Is The Bird's Nest Fern Poisonous?
No, this fern isn't toxic to people, cats or dogs.

Anything else?
Ferns in general are quite sensitive to chemicals so you must avoid leaf shine products to prevent issues. The leaves are naturally glossy anyway, but of course if they start to dull from dust you can just pop the plant under a warm shower for a minute to wash the grime away.

Bird Nest Fern Problems
Why are there are dark brown spots on the fronds / leaves?

In most cases these spots are actually spores, which are basically seeds. It's perfectly normal and indicates you've a mature and healthy plant, just leave them as they are.

Make sure however the brown spots aren't Scale Insects which can look awfully similar. Spores will be regularly spaced and only appear on older Bird Nest Ferns, whereas Scale will have a random pattern and can afflict a plant at any age. If you do have a Scale Insect problem get rid of them quickly to prevent them from spreading to other houseplants. The link above will help you get to grips with doing this.

Why are there brown tips on the leaves on my bird's nest fern?

In most cases this is a result of dry air, or allowing the soil to dry out too much before re watering. On occasion it can also be an indication you're overwatering. Remember that the soil should be moist for much of the time, not really dry or really wet.

Why are the leaves on my bird's nest fern turning yellow?

If the yellowing starts at the ends of the fronds this is probably normal aging. If the yellow is starting from the base of the fronds then the temperature is likely on the high side, find a cooler place in your home for it to live. Other causes could be from using hard cold water, exposure to draughts, or chemicals.

https://www.ourhouseplants.com/plants/bird-nest-fern