wet bit is irrelevant for this project.

So I have "repeated" my analysis from Gippsland to cover the SE Corner.  The summary data from this is covered in additional pages in the Revised Google Sheet on Nightbird in the SE Corners.  I hope the tab titles make it clear which data is what. 

There are many ways of comparing the different sets of information.  From a purist view, the analysis is undoubtedly complicated by Birdata having taking in a proportion of eBird records up to 2021.  (I have no information about why the process hasn't been continued past that year, but suspect shortage of resources is at least partly to blame.)  

Data Access

Before getting to the results and analysis a crucial issue is getting access to the data.  This differs greatly between eBird and Birdata and resolving the various issues has caused the analysis to become rather iterative (a technically nicer description than "going round in circles").

eBird

Getting access to data reported in eBird at the individual record level is quite simple,  Send them a message seeking access for a sensible reason (eg "reporting bird information to the local community") and authorisation for access - valid for a year - is received by email quite soon.

The main issue with eBird is that the smallest area for which data can be downloaded is the equivalent to US County, which in Australia is LGA.  So I can get East Gippsland (~500k records) and Bega Valley (207 k records) Shires but have to get creative to filter data for Mallacoota District.  No conceptual biggy, but a pain.

Birdata

It is possible to get access to summary data (eg a species list for a defined period) for a custom area, such as the Mallacoota District, very easily from the Birdata website.  In making that comment as a general-interest punter I found myself unable to access some data for Powerful Owl and Barking Owl, probably due to their threatened status.  Fortunately an administrator was able to give me what I needed.

However I have found it impossible to get access to unit record data,  similar to that from eBird, other than by involving the staff of BLA.  While the staff are very helpful (and provided the core data for the SE Corner which I have used in this work) they cannot be expected to work "as and when" a single member of Birdlife, such as myself, comes up with bright ideas.  So when I wanted slightly different data I have had to work out how to extract it from that which I had.  Those processes are described below.

I have received some summary data for Gippsland from a colleague with greater experience in handling these data and by getting a trifle creative, have managed to fill the major gaps.  One unusual data item which emerged in this exercise was the very high number of reports of Southern Boobook in the Birdata East Gippsland Region.  This became more intriguing when the reports for East Gippsland Shire were considered: this showed 618 reports of Southern Boobook, which agrees very well with the 630 reports one eBird for this species in the Shire.  This left nearly 1500 records in the relatively small Wellington Shire.  My colleague had already investigated this (emphasis added by me):

"... this is due to repeated 2Ha 20 min surveys over many years at one location near Stratford. There are 1223 records for Boobook at this location where there has been one bird in residence in the garage for 6 years according to a note I found in one of the surveys. Which goes to show how careful we need to be when interpreting bird data surveys."

My overall feeling is that it would be good if BLA could provide more comprehensive data access as is possible with eBird.  However I recognise that this might involve significant resources (and possibly a change in philosophy) within BLA.

Other Systems

The two systems described above are those most widely used by birders but there are a few other systems used of which I describe, and discount for this exercise, a few below.

iNaturalist

An excellent US based system which I use for everything except birds.  The problem for birding purposes is that it is driven by photographs: not bad for flowers, fungi and reptiles but ungood for birds bouncing around in trees or out on the horizon!  No birders that I know use this system.

Government recording systems

Both the NSW and Vic Government wildlife agencies have in-house systems which are mandatory for use by their staff and contractors.  For recreational birders the systems are not user friendly for input, and I haven't tried getting data out for many years.  

The agency executives love them as they have everything under control and avoids conflict with policy objectives.  I don't include any data from these systems below, but suspect it is trivial in number of records compared to the two major birding systems.

Selection and presentation of data

Other than the summary Birdata information for Gippsland (both East Gippsland Shire and the Birdata East Gippsland Region, which also includes Wellington Shire) I also had access to a set of data obtained from BLA which included individual records for Bega Valley Shire plus postcodes 3891 and 3892 (which comprise the Mallacoota District)

Of course the data for Mallacoota District is also in both the Birdata East Gippsland Region/East Gippsland Shire and SE Corner sets.  As the Mallacoota District is not a simple shape for assessing the detailed data in the SE Corner database, I identified the records from this area by reviewing the location names and flagging those in the area.  I did this in a two stage process:

1. Reviewing and marking the names of locations with more than 45 records; and then
2. Sorting that file by latitude and checking the names close to marked records.

