Coccyzus Americanus Research Articles

Using autonomous recording units to identify and monitor western yellow‐billed cuckoo habitat

AbstractAutonomous recording units (ARUs) paired with signal classification software can be used to detect species‐specific calls, making them useful for evaluating patterns in avian occurrence and activity. However, classification of target signals is not always reliable and may be especially challenging for species that vocalize infrequently. We assessed the use of ARUs to identify and monitor habitat for a cryptic and federally threatened distinct population segment, the western yellow‐billed cuckoo (Coccyzus americanus) in mountainous xeroriparian drainages. Using Kaleidoscope Pro, we developed a call‐classifier and processed acoustic data collected in sites also surveyed using traditional human‐observer methods, applying the same spatial and temporal detection criteria to estimate breeding territories for each method. The classifier detected a total of 4,061 true positive calls at 4 sites, had an overall precision score of 0.07, recall score of 0.09, and F‐score (beta = 1) of 0.08, indicating high false positive and false negative classification rates. Our results were, however, consistent with other ARU studies of rare and cryptic species and ARUs estimated occupancy as effectively as human surveys with as little as 2 hours of daily recording. Total detections varied among sites, likely due to differences in cuckoo population densities and the interaction between topography and ARU detection space. Our results suggest that despite performance shortcomings of call‐classifiers, ARUs can be effective for monitoring cuckoos, with potential for providing higher resolution temporal and spatial information on activity and habitat use and may be particularly effective in remote locations where cuckoos often occur.

Dynamic, multi-scale analyses indicate site- and landscape-level forest cover drive Yellow-billed and Black-billed Cuckoo interannual turnover.

Studies of habitat use in breeding birds often assume species have relatively stable breeding distributions. Some species, however, display considerable year-to-year variability, complicating efforts to determine suitable or preferred habitats. After returning to their breeding range, Black-billed Cuckoos (Coccyzus erythropthalmus) and Yellow-billed Cuckoos (C. americanus) are thought to range widely before nesting, resulting in high rates of interannual breeding-site turnover, potentially contributing to conflicting habitat associations found in past studies. However, difficulty detecting these rare and declining species could lead to overinflated estimates of interannual turnover. Using broadcast surveys to increase detection probability, we collected detection/non-detection data in 2019 and 2020 at 41 publicly owned sites in Illinois and performed a dynamic, multi-scale occupancy analysis for each species to separate detection probability from potential interannual turnover and determine landscape and small-scale variables driving habitat use and occupancy dynamics. We found strong support for interannual turnover for both species based on poor performance of non-dynamic models and variation in estimated annual occupancy (20% and 21% increase between years for Black-billed and Yellow-billed Cuckoos, respectively). Black-billed Cuckoos persisted at sites with less forest in the surrounding landscape and used areas with denser understory vegetation. Yellow-billed Cuckoos colonized sites with greater canopy cover, avoided developed landscapes, and used areas with a shorter subcanopy layer. The dynamic nature of habitat use in these two cuckoo species suggests the importance of coordinating management and conservation across a broader spatial scale. Managing for larger patches of dense shrubs in less forested landscapes would benefit Black-billed Cuckoos while Yellow-billed cuckoos would benefit from management creating forested areas with open understories in less-developed landscapes.

Breeding by western Yellow-billed Cuckoos in xeroriparian habitat in southeastern Arizona

Breeding by western Yellow-billed Cuckoos in xeroriparian habitat in southeastern Arizona

Abundance and occupancy of the western yellow-billed cuckoo (Coccyzus americanus) in Sonora, Mexico

