Just a brief comment on the poems cited - to me there is no 'issue' with these two being 'too similar'; because they're not.
The two items they share are 'headache' and 'bird'. Otherwise the tanka also includes 'dream', 'song (notes)', 'dawn' and 'cold light'; while the haiku has 'feeding bird' (not singing, and not plural birds) and 'wooden blind' (time of day not stated, could be an afternoon nap because of the headache).
Think of all the poems written about walking on a beach and seeing the clouds in footprints ... all the poems written about cherry blossoms ... all the poems written about autumn leaves. Some topics are very popular, others less so. Just because two poems are on the same topic doesn't make them a problem. The content of the poems cited is, in my opinion, dissimilar, while describing the common human experience of a headache.
The two items they share are 'headache' and 'bird'. Otherwise the tanka also includes 'dream', 'song (notes)', 'dawn' and 'cold light'; while the haiku has 'feeding bird' (not singing, and not plural birds) and 'wooden blind' (time of day not stated, could be an afternoon nap because of the headache).
Think of all the poems written about walking on a beach and seeing the clouds in footprints ... all the poems written about cherry blossoms ... all the poems written about autumn leaves. Some topics are very popular, others less so. Just because two poems are on the same topic doesn't make them a problem. The content of the poems cited is, in my opinion, dissimilar, while describing the common human experience of a headache.