Birds are useful and harmful, depending on the context. Every species shares different traits, thus contributing to different ecosystem services and posing different possible harmful outcomes. Vultures for example clean the environment from microorganisms, that might cause pests and epidemics, like the swine flu spreading over europe currently. If vultures were not reduced to a fraction of their original numbers and limited to a tiny proportion of land on the continent, they would prevent swine flu from spreading by neutralizing the microorganisms that spread from deceased pigs. Due to the absence of vultures nowadays the pest ist spreading extensively and causes major economical damage. 

Birds are useful and harmful, depending on the context. Every species shares different traits, thus contributing to different ecosystem services and posing different possible harmful outcomes. Vultures for example clean the environment from microorganisms, that might cause pests and epidemics, like the swine flu spreading over europe currently. If vultures were not reduced to a fraction of their original numbers and limited to a tiny proportion of land on the continent, they would prevent swine flu from spreading by neutralizing the microorganisms that spread from deceased pigs. Due to the absence of vultures nowadays the pest ist spreading extensively and causes major economical damage.

Birds are useful and harmful, depending on the context. Every species shares different traits, thus contributing to different ecosystem services and posing different possible harmful outcomes. Vultures for example clean the environment from microorganisms, that might cause pests and epidemics, like the swine flu spreading over europe currently. If vultures were not reduced to a fraction of their original numbers and limited to a tiny proportion of land on the continent, they would prevent swine flu from spreading by neutralizing the microorganisms that spread from deceased pigs. Due to the absence of vultures nowadays the pest ist spreading extensively and causes major economical damage.