Here are some of my favourite natural history art blogs. I won't say much about them—good art represents itself.
Sherrie York at Brush and baren
Debby Cotter Kaspari at Drawing the Motmot
Carel Brest van Kempen at Rigor Vitae
Natural History Artworks
Olduvai George
This ain't the complete list. Not by a long way. More soon.