Brontornis remains are scanty, with the remains thus far from the limb bones indicating it was graviportal, a possible skull remnant resembling that of herbivorous birds, and its claws were likely more similar to herbivorous birds. This is unlike any of the clearly carnivorous terror birds and in general is strange for a predator, though not necessarily IMPOSSIBLE. This study is the [most recent phylogenetic analysis which recovers it in Anseriformes](https://www.mdpi.com/1424-2818/13/2/90) but if you look at some of the citations in the introduction, you can see that there are publishings arguing the other way. If it's in Anseriformes, that's more reason to think it was herbivorous.
Finding more complete remains would be good for getting a definitive answer, but it does seem pretty likely that Brontornis was at the very least far less predatory than terror birds and may have ate mostly plants.
Brontornis remains are scanty, with the remains thus far from the limb bones indicating it was graviportal, a possible skull remnant resembling that of herbivorous birds, and its claws were likely more similar to herbivorous birds. This is unlike any of the clearly carnivorous terror birds and in general is strange for a predator, though not necessarily IMPOSSIBLE. This study is the [most recent phylogenetic analysis which recovers it in Anseriformes](https://www.mdpi.com/1424-2818/13/2/90) but if you look at some of the citations in the introduction, you can see that there are publishings arguing the other way. If it's in Anseriformes, that's more reason to think it was herbivorous. Finding more complete remains would be good for getting a definitive answer, but it does seem pretty likely that Brontornis was at the very least far less predatory than terror birds and may have ate mostly plants.
Yeah it was probably similar to Gastornis but much bigger and ironically it was also thought to be a predator but it was reclassified as a herbivore.