First, sparrows are alert and react strongly to foreign stimuli. This is the stress response mechanism of sparrows. That is, when a sparrow encounters an emergency, adrenaline will increase sharply, and breathing, heartbeat and blood pressure will increase. After being picked up by humans, sparrows will see a completely strange world, surrounded by a monster all day. These scenes make the sparrows that have started the emergency mechanism more afraid, and will continue to do so. If the tension and fear of sparrows are not alleviated, the body will produce toxins, which will even affect the endocrine of birds and even the normal operation of organs, eventually leading to the death of sparrows.
Second, death is generally scary. Sparrows are very clever and witty birds. Their reaction speed is very sensitive and they are very small. Usually when caught by humans, sparrows can easily find and escape. Sparrows that can be caught by humans are generally sparrows that are exhausted during the flight or have internal organs injured when they break free, especially sparrows that we can easily pick up on the roadside, and most of them are old, weak and sick. At this time, in order to take them home early, we held their hands and didn't hurt them again without any weight. Such a sparrow can't eat anything when it is brought home, and it becomes dying. At this time, their internal organs should have bled a lot, and sparrows will die from injuries.
Third, because sparrows are so common, we subconsciously think sparrows are easy to feed, and we will keep them in cages when we find or catch them. But in fact, sparrows will be very anxious when they enter a strange environment. They always want to break through the cage and return to the original world. Sparrows in a hurry will start flying around in cages, and healthy sparrows will be scarred without eating or drinking. In the end, they either died of injuries or starved to death. Moreover, sparrows are social animals. If you take sparrows home alone and raise them privately, they will live a solitary life that they have never lived before. Sparrows will not be able to adapt to life without a partner, stay depressed for a long time, lose their appetite and eventually starve to death.