Ask Mr. Smarty Plants

Curiously, I could not find any creditable references (other than our Native Plant Database that has since been revised) saying that Nothoscordum bivalve (Crow poison) is poisonous either.  I searched all the toxic plant databases that we normally use: 

Cornell University Plants Poisonous to Livestock

University of Pennsylvania Poisonous Plants

Toxic Plants of Texas

Poisonous Plants and Mushrooms of North Carolina

Canadian Poisonous Plants Information System

Also, it's not on the Texas Poison Center Network Poisonous Plants List.

I did a search in academic bibliographic databases and have looked through all my Texas wildflower books and all the edible/poisonous plants books that I own. 

Here are a couple of quotes about N. bivalve in two of the books that focus on Texas plants:

1)  Tull, Delena. Edible and Useful Plants of Texas and the Southwest.  Austin:  University of Texas Press.  1999.   About crow poison:  "I have found no information to indicate whether or not it truly is toxic, so we can only assume that it could cause poisoning."

2)  Scott B. Fleenor & Stephen Welton Taber.  Plants of Central Texas Wetlands.  Lubbock:  Texas Tech University Press.  2009.  About crow poison:  "It is not apparently poisonous."

Not being listed by any of the above sources doesn't guarantee that it isn't toxic, but it probably does mean that it is not dangerously toxic.   I  would advise against eating any part of it, however, since many plants in the Family Liliaceae (Lily Family) are toxic—some of them deadly.  For instance, the Poisonous Plants of North Carolina database lists Allium spp. (wild onions and wild garlic) as mildly toxic—"causes only low toxicity if eaten".  N. bivalve, crow poison looks very much like the Allium spp. and is often mistaken for them.  You can distinguish the crow poison from the Alliums because crow poison lacks the onion/garlic smell when leaves or other plant parts are crushed. 

On the other hand, Zigadenus nuttallii (Death camas), as well as other members of the genus Zigadenus, are considered highly toxic.  Here are references in several of the above toxic plant databases:

Poisonous Plants of North Carolina lists Zigadenus spp. as "highly toxic, may be fatal if eaten!"

Canadian Poisonous Plants Information System lists Zigadenus elegans (Mountain death camas) and  Zigadenus venenosus (Meadow death camas) as toxic.

Toxic Plants of Texas lists Z. nuttallii.

I couldn't learn why Nothoscordum bivalve has the common name 'crow poison', but I did find one explanation of why another plant with this common name is so called.  This plant happens to be a member of the genus Zigadenus—Zigadenus densus (Crow poison or Oceola's plume).  You can read the explanatiion on Darryl Searcy's webpage Flowers of the Escambia—(Escambia is the name of a river and the region along the river in Alabama and Florida).  Mr. Searcy's explanation is that in former times people would make a pulp of the bulb of the plants and spread on the feathers on the heads of chickens.  If a crow or hawk killed the chicken and ate it, it would soon die itself.

Finally, I can't really tell you whether or not Nothoscordum bivalve (crow poison or false garlic) is toxic to any degree.   If it does have some toxicity, it doesn't appear to be deadly. Given the fact that its distribution covers much of the eastern US and it is frequently mistaken for Allium canadense (Meadow garlic) that people commonly eat or use for cooking, it would have been reported by now if it were highly toxic.  However, since its toxicity is in question, I would advise against eating any part of it.