King penguin becomes a knight; his relatives are endangered by global warming

Military penguin becomes a 'Sir':

A penguin who was previously made a Colonel-in-Chief of the Norwegian Army has been knighted at Edinburgh Zoo.

Penguin Nils Olav has been an honorary member and mascot of the Norwegian King's Guard since 1972.

Over the years, he has been promoted through the ranks after being adopted by Royal Guard who visited the zoo.

During the ceremony, Nils had a sword dubbed on each side of his head, where his shoulders should be, to confirm his regimental knighthood.

The Beeb also reports that "The proud penguin was on his best behaviour throughout most of the ceremony, but shortly before the ritual was concluded, and possibly suffering a bout of nerves, he was seen to deposit a discreet white puddle on the ground."

King penguins are the second largest species of penguin, behind the emperor penguin. They nest on islands around the edge of Antarctica, and feed on fish squid and krill in the open sea off of Antarctica.

A study by Norwegian, French, and South African researchers earlier this year found that the penguins are at risk because of global warming. Warmer years resulted in two effects: an immediate decrease in breeding activity, and a decrease in penguin survival (measured two years after a warm year). Warm years reduce the number of prey available to penguins, reducing chick survival, as well as weakening growing juveniles. The mechanisms are a bit more elaborate than that, and the way they traced the causation is pretty neat, really.

Basically, the penguins feed near to shore during the summer. The fish that adults gather near-shore are adapted to a narrow temperature range, and become harder to catch in hot years. This reduces the amount of food brought to nestlings and to incubating penguins (one parent remains to incubate the egg for weeks at a time while the other feeds heavily). Penguins who cannot gather enough food may simply abandon reproduction for that year, since there is a tradeoff between how much food they can provide to offspring and the fat reserves they must build up to survive the winter and reproduce the next year. Birds are more likely to abandon their egg and start fishing early if they hadn't been able to feed enough before laying eggs, or if their partner cannot return to the nest early enough.

The two year lag is driven by the winter foraging. The prey fish move north (away from the pole) and deeper, making them harder to catch. So penguins shift to squid and krill for the winter, which they use to feed themselves and their offspring. Those prey items, like the fish, are dependent on oceanic algae, which are also highly sensitive to temperature. A warm year therefore reduces the number and size of prey items in the subsequent year.

Being unable to feed adequately in the year after a warm year leaves penguins with a tradeoff between sustaining their young that year versus protecting themselves and having more eggs in future years. The data indicate that the penguins allocate more resources to egg and hatchling survival in the first year after a warm year, leaving them weakened in the second year. Those weaker penguins are then more likely to die in the second year, explaining the lag in adult survival.

There is an extensive literature describing the long-term effects of such trade-offs in long-lived species, and applying those models to the penguins yields worrying results:

Importantly, and according to life-history theory in long-lived species, king penguin populations would not be sustained with a 9% drop in their adult survival such as that we show for an increase of only 0.26°C in SST [sea surface temperature]. … in line with the last Intergovernmental Panel on Climate Change (IPCC)-2007 estimation of a linear increasing trend of 0.74°C of global surface temperature during the last century and a further warming of ≈0.2°C per decade for the next two decades (37), the warming of the Southern Ocean certainly represents a major threat for penguins.

In other words, the warming we've seen in the last few years is enough to pose a long-term risk to the survival of the species (which numbers about a million right now), but the population is dealing with a legacy of warming that hasn't fully caught up with the species' demographics, and the warming trend continues to accelerate.

The authors conclude by noting that "Some other seabird communities in Antarctica might be affected by such a cascade of effects of Southern Ocean warming." That includes other penguin species, but also the range of great seabirds that nest and forage in the southern oceans. Many of them come to land only rarely, and are therefore difficult to monitor. Penguins like Sir Nils Olav may be the best way to tell what's happening to a range of other species.