Are elder leaves poisonous to chickens?

[President Bartlet]

Does anyone know if the leaves of an elder tree are poisonous? Last year our chickens ignored them, this year we've noticed a couple of hens eating them (fallen ones- they can't reach the branches). Then one died unexpectedly and I was a little concerned that the two may be connected. We've moved them to a run away from the tree, but it's not an ideal situation.

[southeast-isher]

I can only answer what the case is for us humans, from wikipedia:

The leaves, twigs, branches, seeds and roots contain a cyanide producing glycoside. Ingesting any of these parts in sufficient quantity can cause a toxic build up of cyanide in the body. In addition, the unripened berry, flowers and "umbels" contain a toxic alkaloid.

Due to the possibility of cyanide poisoning, children should be discouraged from making whistles, slingshots or other toys from elderberry wood. In addition, "herbal teas" made with elderberry leaves (which contain cyanide inducing glycosides) should be treated with high caution. However, ripe berries (pulp and skin) are safe to eat.