The Big Sibley is a fun book,and a good reference,with quite a lot of visual information,and definitely recreational..but it does not have much information on habitat ,behavior ,or anything really...There is only a brief introduction to each genus,a simple description ,and then ,most of the text is used in quite subjective descriptions of birds voices(kikrrri kikrrri kikrrri,..iif iif iif ,WEEpa WEEpaquiquiquiquiquiquiqi...).
This is very interesting info,no doubt,but i would rather have some more other aspects of the bird life explained there.For more information you would need the companion volume to the Sibleys guide..i forgot the title
The smaller field West and East versions seem to have more information about biology ,habitat ,behavior etc,and they would be more handy in the field...
Kaufman is very good ,i think he is right on the spot,with the synthesis of information comprised there..of course is a small volume,and you will miss some plumages,and details of feathers in the( Photo) illustrations ..
There is where Sibleys Excels...