Is it known to which bird species 雎鸠 refers? 关关雎鸠，在河之洲。is a very well known line. 

When I look up 雎鸠 in Baidu, I see pictures of ospreys, cormorants，herons, seagulls and other species.

Is it known to which bird species 雎鸠 refers?

According to this site, Pandion haliaetus is not found in China.

So I'm still wondering what 雎鸠 might be.
雎鸠 https://baike.baidu.com/item/%E9%9B%8E%E9%B8%A0
今江东呼之为鹗 (is called 鹗 in Jiangdong today)
好在江渚山边食鱼。(like to hunt fish in river and mountainside)
《毛诗·传》日：鸟鹫而有别 (similar to eagle but different, and we know hawk and osprey look similar but smaller than eagle)

From Google Translate:

鹗: osprey
osprey: 鱼鹰; 鹗; 雎

Based on the search results, 雎鸠 or 雎 is &quot;osprey&quot; (&quot;fish hawk&quot; seems like it's nickname) . Since zoology is a recent thing, what the author described, might be some kind of small sized raptor bird that hunted nearby river, very likely been osprey or fish hawk (if they are not the same thing)