Is this plant poisonous to chickens?

[Darcy414]

Any idea what these are? I’m in New Hampshire and they have been popping up all over my yard.

 

[so lucky]

Is there a tree nearby that has leaves like that? It looks like a bunch of tree seedlings.

 

[Folly's place]

The third picture looks like an aspen/ poplar seedling.
You can send pictures or take plants to a horticulture expert, or maybe someone at a nursery.
Most times free ranging chickens avoid toxic plants, as long as there are plenty of other choices available. If the only plant is a toxic plant, they may eat it, but not when running around outside.
Mary