That machine is a 150 International Harvester Drott Crawler....a real antique, 1959 model. I just bough 20 acres of land, thickly wooded, and with the crawler, it is a matter of pushing the tree over and then sinking the shovel in under the root ball and pushing it out, roots and all. If you look close, you can see it is a clam shell bucket, so it can grip a stump, or a log and pull or pick it up. I use this machine for demolition work in our construction business, but it serves duty at the farm. Cost was $5000...a real bargain.
If you plan on sawing the trees for lumber, you do not want to push them over...it strains the logs and breaks the fibers....hard to believe, but true...that isn't to say you can't get good logs out of trees that were pushed, but it is best to cut them. If the trees are large, look forward to a lot of work, and you won't be using a chain to pull them out.....rent an excavator or dozer for a weekend...and plan on it being a long weekend. And always, clear as you cut...don't just shove brush piles up.