Bat flyout early March 2025

On 27 February I wandered to the small grassy area at Mullet Creek to check the fruit bats.  There seemed to be quite a few around, coming out nearly to Karbeethong Avenue, but looking up the Creek from Lakeside Drive showed few (whereas a full camp has 100s along Lakeside) so the camp is filling but has a long way to go.

Looking out at the Inlet about 1945 hrs on 3 March there was a lot of movement from the Mullet Creek camp of Grey-headed Flying Foxes.  The first two images show them heading out over Bottom Lake, but in many cases turning back and heading towards Genoa Rd (as apparent from the images).

We then went out the front of the house and there were good numbers coming direct over the house.  I suspect those that weren't aiming for a fig tree on Intervale Drive were heading for Shady Gully.

Looking further up Angophora Drive there was a large stream heading towards Genoa Rd and doubtless the forests on the far side thereof.  I noticed a fair amount of eucalypt blossom there when heading to the WWTP yesterday,

It was pretty dark by the time I got back to the lake view but it did seem that a fair stream had established heading at low level across the Inlet.

I do note that today was much cooler than other recent days so possibly the departure was earlier?

On 4 March I went down to Mullet Creek, arriving at 1945 hrs.  There was not a bat in the sky.  At 1952 hrs the first mammal poked its wing above the tree line and within a minute the sky was beginning to fill.

By 1955 the sky over the camp was full.  By counting the number of bats in portions of this image (totalling 40 sq cm) and expanding that total by the area covered by bats (220 sq cm) the image contains about 560 bats.

This image from 1957 hrs shows the extent of the swarm: they are basically swirling and  flying away from the camera.  In past years the flight path has been lower and towards the camera position.

The key point of this next image is the faint bats such as those shown in the ellipse: they are a secondary 'column' rising from further up the creek, suggesting that the extent of the camp on the ground is quite large.

The Wascally Wabbit would be saying "That's all, folks."  Within a few seconds at 2001hrs there was again not a bat in the sky.

Assuming that it takes a minute for the bats to fly out of view (very dodgy) and that my counted image only covers half the swarm (very dodgy) I end up with the camp currently comprising

 567 bats * 8 minutes * 2 proportion of swarm covered = 9072 bats (say 9,500 =/- 500).  The key element there is the short period to empty the camp: as the camp fills the flyout time will get a lot longer, and I would expect the proportion covered by any image will get lower.

In 2024 we noticed quite a few bats returning to the camp - probably coming back from the Howe - by routes over our house just before dawn.  So far I haven't seen any returns (most likely because the bats are not yet going across the Inlet).  On the morning of 6 March I did hear a few calls around 0615 but it was still too dark to see anything and the calls could have been coming up from the camp.