Possible Bittern Communal Roosting at Ellesmere

[Adam C]

Hi all.

A fishing contact of mine posted a pretty crazy recording this week of 9 Bittern (yes thats right 9) at the mouth of the Halswell on Thursday Evening. It was on his phone but clearly showed at least 7 or 8 birds all in flight together and several perched on top of shrubs in the raupo with their heads stretched up. He sees them there regularly but was rather blown away seeing 9 at once as anybody would be.

As mentioned Fraser Gurney, myself and Paul Francis had a look on Sunday morning and pretty easily found 4 birds. 2 in flight (together) and 2 feeding in the canal.

Been scratching my head a bit over this and was wondering if there was some kind of social breeding behavior going on but doing a bit of internet digging I found an article on Eurasian Bitterns suggesting they quite often have a communal roost at night arriving just before sunset.

Some extracts below:

'Harris (2006) also describes the use of wet reedbeds as
communal roost sites to reduce the risk of predation'

'Social interactions between Eurasian Bitterns were most regularly
observed during March, in the period immediately prior to sunset,
the time of year when the species became more visible, either due
to behavioural changes or increased numbers, than in midwinter.
Birds assumed an upright posture either at water level or
‘perched’ in the vegetation; the heads of several Eurasian Bitterns
could be seen above the tops of the emergent vegetation (Plate
3) in the ten minutes before and after sunset. Individuals would
occasionally tilt the head from side to side, giving the impression
of observing their surroundings. Kushlan (2011) suggested this
posture may allow the scanning of a larger feeding area. From
time to time, birds fluffed up neck feathers and swayed their neck
from side to side. Hancock & Kushlan (1984) describe this neckfluffing as part of ardeid courtship display; but here it appeared
to be an antagonistic display, given the proximity of other birds'

So I'm pretty sure this is what's going on here. It may not happen year round when birds disperse over winter or pair up for breeding but as appears to be the case here, at certain times of year, this does happen in areas where there are still enough Bitterns like Ellesmere which is pretty exciting in 2022!

Unfortunately, he hasn't responded to me sharing the link as wants to keep it a little under the radar (not a bad thing) but frustrating considering the importance of the sighting.

Lets keep it off facebook however as the birds are probably there for good reason. Lack of disturbance other than a few (hopefully) quiet fisherman.

Adam

[andrewcrossland]

Hi Adam, do you reckon you can post an aerial photo with a X marking where they were? Was it in the Raupo patches around the boat ramp at the road end past greenpark huts? Or the very end of the stop back where the cabal enters the lake?

I’m keen to know as I’d like to look at tue possibility of creating a cross-boundary wildlife reserve there.
CCC and SDC

Cheers

[Adam C]

I'll email you a map Andrew.

[Jan]

A few years ago there were 4 fledgling bitterns hanging out near the boatramp end of the canal, so birds most likely breed near there. I've seen birds flying over the canal on several occasions. The opposite side of the canal is hard to access and is most likely little disturbed by people.

[Adam C]

Might be one for you to follow up on Andrew but apparently, there was a Gun Dog Competition with Dead pigeon slinging and Gunshots, dogs and people all through the raupo in that exact spot this morning. My mate was there fishing and saw 2 bitterns flushed and vacate the area. Said it was bedlam. Few quiet fishos turned up for an opening day fish and were really pissed too.

These guys really couldn't have chosen a worse spot.

[Jan]

Isn't that area under DOC control? I thought they did those gundog trials at the Creamery ponds. The latter have recently seen all the surrounding trees felled and the ponds are now without shelter of any sort. I suppose this site will now be a subdivision duckpond, how can this happen? There needs to be some control over where duckshooters do these events and eventually duckshooting should be banned, like it has been in Australia [parts of]. There's no need for fish and game to protect sites for mallards to breed. They should be regarded as pests.

[andrewcrossland]

Haha! Interesting you should mention that - this may take 2 or 3 posts but I'll start at the beginning.............

I went out there today to have a look as I'm very interested in getting a cross-boundary willdife reserve created there and was keen to get some habitat pics and maybe catch a nice quiet shot of a bittern. I should have realised that a Saturday morning (despite the threat of trillions of midges) was going to see the site over-run with people....................

Yep, I counted 17 vehicles parked on the access track just west of the raupo area where most of the bittern sightings have been, and another 5 cars (with more moving there later), parked in a grassy area within the saltmarsh shrubland zone. There was even an admin tent set up. Loads of people and all of them with dogs. hmmm, ok.........

