Roost Counts
For a successful roost count it is important that all the significant roosts are identified, and you also need to know when during the year the parrots roost together since the best method is to monitor the roosts simultaneously. The problems come when parrots change their roost locations a lot, as this makes it difficult to track them.
Nest Enumeration
Nest enumeration requires identification of the colonies and deciding when the best time to count them is, however, some experts have stated that as much as 80% of the population are not covered by nest enumeration. It is not a suitable method when the roosts are kept in locations that are hard to access, or where parrots are dispersed over a wide range of nests. Another thing that can influence this method is changes in the food supplies of a species.
Moving/Line Transects
An example of this is counting from a river whilst on a boat, and obviously such a method has a lot of challenges that limit its accuracy. Although it is a difficult to track the populations it can be a useful way to measure density differences across a habitat.
Mark-Resighting Studies
Marking birds is hard work, and almost impossible with some species of parrot that are difficult to capture. Furthermore, you may make a bird more vulnerable to predators by marking it.
Fixed Lookout Counts
This is a good method, but it relies on knowing how representative your look out spot is.
If you have a care of parrots and conservation are of interest to you, or you just have a pet parrot then Danny Oakes' articles on all things aviculture should be of interest to you.
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