Unveiling factors that determine abundance and distribution of endangered wildlife species has important implications for their conservation across international boundaries. For instance, the Western Distinct Population (as defined by the U.S. Fish and Wildlife Service) of the yellow-billed cuckoo Coccyzus americanus (Linnaeus, 1758) has disappeared in most of the species’ range across western United States and southwestern Canada but little is known about the conservation status at the southern edge of its breeding distribution in Mexico. To fill this information gap, we estimated abundance and occupancy rates of yellow-billed cuckoos using a standard broadcast call survey protocol. We used Bayesian spatial count models to estimate cuckoo population density at survey sites. We used Bayesian hierarchical models to estimate the effects of geography, climate, and vegetation on occupancy rates while accounting for imperfect detection. Mean cuckoo count per transect for all sites was [Formula: see text] = 9.00 ± 0.45 cuckoos. Overall cuckoo density was [Formula: see text] = 13.18 cuckoos/km2( SD([Formula: see text]) = 5.61 cuckoos/km2). Overall cuckoo occupancy in Sonora was [Formula: see text] = 0.538 (95% credible interval ( ψ) = 0.488–0.600), but showed strong geographic variation. Relatively high occupancy levels suggest yellow-billed cuckoo populations in Sonora may be robust, but they are largely reliant on declining high-tree cover.

Arthropod associates of a Yellow-billed Cuckoo Coccyzus americanus on Vaca Key, Monroe County, Florida, USA

Examination of a carcass of a Yellow-billed Cuckoo Coccyzus americanus (L.) (Cuculiformes: Cuculidae) provided the first record of a louse in the genus Cuculoecus (Psocodea: Philopteridae), a springtail Seira brasiliana (Arlé) (Collembola: Entomobryidae), and a tetranychid mite in the genus Oligonychus (Trombidiformes: Tetranychidae), from Vaca Key, Monroe County, Florida, USA.

Depleted lean body mass after crossing an ecological barrier differentially affects stopover duration and refuelling rate among species of long‐distance migratory birds

Abstract During the long‐distance migratory flights of birds, lean mass breakdown occurs in concert with fat catabolism and is expected to have repercussions on total stopover duration because birds require time to rebuild lean tissue before accumulating fat reserves. Despite this, little is known about the role of in‐flight lean mass breakdown on stopover duration because direct measurements are restricted by the destructive nature of traditional body composition analysis and the technological limitations of tracking small birds over large expanses. We used non‐lethal, non‐invasive Quantitative Magnetic Resonance technology and plasma metabolite profiling to measure the body composition and physiological state of free‐living birds captured at a migratory stopover site after flight across the Gulf of Mexico, and an automated radiotelemetry array covering ~5000 km2 to track stopover duration and regional movements. We tested whether stopover duration is prolonged in individuals arriving with lower lean mass and investigated how lean mass affects regional movements. Stopover duration decreased by 22% for each additional gram of lean mass in Northern Waterthrush (Parkesia noveboracensis), but this relationship was not apparent in Swainson's Thrush (Catharus ustulatus), Grey‐cheeked Thrush (Catharus minimus) or Yellow‐billed Cuckoo (Coccyzus americanus), even though these species also arrived with depleted lean mass. Stopover duration increased for Swainson's Thrush with higher plasma uric acid, a marker of protein catabolism. Northern Waterthrush with higher plasma triglycerides had longer stopover duration. Our findings suggest that migratory birds may compensate for substantial lean mass losses by increasing refuelling rate or moving to a different stopover site, and highlights species‐level differences in lean mass breakdown and the associated impacts on physiological function. Our results highlight the strategies used by different species to recover from a trans‐Gulf of Mexico flight and resume migration, which improves our understanding of the annual cycle of migratory birds. Read the free Plain Language Summary for this article on the Journal blog.

