Dark-Eyed Juncos and "The Good Old Boys Club"

By Dave Hanks

Testosterone works in several ways. It enhances male characteristics, sharpens the sex drive, and increases feelings of aggression. Its effect on Dark-Eyed Juncos is very amusing. Males in winter will form groups and force females and immature birds to the less desirable peripheries. It’s like they’ve formed a “good old boys club.” There will be a hierarchy within the group. The more testosterone produced, the greater the aggressive nature, and therefore a higher ranking.

A higher level of the hormone induces a more intense feather coloration - especially the white stripes down the sides of the tail. Testosterone makes for better singers, to match all the other extras. Females are more apt to select these males for pair bonds. However, they make poorer mates. They help very little with raising the brood, spending most of their time singing and displaying on their territories to other males. There is, however, a price to pay for all this glory – a shorter life span is the cost.

The Dark-Eyed Junco is actually a type of sparrow. This six inch species comes in several varieties. Slate-Colored, Pink-Sided, Red-Backed, Gray-Headed, and Oregon are some of the races. The Oregon Junco and Gray-Headed Junco are our most common types.

Juncos are widespread over the United States and are very common at bird feeders. The feeders need to be on the ground for them, as they are ground feeders. Lake Cleveland has a sizable population of Gray-Headed ones. The Oregon is more likely to be at feeders here in Burley, with an occasional Slate-Colored in winter.

You are driving on a forest road enjoying the things around you. You notice small birds flying across the road that are hard to see well enough to identify positively. However, if there is noticeable white in their tail, the probability is high that you are seeing Dark-Eyed Juncos.

(An Oregon Junco: Black head, rusty sides, white belly)