I will first start with the destruction of the rainforests of the world. One acre disappears every second. Gone forever. And with those acres go countless species of birds, other wildlife, and plants. The known species and the unknown. And because we will probably never have those acres back, the brids that fled those acres and the ones in untouched areas will have a smaller area in which to live. This means more competition for food, which further lowers their numbers. If other animals prey on these birds, they too probably moved to this untouched area. This would also lower their numbers.
As you can see, the destruction of their habitat, the rainforest, greatly affects the birds' populations. Even as you read this report, this is happening somewhere in one of the world's rainforests.
Next I will generalize the destruction of areas such as forests, grasslands, and marshes. The main reason for the destruction of these areas are for wood and places to build as our population grows. We sometimes forget about the present inhabitants of the area. If you drain a marsh, a bird adapted to it will probably not survive. The same holds true for the inhabitants of the forest and the grassland.
As you can see, the destruction of habitats is one of the greatest environmental disasters for birds and other wildlife on our planet. If one species would die out, or become greatly low in numbers, other species would suffer, and some might explode in population. This would disrupt the food chain that bird was part of. We must do something to stop this if we ourselves are to survive.