Posted on by Phillip Island Nature Parks
It’s a pastime usually reserved for insomniacs and sheep, but biologists have taken it one step further with 40 plus years of penguin counting at the world-famous penguin colony on Phillip Island, and their results are having important implications for conservation.
With an estimated 32,000 breeding penguins at the Phillip Island colony, counting penguins is far from lulling the researchers to sleep. Just ask Dr Duncan Sutherland, penguin biologist at Phillip Island Nature Parks and lead author on a study about estimating population trends recently published in the journal Biodiversity and Conservation.
“Little penguins aren’t the easiest animal to count given they come ashore at night, live in burrows on land and spend most of their time at sea, but accurately knowing the population size and any changes has a critical impact on what we do to protect the species.”
Three counting methods have been employed over the last 30 years, with the most regular being the nightly count conducted at the Penguin Parade as the birds cross the beach – nothing more than a ranger with decent arithmetic and a pair of binoculars. An average of 572 penguins crossed the Penguin Parade beach during the Parade each evening from 1984 to 2011.
Other methods of estimating penguin numbers, however, are far more sophisticated and include GPS mapping of burrows and demographic modelling based on survival and recruitment.
“The Penguin Parade only accounts for 10 per cent of the colony and the nightly beach count isn’t a reliable estimate of trends in the entire colony,” Duncan explains.
“To get a more accurate picture we’ve conducted 13 colony-wide surveys in eight separate years to estimate burrow density and burrow occupancy rates, and we’ve done modelling based on survival and recruitment rates measured at three sites each year.”
And it has been good news for Phillip Island’s most famous residents with trends indicating a doubling of the population from 1984 to 2011, coinciding with the Summerland Housing Estate Buyback Scheme by the Victoria Government and an expansion of habitat. The scheme was initiated in the mid-1980s following concern about penguin mortalities due to pets, foxes, fire and habitat destruction. More than 180 buildings were removed from the penguin colony in a 30 year period.
It hasn’t all been smooth swimming for the seabirds though, with a mass pilchard mortality in the mid-1990s resulting in a substantial decline in the penguin population in 1995 and 1997 and poor breeding performance.
“Knowing the population trends is vital to protecting this colony,” Duncan says.
“Historically, 10 penguin colonies existed on Phillip Island but in the last 100 years predation by dogs, foxes and cats, and habitat loss from urbanisation and agriculture, wiped out nine of those colonies.
“The Summerland Peninsula colony, including the Penguin Parade, is the last remaining population of penguins on the island. Although it’s one of the largest in Australia, things like food availability and predation can still have a dramatic impact.”