A bait ball in the ocean is the name given to a tight, spherical group of
small fish or other small creatures that swim together for protection when
threatened by predators. It's a bit like starlings swirling around when they
come into roost. By packing close together into a ball, thousands of
animals act as one large shape to confuse attackers and protect individuals on
the inside.
Hundreds of guillemots and razorbills dive deep into the water creating bait
balls and driving them to the surface. Eventually the fish have nowhere to go
and will leap clear of the water to avoid their pursuers. This attracts other
birds which either can't dive or can't go as deep as the auks such as gannets,
kittiwakes, shearwaters and petrels. These in turn attract other predators
such as skuas. There can be hundreds or even thousands of birds feeding in the
vicinity of a bait ball and these are known as feeding frenzies which can been
seen from quite a distance.
Unsurprisingly, cetaceans are also attracted to bait balls, so if we see a
feeding frenzy it's always worth watching for a while because whales often
surface in the middle of them. A couple of years ago I watched in awe as
humpback whales drove North Atlantic Krill to the surface (opens in a new window) and created a massive orange pink bait ball
which eventually also attempted to leap clear of the water.
This afternoon I was out again on the Minch with Steve Truluck and Hebridean
Whale Cruises. We headed from Gairloch towards Kilt Rock on Skye and there
were feeding frenzies everywhere.
We could see minke whales approaching and then suddenly they began lung
feeding, where they literally lung forward at speed with their mouths open and
take as much as they can before closing their mouths and expelling the water
through baleen plates in their mouths which replace teeth in some species of
whale.
A minke whale lung feeding with tiny fish flying in all directions.
We saw around 10 minke whales today.
In the middle of one of the bait balls was this fabulous great
shearwater. This was only my second ever sighting of great shearwater in Scottish waters, following the incredible spectacle from a couple of years ago when Ray and I saw around 1000 birds from the Barra to Oban ferry (opens in a new window). That was one of the greatest experiences of my life, but those birds were just flying. It was great to see one today coming to a bait ball and to see it so close!
It was very aggressive, holding it's wings up in a warning gesture and
generally looking very menacing!
After feeding though, it allowed very close approach.
And the excitement didn't stop there. Suddenly I noticed that there was a
juvenile Sabine's gull in amongst the kittiwakes, and it was also feeding
from the bait ball.
Sabine's gull (right) with kittiwakes. Amazingly, though not obvious from these photos, the bird seemed to have an injured right leg which was permanently hanging down. Steve mentioned that the bird they saw on a cruise on Sunday also had its right leg hanging down, so possibly the same bird! Apparently that was well north of Kilt Rock though.
A pale phase juvenile long-tailed skua was sitting on the water, apparently
beyond the abilities of my camera. You can see that it has a pale head, so definitely not the bird that we saw from my last trip out which had dark head and looked more like an intermediate phase to me.
There were several Manx shearwaters and about four sooty's, plus a few storm
petrels.
Sooty shearwater.
An Arctic skua joined the party and chased kittiwakes to force them to drop
their meals. Strange really, surely it would be easier for the skua to just
drop onto the bait balls and take it's own fish from the surface rather than
expend energy chasing kittiwakes? Perhaps it just can't help itself!
Today's route.
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