This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

v. to watch birds, especially in their natural habitats, for enjoyment or as a hobby; to bird{3}.

v. watch and study birds in their natural habitat

"That's why I've always believed that people who hunt, fish, hike, birdwatch or engage in any other nature-based activity tend to be - on average - much happier, less stressed and more laid-back than their angst-ridden concrete-dwelling cousins."

observe   

bird{3}   

bird{3}