Sandhill Cranes and Platte River Water Quality: Bacteria During the Spring Migration

Study area and sampling sites on the central Platte River. USGS (Vogel and others, 2013).

A crowded stopover

The central Platte River in Nebraska supplies drinking water, irrigation, groundwater recharge and recreation — above all bird watching in spring. From late February to early April, about 600,000 sandhill cranes (Grus canadensis) stop here on their way north up the Central Flyway, fattening up for the nesting season. Endangered whooping cranes and millions of waterfowl and shorebirds pass through too. The cranes crowd onto sandbars in shallow water along an 80-mile stretch between Overton and Grand Island.

Migratory birds can carry pathogens long distances and spread them in their feces. Those that waterfowl carry and that affect people or agriculture include avian influenza, E. coli, Cryptosporidium, Giardia, Campylobacter and Legionella. The river can pass them on to people and animals.

The study

The USGS Nebraska Water Science Center sampled water, sediment and feces between February and April of 2009 and 2010, during the migration:

• Water: upstream of the densest roosts (Overton), mid-reach (Denman) and downstream (Grand Island).
• Riverbed sediment: near the Crane Trust visitor center, where cranes had roosted the night before.
• Feces: from places where cranes and waterfowl gathered.

Samples were tested for avian influenza, E. coli, Enterococci, Cryptosporidium, Giardia, Campylobacter and Legionella.

The Platte River from the Crane Trust near Alda, April 6, 2009. Matt Moser, USGS.

What they found

• Timing: peak E. coli and Campylobacter densities coincided with the peak crane count.
• Night: at the most downstream site in 2010, E. coli and Enterococci were higher in samples taken between 2230 and 1100 hours — the cranes' overnight roost plus the time bacteria take to travel downstream.

E. coli and Enterococci densities (most probable number per 100 milliliters) near Grand Island, March 22–25, 2010. USGS (Vogel and others, 2013).

• Downstream vs. upstream: in migration season, bacterial densities at the downstream sites were significantly higher than upstream (95% confidence for E. coli, 90% for Enterococci) and higher than at any site outside the migration.
• A crane fingerprint: a crane-specific Bacteroidetes genetic marker turned up in water only at the two downstream sites during migration, and in roost sediment only during migration, along with Enterococci.
• Campylobacter jejuni appears to be a common pathogen in crane droppings. It and Giardia — found in crane feces but not goose feces — were detected in the river only during the 2009 migration, when there was no substantial rain or snowmelt runoff.

Geese in the Platte River near Denman, from the Nebraska Highway 10D bridge. Matt Moser, USGS.

Why it matters

Crane droppings carry several fecal-indicator bacteria and a range of viral, protozoan and bacterial pathogens, found more often and in higher densities in the river's water and sediment when the cranes are there — especially during evening roosts. That makes the river a source of exposure for anyone using untreated water: local recreationists, livestock and wildlife.

Geese, ducks and sandhill cranes on Big Platte Lake beside the Platte River at Denman. Matt Moser, USGS.

Sources

Based on Moser MT, "Microbial water quality during the northern migration of Sandhill Cranes (Grus canadensis) at the central Platte River, Nebraska," U.S. Geological Survey Fact Sheet 2014–3094, summarizing Vogel and others (2013), Water, Air, & Soil Pollution; a work of the United States government in the public domain. Figures from the fact sheet's PDF; its cover photograph, used with a private photographer's permission, is not reproduced.