|I've read in several books that the seeds from golden chain trees are poisonous. How would this affect the wild-life that frequents my yard... namely any birds, rabbits or squirrels?
According to the listing of toxic plants at the Cornell University Poisonous Plants Informational Database, Laburnum anagyroides (common laburnum) is poisonous to cattle, dogs, humans, horses, and swine and the poisonous substance, cytisine, is contained not just in the pods but in the entire plant.
Historically, laburnum has been considered highly poisonous as indicated by Mrs. Grieve writing in A Modern Herbal.
On the other hand, these trees have been grown in gardens for a long time and grow wild in Europe and I would suspect that just as the wild creatures somehow know not to eat other harmful plants, they would know not to eat this one.
I have one of these trees and also grow baptisia (a perennial that apparently contains the same poisonous substance) and have never noticed any ill effects attributable to these plants although there are all kinds of wild animals and birds in my yard all the time since I live in a rural area. If you are truly worried, you might check with your veterinarian and/or a wildlife biologist for commentary about it.
I personally would be more worried that a small child might find the seeds attractive enough to pop into their mouth and suck on.... It is surprising how many plants are actually considered poisonous when you stop to think about it, even common ones such as yew and philodendron and daffodils.
I'm sorry I can't give you a more precise answer but I hope this helps you in your research.