A group of finches is called a charm, and house finches are one of the more charming bird species. Once popular as pets, their adaptability has allowed them to thrive in many environments to which they have been introduced.

To control the porcupine population, logging companies in Northern New England released fishers into the region. As you might imagine, porcupines, with 30,000 barbed quills, are difficult to kill, but fishers have developed techniques that help them in this battle.

Wherever humans grow food or cook it, rats follow, and killing them may be a losing battle: The remaining rats reproduce more as their population declines.

Sapsuckers peck holes into trees to create reservoirs called sap wells, collecting it with brushlike tongues. They also become food repositories that serve butterflies, beetles, moths and flies, while sapsuckers’ nest cavities get used by squirrels and owls.

Harvard students of the early 1900s took young squirrels to raise, “carrying them about in their pockets until more than half grown, and letting them run about the tables at Memorial and Randall halls at will during mealtime.”

Many people have anecdotes about the intelligence of crows, which have brains accounting for almost 2 percent of its body mass – similar to that of humans.

Though they have ratlike tails, muskrats are not rats. And since muskrat pairs mark the border of their territory with musk, you might think this is the origin of the name – but you’d be wrong again. What is true about these creatures?

The white-breasted nuthatch hops down tree trunks head first like a squirrel, “wonderful little gymnasts [that] keep their nerves as cool as the thermometer in January.”

There are only about 50 breeding pairs of loons in Massachusetts, where the birds were once abundant. If you are lucky, you might see a loon on Fresh Pond.

The white-throated sparrow is a fascinating bird with unique characteristics not found in other bird species whose behavior raises many questions – even about us.