"We see slower start shopping in December as a consequence, so I think some spending is brought to November."
Mr Birtles, who could not provide specific information about trading companies before releasing half-year results next month, said Boxing Day sales had been "quite solid".
Super Retail, which also owns BCF (Boating, Camping, Fishing), Rays and the Macpac chain, joins a series of other companies in the retail sector to provide mixed Christmas report cards.
The rival outdoor network, Kathmandu, in early January revealed a surprise fall in December sales, triggering a selloff in stock markets across the sector.
Department store David Jones also said they had a weak December, while Kmart from Wesfarmers saw sales decline in the months before Christmas.
Super Retail said Tuesday that the head of its outdoor division Anthony Heraghty would take over from Birtles at the end of March.
Birtles has been the chief executive of the group for the past 13 years, and announced his resignation in October.
In the absence of a replacement, the announcement frightened investors and sent its shares plummeted 21 percent over five days, from $ 9.35 to $ 7.38.
The stock has slid further since then, closing at $ 6.90 on Monday, and jumping 2.75 percent to $ 7.09 on Tuesday's announcement.
Investors were relieved by the appointment of Heraghty, said Birtles.
We will see a continuation of what we do rather than any radical change.
chief executive Peter Birtles
"What is definitely well received is someone who knows the business, and understands what we have," he said.
"We will therefore see a continuation of what we do rather than any radical change, and with major changes in potential costs or any type of business revaluation."
Mr. Heraghty joined Super Retail in 2015. He previously held senior roles in Bonds owners, Pacific Brands, and oversaw the evolution of iconic lingerie brands from wholesale operations to direct-to-consumer retail businesses.
Previously, he was director of global marketing at Foster's Group. Mr. Heraghty mobilized last year's acquisition of outside the New Zealand Macpac brand, which is now joining the existing camping supply chain Sinar.
He will take a little salary deduction from his predecessor, with a basic salary of $ 1 million per year compared to $ 1.23 million Mr. Birtles, with short-term and long-term annual bonuses of up to $ 1.6 million.
Birtles will continue to present the results of the group's first round in February.