Burrowing birds plant vegetation in a desert landscape
Burrowing birds create pockets of rich plant life.
In the desert coastal deserts of Peru, tiny patches, surprisingly rich in plant life, dot the landscape. Scientists say that birds can hide behind it.
Researchers at the National University of San Marcos in Lima, report to Peru in the October Journal of Drylands that they dig sand mounds dug by nesting owls, and miner birds produce more seedlings and exclusive plant varieties compared to surrounding undisturbed soils. Although there are fewer seeds in mounds, structures can provide a protected and moist environment for germination at the beginning of the growing season – unlike neighboring crusty soils covered with cyanobacteria, lichens, mosses and algae.
“The ability of seeds to germinate in the desert is not an easy task,” said Jane Belnap, a US geological survey engineer from Moab, Utah who did not participate in the study, “especially if you have bark.”
This crust inhibits seed growth in two ways. Seeds twisted from above are exposed to harsh conditions and may not germinate at all. And the bark itself can serve as a barrier to water for penetrating buried seeds and for emergence of seedlings.
But when burrowing birds break the bark and dig sand, the seeds can mix with the sand, and water can accumulate between the abandoned sand and the crust, the researchers say. This allows the seeds to dig in and accumulate the moisture necessary for germination.
Although burrowing mammals are known to destroy compacted soils and create nutrient-rich hot spots that are ideal for planting, this study is the first to document similar ecosystem engineering by dryland birds.
In 2016, Maria Cristina Rengifo-Fiffer, now an environmentalist at the University of Northern Arizona at Flagstaff, was gathering soil in the Lahai National Forest in Peru. The area is located in the Atacama Desert (SN: 2/27/18), where crowbars or oases of fog exist. It rarely rains there, and most plants rely on three months of winter fog to complete their life cycle.
Samples were obtained from 61 barrows obtained by three species of birds – a burrowing owl (Athene cunicularia), a coastal miner (Geositta peruviana) and a grayish miner (G. maritima), as well as from the adjacent untouched areas. She watered the soil and allowed the seeds to germinate in the greenhouse, using this as an indicator of how many viable seeds were in the soil.
In bird mounds, on average, 1,015 seeds were contained per square meter, while on land plots of the same size there were 2,740 seeds, were discovered by Rengifo-Fifer and ecologist Cesar Arana.
But the catalog of natural sprouting in the desert found that the soil abandoned by birds was much more fertile than the bark: an average of 213 seedlings sprouted from bird mounds compared to 176 that appeared on neighboring crusty soils.
Researchers also found that five plant species appear exclusively in areas affected by birds, including the species Amaranthaceae and Malvaceae. Rengifo-Fiffer says that these “microbeats” created by digging birds are important for maintaining plant diversity.