Tiny geolocators measure light levels and atmospheric pressure to reveal the migrations of small songbirds – including the yellow-rumped warbler, also known as a butter-butt – in unprecedented detail.
Squinting through my binoculars, I scanned the dense branches of a black spruce, trying my best to catch a glimpse of the thin legs of a small black, white and yellow songbird. I was on the hunt for … [+8744 chars]