And something similar is true for species all over the world. The interesting thing is that the breeding season of the entire avifauna of a geographic area is about 1.35x the average season of the component species. In other words, add up all the breeding lengths of all species - some nest over a period of 6 weeks and some nest over a period of maybe 3 months. Take the average of these and multiply that average by 1.35 and you'll come up with the total time over which all the birds in that area breed. West Java 9.89 months total season and the average nesting season per species is 7.54 months.
Birds are also different sizes and come in large, medium, and small.
Schoener looked at hundreds of species of insectivorous birds in different areas of the world. Lumped all into temperate or tropical groups. He found that there are more species and a larger range of bill sizes in the tropics because there are more arthropods in the tropical forest and larger ones as well than in the temperate zones. Because larger birds can handle larger prey and a wider range of sizes. Now let's look at community structure which has evolved from the various feeding habits of birds.