As far as I can see from the article the "birds" were of the ostrich kind, not the flying kind we imagine when hearing the word "bird". As far as I know the modern science also says that many dinosaurs that didn't fly also had feathers. So why aren't the other dinosaurs considered "elephant birds" while this creature is?
More info <a href="http://www.sciencemag.org/news/2018/09/new-find-clears-madagascar-s-first-settlers-wiping-out-world-s-largest-bird" rel="nofollow">http://www.sciencemag.org/news/2018/09/new-find-clears-madag...</a><p>Paper <a href="http://advances.sciencemag.org/content/advances/4/9/eaat6925.full.pdf" rel="nofollow">http://advances.sciencemag.org/content/advances/4/9/eaat6925...</a>
Were these birds bigger than dinosaurs?<p><a href="https://blogs.scientificamerican.com/tetrapod-zoology/the-birds-are-not-dinosaurs-movement/" rel="nofollow">https://blogs.scientificamerican.com/tetrapod-zoology/the-bi...</a>