It is definitely an error and wrong and confusing. But calling the contributors lazy is not proper or kind or grateful. Would you call your teacher lazy if s/he forgot to correct something. Have you ever tried to deal with a huge bulk of work as appears on Duo? Have you never made an error? Really now? An apology is due.
I rather sensed you were new. Here are some user created sites which may come in useful. http://duolingo.wikia.com/wiki/Duolingo_Wiki#Getting_Help
Was the duck holding meat? I hope it's that...I've never eaten duck before