Life aloft: The unexplored ecosystem above your head

7 June 2017

We have nature reserves on land and at sea, but the sky has never been considered a habitat, let alone one worth preserving, until now

By Lesley Evans Ogden

THE Federal Bureau of Investigation has a spectacular view of the city skyline from its Chicago office tower. But when special agent Julia Meredith arrived at work one Monday morning, her eyes were focused firmly on the ground. That’s where the bodies were – more than 10 of them.

Some of the dead were Blackburnian warblers, birds with bright yellow and orange plumage that are rarely seen in the city. They had been on their way to their wintering grounds in South America when they had collided with the building’s glass facade. “They had come all this way and here they were, dead,” says Meredith.

It’s not an isolated incident. Just last month, 395 migrating birds were killed in one building strike in Galveston, Texas. The world over, wherever humans are extending their buildings, machines and light into the sky, the lives of aerial creatures are at increasing risk. We don’t have very accurate figures, but in the US, casualties are thought to run into the hundreds of millions every year. Yet while efforts to protect areas on land and in water have accelerated since the 1970s, the sky has been almost entirely ignored.

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Steep declines in Kauai's seabird populations, radar reveals

Date: June 1, 2017

Source: American Ornithological Society Publications Office

The island of Kauai is home to two endangered seabirds, the Hawaiian Petrel and the Newell's Shearwater. Monitoring these birds, which are nocturnal and nest in hard-to-access areas, is challenging, but observing the movements of birds via radar offers a solution. A new study from The Condor: Ornithological Applications takes a fresh look at two decades of radar data -- and comes to worrying conclusions about the status of both species.

To assess the population trends and distribution of the birds in recent decades, André Raine of the Kauai Endangered Seabird Recovery Project and his colleagues examined past and contemporary radar surveys as well as data on the numbers of shearwater fledglings rescued after being attracted to artificial lights. Their results shows continuing population declines in both species over the last twenty years -- a 78% reduction in radar detections for Hawaiian Petrels and a 94% reduction for Newell's Shearwaters, with the shearwater decline mirrored in decreasing numbers of recovered fledglings over time.

For shearwaters, this is consistent with previously published work, but past analyses of petrel radar data suggested their population was stable or potentially increasing. The researchers attribute the difference to the fact that for this new study, they carefully standardized the data based on sunset times, which ensured that the time periods (and thus bird movement periods) under consideration remained constant from the beginning to the end of the survey period. They believe that the steep declines may have commenced in earnest in the aftermath of Hurricane Iniki in 1992, which led to permanent ecological changes such as the opening of new routes for invasion by exotic predators and plants, as well as significant infrastructure changes across the island.

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New details on nest preferences of declining sparrow

Date: May 31, 2017

Source: American Ornithological Society Publications Office

Theory says that birds should choose nest sites that minimize their risk of predation, but studies often fail to show a connection between nest site selection and nest survival. Understanding these relationships can be key for managing declining species, and a new study from The Condor: Ornithological Applications explores the nest site preferences of Bachman's Sparrow, a vulnerable songbird dependent on regularly burned longleaf pine forests in the southeastern U.S.

Jason Winiarski of North Carolina State University and his colleagues monitored a total of 132 Bachman's Sparrow nests in two regions of North Carolina, the Coastal Plain and the Sandhills, measuring a variety of vegetation characteristics. They found several differences between the two regions in what sparrows looked for in a nest site -- in the Coastal Plain, they favored low grass density and greater woody vegetation density, while birds in the Sandhills selected intermediate grass density and greater tree basal area. However, none of these features turned out to be related to nest survival.

According to the researchers, the differences between the two regions are likely due to differences in the available plant communities. Bachman's Sparrows also could be selecting nest sites that allow easy access to nests or maximize the survival of fledglings once they leave, and these aspects may warrant further investigation. Regardless, Winiarski and his colleagues believe their results show the importance of management that mimics historical fire regimes in longleaf pine ecosystems, in order to maintain the diverse groundcover types used by the birds.

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