The male Bobolink is the only American bird that is black on the bottom and white on the top with straw coloring on the back of its head. That striking plumage is only during breeding season, however. The rest of the year he resumes his overall drab coloring. The female looks more like a sparrow, her coloring more camouflaged as is the case with most females. Bobolinks live in grasslands and meadows during breeding season, making bulky cup nests of soft vegetative materials placed low in the grass. (It's important to stay on the paths to avoid damage to nests!)
The Bobolink migrates 16,250 miles each way to and from South America, using both the earth's magnetic field and stars to navigate. That's a huge trip by airplane never mind under one's own power!
When you go to Chestnut Hill Farm or any other Bobolink friendly habitat, you may not immediately see them. They are typically low in the grass. When I walk down the trail and they perceive me as a danger, they start popping up and calling and flying away.
This is the typical distant view
I saw a lot more males than females, but did catch a glimpse of two females, one of which cooperatively posed for a few photos. The males do occasionally perch on higher grass stalks for pictures, too.