1. Birds have great economic and ecological value to society by providing vital Ecosystem Services.
Large birds destroy numerous rodent pests that consume human food and spread deseases.
Smaller birds consume enormous quantities of insects that attack forest trees, services valued at up to $5000/year/square mile of forest. Smaller birds also consume enormous quantities of insects that damage food crops. For example, they consume up to 98% of over-wintering moth larvae on apple trees.
2. Birds also have economic value to society by generating over $20 billion per year spent on bird-related materials and activities.
Up to 63 million people in the US regard themselves as at least casual bird watchers.
According to Birding in the United States: A Demographic and Economic Analysis report, bird watchers spend nearly $41 billion annually on trips and equipment. Local community economies benefit from the $14.9 billion that birdwatchers spend on food, lodging and transportation. In 2011, 666,000 jobs were created as a result of birdwatching expenditures. (Read complete report here)
3. Birds serve as the best overall indicators of environmental health because we detect and count them much more easily than other kinds of animals.
Birds and people (but not most mammals!) experience the world mostly through hearing and sight so when birds communicate with each other people, can detect them. Most mammals stress smell so they "see" the world largely through their noses, which makes it hard for people to detect and count mammals, especially small species. Also most people and most birds are active during the day, while most mammals are active at night.
4. Birds enrich people's lives throug the aesthetic enjoyment they provide.
Birds are easily detected so they provide contact with nature, something that more and more reseearch shows has psychological value to people (read about Nature Deficit Disorder). Because birds and people perceive the world in similar ways, we can "tune into" their lives and enjoy their beauty by seeing their often musical songs.
5. Birds have great scientific value as research subjects and have provided key findings related to flight, vision, behavior, physiology, ecology, and evolution
6. Birds of course have intrinsic value and the great diversity they show in species numbers (about 10,000) and size and form (think hummingbirds to ostriches) enriches our world.
Please keep in mind that all of biodiversity is important. It's just that birds do have some special values!