New breeding habitat discovered for rare Yellow-billed Cuckoos
A threatened bird species is nesting in surprising areas.
News Release
Media Contacts:
Charles Drost, 928-556-7187, charles_drost@usgs.gov
Paul Laustsen, 650-847-8522, plaustsen@usgs.gov
FLAGSTAFF, Ariz. – The western population of yellow-billed cuckoos (Coccyzus americanus occidentalis) was thought to nest only in mid-elevation riparian areas dominated by cottonwood and willow trees, with perennial surface water.
A new paper published in the Journal of Field Ornithology documents, for the first time, the wide extent of their occurrence and nesting in arid habitats in foothill, mountain, and lowland drainages of the “Sky Islands” in southeast Arizona, and their use of arid drainage tree species such as oak, mesquite, hackberry, juniper, ash, and acacia — a dramatic difference to their cottonwood/willow "typical" streamside habitat.
While cuckoos had been thought to occupy dry, hot areas on occasion, previous surveys had not identified extensive use or nesting there.
Yellow-billed cuckoos once ranged all the way from British Columbia south to Mexico. Over the 20th century, populations of cuckoos in western North America have declined by as much as 95%.* Their remaining stronghold in the U.S. is primarily in Arizona and New Mexico.
Previous studies in the southwest U.S. mostly focused on riparian areas. The most recent extensive surveys by the U.S. Geological Survey and cooperators documented 400-425 cuckoos in Arizona, almost all along rivers and perennial streams.
Detecting yellow-billed cuckoo nesting habitat is challenging. They are rather secretive birds with large home ranges, infrequent calls, concealed nests, and a nomadic period before nesting when they travel widely to assess prey availability, such as caterpillars, insects, and wild fruits at potential nesting sites. This makes it difficult to determine whether they are passing through or nesting in an area.
Yellow-billed cuckoos also are late nesters. Unlike many birds that breed in the spring, yellow-billed cuckoos nest from May to September, with peak nesting in July and August – the hottest months in the desert. The newly identified xeric nesting areas are places that are less used by hikers and birders during these months. However, anecdotal reports of cuckoos in oak woodlands, and documented sightings by birders recorded on the online eBird platform spurred further analysis of cuckoos in arid southeastern Arizona locations, leading to this study.
The study surveyed these “xeroriparian” sites over a four-year period using a standard U.S. Fish and Wildlife Service -accepted survey protocol. The team of researchers included the USGS, USFWS, Northern Arizona University, U.S. Forest Service, and the Audubon Society. The study areas included major mountain ranges and foothills between the San Pedro River and the Baboquivari Mountains, with additional historic data collected east of the San Pedro River.
They found nesting cuckoos mostly in the western portion of the Sky Islands, particularly in the region extending from the Baboquivari Mountains in the west, east through the Altar Valley, Atascosa Highlands, Santa Rita Mountains, Patagonia Mountains, Canelo Hills, San Rafael Valley, and western side of the Huachuca Mountains. They observed fewer cuckoos in the Whetstone Mountains, Rincon Mountains, and Santa Catalina Mountains.
The numbers of nesting pairs found by this study in new dry habitats — 100 new sites, including many with multiple nests or territories — are a significant addition to the known population in the western U.S., says USGS research zoologist Charles Drost. And researchers found that population numbers of breeding pairs in these dry foothill and mountain canyons are comparable to numbers in the generally recognized breeding habitat of lowland, gallery riparian forests.
The results indicate that yellow-billed cuckoos use a broader range of vegetative communities than previously known.
Given that cuckoo numbers outside of Arizona and New Mexico are very small, this study underscores the regional importance of southeast Arizona xeroriparian habitat. These areas may be important to the long-term persistence and recovery of the species in its western range, and as riparian habitat continues to decline due to drought and water use.
Sky Islands are isolated mountain ranges that rise 3000-10,000 ft. above the expansive Sonoran Desert. These ‘Islands’ are hotspots of biodiversity with plants and animals that require high elevation, montane and subalpine environments — species that could not survive in hot deserts.
Whether and how often cuckoos move between these riparian and xeroriparian habitats, both within and between years, remains an important question. Additional survey efforts in under-surveyed areas of the Sky Islands region in both the US and Mexico could help to further refine distribution and population estimates.
Working with over 100 partners and stakeholders, the USGS is now able to verify the presence of this elusive species with more specificity than before. Now we know that yellow-billed cuckoos are among the suite of species that benefits from the rich biodiversity of southern Arizona’s Sky Islands.
The areas at the base of some of these mountain systems, where the deserts and mountains meet, represent an important addition to known habitat and can support future western yellow-billed cuckoo conservation and management.
The study is published here: Beauregard, N.D., Theimer, T.C., Sferra, S.J., and Drost, C.A., 2024, Breeding by western yellow-billed cuckoos in xeroriparian habitat in southeastern Arizona: Journal of Field Ornithology, https://doi.org/10.5751/JFO-00539-950401
Associated data: Beauregard, N.D., Theimer, T.C., Sferra, S.J., and Drost, C.A., 2024, Survey results for yellow-billed cuckoo occupancy and nesting in xeroriparian habitat in southeastern Arizona from 2013 through 2020: U.S. Geological Survey data release, https://doi.org/10.5751/JFO-00539-950401.
* A previous version of this release had a factual error stating that the Yellow-billed cuckoo population declined by over 50%.
A comparison between previously known riparian habitat vs. newly discovered xeroriparian nesting habitat:
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