TITLE:     The impact of pack ice on the distribution of Adelie Penguin
           populations
AUTHOR:    W Trivelpiece, S Trivelpiece, W Fraser, S Emslie and N Karnovsky  
PAGE:      269 of SCAR SIXTH BIOLOGY SYMPOSIUM, Antarctic Communities: Species,
	   Structure and Survival 
ABSTRACT:  A key to understanding the breeding strategy and distribution of
Adelie Penguin populations is the animal's obligate dependence on pack ice.
We know from winter research cruises in the Weddell and Bellingshausen Seas,
that Adelie penguins are confined to the pack ice environment during the
winter.  We hypothesize that the reason they are able to begin breeding at
such early dates, a critical factor in an environment of short summer seasons,
is their reliance on the pack ice spring bloom as a food resource after clutch
completion.  Both sexes, females first, have lengthy (11-14 days) first trips
to sea following the prolonged, three-week courtship fast.  We suggest that
this first long trip is necessary to allow the pair time to return to the pack
ice edge to feed - this being the only predictable source of food in the early
spring period.
 We hypothesize that there are two distinct Adelie populations inhabiting the
 Antarctic Peninsula region.  One is distributed from Anvers Island, south and
 winters in the Bellingshausen Sea pack ice; the second occurs from King
 George Island, east and winters in the Weddell Sea pack ice.  We suggest that
 the reason there are no Adelies breeding between King George and Anvers
 Islands (approx. 400 km gap), yet over one million Chinstraps breed there, is
 because this gap represents a middle "no man's land", that is, on average,
 too far from either the Weddell or Bellingshausen Sea areas to allow pairs to
 successfully complete the first incubation shifts.  A preliminary inspection
 of the Adelie Penguin's circumpolar distribution suggests that there are
 several discrete population centers around Antarctica, each associated with
 an area of residual pack ice.  Given the Adelie Penguin's affinity for its
 natal colony, we suggest that these areas may represent genetically isolated
 populations which may be expected to have distinctive demographic characters
 adapted to the environmental conditions prevalent in these areas.