Prepared by the San Luis Valley Ecosystem Council, Spring 2021
Written by Zaylah Pearson-Good
All photos by NPS/Patrick Myers
Cinnamon Teal by NPS/Patrick Myers
Each spring and fall, thousands of feathers slice through the brisk San Luis Valley (SLV) sky, alerting resident wildlife, local farmers, and eager birders to the change of season. Ranging from shorebirds to songbirds, a myriad of avian species visit this high-elevation desert as they migrate along the Central Flyway to their breeding and wintering grounds. Nurtured by the Valley’s mosaic of wetlands, riparian corridors, and agricultural fields, the SLV is a critical stopover for these determined travelers.
Foundational to the health of any stopover habitat is the presence of water. As local hydrology continues to be threatened by high agricultural demands, persistent drought, mining of the aquifer, and water export proposals, the future of the San Luis Valley as a migratory stopover is unknown. By protecting both ground and surface water reserves, we honor the miraculous winged creatures that bring energy, life, and color to the San Luis Valley.
The Importance of Migratory Stopovers
From distributing nutrients, seeds, and pollen, to balancing local food chains, animal migrations enhance ecosystem health. Spanning hundreds to thousands of miles in distance, these impressive voyages speak to the beauty, intelligence, endurance, and collective determination of species worldwide. Coming at tremendous energetic costs, migrations also highlight the importance of maintaining healthy habitat along migratory corridors.
Jenny Nehring and Cary Aloia, SLV biologists and partners at Wetland Dynamics, explain that many people “overemphasize the importance of wintering and breeding grounds,” when in fact, a successful migration also requires the presence of intact, resource rich habitats along the way (Interview, 2021). Without areas to rest and refuel like the SLV, birds would arrive to their destinations underweight and undernourished. For this reason, birds navigate not by the arbitrary borders and boundaries designed by humans, but by the geographical landmarks, such as rivers and wetlands, that represent feeding and resting opportunities.
Connected by threads of wetland and marsh habitats, the Central Flyway offers safe passage to thousands of birds during their biannual migrations. From the thick boreal forests of Canada to the Gulf Coast of Texas, this flight path is believed to support the movement of over 400 bird species each year (Bode, 2020). The San Luis Valley, a vast high desert shrubland in Southern Colorado, is a critical stopover for many migratory species. Blessed with interspersed wetlands, it is an especially important stop for Central and Pacific Flyway ducks, water birds, shorebirds, and the iconic Sandhill Crane (Ducks Unlimited).
SLV Significance to Migratory Birds
According to soil scientist and field ornithologist John Rawinski, the SLV’s drastic range in elevation, and therefore climate, creates a variety of distinct habitats for birds. Cradled by the impressive San Juan Mountains to the west and Sangre de Cristo’s to the east, the semiarid San Luis Valley ranges in elevation from 7,600 feet on the valley floor to over 14,000 feet in the Sangre de Cristo Mountains. From the harsh alpine tundra to the tranquil grasslands of the lowlands, this diverse habitat in the SLV yields impressive avian biodiversity. Over 360 species have been recorded in this Valley and surrounding mountains (Rawinski, Interview, 2021). Over 250 bird species have been identified at the Great Sand Dunes National Park and Preserve alone. Of this count, many are migratory species including the Great Blue Heron, American Avocet, Snowy Plover, Burrowing Owl, Black-chinned Hummingbird, Lewis’ Woodpecker, and Cedar Waxwing, (GSDNPPC,pgs. 1-8).
The SLV Wetland and Wildlife Conservation Assessment identifies the San Luis Valley as being the “southernmost significant waterbird production area in the Central Flyway and the most important waterfowl production area in Colorado…” (Wetland Dynamics, 2019, pg. 19). For birds that winter in Mexico and South America, the area is ideal for breeding. In fact, it is one of North America’s most critical breeding grounds for various species of duck and colonial wading birds, specifically the Cinnamon Teal (Ducks Unlimited). Similarly, priority duck species, such as Mallard and Northern Pintail depend on the Valley’s flooded wetlands and densely vegetated habitats for migration, nesting, and wintering (Wetland Dynamics, 2019, pg. 19).
