Massing martins

Thousands of purple martins are roosting on their way to Brazil

Purple martins gather on power lines at sunset Aug. 10 along Industrial Harbor Drive in Little Rock.
Purple martins gather on power lines at sunset Aug. 10 along Industrial Harbor Drive in Little Rock.

Tens of thousands of America's Most Wanted Bird -- purple martins -- have stopped in at Little Rock on their way to wintering grounds in South America.

photo

Special to the Democrat-Gazette

Purple martins are migratory birds that overwinter in Brazil; on their way south, they linger in Arkansas to fuel up on insects.

photo

Special to the Democrat-Gazette

Tens of thousands of purple martins perch on power lines in the Little Rock Port area around sunset, but at 8 p.m. they depart en masse and vanish into the darkness.

The birds have congregated near sundown in the industrial area at Little Rock's slackwater harbor near the Arkansas River and Interstate 440.

This large flock was detected Aug. 1 by radar analysts with the University of Oklahoma at Norman. Animal Migration Research Group aeroecology experts spotted a distinctive signal typical of purple martins on the National Oceanic and Atmospheric Administration's Next Generation Radars (NEXRAD) scans of Little Rock.

Joe Siegrist, research director of the Purple Martin Conservation Association in Erie, Pa., works with the Oklahoma group to track purple martin roosts across the nation. He notified Audubon Arkansas about the radar signal. He asked that birdwatchers investigate the Little Rock Port area to confirm that the signals were in fact produced by a flock of martins, and if so to estimate their number and their roosting conditions.

Dan Scheiman, ornithologist of Audubon Arkansas, passed Siegrist's request to birders across the state via the online discussion list ARBird-L, a listserv for birdwatchers that is hosted by the University of Arkansas.

When martins come together before migration, they spend their days foraging in a general area but collect in one location in the late afternoon. By day, that roost could be empty, but in the late afternoon and evening, usually 30 minutes to an hour before sundown, the birds pack in.

Perching close to one another, they remain through the night. At dawn, they disseminate to feed.

I visited the site Aug. 3 as the sun was going down and confirmed the radar's indication of a great number of martins. They were swarming just above the ground and in the air, but mostly they perched on power lines along a half mile of Industrial Harbor Road. Since light was poor in the cloudy late afternoon, I was unable to make a good estimate of their number.

I reported what I saw and the loud liquid songs of the martins I heard to Siegrist using an electronic form on the association's website, and he replied to my report with a lengthy phone call.

Siegrist says, "A state the size of Arkansas might host as many as 10 such roosting sites each year during late summer, and some of the birds might remain around the river in Little Rock for another four to six weeks."

"Basically," Siegrist told the Democrat-Gazette, "the roosts look like exploding circles on radar when they disperse in the morning." The pattern can be seen in an archival radar image from Wilmington, Ohio, on the National Weather Service Forecast Office site erh.noaa.gov/iln/research/birds.

Jeff Kelly, director of the Oklahoma University team, told Siegrist that the roost in the Little Rock Port area has been showing up since the team started looking for purple martins using radar in 2009, but it hadn't been confirmed by eyewitnesses until now. Kelly checked archived radar images from 2004 and the roost was not visible.

Siegrist explained that roosts must attain a large size before they can be seen on radar.

EVEN MORE

I returned to the site the next evening. The birds were there in what seemed to be even greater numbers. Martins perched shoulder-to-shoulder on two miles of electrical wires strung on wooden utility poles 50 feet tall.

The wires were loaded. I calculated three birds a foot for two miles, or 31,680 birds perched on the lines. In addition, a dark cloud of martins swirled overhead, with more birds continuing to arrive from the east and west until the sun was so low they could no longer be seen.

In addition to those perched on the distribution power lines and those swarming, at least a thousand martins were atop a nearby high-voltage power transmission tower and its cables.

Many birds alighted on the asphalt road to collect grit to grind food in their gullets, and some were foraging in the short grass between the road and a drainage ditch. Altogether, as I reported to the Purple Martin Conservation group and ARBird, there were at least 40,000 martins at the Little Rock Port roosting site.

The port complex where the martins are gathering each evening is a restricted area, and occasionally locked gates prevent access down Lindsey Road to the place where the martins roost. Those who enter the area are subject to search, and a sign at the gate describes security restrictions.

