The migration is in progress. The birds have started flying out of Maine. Over the next two weeks, the net will become a torrent. Where will they all go?
Good question. Birds are disappearing from the planet at an alarming rate. In North America alone, nearly three billion birds have disappeared in the past 50 years.
Collisions with man-made structures and predation by outdoor cats account for much of the decline, but habitat loss is likely the main cause. For migratory species, their summer and winter habitats must be conserved if we are to slow the trend.
This is how Emily Filiberti ended up on an internship in a nature reserve in Jamaica a few years ago. Filiberti is now a graduate student at the University of Maine. She spent this summer in Wisconsin tracking golden-winged warblers, a species that is disappearing even faster than most other birds. It was there that she made an astonishing discovery.
Last spring, Filiberti and his crew captured some of the golden-winged warblers in the search area and fitted them with Nano Tags. These tiny transmitters are part of the Motus wildlife tracking system, a technology less than ten years old that takes advantage of miniaturized electronics. The transmitters are so small that they can be attached to butterflies.
Suddenly, the receiving station picked up a signal from a different species, a female American Redstart that had been tagged in Jamaica. In fact, he had been tagged two months earlier by his former supervisor, at the exact same place where Filiberti had studied.
Eight days later, the station picked up the signal. This bird was not just passing through. It was probably nesting. Using a hand-held antenna and immense patience, Filiberti managed to track the redstart to its nest and even peek at two spotted eggs for a moment when the bird emerged. for a snack.
So there you have it, an individual bird whose exact winter and summer territories were known – 2,000 miles apart. The odds against such a discovery are incalculable.
First, redstarts have one of the widest breeding ranges of any warbler in North America, extending west across the continent from Newfoundland to British Columbia, and south almost to the gulf coast. That’s a lot of real estate. Second, migration is dangerous. Many birds do not survive the journey at all. Third, how many times can the same researcher have studied both sites at each end of the migration?
Maybe that’s the future. Traditional bird banding remains valuable, but advances in technology allow some birds to be tracked by satellite, using GPS transmitters. Motus technology is a game changer. With enough receiving stations set up along migration routes, the exact route taken by tagged birds becomes clearer.
Amber Roth is Filiberti’s college advisor. Amber is using Motus technology to study some of Maine’s most vulnerable species.
Grassland birds are in precipitous decline. When bobolinks leave the fields of Maine, they migrate to the grasslands of Argentina. A tagged Bobolink’s signal was picked up at 13 different stations during its journey south. The bird disappeared when it crossed the Caribbean, but the signal sounded again when it made landfall in Colombia.
This type of monitoring enhances the ability of scientists to track bird populations. Each field guide features range maps for each species, showing the full extent of where the birds breed, migrate and overwinter.
What the books don’t show is that different geographic populations migrate to different places. For example, east coast birds may winter in the Caribbean islands, while west coast birds head for Central America. Knowing these details improves our chances of conserving particularly important bird areas.
We can also follow the migration patterns of males, females and nestlings to see if there are any significant differences. These differences are particularly noticeable in certain species.
For example, adult male shorebirds typically leave their breeding grounds before females, which then leave before the young.
As expected with such a small transmitter, the signal is not strong. A tagged bird must be within 15 kilometers of the receiving station to be picked up, and much closer if hills and trees get in the way. Over short distances, biologists can use a hand-held antenna to locate a stationary bird, as Filiberti did.
How exciting it will be if this little redstart returns to Jamaica and pings the station upon arrival! We cheer him on.
More articles from the BDN