For bigger bird species and waterfowl, the Valley functions as a vital rest-stop to regain stamina for the journey onward. For example, the SLV is an important destination for nearly the entire Rocky Mountain Population of Greater Sandhill Cranes as they fly along the Central Flyway. Due to their spectacular numbers and continued presence, this iconic wading bird highlights the value of the SLV’s high quality habitat.
Sandhill Cranes in the SLV
Sandhill Cranes West of Dunes by NPS/Patrick Myers
Dynamic, loud, and majestic, the Rocky Mountain Sandhill Greater Sandhill Crane migration has attracted perhaps the most attention out of any bird to visit the Valley. These grey, long-bodied creatures have flocked to the San Luis Valley for ages, inspiring ancient Native American petroglyphs that date back up to 3,000 years (Rawinski, Interview, 2021). Spanning nearly 6 feet in length, the “Big Bird” petroglyph located outside of Del Norte speaks to the impact that cranes have always had on SLV residents.
As the cultural landscape of the region changed throughout time, so did the cranes’ relationship to the land. For example, early cranes primarily ate the resources found in wetlands such as mice, frogs, snails, tubers, and invertebrates (Rawinski, Interview, 2021). As European settlement and widespread agriculture took root in the SLV, cranes adapted their diet to become more general. Waste grain from farmlands, especially barley, began to comprise a large portion of their diet. While the cultural and physical environment has changed overtime, humans continue to celebrate this majestic bird. Since 1983, locals and tourists have gathered to honor, experience, and learn from the species at the Monte Vista Crane Festival. The annual celebration attracts thousands of visitors each year to marvel at nearly 20,000 dancing, chortling, and swooping cranes.
Experiencing a Sandhill Crane migration can be a surreal and incredible moment. Cody Wagner, Conservation Program Manager at the Ian Nicolson Audubon Center (INAC), shares that Sandhill Crane migrations are “one of the last great migrations on the planet,” comparable to the caribou in Canada (Interview, 2021). It is incredibly powerful, and spiritual for some, to witness such a large quantity of charismatic travelers.
Like the SLV, Nebraska’s Platte River (INAC’s location) is a critical stopover for cranes along the Central Flyway, hosting copious amounts of birds each season. Wagner reports that there can be as many as 200,000 Lesser Sandhill Cranes on any 5-mile segment of the river at a given time. One thing that Wagner loves about being surrounded by so many cranes is that by watching them, you find they have a lot of relatable qualities. Like humans, cranes dance, play, get loud, and also show both an awkward and elegant side. When out on the river, he describes their calls as being “ancient,” “unique,” and “a thing of beauty.” (Wagner, Interview, 2021).
Local SLV ornithologist and soil scientist John Rawinski shares a similar sentiment with Wagner. Visiting the cranes every chance he gets at the Monte Vista Refuge, he describes the encounter as deeply therapeutic. By “observing the beautiful sounds of the cranes, their majestic flight, and archaic appearance” it sets his day at peace (Interview, 2021). While he acknowledges that one can view the migration of the cranes in various locations on the continent, there is something extraordinary about their presence in the SLV. Snow-capped peaks, a crisp blue sky, and a vast open valley all combine to set an incredible backdrop for the spectacular crane spectacle.
SLV Significance to Cranes
Due to the memory of high-quality resources, nearly the entire population of Rocky Mountain Sandhills bottleneck in the SLV during their migration (Nehring & Aloia, Interview, 2021). In early February, the birds follow the Rio Grande River northward from their wintering grounds in New Mexico’s Bosque del Apache National Wildlife Refuge. Upon reaching the SLV, they scatter themselves throughout barley fields, lakes, wetlands, and the Rio Grande, feeding on high calorie grains and nutrient dense aquatic invertebrates.