This is logically sound and appeared to give a sensible answer.  The calculation of the unduplicated numbers of nightbirds ((SE Corner  - Mallacoota =Bega Valley) + East Gippsland Shire = Birdata Sum) is shown in the page "Calc Birdata Total" in the linked Google Sheet.

For the eBird comparison I have simply added the totals for East Gippsland and Bega Valley Shires but have shown the Mallacoota data as I present that in some analyses.

Note that the species are presented in taxonomic order using a code I have developed to combine the order of species as shown by Birdata and eBird.  Hopefully the foolishness (hubris?) that has led to the two different systems will disappear in future as both Birdlife and Cornell have adopted the Avilist taxonomy.

Effort involved in Birding

I have previously investigated, for the Mallacoota District, the resource factors that might affect the birding data collected through citizen science activities.  An obvious finding was that the more effort put in, the more species are found. This will be particularly the case for Nightbirds where more than usual effort is required to go out at night and find the birds (with a possible exception of calling Boobooks).  There are many ways of illustrating attributes of the areas I am canvassing in this exercise.  A selection of these are shown in the page "Attributes of the areas" in the linked Google Sheet.  

It should be noted that this area of enquiry raises many opportunities to become diverted down unexpected avenues of enquiry which I often call 'rabbit burrows'.  There are more potential burrows here than in Watership Down, so I have tried to keep a focus, at the risk of not fully covering some key possibilities.

Clearly East Gippsland is much larger, with about 4 x the area, and 3 x the number of eBird checklists and number of records than Mallacoota District.  

Compared to Bega Valley, East Gippsland is about 3 x the area and the number of eBird checklists and number of records.  A most telling measure is the number of record/observer suggesting to me that there are more resident/regular eBirders in the 'rest of East Gippsland' than Mallacoota and more in both those than Bega Valley.

It wasn't possible for me to access, directly, the number of sampling events or observers for Birdata. For the SE Corner, where I had access to unit record data I felt that taking an event starting at a specific time and date at a specific location was a good indication of a specific sample event and counted the number of those events.  For both number of Birdata records per site and records per event Bega Valley is about 1/3rd the value for the Mallacoota records.  As with the eBird records I feel this indicates a much lower level of resident activity in Bega Valley than in Mallacoota.

A crucial point noted during my analysis was the difference in number of species per survey between (eg) the Birdata information for Bega Valley and the eBird data for Mallacoota.  This is summarised in the page '#Species X survey' in the linked Google sheet.  The differences are quite dramatic:

• For Bega Valley 48% of Birdata surveys report a single species and 72% cover 1 to 5 species.  The equivalent numbers for Mallacoota are 12% and 25% (for eBird) and 7% and 16% (for Birdata);
• The largest category of species counts for Mallacoota in both systems is 11-30 species per survey with 45% of surveys. For Bega that group comprises 14% of the total for Birdata.

For Mallacoota these findings match well with my knowledge of the users of the two systems.

Analysis of results

There are an almost infinite range of ways of analysing these data.  My approach will be to look at three aspects of the data for Nightbirds:

1. Compare the data for the two data systems for the whole project area;
2. Compare the data for the three survey areas looking at both data systems; and
3. Comment on the impact of timing of Surveys for the species .

I have also ranked the top 9 species (omitting Tasmanian Boobook) in ascending order of number of records as shown in the page 'Ranks' in the linked Google Sheet.  This means that the numerically largest rank (in this case 9) is given to the species with the greatest number of records which gives the correct appearance to the charts below..  I think the rather blunt approach of ranks is appropriate given the impact that collection practices might have on the precise values compiled.

Comparison of Data Systems

See page 'Totals both systems' in the linked Google Sheet.

An issue to note is that Birdata has imported some data, up to 2021, from eBird (when some criteria regarding collection protocol are met).  I have not (yet) investigated the impact of that in this project but in another project (looking at Pacific Gulled in the City of Port Phillip) it made a dramatic change to some results.

