You will know a great deal about how you’re doing with your toy and perch choice by your birds. Are they moving about the cage using perches? Do they seem happy? Are they getting along well with each other? Are they getting good health reports from their avian veterinarian?
Birds that are crowded in a cage, either by other birds or the cage accessories, would be stressed, not happy and prone to infection because of that stress. Birds that are crowded may pick at each other or squabble.
Place perches so that droppings do not fall into either food or water bowls or over other perches.
If you have multiple birds in a cage, provide multiple food bowls to reduce the chances of a bully bird preventing a cage mate from eating. (If a bird is getting picked on or appears stressed by the presence of other birds, a separate cage is necessary.)
For a shy bird, a row of toys can form a sort of retreat, a place to go when there’s too much going on around the cage.
A general rule of a minimum of five toys is sufficient, especially if you begin the practice of rotating toys in and out to provide variety for your birds. If daily toy exchanges doesn’t fit into your lifestyle, consider weekly changes.
Watch the condition of perches. Natural perches are a good source of entertainment for hookbills that enjoy stripping the bark, but these will need frequent replacing. Dowel perches should be scraped or washed regularly to prevent disease and rope perches can quickly become soiled or frayed.
You don’t need to buy a new toy every day to provide variety for a companion bird. If you have a set of a few toys that you alternate in your birds’ cages, then you would be providing stimulation for your birds. You could keep a few toys in the cage that don’t change. Some “toys” are really a part of your birds’ diets, like a skewer of fresh vegetables that they can play with or toasted oats strung on a shoe lace to entertain your hookbills. Large pieces of corn on the cob or broccoli that your birds can shred is entertaining for them as well.
The Psitticine Research Project at the University of California in Davis, California has done some behavioral studies about parrots and toys. In the colonies of birds (cockatiels and orange-winged Amazons), researchers found that the birds welcomed a new toy every day as much as they did a bowl of food. Making sure that your birds are happy may not be a question of the number of toys and perches you provide, but whether you offer them novelty and entertainment in their daily routine.