Kiwi blokes are bucking international evidence showing fewer boys are born in colder years, with researchers putting it down to their robust nature.
Studies from the United States National Academy of Sciences and the University of Helsinki in 2008 found fewer boys are born in colder years in Scandinavia, while a 1998 German study found more boys were born in that country in summer.
But Victoria University researchers have found no such link in New Zealand.
A team from the university's School of Biological Sciences analysed data on births and temperatures in New Zealand dating back to 1876 and found no relationship at all between the weather and the gender split.
There was also no difference in the likelihood of having a male or female baby in data from Northland and Southland - despite the temperature difference.
Research leader Dr Barnaby Dixson says there are several theories to explain the findings.
"Previous research has shown that male foetuses are relatively fragile and sensitive to the cold so if the temperature is low, or the environment is harsh, it is thought that the male foetus is less likely to survive," Dr Dixson said.
"It's possible the temperatures in New Zealand are not sufficiently cold or harsh to have an impact on developing males, or perhaps New Zealand males aren't as delicate as others."
NZN