It is notable that 6 species have the same rank in both systems, and the largest difference is only 2.  I take this to suggest that overall both systems are "telling the same story".

The differences in number are a little more evident and more puzzling.  

A first issue is that there are many more eBird surveys in East Gippsland than Bega Valley but more Birdata Surveys in Bega than Mallacoota. I have attempted to overcome this by presenting reporting rates using number of surveys as the denominator.  

Excluding the Tasmanian Boobook, for eBird the reporting rates for Nightbird species are higher, often notably, in eBird than Birdata for 7 of the 9 species.  The notably high values are mainly for species with high site fidelity for roosting sites.  I am, and have been for a long time, intrigued by the low reporting rate in eBird for Tawny Frogmouth in Mallacoota.  I can offer no explanation for the relatively high reporting rates for Boobook and Masked Owl in eBird.  Possibly the established sites for those species are well known to visiting eBirders who put in time to visit those sites?

Comparison of Areas

The three areas are Mallacoota District; Rest of East Gippsland; and Bega Valley Shire.

The results for the areas are shown in the page "Totals and Rates SE Corner" in the linked Google Sheet.  There are marked differences between the results from eBird and Birdata.  In view of: 

• the reliance of the Birdata series on records with very few species, 
• the fact that I don't have access to measures of effort for the "Rest of East Gippsland" and 
• the confusion possible with some eBird 

I  will focus on the eBird data in commenting on the three areas in eBird.

As a first step I looked at the the 3 way differences shown in columns J to L in the page.  My first step was to look at the modulus of the differences (ie magnitude of the difference regardless of sign: -1.6 and +1.6 both show the same size of difference)   Adding those differences and summing the result gives:

Mallacoota - Rest of East Gippsland     1.56

Mallacoota - Bega Valley                      2.03

Rest of East Gippsland  - Bega Valley  2.35

Clearly the 2 Victorian areas are much more alike than either is to Bega Valley. 

My second step was to examine the eBird reporting rates for each species shown in columns G to I of the same page.  My basic approach was to identify the highest rates for each species and highlight those cells in yellow.  Where 2 (or all 3) areas were similar I marked the similar ones. In summary:

• Tawny Frogmouth: much higher reporting rate in Rest of East Gippsland than either Mallacoota or Bega Valley.
• White-throated Nightjar: Much higher rate in Mallacoota with the other two areas similar.  The species was reported from 43 localities in Mallacoota with the largest number of reports coming from Watertrust Road area (26 reports) and Shipwreck Creek area(22 reports).
• Australian Owlet-nightjar: all three areas close to a rate of 0.7.  As noted repeat sightings likely once a roosting hollow is identified.
• Sooty Owl: the 2 East Gippsland areas very similar rates, about double that of Bega Valley.  In Mallacoota, Watertrust Road area has most sightings (probably because it is drivable and powerlines make good sites from which to hunt,
• Australian Masked-Owl: the 2 East Gippsland areas very similar rates, about ten times that of Bega Valley.  Again, Watertrust Road is the source of the highest number of reports.
• Eastern Barn Owl: All three areas have - to me - surprisingly low rates with Rest of East Gippsland higher than the other two areas.  This possibly reflects the species preferring open country rather than forest.
• Powerful Owl: similar, modest, rates in all three areas.  Given the size of territory occupied by members of this species modest rates are not a surprise.  
• Barking Owl: Higher, but still low, rate in Bega Valley and not reported at all in Mallacoota.  ABG notes less common in Southern Australia.
• Australian Boobook: Highest rate in Rest of Eat Gippsland but Mallacoota similar(ish).  Much lower rate in Bega Valley.  Reported from many (256) locations in Rest of East Gippsland with a single observations for most localities.  In Mallacoota the localities with most observations are near accommodation (Gipsy Point and the Author's house!)

The author's impression of the habitats and topography of the various areas is that they are broadly similar in nature, with Mallacoota having a larger proportion of wooded country and Bega possibly having a higher proportion of foothills and higher country.  

