Answer:
147 hummingbirds are in the sanctuary.
Explanation:
The answer can be found using the given percentage. Stating that 35% of the birds in the sanctuary are hummingbirds means that the amount of hummingbirds is 0.35 times the total amount of birds.

Percentages can always be converted to a decimal number:
(1% = 0.01 ; 10% = 0.10 ; 100% = 1.00; etc.)