While waste grains from the agricultural fields provide the birds with energy-rich carbohydrates, they derive the majority of their nutrients from invertebrates, which are especially important for healthy eggshell production (Wagner, Interview, 2021). For 1-2 month periods, flocks of cranes congregate in the region’s National Wildlife Refuges (Alamosa, Monte Vista, Baca), Blanca Wetlands, and Russell and San Luis Lakes State Wildlife Area, where there are high concentrations of viable habitat (Wetland Dynamics, pg. 73).
Travelling up to 300 miles in a single day, Sandhills exert incredible energy during their biannual migrations (INAC). The stopover in the Valley allows the cranes to regain energy and strength to complete the journey to their breeding grounds in the greater Yellowstone ecosystem (including portions of Wyoming, Montana, Idaho, and Utah). The Lesser Sandhill Crane, a slightly smaller version of the Greater Sandhill, travels even farther with its northern territory extending into the arctic. In the fall, the Valley will again serve as a rest-stop for the cranes as they venture back to their winter home in New Mexico.
John Rawinski speaks to the importance of the Valley as a safe resting place for the cranes. He describes the aquatic habitats of the San Luis Valley as a“safe haven” for birds to relax and rest (Interview, 2021). By roosting in 6-8 inches of water, Sandhills are protected from predators such as coyotes, raccoons, and foxes. Water serves as an alarm system for the birds, as few predators can enter their roosting habitats without splashing loudly and alerting the birds to danger.
From a conservationist perspective, the current Rocky Mountain Population of Greater Sandhill Cranes is stable. As omnivores, cranes have a fairly generalist and diverse diet, which speaks to their resilience as they do not depend on one sole food source to be well nourished. As well, cranes can modify their route if they sense insufficient resources along their traditional path. Rerouting demands additional energy, however, which can hurt crane populations and lead to malnourishment and unhealthy body weight (Nehring & Aloia, Interview, 2021). Efficiency is an important component to avian migration, and thus is the significance behind reliable, consistent stopover destinations.
While cranes fortunately exhibit some resilient traits, they are currently vulnerable due to loss of habitat and the unforeseen impacts of climate change. The species, along with other migratory birds, cannot survive without wetlands. Wetlands are currently one of the most endangered ecosystems in North America, putting the cranes and countless other species in danger. By recognizing the significance of the San Luis Valley as a migratory stopover, we are helping to keep habitat along migratory corridors connected. In this way, conserving ecosystems in the Valley is essential for the wellbeing of all birds along the Central Flyway.
The Importance of Water
Receiving less than 8 inches of precipitation each year, the San Luis Valley is one of the driest regions in the state of Colorado. In the past two decades, drought, reduced precipitation, and high rates of ground and surface water withdrawals have threatened some of the Valley’s most precious habitats: wetland and riparian areas.
Sunset Over Wetland by NPS/Patrick Myers
SLV Wetland Habitats
Whether it is for nesting, breeding, feeding, or resting, all species that migrate through the San Luis Valley depend on the region’s wetlands. Wetlands are highly productive ecosystems that exist in low-lying depressions in the terrain. They are often referred to as the “kidneys” of the earth because they filter out pollutants, excess nutrients, and sediment from surface waters. They are also essential to the recharging of groundwater and protection against flooding and erosion events.
Depending on the type of wetland, the habitat may be wet permanently, semi-permanently, seasonally, or temporarily. Variations in soil type, elevation, location, vegetation and climate create distinct types of wetland habitats, that service wildlife in different ways and at different times in their life history (Wetland Dynamics, pg. 17). For example, the Mallard and Northern Pintail ducks require wetlands with shallow water to forage, but seek refuge in wetlands with tall emergent vegetation during sheltering periods (Wetland Dynamics, pg. 20). During nesting, both waterfowl species require distinct habitat, with the Mallards preferring habitats abundant with Baltic rush, and the Pintails choosing less dense vegetation, such as greasewood (Wetland Dynamics, pg. 20).
