King penguins on a subantarctic island are now breeding 19 days earlier than in 2000, and more chicks are surviving the winter, a new study has found.
This change has turned ocean warming into a short-term benefit for species that may still lose it.
King Penguin on Possession Island
On Possession Island, a remote island in the southern Indian Ocean between Antarctica and Madagascar, researchers tracked down a colony that was beginning to reproduce significantly earlier than before.
Based on 24 years of records of tagged birds, Gael Bardon from the Center des Sciences de Monaco (CSM) linked that early start to a marked increase in chick survival.
By 2023, chick survival will be 62 percent, up from 44 percent in 2000. This indicates that this change in timing had real biological effects.
These benefits do not eliminate the underlying risks, and the benefits will persist as long as penguins can still access the food that allows them to do so.
Why early breeding is helpful
For king penguins, the timing of life events determines whether the chicks are able to store enough fat before the onset of winter.
Each pair raises one chick, and while the chicks wait on land, the adults must shuttle fish back from the sea.
An earlier start lengthens the feeding period, allowing the chick to add to its reserves before the long winter fast takes energy away.
If the season starts later, many chicks will be smaller and more likely to starve by the time they reach the harshest months.
Food sources for king penguins
Far south of the colony is a polar front, where warm and cold water meet and food is concentrated.
There, the mixing lifts nutrients toward the surface, where they become food for plankton that support lanternfish, the penguins’ main prey during the breeding season.
Warmer water can help those fish, but the same warming will push this rich feeding ground further south.
This distance is important because on long hunting trips, parents spend time and energy feeding their chicks.
Signal from seawater
Near its feeding zone, ocean warmth and chlorophyll a, a pigment used to track plankton near the surface, moved with the timing of reproduction.
Lower plankton and water near 40 degrees Fahrenheit are consistent with early reproduction, likely because lanternfish were more available.
At first the link sounds backwards, but the plankton left behind may indicate that the herbivores and fish below are out of sync.
Therefore, the ocean appears to be a chain of delayed reactions, rather than a simple story of warm water benefits.
Benefits will arrive later
Breeding success reflected not only the weather the parents faced that season, but also the ocean conditions a year or two earlier.
This delay makes sense because penguins hunt older fish and squid. Penguin populations depend on how well their offspring fare while growing up and navigating changing oceans.
Birds that eat well one year can breed stronger the next year, so adult birds may pass on the benefits.
These delays are a warning that today’s delicious food season may still be shaped in part by yesterday’s ocean conditions.
King penguin hunting style
Even today, not all king penguins hunt in the same way, and that diversity may be what buys them time.
Some birds head south to the best fronts, while others stay close to the colony and switch to prey such as squid.
There are no breeding islands further south of Crozet Island, so extending each hunt may be the only option if the front continues to move.
That flexibility can soften the blow, but it can’t erase a future in which our richest water continues to slip away.
Why the numbers have stagnated
An increase in the number of surviving king penguin chicks does not automatically lead to a larger population on Possession Island, which already appears to be very close to reaching effective population limits.
When breeding space and local resources become tight, extra young birds may not be packed into a complete colony and may settle elsewhere.
That possibility applies to species spread across scattered sub-Antarctic islands, where increases in one location may later appear elsewhere.
In other words, the health of a population may be more difficult to judge from a single coast than from a broader archipelago.
unusual bright spot
This result stands out against broader patterns of early reproduction across penguins, as timing does not benefit all species equally.
Penguin research at Oxford Brookes University helps explain why the discovery seemed unusual to ecologist Tom Hart.
“This is a rare victory,” said Hart, who was not directly involved in the study. Still, the rare victory is not permanent if the underlying ocean system continues to change.
King penguins in a warming world
Previous studies have already warned that king penguins could be stumbled if their fishing grounds are too far away from their breeding islands.
A 2008 study found that warmer oceans reduced adult survival rates because parents had to travel farther to find food.
Burdon’s paper points out that the same danger will continue, with the best conditions centered around waters around 40 degrees Fahrenheit.
If that sweet spot moves warmer or farther south, the early breeding advantage can quickly disappear.
In summary, king penguins are now able to maintain breeding success by changing their timing, diet, and routes to suit the warmer Southern Ocean.
This adaptation is certainly real, but it is also narrow, and the coming decades will test whether flexibility can outweigh movement in food webs.
This study scientific progress.
—–
Like what you read? Subscribe to our newsletter for fascinating articles, exclusive content and the latest updates.
Check out EarthSnap, a free app from Eric Ralls and Earth.com.
—–
#King #penguins #thriving #warm #Antarctic #climate #offering #hope