Air carrier Captain reported a new landfill pit near AUS Runway 36L is attracting birds and potentially causing thermals.

Narrative

There is a new landfill pit that garbage is being dumped into on a 1 mile final to Runway 36L. We cross that point at 500 feet RA. I've noticed excavating on previous flights but on Day 0 I saw that garbage was being dumped into this pit. Landfills create thermals and attract large birds like seagulls. Not a great idea just short of a runway. I again flew into AUS the next day; Day 1; and I saw more garbage being dumped into there. On the ground I mentioned to my FO that this new landfill pit will cause thermals and attract birds; so be wary on upcoming flights. On our taxi out to 36R on our next flight on the same day; we heard planes landing on 36L telling Tower that there were large birds at 200 feet. My FO and I could see these birds.Why in the world is a garbage pit allowed at the end of a runway? Especially at a major airport? This should NOT be allowed.