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Scientists Launch 5-year Study on How Noise and Light Affect Songbirds

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Glaring lights and the grinding, metallic clatter of pumpjacks in an oil field would hardly seem the place to put one’s eyes and ears on songbirds.

But a team of avian researchers deems these brightly lit cacophonies in New Mexico’s San Juan Basin as ideal settings to study how such sensory intrusions affect the birds’ survival, reproduction and general health.

Although it would seem basic logic that artificial light and noise would have an unnatural effect on birds, scientists are still learning what those impacts are.

And as human populations swell, generating more light and sounds, researchers are curious about how those multiplying stressors in the environment might compound those caused by climate change.

A research team at California Polytechnic State University is conducting a five-year ecological study of a half-dozen songbird species in northwestern New Mexico oil fields, an environment that allows them to zero in on the specific impacts of noise and light pollution.

Early studies that examined whether excessive noise and light decreased bird populations were done in more urban settings, where the birds faced a jumble of deadly threats such as prowling cats, toxic chemicals and speeding cars, said Clint Francis, an ecology professor at the university.

The next step was to isolate either noise or light in a rural area to see how one or the other affects the songbirds, Francis said, noting he did such research in this same northwestern New Mexico region in 2005.

The aim now is to observe how the two together affect the birds in a locale where they can be clearly measured in tandem, he said.

“That’s why we chose to do this experimental approach where we try to hold everything constant but vary noise and light pollution to try to understand whether there is, perhaps, surprising cumulative effects when you have both of those stimuli together,” Francis said.

The study was funded by a grant of nearly $900,000 from the National Science Foundation.

The team set up an experimental lighting system mimicking streetlights to analyze their influences apart from other urban factors.

One of the things they hope to determine is what traits allow birds to thrive in areas engulfed in noise and light, Francis said. Another is whether this type of pollution has the same effect on all species.

A fundamental point would be how well the birds adapt, he said. For instance, do the changes in the birds’ behavior and hormones indicate whether they will successfully reproduce?

Broad spectrum of birds

The research will focus on six types of songbirds: ash-throated flycatchers, gray flycatchers, mountain bluebirds, Western bluebirds, chipping sparrows and house finches.

The team chose species that together represent a broad array of songbirds.

Three of them nest on branches and other open spaces, and three nest inside cavities in trees. The house finch and Western bluebird prefer urban environments, while others are at home in rural and suburban areas, Francis said.

Their diets also vary, ranging from seeds and insects to berries and flower buds.

“Humans are changing the environment at a more rapid pace than has ever been seen in Earth’s history, so animals are facing all kinds of unanticipated stresses,” said Tim Wright, a New Mexico State University biology professor.

Wright is not involved in the study but said he’s a longtime fan of Francis’ work.

One thing that’s still unknown, he said, is how well the birds will adapt to noise and light stresses, both through behavior and biology; or they could evolve genetically, which will take generations.

“Are they able to adjust and reproduce or are these impacts so grave that [they’re] really starting to decline in population?” Wright said.

One response the team is studying is whether heightened stress hormones mean a bird is adapting to the disruptive stimuli or whether it’s signaling a level of distress that could erode the bird’s health and chance of survival.

A surprise finding is some birds’ stress hormones drop when they’re exposed to repetitive noise, Francis said.

This seems to indicate the birds, after being continually agitated by the sounds, are becoming numb to them.

This more listless state makes the birds less alert and reactive to predators, to which they are already more vulnerable because the noise prevents them from hearing the animals approach, he said.

An ecologist at the Randall Davey Audubon Center, who’s also not involved in the study, said it’s useful to learn how artificial changes in the environment affect songbirds as human populations intrude more in their nesting grounds.

“The noise pollution, the light pollution — as much information we can get on that will be beneficial,” given almost a third of the bird population has been lost in the past half-century, said Tucker Davidson, a senior water associate at the center who has studied birds’ nesting survival and selection.

Davidson said the Cal Poly research team picked a good group of songbirds to study, in part because their nesting varies. That will allow the scientists to see if there are differences in how the ones in enclosed spaces fare, where they’d be less exposed to brighter lights, compared with those with no visual shields.

He agreed they were representative of the larger population and noted all of them fly to the Audubon center at various times of the year.

The study area is also ideal because the piñon woodlands surrounding the oil fields will draw a diverse assortment of birds, he said.

Not all effects are bad

Davidson said he’ll be interested to see if this study reveals more adverse impacts from noise.

Audubon has a “lights out” program that encourages building owners at night to turn off outside lights that can disorient migrating birds and cause them to fly into windows or structures, he said.

A “noise out” program might be something to explore if studies such as these show an excessive amount is harmful to birds, he added.

In one study conducted in an oil field near the Rocky Mountains, birds that would forage as close as 5 meters to an oil pad would be driven as far as 50 meters away if the motors were running, Davidson said.

Francis said he learned in his early fieldwork that noise from oil operations spooked away about a third of bird species in the area.

However, a surprising discovery was the birds that stuck around thrived because the noise also drove off predators.

The survival rates of nestlings went from 50% to more than 90% because they didn’t have those animals preying on them, he said.

As for night-time lights, aside from disorienting birds, they can flood the pineal gland, inhibiting the release of melatonin and disrupting sleep cycles. Lights also make the birds more visible to predators.

However, lights also have the benefit of drawing insects, creating a plentiful food source in a small area, Francis said. And the lights extend the hours hungry birds can forage.

Still, it’s unclear how helpful these lit environments are in the long run.

“Does that mean they’re ultimately more successful?” Francis said. “That’s what we need to find out over this five-year study.”

Connected to climate change

There’s also an indirect link to climate change impacts.

Birds follow their normal biological clocks, flying south at the end of winter and laying eggs at the time when their food sources are normally reaching their peak.

But climate change is warming temperatures earlier in the year, resulting in insects and plants emerging sooner. That throws off the timing for birds, leaving them migrating and breeding too late.

Noise and light can aggravate the adverse effects of climate change when it comes to birds’ reproduction, Francis said.

If there’s too much noise, the female birds can’t hear the males’ mating calls that act as a biological cue to couple, he said. This can cause a mismatch between the male’s and female’s readiness to reproduce.

And if a forest is too brightly lit, it can give a miscue to female birds that read it as the days getting longer, priming them to mate earlier than they should, Francis said.

Many knowledge gaps exist about light and noise effects on birds because it’s a relatively new field of study, he said.

Francis hopes the study will uncover information that can help people adjust their noise and light to coexist better with birds.

“We can know which aspects in an urban environment to tweak to make them more bird-friendly,” he said.

Source: Santa Fenew Mexican