Female hummingbirds look like males to avoid attacks, study suggests

https://www.theguardian.com/environment/2021/aug/26/female-hummingbirds-mimic-males-to-avoid-attacks-study-suggests

I remember staying at lovely place Mt. Washington in New Hampshire and in the morning seeing more hummingbirds than I've ever seen in my life. They were feisty and fighting with one another (even though there were plentiful feeding options - so their presence was clearly common at this place).