the least auklet , aethia pusilla , is a seabird and the smallest species of auk .
it is the most abundant seabird in north america , and one of the most abundant in the world , with a population of around nine million birds .
they breed on the islands of alaska and siberia , and spend the winter close to the edge of the ice sheet .
their largest colonies are on the aleutian islands , st .
lawrence island and little diomede island .
least auklets feed predominantly on calanoid copepods , particularly those of the genus neocalanus .
they also eat euphausiids , pteropods and other zooplankton species .
they hunt for these in stratified waters caused where upwelling and thermoclines cause these prey items to be tightly clumped together .
like all auks they are pursuit divers , using their wings to provide thrust and "fly" under the water .
they are voracious predators , consuming 86% of their body weight each day .
least auklets are highly colonial , nesting in rocky crevices in colonies of up to a million birds .
these colonies are often mixed , with other species of auklet nesting with , and competing with the least auklets .
while this coexistence with other species may bring the benefits of protection from predators , least auklets are vulnerable to being displaced from their nesting sites by the larger crested auklets .
a single egg is laid in the crevice and incubated for a month , after which a semi-precocial black downy chick is hatched .
both parents share incubation duties , as well as brooding and feeding duties .
unlike many auks , which are fed fish carried crosswise in the bill , chicks of the least auklet are fed copepods and other zooplankton from a sublingual pouch , as are other small auklets .
the chicks receive no further parental care after they fledge , and can dive to hunt as soon as they leave the nest .
least auklets are vulnerable to oil spills and introduced species .
the introduction of arctic foxes to many of the aleutian islands caused the species to be wiped out on many of those islands , and rats are also a problem on many islands .
however , at present they are still a very common species .