MYSTERIOUS DEPARTURES

Over the next four days, one or more birdwatchers visited the roost each evening and reported to the online list. Their consensus was that the number of birds using the roost was rising daily.

There is a small mountain of scrap metal between the poles and the tower where the purple martins are being seen. Sparrows, mourning doves and scissor-tailed flycatchers perch there in the late evening -- as if seeking refuge from the confusion of the swooping martins.

Cindy Franklin, a longtime member of the Central Arkansas Audubon Society, posted Aug. 7, "As the evening wore on, martins packed together like sardines completely filled 12 spans of wire between the wooden poles."

She estimated seeing bird density "double, if not triple" what I saw.

As the light was falling about 8 p.m., a steady stream of martins took off and passed over where she stood at the corner of Slackwater Harbor Drive and Industrial Harbor Road, headed north across the river.

"Massive does not begin to describe the size of that cloud of birds," she reported. "Had to be tens of thousands of birds in that swirling mass out over the wetlands across the river. The cloud was at distance, but I estimate it was at least 500, if not a thousand feet high, and at least a half mile wide."

At 8 p.m. Aug. 8, 12 birding enthusiasts showed up on Slackwater Harbor Drive. The martins on this night collected first on the transmission tower and then began to land on the power lines, but their appearance was tardy and at their peak there were only about half as many as the night before. At 8:20, the birds began to depart much in the same way Franklin described the day before.

Reports from birders who visited on successive nights suggest this pattern: The birds gather on the power lines before sunset. But sometime around 8 p.m., they dive en masse into the air and rise as a swirling cloud to vanish into the darkness to the north.

MUCH TO KNOW

Why were the birds flying off into the night? Was it too crowded at the port? Do they spend the night in trees across the river? Siegrist told me that some of the martins may leave for Brazil earlier than others, but would they take off at night?

Maybe they were spooked by a predator. Franklin reported seeing six American kestrels, small hawks that occasionally feed on small birds, while the martins were gathering Aug. 8.

Siegrist also noted that "while the roosting of martins on power lines is not unheard of, it is unusual. Most of the time purple martins roost in a small group of trees that stand apart from other trees on relatively level ground or on marshy islands protected by water. Martins have adapted more closely with the development of humans than many other species of birds."

As to why they would light on these power lines instead of a thousand others seemingly just like them is "a mystery," he said.

Roosting martins have congregated in extreme southeastern Little Rock before. Karen Rowe, migratory species specialist with the Arkansas Game and Fish Commission, checked Arkansas Audubon Society records and found reports from 2006 and 2009 of a roost of more than 1,000 purple martins in trees by a car rental parking garage near the Bill and Hillary Clinton National Airport, Adams Field.

Numbers of those birds died, Rowe said, and necropsies suggested the cause was blunt force trauma; also it appeared a raptor was hunting them. She worked with airport crews to have the trees removed, which seemed to make the martins go elsewhere. "The airport grounds manager told me [Wednesday] that there are no longer problems with purple martins in the garage and none are being found dead," she said.

CAUSE FOR CONCERN

Tens of thousands of migrating purple martins roost in late summer on Bird Island in Lake Ouachita, west of Hot Springs. The National Audubon Society has designated the island an "Important Bird Area," and it has become a tourist attraction. Lake Ouachita State Park conducts boat tours.

The Bird Island roost also attracts harmful attention, Rowe said.

The game and fish commission "had to initiate patrols on Lake Ouachita because unethical boaters were going to the martin roost on Bird Island in the evening and blowing air horns to flush the birds from the roost," she told the Democrat-Gazette. "While harassing martins is not a violation of state or federal law, it causes the birds to needlessly expend valuable energy at a time when they are trying to greatly boost fat stores for migration."

The martins at the Little Rock port also are storing energy for a daunting ordeal, Rowe said. Flushing them for the amusement of seeing them fly would weaken them, by the thousands, making them less likely to survive their long flight -- and less likely to revisit Little Rock in the future.

Celia Storey added some information to this report.

Jerry Butler is a freelance writer who writes about Arkansas birds and the people who enjoy them. He welcomes comments at jerrysharon.butler@gmail.com.

ActiveStyle on 08/17/2015

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