Where are these supposedly intelligent mammals now, then?

Well, that's one possible great filter down then. If it happened twice on one planet it's safe to assume that, given similar circumstances, it could happen again, or already has elsewhere.

Being real, read the article.

Summarizing it won't really be useful, or I'd try.

But, assuming everything they're talking about proves out to be true, this is way cooler than the title makes it seem, on multiple levels. It gives hints at evolutionary pathways for intelligence in more than just what's found in mammals and birds.

It gives a glimpse at how our intelligence functions at a fundamental level, maybe eventually leading to a reasonable degree of evidence about our selfness, our ability to exist as something other than our animal instincts as well as the things that make us individuals.

But, most importantly to me, it implies that intelligence isn't a rare and difficult to produce thing evolutionarily. The article also mentions the potential for studies into octopus intelligence using the same methodology. If there's three independently evolved intelligence structures on one planet, extrapolate the possibilities. Even if it's just two, that's still astounding in relation to the question of intelligence as a probability with the presence of any life, given enough time. But three? That's mind bogglingly indicative that life and intelligence are very likely to go together anywhere life might exist.

In the Movie Matrix, initially the script argued (Spoilers from here) that the machines used human brains as computation farms, but studio execs thought it was "too complicated".

I would argue that using birds (corvids?) seems more cost effective based on energy efficiency per brain gram. Machines would only need a steady supply of corn.

If you enjoy this idea then you'd probably like Children of Time by Adrian Tchaikovsky and its sequals. Adrian did, imo, an excellent job imagining how other intelligent earth species would behave and form societies.

Any evidence of how far back in their dinosaur lineage the avian DVR originated?

Researchers Still Unable To Count How Many Times Stupidity Evolved Independently On Earth; Nation's Leading Number Lab Says Quantum Computing Breakthroughs Necessary