Re: Penguins of the North...?

[Ronald Orenstein <ornstn@rogers.com>]

At 06:57 PM 09/01/02 +0100, David Marjanovic wrote:
> I don't know how much it actually matters or whether only the flightless
> ones -- *Pinguinus*, *Mancalla* and AFAIK none others, plus the plotopterid
> pelicans -- could be counted as possible competition in the first place.

Well, I would say that it is not necessary for both birds to be flightless 
to be competitors, as long as they swim and feed in a fairly similar way 
(ie as wing-propelled divers).  Perhaps more to the point is that auks in 
general run quite a bit smaller than penguins in general - the largest auk, 
the extinct Great Auk, weighed about 4-5 kilos (the largest mancallids were 
about the same size or slightly smaller) while a large male Emperor 
Penguin, the largest living species, may weigh anywhere from 23 to 40 kilos 
depending on the time of year and the state of its fat reserves.  In this 
regard the plotopterids may have been more direct equivalents; but remember 
that seals and even large whales have been considered to be competitors 
with penguins for foods like krill.

In fact the closest southern-hemisphere parallels to the smallest auks are 
not penguins, but the four species of diving petrel (Pelecanoides), birds 
of the south temperate and subantarctic regions.  I don't think any 
experienced birder would mistake a penguin for an auk, but a diving petrel 
is almost a dead ringer in shape, size and behaviour for a small auk like a 
Dovekie (Little Auk in Europe).


> It's not transportation why cold currents are -- apparently -- essential.
> The nutrients they bring are what matters. Close to the Pacific coast of SA
> the Humboldt Stream is teeming with life, whereas farther to the west
> there's nothing but blue desert. Equatorial waters don't support such
> ecosystems.

In their book "The Auks" (Oxford UP) Anthonu Gaston and Ian Jones note 
that, unlike some other northern seabirds such as gannets and skuas, auks 
are restricted to temperate waters even in winter, "Presumably... because 
their feeding adaptations are specific to cold marine ecosystems".  Besides 
the biomass of prey, "burst swimming speeds of most fishes double between 
water temperatures of 5 and 15 degrees [C].  If the swimming speeds of the 
warm-blooded auks remain unchanged, underwater pursuit of fish must become 
more difficult as water temperature increases".

> IMHO it's just the same thing as with penguins -- the cold currents from the
> north don't reach the equator either. (That's particularly extreme in the
> Atlantic where the Gulf Stream keeps all cold waters north of almost
> Newfoundland.)
> Were is the southernmost auk? In California? Where were the southernmost
> plotopterids?

I don't know about plotopterids but the most southerly auk breeding 
colonies are in the Gulf of California at 29.5 degrees N.  In the Old world 
auks reach Quingdao Island in China (30.2 degrees N).  Auks are, with rare 
exceptions, not long-distance migrants and the lack of this pattern may 
explain, according to Gaston and Jones, why they never developed 
trans-equatorial "leapfrog" migration patterns shown by other seabirds 
(most notably the Arctic Tern).

--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court
Mississauga, Ontario, Canada L5L 3W2          mailto:ornstn@rogers.com