I have looked at the habitat and prey preferences of the 9 species (excluding the Morepork as there are so few records) as given in the Australian Bird Guide (ABG) with prey preferences for 2 species coming from HANZAB as ABG is silent on those details.  These are shown in a page Habitat and Food in the linked Google Sheet.  I cannot see any reason in there for the differences in reporting rates as shown in the data I have compiled.

Timing of Observations

In my previous post on this topic I included commentary on the timing of observations of Nightbirds and feel this is an important subtopic for trying to understand the differences in reporting of this group of species. 

This section begins with a summary chart of the percentage of total number of events starting in three time ranges.  The choice of these ranges is explained in the previous post.  It should be noted that a fourth 'range' - "Time NS" is shown to account for records using the Historic protocol where start times are not known.

A second chart shows a similar chart but limited to the events in which a Nightbird was recorded.  The difference between the two charts is clear.

A notable point of detail is the higher proportion of daytime observations in the Rest of East Gippsland than either of the other two areas.  It is probable that this is related to the relatively high reporting rate of Tawny Frogmouths (65% of which in the Rest of East Gippsland were seen in the daytime).

I have also computed the correlation coefficients for the series of time observations for Nightbird events.  This gives a very high level of correlation between Mallacoota and Bega Valley and a lower (but at 90% still quite high) between the Rest of East Gippsland and both of the other areas.

Draft July Weather report

As the month has ended on a Thursday I am rather busy with other tasks for the next couple of days so have done a very concise report, and will try to add more detail in a few days.

In summary a slightly warm month, with a very wet start and a damp end but dry in the middle.  It was very windy later in the month.

Rain

The total fall (122.8mm) was almost exactly the same as last year (122.4mm) and well above the median.

It was not evenly spread, but almost all in the first three and last two days.

Every month so far this year has been well above median, and at the end of July we are already above the annual total for 18 of the last 48 years. Not surprisingly, my pro-rata estimate is producing an estimate well above average.  If this continues we will have the second highest annual fall recorded at my WS or the BoM Airport site.

Temperatures

The temperature anomaly was close to +0.5C with the minima more above average than the maxima.  The development of the final value shows a cold start to the month with the fluctuating close to the final value from mid-month.

A plot of daily extremes shows the minimum showing a number of very high readings and a cold spell in the middle of the month.  The maxima were generally a little above average (although the end of the month was cool/

Humidity

In essence follows the rainfall with high values at the ends of the month and low in the middle.

Wind

The longest run for the month 298km on the 22nd was the longest daily run I have recorded in July.  Together with the 228 (4th longest) on the 26th we got a well above average mean run for the month.  The highest gust (59.5 kph on the 26th ) was the fastest for a July day and 9th fastest ever recorded at my WS (the highest was 72.4kph on 7 September 2019.

Today at the Poo pits

 I do of course refer to the Mallacoota Waste Water Treatment Plant (WWTP), and thank East Gippsland Water for allowing birding entry to the Plant.  It is a very important site for birds in the area.  I try to visit at least once a month to stand a chance of ticking some duck species that are only seen there (at least as far as places I visit show).

Today I added 11 species to my July list for the Mallacoota District and I think 6 species to the overall District list for the month.  My checklist is here showing 32 species in total.  A few snaps follow.

When I took a photo of a female Scarlet Robin at the Airport recently the photos f the male bird were suitable to consider at the WWTP.  Today I got a nice snap of a male.

I then tried taking one with digital zoom turned on with my 400mm lens, and it came out not too bad, if you don't want to see the red breast!

Getting to the ponds the large pond was almost devoid of birds, possibly reflecting the depth of the water putting food plants out of reach.  There were still 3 Musk Ducks there.

This shows part of the horde of Hoary-headed Grebes on Pond 2.  There were far fewer than usual on ponds 3 and 4.  A good flock of Shelduck on the bank (and more swimming in Pond 1.

More Grebes, Teal and Black Duck on Pond 1.

I was disappointed to not be able to spot any Pink-eared Ducks nor Australasian Shovelers on any of the ponds today.  Both were here in fair numbers at the end of June.  Walking back down the road I was pleased to see a second Flame Robin on a fence: they are altitudinal migrants who leave the high country in Winter.

