Burrowing birds create pockets of rich plant life in a desert landscape
Mounds of sand dug out by nest-digging birds are microhabitats where seeds can germinate
In the rain-starved deserts of coastal Peru, tiny patches surprisingly rich in plant life dot the landscape. Burrowing birds may be responsible, scientists say.
Mounds of sand shoveled out by nest-digging burrowing owls and miner birds harbor more seedlings and exclusive plant varieties compared with surrounding undisturbed soils, researchers from the National University of San Marcos in Lima, Peru report in the October Journal of Arid Environments. Although the mounds hold fewer seeds, the structures may provide a sheltered and moist germination environment at the start of the growing season — unlike adjacent crusty soils carpeted with cyanobacteria, lichen, moss and algae.
“The ability of seeds to germinate in the desert is a daunting task,” says Jayne Belnap, a U.S. Geological Survey ecologist based in Moab, Utah, who wasn’t involved in the study, “especially if you have a crust.”
That crust inhibits seed growth in two ways. Seeds stranded on top are exposed to the harsh environment, and may not be able to sprout at all. And the crust itself can act as a barrier for water to reach buried seeds, and for seedlings to emerge.
But when burrowing birds break the crust and dig up sand, seeds can mix into the sand, and water may pool between the tossed sand and crust, the researchers say. That allows seeds to become buried and accumulate moisture needed to germinate.
While it’s known that burrowing mammals can break compacted soils and create nutrient-rich hot spots ideal for plant establishment, this study is the first to document similar ecosystem engineering done by dryland birds.
In 2016, Maria Cristina Rengifo-Faiffer, an ecologist now at Northern Arizona University in Flagstaff, collected soils in the National Reserve of Lachay in Peru. The area lies in a part of the Atacama Desert (SN: 2/27/18) where lomas, or mist oases, exist. It rarely rains there and most plants rely on three months of winter fog to complete their life cycle.