Located in southeastern Colorado, John Martin Reservoir has a small nesting population of piping plovers and interior least terns.
The identification of these two particular species that heavily rely upon the reservoir’s shoreline, directed the need for habitat improvement to be focused on threatened and endangered species. The interior least tern was listed on the Threatened and Endangered Species List in 1985 by the U.S. Fish and Wildlife Service. In 1986 the piping plover was added to the list.
Both are migratory bird species. Plovers arrive in southeastern Colorado in late April to early May and terns arrive mid to late May. These birds return to the reservoir every year to breed and to incubate their young. From 1990 to 2012, up to 14 piping plover nests and 24 least tern nests were recorded annually.
Unfortunately, this number has declined significantly in recent years. This means more focus on habitat improvement. With John Martin and small nearby lakes being the only places in Colorado where these birds are found, the monitoring and protection of these species is critical to supporting their status in Colorado.
It did not take long for the presence of plovers and terns to grasp the attention of many organizations, turning the protection of these birds into a long-lasting group effort. Working with Colorado Parks and Wildlife (CPW) and the USGS Northern Prairie Wildlife Research Center (NPWRC), the United States Army Corps of Engineers (USACE) continues to protect and preserve nesting habitat for plovers and terns.
Population monitoring is also a primary focus as the banding of unmarked birds allows for the documentation of returning birds and the estimation of annual survival. It also provides an insight to the success of the breeding season as juveniles recruiting back into the population can be recorded. The loss of nesting habitat, predation, and human disturbance pose major threats to the plover and tern populations and threaten their successful nesting.
Necessary actions taken to address these concerns extends to habitat creation and improvement; the closure of nesting areas to protect breeding sites from disturbance; predation control; sandbar augmentation; vegetation management; and inundation mitigation, all in accordance with the U.S. Fish and Wildlife Service’s Biological Opinion.
The recovery plan for the plover and tern habitat improvement requires the protection, enhancement, and restoration of essential breeding habitat. Both species have similar nesting habitat requirements and often nest along the same shorelines.
The interior least tern and the piping plover are both ground nesters, historically nesting along vegetation-free sand and gravel islands and sandy beaches not at risk for inundation during incubation and while chicks are preparing for flight.
With both plovers and terns being ground nesters, their nest placement poses numerous risks to successful breeding. Nests consist of little more than a shallow depression in the sand or gravel and are easily missed as the eggs and chicks are well camouflaged to their surroundings. While this does help protect from predators, nests and eggs can be easily destroyed by vehicular and foot traffic as they are difficult to see.
As John Martin Reservoir is a prime location for recreational use in southeastern Colorado, easy public access to nesting sites has greatly encouraged human disturbance during nesting season and posing a serious risk to plover and tern populations.
In a previous response to such pressures, efforts were increased by USACE to reduce the negative impacts of recreational activities on breeding habitat during nesting season. More drastic measures were taken as trenches were dug out, buoys placed along nesting islands, and informational and restricted access signs were posted to reduce human disturbance. While there still remains some evidence of disturbance, the impacts of recreational activity has decreased significantly in these protected areas.
Lack of habitat management also poses a major risk to plover and tern populations, allowing unwanted vegetative growth to make these sites unsuitable for successful nesting.
Invasive plants have continued to spread aggressively, greatly reducing nesting habitat and providing ideal conditions for predators. As ground nesters, plovers and terns are highly susceptible to predation with a wide variety of avian and terrestrial predators posing a risk to eggs, chicks, and adults.
Thick vegetation significantly promotes predation by hiding predators and supporting perching. Eagles, owls, hawks, raccoons, skunks, coyotes, and bobcats are only a few examples of common predators of plovers and terns at John Martin Reservoir.
Limited breeding habitat further increases predation risk as there is a higher concentration of birds in what little area remains suitable for nesting. The lack of vegetation management restricts breeding habitat to shoreline presenting with easy public access, inundation, and high predation risk, reducing the area of sandy beaches these birds can utilize for nesting. This is an issue that has been greatly addressed over the recent years.
With a clear understanding of plover and tern nesting behavior and breeding habitat needs, USACE’s natural resources specialists Chris Gauger, Katie Schober, Laura Nelson, and Patrick Greenbank, are currently working with CPW on the Shoreline Habitat Improvement Project.
Beginning in early March 2020, the recovery plan for the plover and tern habitat improvement has focused on vegetation management and sandbar augmentation along the John Martin Reservoir shoreline by routine mowing and trimming, and the use of herbicides for the purpose of vegetation control. The use of herbicides for vegetation control reduces maintenance needs, discourages erosion, soil compaction, and resprouting, and increasing the amount of area that can be maintained. Herbicide use also alleviates concerns with potential risks of sinking heavy equipment and steep terrain.
Habitat improvement has focused primarily on historic nesting grounds, roughly 602 acres of prime breeding habitat, where plovers and terns have been recorded nesting. After completing habitat improvement along these primary areas, more shoreline can be enhanced to expand these nesting grounds.
The purpose of the habitat improvement project is for vegetation management to reduce the risks of predation, inundation, and human disturbance threatening breeding success while returning the shoreline to prime nesting habitat.
Plovers have already arrived at the reservoir this year, inhibiting any further vegetation control. Habitat improvement will continue after breeding season, as both species leave in late summer after nesting season.
The return of invasive plant species and vegetation overgrowth will be monitored and maintained on a regular basis. This in an ongoing project that will continue over the course of many years requiring continued routine maintenance. Success will be monitored by measuring sandbar augmentation and the success of breeding season by population monitoring.
It is anticipated, there will be a positive impact on plover and tern populations over the years as nesting habitat is improved and expanded.
While threats to plover and tern populations remain an issue, the reservoir continues to show significant potential for returning the shoreline to prime nesting habitat. Vegetation management carried out under the Shoreline Habitat Improvement Project will help reduce the risks of predation, inundation, and human disturbance threatening breeding success. Habitat improvement will continue after breeding season to control invasive plant species and vegetation overgrowth.
The recovery plan actions highly support the protection, enhancement, and restoration of essential plover and tern breeding habitat, returning the shoreline to prime nesting habitat and allowing plovers and terns to utilize more shoreline for successful nesting.
Without enhancing nesting sites, it is highly likely the number of nests would continue to decline as preferred nesting habitat continues to be lost due to excessive vegetative growth.
Habitat improvement has proven to be essential to supporting plover and tern populations as well as encouraging the return of plovers and terns to the reservoir and to Colorado. Continuing with the habitat improvement recovery plan, it is expected to see the reservoir’s shoreline return to prime breeding habitat for plovers and terns. The protection of threatened and endangered species continuing to be a major focus for the U.S. Army Corps of Engineers here at John Martin Reservoir even during these difficult times.