This morning, while I was sitting on the window seat with a cup of tea and my laptop, I witnessed what I consider to be an amazing event. I’d noticed from the kitchen window that the Little Black Shags were out in the bay again. Although I’d been told that they sometimes visited Shoal Bay, the only other time I’d noticed them was at dusk on 31st May when I took the photo below. On that occasion, there were ~200 of them on the sand bar running (west) out from Lansdowne St. They appeared to be resting, and flew off as I quietly approached to take photos, much to my disappointment, as I hadn’t wanted to disturb them.
I was pleased to see that they were out in the bay again, and got out my binoculars to watch them. Unlike the previous sighting, this time they were sitting on the water in a tight group. There were several black-backed Gulls coming and going nearby, but the Shags appeared just to be sitting in shallow water in the middle of the bay. After watching them for a bit, I noticed that they had begun to move, as though they were floating out with the tide. However, since the tide was coming in (about halfway already), they must have been actively paddling. Instead of remaining in their group, they began to stretch out, so that by the time they were level with our place they were almost in single file. This allowed me to count them as they went by, ~100 ± 10, stretching out over perhaps 200 m. They appeared to be swimming in a long line towards the end of the Lansdowne sandbank about 500–700 m away, where I had seen them previously, so I assumed that they were going to roost there as the tide flowed in. They then went out of sight behind some trees, and I got on with what I as doing. After several minutes (perhaps 10?), I became aware of a lot of activity at the edge of the water out from our place. It was the Shags again, this time at the southern side of the bay, and moving back up. They were flying very low over the water at the edge of the tide, landing and diving under immediately. It would have been very shallow, and the activity was frenzied. Birds were continually flying, landing & diving, coming up, and flying a little further as they headed up the bay along the water line. They reminded me of what I think rugby players call a “rolling maul”, you know, when they get their heads down and move forward as one pack. I noticed also that the black-backed Gulls were getting in on the action, which made me think there was food involved. After a time the activity eased off, and the Shags all flew back together to the end of the Lansdowne sand spit. I watched them land at the edge of the water, flapping about and hanging out their wings. They then stayed for an hour or more, resting in their huddle, and moving to higher ground with the incoming tide.
I imagine that what I witnessed was a coordinated, and very successful, fishing expedition! It could only have worked as the tide was coming in, in a large flat tidal bay such as Shoal Bay. How the birds all knew what to do, I can’t begin to guess. That they were spread out in a single line over such a distance, swimming against the tide towards the end of the Lansdowne sand bank suggests to me that they all knew the procedure. I am sure they were herding small fish first towards the sandbank, and then cutting them off as they chased them into the shallows. I wish I’d “cottoned on” to what they were doing sooner, as I could then have photographed the frenzy at the shoreline as they were flying, diving, and herding. The black-backed Gulls obviously knew what was about to happen. They took no part in the “herding” (if that’s what it was), but were certainly about during the frenzy along the edge of the water! Fascinating. The whole procedure took about 30–45 minutes, and I expect that they gave up once their tummies were full as they made no attempt to repeat it all again. Although, they may have known it would not work as well again as the tide was already over 1 m deep in the middle of the bay.
Shoal Bay, Auckland
4 July 2010