A habitat shot!

I was quite excited to see a White-necked Heron fly off the small dam.  They are not common in the District, especially away from the Genoa Flats.  Raptors were a little sparse with a Brown Goshawk seen and a Whistling Kite heard.  Parrots and Cockatoos were absent.

Some Natural History Snaps

 The first image is of a pair of Masked Lapwings which have nested across the road - much to the joy of our neighbours on whose lawn they used to nest!

On Wednesday I drove around the Airstrip where there were 6 Scarlet Robins, in pairs.

There were 4 Kookaburras in this group, but only 3 fitted in the image.  2 singles were elsewhere.

On the 26th we went for a walk along the Narrows.  This was a nice sight with 2 Little Black Cormorants, 1 Great Cormorant and, at the back, a Darter.  They had all gone when we returned, replced by 2 Little Pied Cormorants.

The real excitement began when we spotted this seal, about half way along the Narrows.  It  was very active, I suspect attending to a school of Salmon.

It seemed to rise up and throw something - presumable a fish.  Trying to stun it?  It made a huge splash!

Then a Sea-Eagle got in the act: the ripples on the right edge are where the seal had just dived.

Then a second Eagle appeared.  It looked to have browner plumage, so possibly a young bird?

Hmmm.  Both of these look pretty adult in the images.  They were quite active so now I am wondering if there were 3!

Nightbirds

 A recent post by another blogger commented in a Note towards the end of the post, on the relative frequency of recording sightings of Nightbirds across Australia on the Birdata system.  This showed that in Birdata the Tawny Frogmouth was the most commonly reported Nightbird in Australia, with Southern Boobook in second place.

That led me to do a similar analysis for eBird records for East Gippsland (as I have the data readily to hand).  This showed a rather different outcome with Southern Boobook being the most commonly reported “Nightbird”.  Tawny Frogmouth was second.  In correspondence, the author of the original post subsequently provided Birdata information for the Birdata East Gippsland Region (East Gippsland and Wellington Shires) again showing Boobook as the most common species.  These three sets of data are shown in the page ‘cf Birdata’ in this Google Sheet and are summarised in the chart below.  Note that some of the species in the page are omitted from the chart as having relatively few records.

I concluded at the time that the difference in frequency between Birdata and eBird was  probably a reflection of the fact that a high proportion of reports of the Boobook are based on hearing the distinctive and far-carrying onomatopoeic call of the species.  The typical call of Tawny Frogmouth is a quieter and less far-carrying “Ooom”.  Once a Tawny Frogmouth is spotted at a site – not easy due to them being camouflage specialists - repeat sightings are easy, especially in urban areas, as they roost in exposed positions, often in a very tight area within their territory.  (Boobooks tend to roost in dense vegetation so are much harder to see in daylight.)  I will return to this discussion at the end of the note.

In discussion of this Frances commented that she has seen Tawny Frogmouths many times but has never seen a Boobook (although she has heard them many times).  This led me to look at the timing of sightings of Nightbirds in eBird for East Gippsland (Shire).  For simplicity I defined “daytime” as from 0600 hours until 1800 hours.  A more rigorous approach would consider the change of sunrise through the year – at Mallacoota from 0736 in June to 0537 [0437 excluding DST] in December.  (If being obsessive,  it could also adjust for the range of times in East Gippsland: on 24 July sunrise in Mallacoota is 0707 while at Paynesville it is 0716.)  Efficient implementation of such refinements is beyond my computing skill, and would not, I suspect change the outcome in a significant way.)  The following chart shows the number of eBird Nightbird sightings by the hour in which the eBird survey was started.    

I have then calculated and plotted, in the following chart, the % of records for each species that were started in “daytime”.  Tawny Frogmouth stands out as having by far the highest proportion of daytime records.

I have hinted above at the need to bear in mind observer behaviour in interpretation of these data.  I have not attempted a rigorous analysis of the possible behaviours involved (and suspect that even for the eBird data that would be a major project) but the following anecdotes might be relevant.

As a general comment I am relying on the moderators of the Birdata and eBird system having satisfied themselves that records of Barking Owl are in fact those birds and not dyspeptic Jack Russells!

