Midway Atoll has the
second largest Black-footed Albatross population in the world. In
1998, the total number of breeding pairs on Sand, Eastern, and Spit
Islands was 20,240 (9,687; 10,542; 11; respectively)
Feeding Habits
Diurnal surface feeders.
Unlike the Laysan Albatross, whose retinas possess a high level
of rhodopsin enabling better night vision, the black-foots have
limited nocturnal vision. Diet consists primarily of flying fish
eggs. They also feed on squid and crustaceans. Squid, which float
to the surface during darkness, are much more accessible to Laysans.
Black-foots, on the other hand, rely on flying fish eggs, which
are easier to locate during the day. The competition for food between
Black-footed and Laysan Albatross is reduced due to this difference
in prey items and feeding behavior.
Black-foots usually
stay at least 20-30 kilometers offshore during the non-breeding
months (July - November). During these months birds are distributed
throughout the northwestern and northeastern Pacific.
Breeding
Monogamous. If one of
the mates should disappear or die, a new pair bond is created. Nests
are made up of pieces of surrounding grasses, sand, or shrubbery.
Black-foots like to nest in more open, less vegetated areas as compared
to Laysans. The majority of their nests are located near beaches.
Breeding begins in early November. One egg is laid and incubation
lasts about 65 days. Both male and female incubate the egg. Incubation
starts with the females who usually stay for a short two day span.
The male then takes over, sometimes as long as three weeks. If the
egg is infertile or breaks during incubation, relaying will not
occur during that year.
Black-foot chicks begin
to hatch in mid-January. Chicks live on a diet of flying fish eggs
and squid oil. Both adults feed the chick by regurgitation. The
chick will peck at the lower beak of the parent which stimulates
the parent to regurgitate. The rich squid and stomach oil is filled
with fatty acids and nutrients that can sustain a chick for a number
of days while the parent goes out to sea in search of more food.
Fledging occurs 4-5 months after hatching (June and July). Similar
to the Laysans, the parents will often leave before the chicks have
reached their full juvenile plumage. Relying on their fat reserves,
the chicks survive on land, practicing take-offs until they master
flight. Sub-adults return to their natal colony when three years
of age but do not mate and nest until at least age five.