Where did three billion birds go?

In North America, rich in natural delights, cheerful and happy birds are found in abundance.

 But in the past fifty years, the number of birds in North America has shown a clear decline, with an estimated decline of about three billion.

 And all the expat gentlemen see this as a sign of danger. Often, people's morning sounds are accompanied by the buzzing sounds of birds.

 Many people make small bins of bird food on the back side of their house.

  But this scene has changed for the last several years, no longer seeing the flags of birds that used to appear before.

Now the only known birds in the house are very few