As noted above most Nightbirds are hard to spot in daylight.  Some species roost in dense vegetation (eg Boobooks) or hollows (Barn Owl and kin).  Others are very hard to find due to excellent camouflage when roosting (White-throated Nightjar).  Even the Frogmouth, Powerful Owl and Owlet‑nightjar can be difficult to spot, but once a roost site is known, often on a relatively exposed perch, they can often be seen there repeatedly.  For example:

• At my previous place (near Canberra) a pair of Tawny Frogmouths had a territory in our rural yard and I included this species in every list I completed for the site over 8 years. 
• Another Tawny Frogmouth roosted in a suburban garden clearly visible from a well birded urban park (and I am fairly sure included in many lists from the park).
• A Powerful Owl – a species of interest to many observers – took to roosting in an easily accessible site in the Australian National Botanic Gardens (ANBG).  Staff of the ANBG estimated that the presence of this bird brought an extra 400 visitors to the Gardens over a 2 month period of residence.
• Also in ANBG – one of the most popular birding sites in Canberra - Owlet-nightjars roost in hollows in trees, but emerge to bask in sunlight.  They use the same hollow for some time and people visit those places to add the species to their lists.
• For Southern Boobook the data collection for the Atlas of ACT Birds was interesting.  A first tranche of data showed the bird to be entirely urban – apart from one site in the Brindabellas where some birders had camped!  This was resolved to some extent by special night-time visits to the Brindabellas in peak calling season.

While I have not recorded the details, my observation of eBird records  when compiling regular reports on the birds of Mallacoota is that a high proportion of Nightbird records arise when people are driving to Mallacoota after dark and see Owls fly across the Genoa Rd.  These are logged as ‘incidental’ records.

Most other sightings of nightbirds in Mallacoota arise from targeted outings by birders going out after dark to places where the hunting birds perch on infrastructure.  Examples are the powerlines along Watertrust Road and the fence around the Airstrip.  (Even those are not guaranteed to sight the birds: on an outing during one of our Big Weekends 20+ birders – including some nightbird experts – traversed Watertrust Rd over an hour and didn’t see or hear a single bird.)

In terms of comparison between the Australian Birdata information and the Gippsland data it must be noted that the environments covered can have an interesting effect (which I have not come close to sorting out).  Taking the example of Powerful Owl (Powl), until the bird took up residence in ANBG, on the edge of the CBD, it was considered that, near Canberra, they were only found in the forest gullies of the Brindabellas.  A Powl also appeared later, reducing the Ring-tailed Possum population of Inner North Canberra for some 18 months (and leaving the remains on pavement as an easy guide to where it was currently roosting) .  I – and many other birders - listed a bird in Carlton Gardens on the edge of the Melbourne CBD (guano again giving a good hint) while in Mallacoota most reports of the species come from a forest gully only ~500m from the town centre. 

Summary

My summary of this note is that it again illustrates the risks of single-number statistics for natural phenomena. 

For serious consideration of nightbird statistics information about the times at which data were collected is essential. If the number of nightbird records drop is it because the number of birds has dropped or because there are less night time records?   

I would also regard information about the number of sites at which records have been made is very important.  If numbers of Powerful Owl records have dropped in Mallacoota is it because people are not checking the Pumping Station Track?  If the number of Tawny Frogmouth records rises, particularly for a small area, is it because one observer is studying the birds and reporting them every day from one site?

June 2025 Weather report

 A cold and damp month overall.  At least it wasn't windy!

Rainfall

 As with every other month this year we have exceeded the median fall for the month!  For June we managed 95.4 mm, 143% of the median fall for the month.  By the end of the month our fall for the year to date is  728.6 mm or 159.8% of the median fall for that period.  (Another way of looking at that is that we have already recorded more than the annual falls for 6 of the 47 years for which I have records.)  Here is a comparison of this year, last year and the median fall or the 7 years from my Weather Station (WS) at Angophora Drive.

Most of the rain came in the first half of the month.  The very small amounts later in the month are effectively dew condensing out of very humid dawn skies.

