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Cities: They’re not the greenest spaces in the world. But now, some major greening projects are placing roofs in the spotlight, and the results are delightful. In France, all new buildings are required to include or solar panels, and in California, Uruguayan architect Rafael Vinoly recently unveiled plans for what will be the and public park, at 30 acres. All of this is good news for city wildlife. Here’s a sampling of four roofs whose formerly concrete premises are now, literally, for the birds.

Javits Center, New York City

Size: 297,000 square feet

Vegetation: 14 types of sedum, a flowering succulent that grows in thick mats

Key species: Herring Gulls, European Starlings, Barn Swallows

The monumental conference center looming over Manhattan’s West Side used to lure thousands of birds to their deaths via its giant glass windows. But the installation of bird-deterring glass cut fatalities by 90 percent, and now a 6.75-acre rooftop has transformed the Javits Center into an avian haven. Layers of hardy, herbaceous sedum provide perfect nesting habitat for Herring Gulls, which have taken up residence on the roof along with scores of other species. “More than a dozen types of nests have been found on the roof, with several eggs hatched throughout the past year,” says Tony Sclafani, a representative from the Javits Center. Over the spring and summer of 2014, New York City ����APP and Fordham University and counted 524 birds making use of the space, including the American Kestrel, European Starling, Barn Swallows, and the Northern Mockingbird (it also hosts bats and a multitude of insects). According to Sclafani, NYC ����APP also installed special recording equipment on the roof to continually track bird and bat species using the space. In January this year, further renovations, totalling $1 billion, , including a new public green roof terrace and a 34,000-square-foot solar energy array.

City Hall, Chicago

Size: 35,000 square feet

Vegetation: herbaceous plants, grasses, shrubs, trees

Key species: Peregrine Falcon, Olive-sided Flycatcher

This site may be small compared to Javits, but it’s something of a catalyst. Fifteen years ago it triggered a trend that transformed Chicago into one of America’s most verdant cities, with its more than  of vegetated roof space. City Hall’s project began as an experiment to “promote green roofs as a very positive and sustainable strategy for the city,” says David Yocca, an architect from the Conservation Design Forum who was the lead designer on the project. The roof was initially intended to improve the building’s energy usage and reduce rainfall run-off. Now 15 years on, it contains active beehives and 200 plant species that create a leafy stopover spot for migratory songbirds that skirt Lake Michigan. “The grasses are left all winter, they’re not cut back until the spring,” Yocca says. “Many of the flowering perennial plants have seeds that the birds will eat.” Visiting field biologists have recorded a wealth of birdlife there: Field Sparrows, Cape May Warblers, chickadees, wrens, thrushes, woodpeckers, and, notably, Peregrine Falcons, along with rarer birds like the Olive-sided Flycatcher, flock to the site to nest and rest.

Emmen green roof, Switzerland

Size: 150,000 square feet

Vegetation: scrubby grassland

Key species: Northern Lapwing

Since the 1970s, Switzerland’s population of flamboyantly-crested Northern Lapwings has dipped dramatically—from 1,000 breeding pairs to just 150 today. They’ve lost a chunk of their natural marshy habitat to agriculture. But a few of the remaining pairs have abandoned their shrinking habitats for green rooftops, says Stephan Brenneisen, an urban ecologist at Zurich University of Applied Sciences. So, he and colleagues have set out to provide more—they’ve landscaped an existing green roof atop an industrial building complex in Emmen, central Switzerland, to provide improved foraging ground and more accommodating nest habitat for these threatened birds. “Green roofs have the benefit that no ground predators can get the eggs or chicks,” Brenneisen says. “Our research showed that chicks can survive if the design is correct.” These spaces may become key to a species’s survival.  

Wild West End, London

Size: 46,000 square feet (and growing)

Vegetation: grasses, flowering meadowland plants, trees

Key species: Black Redstart

Despite the noisy bustle of traffic and shoppers in London’s West End, the area will soon also be a haven for birds: Major property owners in the area are voluntarily combining forces in a project called “Wild West End” to convert their rooftops into lush oases for wildlife. The Crown Estate, a property owner in the area, is spearheading the project and has already pledged an acre of roof space. Ultimately, this will provide ecological “stepping stones” that link the nearby Regent’s and St. James Parks to each other, creating a lush corridor, says Neil Harwood, an ecologist from Arup, the project’s engineering consultancy. A flagship species set to benefit is the Black Redstart, he adds. “Its natural habitat is gorges and cliffs. It has managed to spread from those areas and take on tall buildings.” Other target species include Blue Tits, goldfinches, Song Thrushes, wrens, and blackbirds. By incorporating various landscape features like bird and bat boxes for nesting, food-producing plants, vegetated walls, and trees at street level, businesses aim to create a continuous green corridor that will attract wildlife to the city’s core. “Even the smallest space can make a contribution,” Harwood says. The Crown Estate in October 2015; at 46,000 square feet, it’s a sky garden designed to attract insects, birds, and bats. Further roof renovations are set to expand and connect green space across West London properties over the coming years.