The SLV supports such a thriving community of migratory species, in part, because of its wide range of seasonal wetlands. In an analysis submitted to the Bureau of Land Management on SLV habitats and bird migration, Animas Biological Studies determined that shallow emergent and playa wetlands are “the most critical habitat type for migratory birds in both spring and fall” (pg. 15). Shallow emergent wetlands host a wide range of migratory species in their shallow pond and marsh like habitats. Characteristic of emergent vegetation like rushes and sedges, these habitats offer excellent feeding, nesting, and resting opportunities for migratory wading birds, waterbirds, and secretive marsh birds (ABS, pg. 3). Due to their semi-permanent to permanent quality, these SLV habitats are believed to be the most densely populated and used habitats by migratory shorebirds and waterbirds (ABS, pg. 3).
Also supporting high biological density and diversity, playa wetlands are some of the Valley’s most unique wetland habitats. Intermittently saturated by either surface or groundwater, these wetlands have high soil alkalinity and salinity that may result in the formation of a white crust during drying cycles. According to John Rawinski, playa wetlands are both the most critical and vulnerable of wetland habitats because they host species that cannot survive in other environments. For example, SLV playas represent the largest nesting area for the Snowy Plover, a threatened North American shorebird that thrives in dry salt flats (Rawinski, Interview, 2021). Additionally, several birds classified as “rare” are known to inhabit these distinctive wetlands, especially at the Great Sand Dunes National Park and Preserve: Long-billed Curlew, Short-eared Owl, Black-crowned Night-heron, Foster’s Tern, and the White-faced Ibis (Malone, p. 3) Playa wetlands are also host to a globally endangered plant species, the slender spider flower (Malone, p. 4).
Wetland threats in the SLV
Wetlands are both the Valley’s most valuable and vulnerable ecosystems. While only representing 2% of Colorado’s total area, wetland and riparian habitats support over 80% of wildlife species throughout their lives (Wetland Dynamics, p 36, 2019). Furthermore, wetlands are believed to be the most imperative habitats for birds that are classified as “at-risk” (Rondeau et al., pg. 93). In other words, Colorado’s most threatened species are also most reliant on wetland ecosystems.
Unfortunately, wetland conservation has been historically insufficient. In a report prepared by the Colorado Natural Heritage Program, the authors write that “Threats to wetland species are high and protection is generally poor” (Rondeau et al., p 128). Cody Wagner with the Audubon confirms this point in saying that many people undervalue these habitats; “Wetlands are held in less esteem by the public and have been historically viewed as a waste of space” (Interview, 2021). As a result, across the country, these habitats have been intentionally drained, burned out, converted into cropland/developments, polluted, or compromised by invasive species.
Due to reduced precipitation, severe droughts, earlier peak runoff, unsustainable agricultural practices, and high demands from water users, wetlands in the SLV have suffered. Wetland Dynamics, a small business committed to the conservation of critical SLV ecosystems, reports that nearly half of the Valley’s total wet acres have been lost since the 1980’s (pg. 80). With water use continuing to exceed supply, conservation of local water resources will be instrumental to restoring and protecting these habitats.
Wetland declines are of great concern for many reasons. Not only does it strain bird migrations, but losses also pose a threat to the surrounding environment. With less available habitat, birds will be forced to congregate in the few viable wetlands that remain. According to a study under the Society for Conservation Biology, wetlands overburdened by high densities of birds can cause “the destruction of wetland vegetation, impose heavy losses in local agricultural crops, increase the risk of infectious disease outbreaks, and decrease water quality” (Post, et al., p. 911). Furthermore, crowded habitat is also detrimental to wildlife, potentially leading to increased competition for resources, poor reproductive success, and reduced longevity.
