A DREAM COME TRUE. GALAPGOS 3. BIRDS AT
SEA
During our two weeks in the Galapagos we stayed aboard the schooner Cachalote.
From the deck and during the many panga-rides (the pangas being the local small
zodiacs) we had ample opportunity to watch the seabirds at sea, of which there
often were a lot.
Not in all cases does the watching of seabirds at sea yield a lot of
information. The elegant Dark-rumped Petrels, by the way now seemingly to be
split off as Galapagos Petrel, I always just saw fly past, in windy weather in
the spectacular arching flight so typical of Pterodroma petrels. Also the
dainty and quite swallow-like Wedge-rumped Petrels one usually only sees flying
past; apparently this species, though diurnal at the colonies, forages mostly
at night. The other common storm-petrel, the still smaller Elliott's Storm
Petrel with its short tail, narrower white rump and more fluttering flight,
does feed during the day, exhibiting the characteristic 'walking on the water'
behaviour that have earned the whole group the name 'petrels' (After Peters
first 'walk on the water'). I noticed several times that these storm petrels
were attracted to sea lions violently throwing around large prey; clearly the
petrels feed on the small bits that are shaken off during this process.
The cozy and quite small Audubon's Shearwaters, by far the most common of the
tubenoses here, one usually seees in level flight, low over the water in
typical shearwater fashion. But now and then they congregate in smaller or even
very large flocks and start feeding. This is clearly at spots where there are
schools of small fish near the surface, often chased from below by larger
predatory fish. We too can in many cases recognize such places, as small
fountains seem to erupt from the surface of the sea, and now and then a largish
fish jumps clear. I had the strong impression that the shearwaters knew how to
interpret these signs, but also that maybe they mostly keep eye with each
other. It might take some time for the first bird to arrive at a spot with
'boiling water', but once one or two had landed, many more come in rapidly. The
shearwaters flop down in the water, look beneath the surface, and in many cases
execute very shallow dives with outstretched wings. In a tight flock it looks
for all the world as if they elbow each other out of the way. The prey is
presumably mainly very small fish. Brown Noddies often hover over the flock in
the hope that some prey is spilled, in which case they are very quick to pick
it up. I do not think the noddies directly harass the shearwaters.
Not rarely such shearwater feeding frenzies also attract the almost always
present Blue-footed Boobies, typical inshore feeders. And in such cases we are
in for much more spectacular fishing. These boobies are pursuit divers, as are
all gannets, and normally they dive almost vertically from a considerable
height and disappear completely under water, to bob up like a cork after a few
seconds. But they are clearly able to vary their techniques after the
circumstances: in the feeding frenzies they often dive from a very shallow
angle, and in the most intense melées they simply flop down and fish from the
surface. These scenes may be impressively hectic and one wonders how the
boobies avoid hitting each other or the shearwaters, when they dive at high
speed in the middle of the throng. But I never saw any accident.
The other boobies dive the same way, but elsewhere, so one gets to see them far
less often. The large and powerful black and white Nazca Boobies fish further
from shore, and the small and agile Red-footed Boobies are fully pelagic and
fly long distances from the feeding area to the colonies. A small group of
these redfoots followed our ship as we steamed south from Genovesa (see part
4); they perched on the rigging, and from there made lightning quick sallies,
trying to catch the flying fish in the air!
Another diver is the Brown Pelican, of which there are always a few around. I
have not generally seen them in the worst feeding frenzies. They often dive
surprisingly close to shore, in very shallow water. The somewhat floppy and
clumsy looking aerial dives look much less accomplished than the very smooth
dives of the boobies, but the pelicans are clearly very efficient fishermen and
surprisingly often 'come up' (they in reality almost never totally submerge)
with a large fish. As described earlier, this is a sign for the ever
opportunistic noddies to fly in and perch on the head of the pelican; I am
somewhat unsure of what they want to achieve, as most of the prey fishes of the
pelicans seem clearly too large for the noddies to swallow. The pelicans also
gulp down their fishes whiole, but probably somehow they are sloppy eaters and
there is spillage for the noddies to catch.
There were no other terns at sea, and the Swallow-tailed Gulls, who also are
pelagic feeders, forage at night and are not often seen away from the colonies
during the day. The other gull of the islands, the all dark Lava Gull, is a
typical gull, scrounging and scavenging along the shores.
We looked in vain for whales and dolphins during this cruise and also saw
probably less than the normal quota of large spectacular fishes, but as I hope
to have shown, there was nevertheless always enough to watch from the upper
deck of the Cachalote to keep us interested.
Wim
Vader, Tromsø Museum
9037
Tromsø, Norway
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