A new Penguin study revealed that breeding success of many seabirds largely depends on their diet and a decline in prey abundance may lead to breeding failure, according to a press release.
Ice loss is threatening the habitat of penguins. Monash University researchers now fear that this may not be the only problems the seabird species may be facing.
Nicole Kowalczyk and associate professor Richard Reina of Monash University studied a penguin colony for almost two years to detail how changes in prey abundance or food sources influenced reproductive success, by tracking the penguins' nesting and feeding behavior during the 2010 and 2011 breeding season.
They were surprised to find that in the absence of anchovy, which accounted for up to 78 per cent of their diet, penguins were flexible to changing their diet if they found an alternative food source like sardines.
"The St Kilda little penguin colony has a short foraging range and displays narrow dietary diversity so this gave us the unique ability to identify how changes in food supply influence their reproduction," Kowalczyk said. "We found that a sharp decline of anchovy in 2010 had a negative impact on little penguin reproduction. However, in 2011, despite the relatively low anchovy abundance, their breeding success was extremely high."
The findings of this study gave rise to confusion on what other factors contributed to breeding failure, since the study clearly showed decrease in number of anchovies was not the only cause of it. The best reason that can explain this is that though penguins are resilient to changes in their preferred prey, their adaptability capacity is limited because of the lack of alternative prey species.
"Our results highlight that resource abundance and the availability of a variety of prey are critical factors in enabling this inshore seabird to adjust to changes in environmental conditions and fluctuations in their primary source of prey," Kowalczyk said. "Dietary changes have been linked to population declines and provide information about foraging conditions, particular prey species and foraging locations that require protection."
The penguin species with the highest population is the Macaroni penguin with 11,654,000 pairs. The species with the lowest population is the endangered Galapagos penguin with between 6,000-15,000 individuals. They can spend up to 75% of their lives in the water. They do all of their hunting in the water. Their prey can be found within 60 feet of the surface, so penguins have no need to swim in deep water. They catch prey in their beaks and swallow them whole as they swim. Some species only leave the water for molting and breeding.