Dynamic occupancy models reveal Black-billed and Yellow-billed Cuckoos have high rates of turnover during the breeding season

Abstract Understanding the conservation needs of rare and hard-to-detect species becomes even more difficult when a species is highly mobile. Black-billed Cuckoos (Coccyzus erythropthalmus) and Yellow-billed Cuckoos (Coccyzus americanus) have experienced extensive range-wide population declines over the last several decades. Low detection probability has made it hard to determine causes of declines and resulted in poorly supported population and trend estimates. However, given evidence that cuckoos make wide-ranging movements during the breeding season, it may be necessary to address issues of both low vocalization rate and availability for detection to better understand these cryptic species. We performed passive and call-broadcast surveys for cuckoos at 41 sites across northern Illinois in 2019 and 2020. We examined the influence of call broadcast and temporal and environmental covariates on detection probability and how habitat covariates affected occupancy, immigration, and emigration both within and among sites. Individual detection probability increased substantially using call broadcasts (12 and 6 times for Black-billed and Yellow-billed Cuckoos, respectively) and detection increased with temperature. Black-billed Cuckoo detection probability also varied temporally, being lowest in the middle of the breeding season. We found strong support for turnover within sites during the breeding season, indicating maintenance of large home ranges, as well as among sites (average emigration probability of 86% and 47% for Black-billed and Yellow-billed Cuckoos, respectively). Black-billed Cuckoos were more likely to use open, shrubby sites and Yellow-billed Cuckoos to use sites with older successional habitat. While turnover rate was affected by habitat covariates, these species’ reliance on ephemeral insect abundance may ultimately be driving occupancy dynamics. Our results suggest that broadcasts are essential for effectively monitoring these cuckoos, but also imply the need to move towards coordinating management at broader spatial scales for these highly mobile species.

New Records of Nematodes in the Yellow-Billed Cuckoo Coccyzus americanus (Cuculiformes: Cuculidae) Based on a Migrant Specimen Found in Brazil

The yellow-billed cuckoo, Coccyzus americanus, is a threatened passerine bird native to North America that migrates to overwinter in South America. Although migratory birds have drawn broad attention, given their assumed role in the long-distance dispersal of parasites, studies on the helminth fauna of this cuculid are scarce. In the present study, nematodes found in the gastrointestinal tract of a specimen of C. americanus found in Belo Horizonte, State of Minas Gerais, southeastern Brazil, were characterized morphologically. Five species of gastrointestinal nematodes belonging to 4 families were identified: Synhimantus (Dispharynx) nasuta (Rudolphi, 1819) and Synhimantus (Dispharynx) resticulaCanavan, 1929 (Acuariidae), Microtetrameres sp. (Tetrameridae), and Cyrnea piayaeSandground, 1929 (Habronematidae) and Subulura halli Barreto, 1918 (Subuluridae). Except for Microtetrameres sp., all other nematodes are reported in this host for the first time. Although it is difficult to accurately determine the geographical origin of infections, it is important to note that Sy. (D.) resticula and Su. halli are reported for the first time in Brazil. Additionally, the absence of the former species infecting hosts where the widespread and generalist Sy. (D.) nasuta was found may indicate that Sy. (D.) resticula have either been overlooked in previous studies or that this nematode is rare indeed. Finally, the geographical distribution of Su. halli is greatly expanded and now includes the Americas. Aspects related to the dispersion of these parasites, both in migrating and native hosts, are briefly discussed.

Using Bioacoustics to Examine Vocal Phenology of Neotropical Migratory Birds on a Wild and Scenic River in Arizona

Passive acoustic recorders have been used successfully as automated survey tools to detect terrestrial wildlife. However, few studies have monitored Neotropical migratory bird use of riparian forest habitat using this technology. Within dryland ecosystems, the forests along rivers support high bird diversity. Many bird species of conservation concern require these floodplain forest habitats for foraging, migration stop-overs, and breeding. Few studies have explored the use of acoustic records in riverine systems designated for conservation for their natural resource value via the Wild and Scenic Rivers Act in the USA. Using acoustic recorders, we document vocal activity of four riparian-obligate species (Bell’s Vireo, Vireo bellii; Summer Tanager, Piranga rubra; Yellow Warbler, Setophaga petechial; and Yellow-billed Cuckoo, Coccyzus americanus) to determine species occurrence along a Wild and Scenic River. We established three study reaches along the perennial Lower Verde River, in the Sonoran Desert of central Arizona, USA. Nine acoustic recorders were used over the period of 80–120 days during the summer of 2018. We measured vegetation composition and structure in 100 m2 plots paired with acoustic recorders. Visualizing vocal activity showed that three species were calling and singing at each reach; whereas, one species, the cuckoo, had fewer recordings and occurred later in the summer. We demonstrate the utility of acoustic monitoring even when applied to rare birds in complex riparian habitats. This information is important for land management and conservation efforts concerning these species of interest and identifying important habitat features in Southwestern US riparian woodlands.

