Tree swallows (Tachycineta bicolor) are back. Anyone who has seen these ridiculously energetic birds can tell that they’re overachievers. They overwinter in parts of the southern US, Mexico, and Central America, and are by far the first swallows to return to the northeast. They’re also changing their behavior due to climate change, laying their eggs more than a week earlier than in the past. Listen to their hyper chirpling here.