Why some birds disappeared?

I am not familiar with the bird called the Bare-throated Bellbir. I tried to find it in my books and on line. However, I do make my yard very friendly our birds here in near Chicago, for both the local birds and the migratory ones. It is becoming spring here in the Northern Hemisphere. Many of the birds that migrated to South America and the southern part of North America , for our winter are now returning. Robins , Crackles and Red winged blackbirds are beginning to build nests. The geese, ducks and Cranes are passing through. Your Bare throated Bellbirs have only moved 500 meters. They are singing which indicates they are staking out a habitat for females and warning other males to stay away. Birds usually sing for a reason. Many birds that migrate lose their ability to produce male hormones when it is not mating season.. This causes their testicles to shrink. It reduces their weight. and saves energy. When it is time to migrate or mate the testicles grow and they again produce male hormones. The begin singing again. Some birds are extremely sensitive to their immediate surroundings. Their needs may be so specific that even small changes cause them to move. We have birds that can only survive in wooded areas that contain young many young pine trees. When all the trees all grow to big or are cut down and and only tiny pines are growing, the birds move out to better forests. Our Kirkland warbler is almost extinct because of this. Maybe the underbrush around the trees you cleared was their habitat? Go see if where they are now has underbrush around the trees in the new area? Were the trees that were cut down for the house area the only ones of their kind on your farm? Some birds are awfully sensitive to any changes in the area. Migrations are not always thousands of Kilometers away. Some are up and down mountains or between the upper mesas to lower valleys. We have Robins in California that spend the summers in the higher areas of the mountains and then in the Winter move down into the warmer valleys. With the changes in your area, predators may have moved in closer to their favorite nesting areas. They will leave quickly to survive. We have a great problem with house cats. Squirrels move into areas when humans come along. They also eat bird eggs and baby birds. The drive away the parent birds or kill them many times. Some birds love to be close to humans. Robins love the short grass of the lawns because it makes hunting worms very easy for them. Humming birds love coming to our sugar water feeders. Some of our wood peckers avoid humans while it is warm but come to our feeders for seeds and fat when it is cold. Your birds moved only 500 meters. If they stay that near they may move closer when they get to know they are safe. You may have to let the brush grow back under your trees. They may be getting ready to migrate. As you can see, there are many reasons for them to move around. You have a very good command of the English language. Your mother tongue is probably Portuguese? When I speak or write in German or French, I know what a difficult time that I have. Congratulation on your courage to express yourself in English.

You have removed the habitat of the birds. They have moved somewhere that they can find a home that they like and can find food. It's why there are animals that are becoming extinct. Because on a larger scale, their habitats have been removed by humans.

could be migration, also possible is predation, or they moved on to a more favorable area away from human interruption.

You have removed the habitat of the birds. They have moved somewhere that they can find a home that they like and can find food. It's why there are animals that are becoming extinct. Because on a larger scale, their habitats have been removed by humans.

could be migration, also possible is predation, or they moved on to a more favorable area away from human interruption.