My pro-rata estimates of the annual fall for 2025 seem to be settling down around 1400 mm for the year in total.  If we achieve anything close to that it will be in the heaviest 5 annual falls since 1975 (including falls at the BoM Airport gauge.)

Temperatures

The anomaly ended the month at -0.53oC which is the first negative value since January this year.  The start of the year was particularly chilly.

My time series of values of the anomaly is very variable, but the moving average, which removes seasonality, shows a plateau effect, at a fairly high level, over the last 2 years

Looking at the daily extreme temperatures  shows the maxima to have fluctuated around the mean values while the minima have more frequently been low.

Minimum temperatures

The average minimum temperature at my WS was 6.23oC and the coldest record here was 2.4oC while the Airport recorded a lowest reading of 2oC - a frost - on 30 June.  The average was the lowest since I started my WS in 2019.  The extreme temperatures were definitely cold, ith 9 minima significantly below the longer term mean minimum (one very significantly below) and only 2 significantly above the longer term mean,

Maximum temperatures

The average maximum temperature at my WS was 19.96oC - very close to the longer term mean - and the warmest record here was 20.6oC on the 24th - very significantly above the longer term monthly average. Overall, maximums were about normal, with 4 records significantly above average and 3 significantly below.

Humidity

The relative humidity was above average for both standard times but the afternoon reading was below last years value - not surprising in view of the rainfall last June!

The daily humidity chart shows an overall high set of readings - with afternoon levels closer than usual to the morning readings.  

The drop in humidity on the 24th is interesting.  Plotting hourly humidity and maximum temperature shows them moving in very different directions.  Both are possibly an effect of the strong NNWly winds recorded on the day.

Wind

The average wind run for the month as a whole was very low - the average of 60km being close to 20 km less than the runs in the other 6 Junes for which I have records.  In contrast the run of 243km on the 24th was longest run I have recorded in a June day.

Tempest recording

A friend whose WS is connected to the Tempest network has given me access to that system.  It includes some additional variables to those from my WS.  

The system recorded 16 lightning strikes (within a 40km radius of Mallacoota which ).  I only have records for 34 months so can't say much about that, other than noting that cooler months are less prone to lightning strikes than summer (several Summer months have over 1000 strikes recorded and February 2025 recorded close to 7,000 strikes in that area).

The system also records solar radiation in a variety of ways.  The following chart shows that recent experience is for relatively low levels of radiation as would be expected given our rain (which requires cloud!)  I shall do a separate post with more details about my interpretation of these data.

May (and Autumn) 2025 Weather Report

Frances commented on the evening of 31 May that "Tomorrow is the first day of Winter." so it behooves me to comment on the summary of the last three months representing Autumn (or as those from the Evil Empire across the Pacific call it, "Fall").

Autumnal Review

My Weather station has now recorded data from Angophora Drive for 7 Autumns.  These are summarised in the page 'Seasonal Summaries' in this Google Sheet.  Summarising further:

• The average daily minimum temperature was the warmest, by 0.3C, of the 7 seasons.  It was 1.01C above the average of the 6 earlier years.
• The average daily maximum temperature was the warmest, by 0.9C, of the 7 seasons.  It was 1.31C above the average of the 6 earlier years.  
• (In both cases the 'runner up' was 2019.)
• Although the station is not well exposed to wind it is interesting that the wind run for the three months is the second lowest of the 7 years.  (This may reflect growth of garden shrubs rather change in the weather!)
• Rainfall was the second highest (90 mm below 2022) and still 150mm above the average.

Monthly material

The month was very wet (only 3 of 46 previous Mays recorded more rain) and warm (temperature anomaly of +1.14C.   Relative humidity was at the high end of the 7 years for which I have data (but not extreme - whether examined for the standard times or for the average of the month as a whole.  Wind run was very low: possibly reflecting a higher than usual proportion of BoM wind records from the Eastern half of the compass, from which my WS is fairly sheltered.

Rainfall

In a post on 23 May to the Facebook Group I commented:

"I was a little surprised yesterday morning at how little rain was being recorded on my WS compared to what I was seeing. On going to check the WS I found that the rainfall collector was full and the filter was blocked by green slime. Never had that happen before in the 12 years I have had the device. Removing the filter let the liquid run through, tipping the cup 10 times!

