Good on you for the reply and the two sources, have an upvote for engaging :)
Quadrant
Well, there's your problem - it's not a science or anthropology journal it's an unabashedly conservative wank fest for overly educated private school chums that utterly hate the proles and Australian aborigines.
> According to University of Michigan professor of anthropology Aram Yengoyan:
Who has spent how much time in Australian aboriginal societies?
> Contemporary European observers of nomadic, tribal Aborigines were in apparent agreement that about 30 per cent of new-born Aboriginal children were routinely killed.
Again, no surprises there - there's an extremely long list of things that early European observers agreed upon about aborigines ... and most of them were garbage, worthless save as justification for having repeated massacres of local groups upset about being pushed from their lands.
> According to Samuel Gason (1845–97), an early settler of the Flinders Ranges, writing of the Dieyerie tribe of the Cooper’s Creek area between South Australia and Queensland, “about thirty per cent are murdered by their mother at birth”.
These are the same early settlers frequently associated with poisoning water holes and killing the very people they spent some time defaming as barbaric.
The problem with all these accounts is that many aboriginal groups continued through until recent times with their traditional practices, in the Western Desert [1], far north Queensland, remote Kimberley regions (where I'm from) etc. and anthropologists didn't find much in the way of actual baby eating.
What you have in the Quadrant article is a collection of all the European "Aboriginals are heathen scum" gossip of times past bundled up and presented as fact.
Your second link, the paper on scihub by Collishaw (1978) is, umm, kind of long winded and noncommittal - it passively rejects the 30% figure thus:
both reported that 30% of the children were killed at birth.
These contrast with other reports from S.W. Australia of infrequent infanticide.
and then never really commits to a frequency figure other than discussing at length the kinds of things that happened at much the same frequency in European countries at the same time - deformed children were often killed at birth, in hard times with not enough to eat weaker children would die to allow stronger children to survive.
It's an odd paper that has a few sound sources (Spencer .. good source, but unsurprisingly had a strong European point of view) but largely appears to repeat a lot of settler gossip.
[1] https://www.bbc.com/news/magazine-30500591