To be fair, the people were moving about relatively slowly and did seem to have their dogs under control - but they did cover a sizeable area and yeah, it was just a totally inappropriate activity at that particular place. There are actually quite large expanses of saltmarsh shrubland on private land around the margins of Lake Ellesmere, but well back (1000+m) from the shore, and aside from scaring a few starlings, sheep or hares, this kind of activity once-in-a-while could probably be run without any issue. But NOT where there's threatened and at risk birdlife present- and NOT in the breeding season.

Some pics:

cars along the track and people observing from a bank (red arrow) pretty close to the Bittern area (yellow arrow). It wasn't the usual boy-racer or swandri-wearing hunter crowd, these were well-heeled folks, with flash vehicles and no doubt included landed gentry, rural royalty and barons of industry within their number.

dog 1.jpg (162.14 KiB) Viewed 914 times

Pic of cars parked and a tent within the more open saltmarsh shrubland/saltmeadow/lowland wet grassland habitats on the edge of the denser bittern saltmarsh habitat:

Dog 2.jpg (243.11 KiB) Viewed 914 times

I just took these are record shots to document this incident, but I didn't really want to "spy" on them. The event was already in progress and the county line where I do in fact have a little bit of authority was 200m away on the other side of the canal (!!).

The dog club people did seem to be fairly well behaved and I didn't see anyone acting like a larrikan while I was there, but I didn't watch them for very long. Thankfully there wasn't a bunch of drones in the sky documenting proceedings?! That wouldn't have been too good. But, yep, a whole bunch of people and dogs walking around in the habitat was just a mad example of people focused on their hobby without any obvious idea of the impact of their presence, nor perhaps any appreciation of how it must look from a frightened Bittern's point-of-view......

This is a map of the area (yellow) where the people and dogs were: They may well have extended their footprint deeper into the core habitat, I don't know....(I really hope not!)

Dog 3.jpg (251.27 KiB) Viewed 914 times

I'll talk to DoC and Selwyn District Council about it and I know they'll be sympathetic, but don't be surprised if there's some significant push back from the dog club. And indeed, in 2020's New Zealand, the benefits of human outdoor recreation seems to trump consideration for wildlife and ecology in the public conscience. That’s why we prioritise and spend millions of $$ on cycleways and dog walking paths in this country and give minimal consideration to creating wildlife sanctuaries and refugia for species pushed to the fringes by the ever-expanding human recreational footprint. Excuse my rant!


more in the next post............

[andrewcrossland]

2nd post, so some pics of the birds scared away from the advance of people and dogs at The Halswell canal today

one of several long-flying Pukeko

Halswell 1.jpg (21.45 KiB) Viewed 903 times

one of several White-faced Herons

Halswell 2.jpg (25.17 KiB) Viewed 903 times

..........and a Bittern....

[andrewcrossland]

The interesting thing about the Bittern, and something that adds weight to the question by Adam C at the start of this topic around whether Bittern roost communally, is the fact that once flushed, this Bittern flew straight out over the lake and headed purposely at about 50m height in a SSE straight line toward kaitorete Spit (about 4.5 km away). I followed it through binocs and lost it to sight when it was easily 2 km distant. I compared birds visible on a headland to the east about 1.1 km away to estimate the smaller size (and greater distance of the bittern).

So aside from it actually leaving the Halswell Canal site entirely (and not just circing and landing in a an alternative raupo patch closeby) - this bird seemed to be engaging in a fairly definitive flight over water toward the far shore of the lake......... hmmm....... does that add weight to the theory that birds (juvensiles?) might disperse by day and fly back in to a roost at dusk (like Night Herons for example?).

Bittern 2.jpg (28.11 KiB) Viewed 901 times

Bittern 3.jpg (128.78 KiB) Viewed 901 times

Bittern 4.jpg (16.45 KiB) Viewed 901 times

some more info on this bird on my ebird log of the sighting https://ebird.org/atlasnz/checklist/S119745182

[Adam C]

Chatted to my contact yesterday who staked it out on Thursday Evening. He counted 5 birds all returning to the exact same spot right on last light so pretty conclusive re the communal roost!

Pretty crazy all of the above. Would not be surprising if the birds are put off returning in any numbers also considering its the start of the fishing season and vehicles will regularly be pulling up early morning over the next few weeks as it's a popular fishing spot. Although it's usually in fishermans interests to go about that activity as quietly as possible.