Comparing the WS records with my Nylex suggests it has been missing about half the falls in the last few weeks. (I am quite happy with records to the end of April.) A comparison with BoM records for the Airport and Gabo, and information from Marty suggests that doubling my records for 18-19 May will give a fair estimate of reality so I have done that. Recording immediately started to match what I was seeing."

So it is possible my records for the month as a whole are a little understated.  I totalled 156.6mm for the month, amounting to 214% of the median for May.  For the year to end May we are at 633mm which is 176% of median falls to the end of May.  Here is a chart of daily fall, including the adjustments described above (note that there are several days early in the month with a record of 0.2mm which barely show up in the chart):

The progress of my prorata estimate for the year is interesting.  Having had falls well over median every month so far this year it is not surprising the prorata estimate is high.

I have added a section at the end of this report comparing 2025 rainfall at the BoM Airport and Gabo Island sites.

Temperatures

The development of the anomaly (difference to long-term mean) shows a cool first few days followed by a warm spell, sustained to the end of the month.

A chart of daily extremes give a pattern consistent with the above.

A time series of anomaly values resembles the Alps. Using a 12 month moving average to remove seasonal factors shows that the series is rising, but applying a trendline to that series suggests it is dropping.  I think "wait and see" is the best option here!

There were no days with both extremes significantly below long term, and only 1 day with both significantly above.

Minimum temperatures

The average minimum for the month was 10.05C, 0.73C above the average minimum for May recorded on my WS.  The lowest I recorded in the month was 5.3C on the 20th: one of only 3 days significantly below the long term average minimum for May.  The highest minimum temperature was 14.9C on the 23rd: 4 days were significantly above long term.  Overall 22 minima were above average and 9 below.

Comparing with recent years the time series for average monthly minima over financial years shows a continuation of 2024-25 as being warmer that usual.

Maximum temperatures

The average maximum for the month was 19.67C, 1.54C above the average minimum for May recorded on my WS.  The highest I recorded in the month was 27.0C on the 6th: one of 10 days significantly above the long term average maximum for May. 3 days (5th to the 7th) were very significantly above average.  The lowest maximum temperature was 11.7C  on the 18th: 2 days were significantly below long term.  Overall 23 maxima were above average and 8 below.

Comparing with recent years the time series for average monthly maxima over financial years shows a continuation of 2024-25 as being warmer that usual.

Humidity

The records for the month were reasonably normal for such a rainy period.

Wind

See comment in preamble.

Extra: Rain at Airport and Gabo

This section arose from a feeling that rainfall recordings at Gabo were lower than I expected compared to those at the Airport.  For the year to date the 2025 ( to 28 May) falls recorded by BoM at the Airport and Gabo were 682mm and 478 mm respectively.  Comparing the daily falls over 148 days there were: 

• 78 days where both sites reported the same amount (mainly 0mm!)
• On another 54 days the difference was less than 5 mm one way or the other.
• On 13 days the Airport recorded greater than 5mm more than Gabo; and 
• On 3 days Gabo was more than 5mm above the Airport.

Three days stand out where the Airport recorded much more than Gabo which I think gave rise to my feelings of doubt:

• 8 February 42.4 mm vs 4.2mm
• 10 February 73.4 mm vs 10.8 mm
• 24 May 76.2 mm vs 49.4 mm

However I think that looking at the overall series I could not conclude there was any consistent pattern I could raise with BoM.

I did also look at Green Cape (GC) but found that 14 days had missing readings and for another 5 days the falls were cumulated over more than 1 day.  One of the missing data periods, in January, included a significant rain event (27 mm at the Airport, 14 at Gabo).  I also couldn't pick a consistent pattern between GC and either of the others where data was available for all three sites. 

My conclusion was that while the differences were surprising given the 2 sites are quite close (17km in a straight line) with apparently similar exposure and neither site affected by hills (on 8 -10 February the wind at Gabo was from SE, on 24/5 it was from NW but Howe Hill is ~8km away), explaining this was above my pay grade!