A man who beat six penguins to death with a stick has been sentenced to 49 hours of community service at a court in north-west Tasmania, with a bird group expressing dismay over the punishment.

The Magistrates Court in Burnie heard Joshua Leigh Jeffrey, 20, and another man bludgeoned the little penguins, also known as fairy penguins, at Sulphur Creek beach on New Year's Day in 2016.

Little penguins are the smallest of the different species. ( Wikimedia: JJ Harrison )

In handing down the sentence Magistrate Tamara Jago described the killings as a "callous act" against "vulnerable penguins".

"They were an easy target," she said.

"The fractures to their head were consistent with blunt force trauma … the attack continued for at least several minutes."

Jeffrey's lawyer Greg Richardson told the court his client had ongoing mental health issues going back to when his client was a child.

Magistrate Jago noted that Jeffrey had "shown no remorse and continues to deny guilt".

Jeffrey was convicted of one count of aggravated cruelty to animals likely to result in death, deformity or serious disablement and one count of take, buy, sell, or possess protected wildlife without authority.

In addition to community service, Jeffrey was ordered to pay court costs of $82.15 and a conviction was recorded under his name.

The court heard nine penguins were found dead, but the cause of death of three could not be established.

In Tasmania, the maximum penalty for aggravated cruelty to animals is five years in jail or a fine of just over $31,000.

The little penguin colony would take "years" to recover after the deaths, an expert said. ( Supplied: Dr Eric Woehler/BirdLife Tasmania )

Local heard 'violent noises' from campsite

The case heard local man Luke Williams had found the bodies of the penguins after he overheard "violent" noises from a nearby campsite.

Joshua Jeffrey had shown "no remorse and continues to deny guilt", the court heard. ( Facebook: Josh Jeffrey )

Dr Eric Woehler from Birds Tasmania issued a statement expressing "extreme disappointment at the leniency of the sentence".

"This is no deterrent whatsoever," Dr Woehler said.

"This will not stop the next person going out and doing exactly the same thing at some time in the future."

He said Jeffrey's punishment "places minimal value on Tasmania's precious wildlife" and set an "unwelcome precedent for future attacks".

"The current penalties are clearly failing to prevent the cruel and senseless killing of wildlife in Tasmania. There is no deterrence in this sentence."

Dr Woehler said the colony at Sulphur Creek would take "years to recover" from the loss of the birds.

"With so many other threats, such as gillnets and dog attacks, the last thing any penguin colony needs is a senseless and cruel attack such as this one," he said.

"Little penguins deserve our protection and care, and I am sure the Tasmanian community would not want to see another attack like this one."