The penguins around Palmer have been under observation since 1975. There are five islands were the penguins are being monitored - Litchfield, Humble, Christine, Cormorant and Torgerson. Access to the islands from tourists, scientists and base personal is now restricted on all islands except Torgerson.

Associate Professor William Fraser of Montana State University hypothesises that the Adelie penguin populations around Palmer station have been subject to a "double whammy" from climate changes in the region. One due to changes in the penguins marine habitat and the other to changes in the penguins terrestrial habitat.

Changes in the populations of other marine species have been noted at Palmer consistent with observed changes in sea ice extent. For example, southern fur seals have increased from 6 individuals in 1975 to 2000 in 1995/6 and southern elephant seals have increased by 300 percent over the same period. Both these species prefer open water (i.e. are ice avoiders) and decreased sea ice could have favoured their expansion. Fur seals have destroyed around 40 percent of the vegetation on Litchfield Island. This island was designated a Specially Protected Area in 1978, largely because of its flora. Chinstrap and Magellanic penguins are also now being reported increasingly at the station, both of these species are normally confined to regions much farther north.

Adelie penguin populations in the region have been declining steady since 1975, consistent with observations in other parts of the Antarctic Peninsula. The populations are now around 40 percent lower than in 1975, with breeding pairs declining from 15,200 to 9,200 though out the area. Evidence of past colonies and direct observations suggest that 21 colonies have become extinct in recent decades.

On Torgenson Island the number of breeding pairs has declined from 8988 to 7308 (19 percent) and on Litchfield Island breeding pairs have declined from 884 to 496 (43 percent). Litchfield Island also has the highest number of extinct colonies in the region (12 out of 21). This may indicate not only that more penguins once lived on the island but declines may have began before 1975.

Fraser and his colleagues propose that the greater decline and colony extinction on Litchfield Island appear to be related to changes in snowfall patterns in the area. There are a number of lines of evidence that support this:

• Reductions in sea ice extent could have favoured increased snow fall as sea ice blocks the exchange of water vapour with the atmosphere and a reduction in the extent of winter sea ice could have increased snowfall over recent decades (increased snow accumulation has been observed in other parts of the Peninsula). Higher temperatures would have also favoured higher precipitation because the warmer atmosphere can hold more water.
• Adelie penguins only nest where mounds and ridges provide ground where neither snow nor meltwater can accumulate. Snow tends to accumulate on the leeward side (Southwest around Palmer) of topographic features due to the dominate wind direction and in the region 18 out of 21 of the colony extinctions have occurred on the Southeast side of high topographic features.
• The position of colonies does not appear to a random process with 55 of the 66 active colonies in the area having aspects other than Southwest.
• The entire rookery on Litchfield Island is on the leeward side of the islands highest topographic feature. Given the above it appears that Litchfield Island once supported habitat that was favourable to nesting and the climate has recently changed, causing the colony extinctions.

An analogue to this process could be drawn from experiences at the joint US-NZ base at Cape Hallet, East Antarctic. The base was built in 1956, and the snowdrifts that developed downwind of the buildings covered several small Adelie penguin colonies. These colonies were initially abandoned, but were subsequently recolonised three decades later when the buildings were removed and the natural patterns of windflow and snow deposition were restored.

While habitat changes appears to mediate population sizes, the final step in the extinction process appears to be aided by predation from Brown Skuas which are effectively able to remove every egg and chick from smaller colonies. Based on the two extinctions recorded on Litchfield Island since 1987, the vulnerable colony size is approximately 25- 30 pairs. In both recorded cases, the colonies became extinct after two consecutive seasons of complete egg and chick loss, suggesting that some critical density of breeding adults is required to maintain colony viability in relation to predation from Brown Skuas.