According to subject verb agreement rule of English grammar subject and the verb associated with it should agree in number i.e singular subject should take singular verb and plural verb will be used when subject is plural.
Here subject is Goffin's cockatoo which is a singular noun hence "is" is the correct verb to be used with this subject while "are" is used and should be replaced with "is".
Answer: The mountain paths were dangerous and couldn't guarantee a safe travel- for example, mountain lions are a true fact. Also, the climate and weather conditions in mountains were too risky, so they had to go around them
