Bird Communities Affected by Noise Pollution

Researchers in Colorado have found that noise pollution adversely affects communities of woodland birds. The three-year study was led by Clinton Francis, a doctoral student in the Department of Ecology and Evolutionary Biology at the University of Colorado-Boulder. Two other scientists that contributed to the study were Dr. Alex Cruz, also of CU-Boulder and Dr. Catherine Ortega, a a former doctoral student of Cruz, of Fort Lewis College.

In their study, the scientists compared the nest number and nesting success of birds on noisy and quiet sites within a pinyon-juniper woodland surrounding natural gas extraction sites containing loud compressors in an area just over the New Mexico border south of Durango, Colorado. The scientists found that 32 species of birds resided in the quiet areas while only 21 species of birds inhabited the noisy areas. The researchers also found that two species of birds preferentially built their nests in the noisy areas—92 percent of all black-chinned hummingbird nests and 94 percent of all house finch nests were found in noisy spots. Two species that overwhelmingly preferred to nest in the quiet areas were mourning doves (97 percent of nests) and black-headed grosbeaks (100 percent of nests). The scientists think that this preference is due in part to the pitch of vocalizations each bird species makes; both black-chinned hummingbirds and house finches vocalize at a pitch higher than the compressor’s noise, meaning the birds can hear each other over the din of the machinery. In comparison, both mourning doves and black-headed grosbeaks vocalize at a lower pitch, which cannot be heard over the sound of the compressor.

The scientists’ research also indicated that those birds that built their nests in the noisier areas tended to have greater reproductive success and were less likely to suffer from nest predation than birds that nested in quieter areas. The researchers concluded that though noise pollution is preferable to some woodland bird species, most others are negatively impacted.

The results of the scientists’ study were published online in the July 23rd edition of the journal Current Biology. The study was funded through a variety of different sources including the Bureau of Land Management and the University of Colorado-Boulder.

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Some Birds Get Their Groove On, Too

Since Snowball’s debut on YouTube in 2007, the cockatoo’s dancing abilities have been viewed over 2 million times. Following the cockatoo’s initial dancing debut to the Backstreet Boys’ hit “Everybody,” Snowball can now also be seen dancing to tunes by Queen, Ringo Starr, and Stevie Nicks. In addition to articles in magazines and newspapers and a stint on “The Late Show with David Letterman,” Snowball is now the subject of two scientific articles published in the journal Current Biology.

African gray parrots are also able to keep a beat when music is playing. (Photo credit: artzy/istockphoto.com)

The ability to keep a beat (whether by tapping one’s foot, bobbing one’s head, or doing some other sort of rhythmic movement, such as dancing) has typically been considered a human characteristic. According to the “vocal learning and rhythmic synchronization” hypothesis, the ability to keep a beat to music requires the brain circuitry necessary for complex vocal learning. In turn, this circuitry necessitates a close connection between auditory and motor circuits in the brain. Animals that are capable of vocal-learning include humans, some birds, cetaceans (dolphins and whales), and pinnipeds (seals, sea lions, walruses).

In an article entitled “Experiential Evidence for Synchronization to a Musical Beat in a Nonhuman Mammal,” researchers from The Neurosciences Institute and the University of California at San Diego studied Snowball’s ability to keep time to a variety of different beats. They found that regardless of the tempo of music, the cockatoo was able to adjust the tempo of its rhythmic movements to keep up with the changing beat. This research indicates that the ability to rhythmically move to a beat is not a solely human characteristic.

In a separate study published in the same issue of Current Biology, scientists from Harvard University, the Massachusetts Institute of Technology (MIT), and Brandeis University examined thousands of videos of dancing animals uploaded to YouTube. The researchers also studied videos of Alex, an African grey parrot that was the subject of many scientific studies over its 30-year life span. In systemically analyzing the videos, the scientists determined that only animals that are capable of vocal mimicry are truly able to keep rhythm with a musical beat. According to their article “Spontaneous Motor Entrainment to Music in Multiple Vocal Mimicking Species,” the researchers conclude that the ability to move rhythmically to an auditory pulse (i.e., music) evolved as a by-product of selection for vocal mimicry.

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Bird Species Takes “Non-Stop Flight” to a Whole New Level

During their south-bound migration, bar-tailed godwits travel non-stop from their breeding grounds in Alaska to their winter grounds in New Zealand. (Illustration credit: USGS)

During their south-bound migration, bar-tailed godwits travel non-stop from their breeding grounds in Alaska to their winter grounds in New Zealand. (Illustration credit: USGS)

Bar-tailed godwits, a type of shorebird, have knocked the eastern curlew off its pedestal and taken over the title as non-stop migration champions. A team of researchers, led by Robert Gill, Jr., at the USGS Alaska Science Center based in Anchorage recently tracked a group of migrating bar-tailed godwits using satellite technology. A female bird referred to as E7 left the Alaskan breeding grounds and flew nonstop directly to its wintering grounds in New Zealand–a trip of over 11,680 kilometers. The flight took eight days, with no stops for food, water, or rest. E7’s flight is the longest direct flight ever recorded for a bird.

The researchers also tracked the flights of eight other females and two males. Seven of the females flew an average of 10,153 km over a period of (at most) 9.4 days. The two males’ flights were of a slightly shorter length, and took place over a period of (at most) 6.6 days.

The researchers monitored the birds’ flight using satellite transmissions. Female birds were implanted with a tiny satellite tracker. Males, which are smaller in size than females, were banded with lightweight external satellite trackers on their legs. Both males and females were also marked with a numbered leg band so that researchers could easily identify individuals in the field. The scientists followed the birds’ migration path in the air by monitoring the latitude and longitude coordinates the birds passed as they flew across the Pacific Ocean.

The southern migration of the bar-tailed godwit from Alaska to New Zealand is the longest known non-stop migration of any bird. On their north-bound return trip back to Alaska, the birds break their migration into two flights. First, they fly from New Zealand to the Yellow Sea in eastern Asia. After resting there, the birds continue their flight on to Alaska.

This female bar-tailed godwit was implanted with a satellite transmitter and given a leg band marked "E1" so that researchers could track its whereabouts in the air and in the field. (Photo credit: Jan van de Kam, NL/USGS)

This female bar-tailed godwit was implanted with a satellite transmitter and given a leg band marked “E1” so that researchers could track its whereabouts in the air and in the field. (Photo credit: Jan van de Kam, NL/USGS)

In studying the bar-tailed godwits’ southern-bound migration, the scientists also discovered that the birds time their migration with favorable tail winds that aid in their flight south. This discovery indicates the importance of weather patterns to the birds’ annual migration. Scientists worry that global climate change could disrupt this connection significantly.

While this study has answered some of the researchers’ questions about the migration of bar-tailed godwits with regard to distance and amount of time it takes, a number of mysteries remain. For example, the scientists wonder how the birds navigate, how they assess weather conditions, and at what altitude they fly. Further research will be necessary to answer these questions.

The full results of the scientists’ research are reported in the October 21st online edition of the Proceedings of the Royal Society B.

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