if you like bird calls, take a second to visit xeno-canto.org, superb amateur birder site that collects audio of bird calls, via (i believe) an cc artist licens

if you like bird calls, take a second to visit xeno-canto.org, superb amateur birder site that collects audio of bird calls, via (i believe) an cc artist license and is totally free. Also, run by Dutch mathematicians!