Early successional riparian vegetation is important for western Yellow‐billed Cuckoo nesting habitat

Western Yellow‐billed Cuckoo (Cuckoo; Coccyzus americanus) populations continue to decline in the western United States despite efforts to increase availability of riparian forest. Cuckoos have unique breeding habitat requirements such as large contiguous tracts of riparian forest (>80 ha), large estimated home ranges (20–90 ha), and dense vertical structure around the nest. However, local habitat‐scale features may be missing in landscapes of predominantly mature riparian forest that may need to be specifically managed for nesting. We used historical nest data (n = 95) from the South Fork Kern River Valley, California, from 1985 to 1996 to identify important nest site features that may be missing in current riparian forests. We found that increased canopy cover and vertical structure at all levels in the canopy greatly increased the probability of Cuckoo nesting. With smaller estimated effect sizes, the probability of Cuckoo nesting increased with increasing willows and forbs and smaller mean tree dbh. Cuckoos selected plots with disproportionately high percent willow cover relative to availability plots regardless of whether sites had low or high percent willow available. Counts of fledged young were positively related to willow percentage. No vegetation variable influenced daily survival rate which was 0.991 (LCI = 0.980, UCI = 0.996). Overall 17‐day nest success was likely high (0.86, LCI = 0.71, UCI = 0.93). In the absence of natural processes that create early successional stage forest, specific management for early successional stage forest is needed to increase the probability of Cuckoo nesting and nest productivity.

Western Yellow‐Billed Cuckoo Nest‐Site Selection and Success in Restored and Natural Riparian Forests

ABSTRACTThe western distinct population segment of yellow‐billed cuckoo (Coccyzus americanus; western cuckoo) has been extirpated from most of its former breeding range in the United States because of widespread loss and degradation of riparian cottonwood (Populus spp.)‐willow (Salix spp.) forests. Restoration and management of breeding habitat is important to the recovery of this federally threatened species, and identification of high‐quality breeding habitat can help improve the success of recovery. In 2005, the Lower Colorado River Multi‐Species Conservation Program, a long‐term, multi‐agency effort, was initiated to maintain and create wildlife habitat within the historical floodplain of the lower Colorado River (LCR) for federally endangered and threatened species, including western cuckoos. We conducted an empirical, multi‐scale field investigation from 2008–2012 to identify habitat characteristics selected by nesting western cuckoos along the LCR. Multiple logistic regression models revealed that western cuckoos selected nest sites characterized by increased densities of small, native, early successional trees measuring 8–23 cm diameter at breast height, and lower diurnal temperature compared to available habitat in restoration and natural forests. Nesting cuckoos selected sites with increased percent canopy closure, which was also important for nest success in restoration sites along the LCR. Our results show habitat components selected by nesting western cuckoos in restoration and natural riparian forests and can help guide the creation, enhancement, and management of riparian forests with habitat conditions necessary to promote nesting of western cuckoos. © 2021 The Wildlife Society.