Willet and White Faced Ibis by NPS/Patrick Myers
Defined as the interface between a river or stream and the surrounding terrain, riparian areas are hotspots for migratory species. Densely vegetated with native grasses, willows, sedges, rushes, and cottonwoods, these areas are sanctuaries for resident and seasonal wildlife in the arid SLV. Common bird species to utilize these local ecosystems include the Bullock’s Oriole, Great Horned Owl, Northern Flicker, American Robin, Yellow Warbler, and the American Kestrel (USFWS, 2014). Similar to wetlands, riparian habitats are some of the sparsest habitats in the region. Riparian habitats support about 80% of resident bird species but represent only 3% of the landscape in the Intermountain West (Wetlands Dynamic, p 20).
Intersecting the SLV near Del Norte, the Rio Grande supports imperative riparian habitat for avian species. For example, the San Luis Hills State Wildlife Area protects 4.5 miles of the Rio Grande, which is considered “Critical Habitat” for the federally-endangered Southwestern Willow Flycatcher (COGO, 2018). The surrounding uplands (sagebrush and grasslands) host Sage Thrashers and Mountain Plovers, both of which are suffering a decline in population (GOCO, 2018). The Higel State Wildlife Area also protects several miles of the Rio Grande. This area is known to be critical habitat and breeding ground for the Willow Flycatcher, and the threatened, Yellow-billed Cuckoo (Wetland Dynamics, pg. 42).
The Rio Grande is considered a critical migratory corridor as it offers species a continuous stretch of riparian habitat along their path. From the San Juan Mountains of southern Colorado to the Gulf of Mexico, the Rio Grande River supports an otherwise thirsty landscape along its 1,900-mile path. Feeding seasonal wetland and riparian habitats, the Rio Grande brings life to parched deserts and valleys, allowing for both human and wildlife communities to thrive.
Jenny Nehring describes the Rio Grande as a “green ribbon in a very dry landscape” that directs birds towards resources along their high-energy voyage (Interview, 2021). The Rio Grande offers safe passage to countless migratory species, including the Sandhills, who utilize the river for both navigation and nourishment. Audubon New Mexico reports that roughly 18,000 Greater Sandhill Cranes, 200,000 waterfowl, and thousands of other water and shorebird species utilize New Mexico’s Rio Grande Corridor. Whether it is for wintering, migration, resting, feeding or nesting, the Rio Grande is an irreplaceable resource for migratory birds.
Threats to the Rio Grande
Excessive water use of the Rio Grande has become a growing concern. As early as the start of the 20thcentury, surveyors were already noticing the impact of SLV irrigation on the river. A USGS survey of the San Luis Valley in the early 1900s relayed that “the waters of this stream [Rio Grande river} are greatly over appropriated, even in the flood season” (Siebenthal, pg. 19). Currently, high water demands by agriculturalists, coupled with the drying impacts of climate change, have continued to tax this critical water supply. The upper Rio Grande is projected to decrease in volume by one-third in the coming years (Audubon New Mexico). Furthermore, over 90% of historical wetlands and riparian habitat along Rio Grande Corridor have already been lost in the last 150 years (Bode, 2020).
Wetland Dynamics shares that with the projected impacts of climate change, warmer water temperature and reduced stream flow could decrease the Rio Grande’s “extent of overall flooding across the watershed” (pg. 28). Already, the Rio Grande Basin Implementation plan is anticipating a 30% decrease in the river’s stream flow (Wetland Dynamics, pg. 28). Reduced flow and thus flooding from the Rio Grande would have dramatic consequences for the wetland and riparian ecosystems that require surface water input. Visiting and resident wildlife would greatly suffer as a result of this major habitat loss.
Young Great Horned Owl by NPS/Patrick Myers
A Changing World for Birds
Due to horrific collapses in bird populations across North America, birds depend on intact and healthy habitats perhaps more than ever. Extreme weather events, droughts, mismanaged resources, development, and loss of habitat have all contributed to the shocking losses in bird life. John Rawinski laments that today “we have 3 billion less birds (down 33%) in North America than we had in 1970” (Interview, 2021). Having started birding in the 70’s himself, he has seen this tremendous decline firsthand. He reports seeing fewer and fewer birds each year, and mass die offs, such as those experienced across the Southwest during the 2020 unseasonal summer snowstorm event. As a passionate birder and scientist, Rawinski begs the question: “Who will speak for the birds?” He urges that we need to start taking action now, before it is too late. Without important resting stops like the SLV, and intact migratory corridors such as the Rio Grande, migratory bird species do not stand a chance against climate change.
