The spoiler below should tell you enough that you need to keep your villagers from starvation smile

Click to reveal..
If you have enough tech points, purchase level two of engineering/construction. Then place a village on the small gap where the stream breaks off into that big lake, down in the corner of the village. The villager will work on a dam, and when it is finished, you can plant crops in the soil that is dampened.

If you don't have enough tech points, find mushrooms on the ground to eat until you have enough. I the cost is somewhere between 3000-5000 tech points, I'm not 100% sure.

If you already have the dam but parrots have eaten it all...

Click to reveal..
Put a farmer on the twisted roots to the right of the big scary head with vines all over it, and he will start to build a scarecrow. Then put the same villager on the roots again, after he has delivered his first load. smile