A team of international scientists is studying the Louisiana waterthrush, a species of conservation concern, at Powdermill Nature Reserve in Ligonier. The songbird is a large warbler yielding vital clues about the health of our watersheds. The Allegheny Front's Deborah Weisberg has the story.
Weisberg: Deep in the woods by Powdermill Run, Marisabel Paulino clips a tiny color-coded bracelet to the leg of a six-day old Louisiana waterthrush. It is nestled in the palm of her hand.
(Sounds of birdsong)
Weisberg: She measures its wing length, then slips the bird into a baggie so it can be weighed.
She calls out the weight to her colleague, Danilo Mahila, who logs it and other details about the bird's condition in a book. Paulino repeats the process with four other chicks, each getting its own ID tag, before Danilo returns them to their nest on the bank of the stream.
Weisberg: By August these birds will be on their way to the Dominican Republic for the winter, where Paulino and her colleagues also live. But Pennsylvania is where the birds come in early spring to breed, and that is of enormous interest to these scientists. Louisiana waterthrushes are disappearing, especially on streams impacted by acid mine drainage, acid rain, and a new threat, methyl mercury from coal-fired power plants. Steve Latta is an ornithologist with the National Aviary.
Latta: We've found that on average waterthrush nesting on acidic streams nest in much lower densities, have larger territories, the number of eggs they lay is reduced the average weight of nestlings lighter than we find on non acidified streams; overall, less than half the number of fledglings on acidified streams as on non-acidified stream
Weisberg: Acidified water isn't impacting the birds directly, but it is robbing them of the forage they need to thrive and reproduce. Waterthrushes feed on aquatic insects such as Mayflies, which are themselves indicators of stream health. When bugs disappear, the birds do too. As part of their study, Latta and his crew monitor insect life where the birds live.
Latta: these yellow squares are plastic sticky traps they're called that we put in each territory to sample flies and insects. We leave them out for two days around the time the nestlings are about to leave the nest to sample what sort of insects,the number and type of insects, that are available presumably as food for birds.
Weisberg: Latta says bug life and waterthrush populations appear to be healthy on Powdermill Run, which is more pristine than other streams in the same watershed. But whether bird numbers here can compensate for declines elsewhere is doubtful.
Latta: We're certainly finding higher densities on non-acidified streams;but the issue really is one of how well they're reproducing,...whether they're reproducing well enough to maintain populations all the evidence suggests that as a species they're not because we're finding declining populations across their range.
Weisberg: The birds are highly territorial, he says, and there is room only for so many on viable streams. Waterthrushes who have to forage too far from their nests leave their chicks open to greater predation. And then there is the long migration to and from Central America each year.
Latta: This nest we banded today the male is a bird we banded last year on Camp Run which is 10 kilometers or so from here so by chance that bird was able to survive both migrations, and survive the overwinter period returned and found territory here on Powdermill Run.
Weisberg: Latta and his crew are today banding the male's companion. They set a net across the stream and capture her on one of her many food runs to the nest.
(Sounds of group pleased to have captured bird)
Weisberg: They put a bracelet on the bird;
(Fluttering sounds heard)
Weisberg: ...Weigh it in a baggie,;measure its wing length....
(Sounds of scientists recording weight, etc.)
Weisberg: And pluck a feather to analyze in a lab, before releasing the bird back to the wild. Latta hopes to see her on Powdermill Run or a nearby stream this time next year, yielding more clues about this species of conservation concern, and what it means to the future of the ecosystem.
Latta: It's very important to understand that if we lose the water thrush, it's an indication of what we have done to our environment. Ultimately that contamination that we're adding to environment is affecting human health and human populations, so it's this idea that the waterthrush is an indicator, a signal of wider problems of the health of the ecosystem that we're focused on.
Weisberg: For the Allegheny Front, I'm Deborah Weisberg