The Importance of Birds Besides their striking beauty and relaxing melodies, birds play essential roles in balancing ecosystems and ensuring a healthy environment. During migrations, birds visit a diverse range of landscapes. Travelling thousands of miles, birds pick up and disperse nutrients and seeds. This process contributes to a more biologically diverse and productive ecosystem. Many birds also consume large quantities of insects as they migrate, which serves as a natural pest control for farmers. Lastly, certain aerial migrants, such as bats and hummingbirds, are important pollinators along their respective flyways. This is especially true for flower pollination.
In addition, birds are sensitive to environmental fluctuation, and therefore are considered good indicators of ecosystem health. Scientists have used the presence or lack of birds to learn about the impact of toxic pollutants such as PCBs and heavy metals in the environment. By ensuring healthy landscapes for birds, we reflect a healthy environment for human residents too. In this way, birds play a helpful role in teaching humans about the land in which they are a part. In the San Luis Valley, the continued visitation of large numbers of migratory species indicates that our landscape is blessed with prosperous habitats capable of supporting a wide range of life forms. With water export proposals such as RWR threatening our local water reserves, we cannot take these ecosystems for granted.
Renewable Water Resources (RWR)
Proposal Connected by a series of pipelines running through Poncha Pass, Renewable Water Resources (RWR) proposes to remove 22,000 acre-feet of SLV water from the deep aquifer each year. This trans-basin water diversion would transfer local water to growing municipalities in the Front Range at the cost of SLV’s economy, ecology and future. Backed by former deputy chief of staff Sean Tonner and former Governor Bill Owens, RWR is one of many nonlocal investors who have attempted to remove thousands of acres of feet of water from the SLV a year. Opposed by SLV water managers, towns, environmental advocacy groups, and many ranchers/farmers, the impacts of RWR’s proposal would have horrific impacts on the local environment.
Potential Impact Central to the study of ecology is that everything is connected. Hydrology is no different. By removing thousands of acres of water out of the deep aquifer each year, the health of the shallow aquifer, as well as wetlands and rivers that sustain life above it, are put at risk. As SLV ground and surface water reserves are already over-appropriated and declining, the San Luis Valley cannot afford to lose any more water. As a scientist and advocate for the environment, John Rawinski notes that, whenever there is potential for water to leave the San Luis Valley, “the big loser is always wildlife” (Interview, 2021). While humans have the ability to buy and transport water, wildlife and the habitats on which they depend do not have this freedom. The resident and migratory species of this Valley cannot afford to lose their most precious resource at the hands of those who desire to profit from it.
Spanning nearly 120 miles from north to south, the San Luis Valley supports vibrant communities of wildlife. Attracting avian species from all across North America, the SLV stands out as a significant stopover for migratory species. High quality wetlands and riparian areas sustain these winged travelers as they cover thousands of miles during their migrations. These incredible voyages attract nature lovers, balance local ecosystems, and encourage local biodiversity. However, the future of the San Luis Valley as a migratory stopover is jeopardized due to water scarcity. The Valley is faced with an urgent call to conserve water resources. For wildlife and human inhabitants, we must prevent water miners from exporting water, implement more sustainable forms of irrigation and land stewardship, consider water re-use, and unite private and public landowners in habitat conservation. The future of wildlife and humans in the San Luis Valley is depending on a commitment to protect our water.
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Wagner, Cody. (Conservation Program Manager at the Ian Nicolson Audubon Center). Personal Interview. Conducted by Zaylah Pearson-Good, 2 March 2021.
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