Challenging our understanding of western Yellow‐billed Cuckoo habitat needs and accepted management practices

Riparian restoration in the southwestern United States frequently involves planting cottonwood (Populus spp.) and willow (Salix spp.). In the absence of flooding and gap‐forming disturbance, planted forests often senesce without further young tree recruitment. This has largely been the case in California riparian systems that historically supported state‐endangered western Yellow‐billed Cuckoo (Coccyzus americanus; Cuckoo). A decline in Cuckoo population numbers in the past 30 years has been associated with forest maturation. Other riparian species of concern show a concomitant decline, indicating the problem is not specific to Cuckoos. Although varying hypotheses exist for recent decline, alternative management practices have not been sufficiently explored to rule out breeding ground habitat quality as a major contributing factor. Few intensive Cuckoo datasets exist to test hypotheses about breeding habitat quality due to extremely low populations in the remaining occupied sites. We used a historical (1986–1996) spot mapping dataset from the South Fork Kern River Valley, CA to identify vegetation characteristics related to Cuckoo and five other sensitive riparian bird territory densities. We found Cuckoo densities were positively associated with increased vertical vegetative structure 1–5 m above ground with a threshold for mean tree height. Sensitive species densities were also related to vertical structure and started to decline with stand height greater than 6–8 m. Naturally regenerated sites had higher densities of most sensitive bird species than planted sites. We provide ideas for restoring mature forest with little vertical structure.

Does Conservation Practice and Site Age Influence Vegetation Structure and Avian Abundance in Restored Fields?

ABSTRACTFarmland set‐aside programs provide important habitat for many wildlife species, yet little information exists regarding how vegetation structure and species respond to conservation practice and site age. This information could provide managers with a guide for how to implement, enhance, and maintain wildlife benefits of conservation programs. We describe how vegetation structure and avian species respond to conservation practice and time since restoration at 172 sites enrolled in the Conservation Reserve Enhancement Program (CREP) in Illinois, USA. We surveyed 172 sites enrolled in 4 different conservation practices (CP) within CREP during the breeding seasons of 2012–2015 using avian point counts and vegetation surveys. Vegetation structure and composition varied among CPs, with hardwood tree plantings (CP3A) having the greatest amount of understory vegetation and tree cover. Conversely, permanent wildlife habitat (CP4D) had the greatest grass cover and least tree cover. Many bird species were found in similar numbers across CP types; however, only dickcissel (Spiza americana) density was greater in sites enrolled as permanent wildlife habitat. Bell's vireo (Vireo bellii) and yellow‐billed cuckoo (Coccyzus americanus) were more numerous in hardwood tree plantings. Dickcissel density decreased and field sparrow (Spizella pusilla) density increased as fields aged, but the relationships were not consistent among CP types. Differences among CPs largely resulted from differences in dominance in woody vegetation due to initial habitat management and differential succession rates. Interestingly, many of our focal species had wider successional tolerances than previously suggested. Overall, our results demonstrate that conservation benefits change over time depending on the starting CP, that there can be considerable similarity in vegetation structure and bird communities among what appear to be very different conservation practices. This information can be used to target conservation benefits toward conservation priority species. © 2020 The Wildlife Society.

Identifying western yellow-billed cuckoo breeding habitat with a dual modelling approach

The western population of the yellow-billed cuckoo (Coccyzus americanus) was recently listed as threatened under the federal Endangered Species Act. Yellow-billed cuckoo conservation efforts require the identification of features and area requirements associated with high quality, riparian forest habitat at spatial scales that range from nest microhabitat to landscape, as well as lower-suitability areas that can be enhanced or restored. Spatially explicit models inform conservation efforts by increasing ecological understanding of a target species, especially at landscape scales. Previous yellow-billed cuckoo modelling efforts derived plant-community maps from aerial photography, an expensive and oftentimes inconsistent approach. Satellite models can remotely map vegetation features (e.g., vegetation density, heterogeneity in vegetation density or structure) across large areas with near perfect repeatability, but they usually cannot identify plant communities. We used aerial photos and satellite imagery, and a hierarchical spatial scale approach, to identify yellow-billed cuckoo breeding habitat along the Lower Colorado River and its tributaries. Aerial-photo and satellite models identified several key features associated with yellow-billed cuckoo breeding locations: (1) a 4.5ha core area of dense cottonwood-willow vegetation, (2) a large native, heterogeneously dense forest (72ha) around the core area, and (3) moderately rough topography. The odds of yellow-billed cuckoo occurrence decreased rapidly as the amount of tamarisk cover increased or when cottonwood-willow vegetation was limited. We achieved model accuracies of 75–80% in the project area the following year after updating the imagery and location data. The two model types had very similar probability maps, largely predicting the same areas as high quality habitat. While each model provided unique information, a dual-modelling approach provided a more complete picture of yellow-billed cuckoo habitat requirements and will be useful for management and conservation activities.

