Completing the same journey they have made for the past 2,000 years, a flock of swifts has flown halfway around the world to nest among the ancient stones of Jerusalem's Western Wall.
The scores of small black birds who spend the spring flying high above Jerusalem's Old City and laying eggs in the cracks in the wall, where it is common for visitors to place prayer notes, have become a focus in efforts to rehabilitate the species' diminishing population worldwide.
Experts have mapped 88 nests in between the giant stones that make up the Western Wall, which was part of the perimeter of the second biblical Temple destroyed by Jerusalem's Roman conquerors in 70 AD. It is one of Judaism's holiest sites.
"This is one of the most ancient places that you have swifts nesting in the world," said Yossi Leshem, director of the International Center for the Study of Bird Migration at Tel Aviv University.
Thanks to his team's efforts, any restoration work done to the wall now must take into account where the swifts nest so as not to disturb them. They are also looking to set up cameras on the wall with live video feed from the nests to be broadcast online to help raise awareness.
Israeli skies are one of the busiest junctions of avian migration routes in the world, but the swifts, which arrive from southern Africa in late February and stay for about 100 days, have a special following among bird lovers.
They spend years in the air -- eating, sleeping and mating in flight -- and only nest to lay eggs.
And they faithfully return to the same breeding grounds, whether it's the Western Wall in Jerusalem, the Church of the Nativity in Bethlehem, the Bauhaus buildings of Tel Aviv, or the roofs of old houses throughout Europe.
But their numbers have dramatically declined in the past decade, in part because modern and renovated buildings are less accommodating.
There is not a complete global tally, but in England their numbers have dropped nearly 50 percent, said Amnonn Hahn, general manager of the Israeli group Friends of the Swifts.
Leshem, Hahn and their partners are joining forces with foreign experts to try to reverse this trend. They are already tracking some of the swifts in Israel with tiny transmitters in order to study their behavior.
"By next year we hope to make it into a big international project, in cooperation with the Palestinians, Jordanians and the European Union," Leshem said.