Thursday, 22 March 2018

Bats get more

We have gone to Mallacoota for a few days.  After the very dry weather of the last three months it felt strange to spend about 80% of the trip driving through drizzle or even light rain.  This image comes from Australia's answer to Eastern Wyoming - the area between Cooma and Nimmitabel.
The temperature in Nimmitabel was 11oC at close to midday.  In contrast at the Eden end of Imlay Rd it was 19oC !

As we drove in from Genoa there was a fair bit of blossom on the Angophora costataI now believe this is Corymbia gummifera - Red Bloodwood - based on a comment by a Vic. DoE officer.  Looking out across the Inlet the far side is very white: should be a good bat flight in that direction tonight,
 We did a short walk on Coulls Inlet where Chestnut Teal were numerous.
 A few Grey Teal were available for contrast.
 I walked down to the bat roost and they got very agitated and noisy about my presence.  Looking down, there was bat poop everywhere.
 Getting a look further into the colony, and listening to the amount of noise, I think there are at least as many as in early February, and possibly more.
 Back at the house again and 4 White-headed Pigeons were waiting for me.  These two are an adult and an immature.  The other two were even greyer s I suspect were very young.
I wandered out at 1900 hrs to see what the bats were doing.  It appeared they had started to fly but were all heading to the West - going downwind. They seemed to be coming up through the gully and even over to the ridge to the South.   However by1915 the ones closer to the Inlet started to fly and they were coming over the house and heading across the Inlet.  It is now 1945 and totally dark but 2 minutes ago I could just pick out bats flying over.  Here are a few photos.  The density of the flock was pretty constant over us for at least 20 minutes and the flight to the West was about the same for the time before they started coming this way.


 As far as I could tell the colony occupies the entire area of trees which I have whited out in this snip from Google Earth.  The area is 30 ha (or 300,000 sq m).  Assuming 1 bat per 5 sq m  - which I think is conservative based on the image above - that gives 60,000 bats.  I now have advice from a Vic Dept of the Environment officer that the size of the camp this year was, when he last measured it, 6.4Ha (and the record is 11.5Ha).  He said that its difficult to count the bats accurately but it would be in the 10s of thousands.
It is now the morning of the 23rd and the noise from the colony is clearly evident.  I couldn't hear any flying over when I just checked. Completing the sensory checklist, olfaction is positive - the smell is detectable at the house!

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