Response of Grassland Birds to Agricultural Intensity at Different Spatial Scales in Texas

The decline in grassland birds is often associated with habitat loss due to intensity of conversion to agricultural lands and the alterations of natural disturbances. We sought to identify agricultural effects at differing scales that correlate to Texas grassland bird abundance, especially northern bobwhite (Colinus virginianus). Ninety-five roadside routes were surveyed in 20 Texas counties ranging from the Oklahoma border to the coastal plains. We conducted point counts in May and June from 2013 to 2016. To estimate the coarse effects of agriculture on bird abundance at a county level, we used number of cattle and area of farmland used per crop type amongst other data from the National Agriculture Statistics Service (NASS, 2012) for analyses. For estimates at finer scales, including the scale of individual routes and points, we obtained annual agricultural data and GIS layers from the NASS. We determined the predictive ability of each agricultural type via linear models and stepwise selection. From 2013 to 2016, we detected 32,373 individual birds, including 5,329 northern bobwhite, from 150,423 point count surveys. Our preliminary results revealed that agriculture only affects a few species at a county level. The top models for rufous-crowned sparrows (Aimophila ruficeps) and field sparrows (Spizella pusilla) included only one predictor from the full model - the number of cattle per county (R2 = 0.10; R2 = 0.29). The top model for yellow-billed cuckoos (Coccyzus americanus) included cattle per county and year, while the best model was found for dickcissels (Spiza americana), which included year and the proportions of woodland agriculture and pasture (R2 = 0.23; R2 = 0.33). While our results may indicate that agriculture impacts some species on coarse scales, it appears that bobwhite are likely impacted only on smaller scales and further analysis will be needed to identify specific impacts of agriculture on these scales.

Avian Nest Success along a Habitat Gradient in the Cross Timbers Oak Savanna

Abstract Oak savanna, once widespread across central North America, has functionally vanished from most of its range due to land conversion or fire suppression and subsequent afforestation. Savanna-associated bird species have exhibited population declines as a result. One of the few areas containing remnant oak savanna is the vast Cross Timbers ecoregion of the south-central Unites States. Previous research in the Midwest showed some bird species exhibited higher rates of nest success (i.e., lower predation of eggs and nestlings) in restored savannas than in closed-canopy forests. Our objective was to quantify patterns of avian nest success across a gradient from open-canopy oak savanna to closed-canopy forest in the Cross Timbers ecoregion of southeastern Kansas. Daily nest survival rates for four common bird species—mourning dove (Zenaida macroura), yellow-billed cuckoo (Coccyzus americanus), brown thrasher (Toxostoma rufum), and northern mockingbird (Mimus polyglottos)—were modeled against covariates ...

A collection of birds from Presidente Kennedy and adjacent areas, Tocantins: a further contribution to knowledge of Amazonian avifauna between the Araguaia and Tocantins Rivers

We report on a collection of birds made at a study site in Presidente Kennedy, midway between the Araguaia and Tocantins Rivers, in north-central Tocantins state, Brazil. Interesting records are presented for 22 species, most of them principally Amazonian taxa with comparatively few previous records for the state of Tocantins, and generally amplifying their local ranges either further south, from the north of the state, or further east, from the banks of the Araguaia River. Among them, we report the first specimen records for Tocantins of hybrids/intermediaries Pyrrhura parakeets of the “ P. perlata-coerulescens ” complex (which was common at our study site), Pearly-breasted Cuckoo Coccyzus euler i, Yellow-billed Cuckoo C. americanus , Rufous-tailed Flatbill Ramphotrigon ruficauda and Sooty Grassquit Tiaris fuliginosus . Our surveys emphasize once more the unusually high component of Amazonian species within the scattered taller forests of this region of predominantly Cerrado physiognomies.

Implications of Climate Change for Bird Conservation in the Southwestern U.S. under Three Alternative Futures.

Future expected changes in climate and human activity threaten many riparian habitats, particularly in the southwestern U.S. Using Maximum Entropy (MaxEnt3.3.3) modeling, we characterized habitat relationships and generated spatial predictions of habitat suitability for the Lucy’s warbler (Oreothlypis luciae), the Southwestern willow flycatcher (Empidonax traillii extimus) and the Western yellow-billed cuckoo (Coccyzus americanus). Our goal was to provide site- and species-specific information that can be used by managers to identify areas for habitat conservation and/or restoration along the Rio Grande in New Mexico. We created models of suitable habitat for each species based on collection and survey samples and climate, biophysical, and vegetation data. We projected habitat suitability under future climates by applying these models to conditions generated from three climate models for 2030, 2060 and 2090. By comparing current and future distributions, we identified how habitats are likely to change as a result of changing climate and the consequences of those changes for these bird species. We also examined whether land ownership of high value sites shifts under changing climate conditions. Habitat suitability models performed well. Biophysical characteristics were more important that climate conditions for predicting habitat suitability with distance to water being the single most important predictor. Climate, though less important, was still influential and led to declines of suitable habitat of more than 60% by 2090. For all species, suitable habitat tended to shrink over time within the study area leaving a few core areas of high importance. Overall, climate changes will increase habitat fragmentation and reduce breeding habitat patch size. The best strategy for conserving bird species within the Rio Grande will include measures to maintain and restore critical habitat refugia. This study provides an example of a presence-only habitat model that can be used to inform the management of species at intermediate scales.

Irrigation and avifaunal change in coastal Northwest Mexico: has irrigated habit attracted threatened migratory species?

Irrigation in desert ecosystems can either reduce or increase species diversity. Groundwater pumping often lowers water tables and reduces natural wetlands, whereas canal irrigation often creates mesic habitat, resulting in great increases in avian diversity from irrigation. Here we compare a dataset of potential natural vegetation to recent datasets from areal and satellite imagery to show that 60% of the land in the coastal plain of southern Sonora and northern Sinaloa lying below 200 m elevation has been converted by irrigation to more mesic habitats. We then use the record of bird specimens in the world’s museums from this same region of Mexico to examine the avian community before and after the development of extensive irrigation. In general these museum records show an increase in the abundance and diversity of breeding birds associated with mesic habitats. Although thorn forest birds have likely decreased in total numbers, most are common enough in the remaining thorn forest that collection records did not indicate their probable decline. Four migrants having most of their breeding ranges in the US or Canada, Yellow-billed Cuckoo, Cliff Swallow, Bell’s Vireo, and Orchard Oriole, apparently have increased dramatically as breeders in irrigated habitats of NW Mexico. Because these species have decreased or even largely disappeared as breeding birds in parts of the US or Canada, further research should assess whether their increases in new mesic habitats of NW Mexico are linked to their declines as breeding birds in Canada and the US For Bell’s Vireo recent specimens from Sinaloa suggest its new breeding population in NW Mexico may be composed partly of the endangered Least Bell’s Vireo.

Yellow-billed Cuckoo (Coccyzus americanus)

Yellow-billed Cuckoo (Coccyzus americanus)