Neotropical Migratory Birds Research Articles

Avian haemosporidians of the genera Plasmodium and Haemoproteus from resident and Neotropical migrant birds in Colombia

Avian haemosporidians of the genera Plasmodium and Haemoproteus are a group of widely distributed blood parasites that can negatively affect the fitness of their hosts. Colombia contains the greatest diversity of birds on the planet, but knowledge about the associations between haemosporidian and its avifauna is scarce and fragmented. We collected blood samples from 255 birds (203 residents and 52 neotropical migrants) belonging to 27 families and 108 species. The study was conducted in six localities in the inter-Andean valleys of the Cauca and Magdalena rivers. Parasites of the genera Plasmodium and Haemoproteus were identified in the samples by morphological and molecular analysis of a fragment of the mitochondrial gene cyt b. Among the samples, 9.3% (n = 24) were positive for Plasmodium or Haemoproteus. Co-infection with Plasmodium and Haemoproteus was found in Red-eyed Vireo. Seventeen haemosporidian lineages were identified, five of which were reported for the first time in resident birds (Common Ground Dove, Checker-throated Stipplethroat, Tropical Kingbird, Pale-breasted Thrush, and Ruddy-breasted Seedeater) and one in the Summer Tanager (neotropical migrant). The research results confirm the wide diversity of haemosporidian present in tropical lowlands and the possible role of neotropical migratory birds in dissemination on haemosporidian along their migratory routes.

Improving the language of migratory bird science in North America

Abstract Several long-accepted terms are widely misused in ornithology and have led to a misperception of important concepts in the ecology of Nearctic–Neotropical migratory birds. The term “North America” (and its ancillary terms “North American species,” “North American habitats,” etc.) is widely used to refer to the United States and Canada, when in fact it should include all of the continent from the Arctic through Panama. In a similar vein, the terms “wintering” and “over-wintering” (whether used to describe the status of individual birds or species, or as a modifier for terms like habitats, ecology, or behavior), “spring migration” and “fall migration” are inappropriate for Nearctic–Neotropical migrants because they explicitly reference conditions in the temperate zone of the continent, even as most such species spend the majority of their annual cycle elsewhere, where these terms are inaccurate and unhelpful. We discuss the pitfalls of using these terms and suggest several alternatives and replacements. In particular, we urge more precision in the use of the term “North America”; for Nearctic–Neotropical migratory species (especially long-distance migrants), we suggest retiring the terms “wintering” and “over-wintering” in favor of “nonbreeding”; and for the same group of species we suggest retiring the terms “spring migration” and “fall migration” in favor of “pre-breeding,” “post-breeding,” or “post-natal” migration.

Modeled distribution shifts of North American birds over four decades based on suitable climate alone do not predict observed shifts

As climate change alters the global environment, it is critical to understand the relationship between shifting climate suitability and species distributions. Key questions include whether observed changes in population abundance are aligned with the velocity and direction of shifts predicted by climate suitability models and if the responses are consistent among species with similar ecological traits. We examined the direction and velocity of the observed abundance-based distribution centroids compared with the model-predicted bioclimatic distribution centroids of 250 bird species across the United States from 1969 to 2011. We hypothesized that there is a significant positive correlation in both direction and velocity between the observed and the modeled shifts. We then tested five additional hypotheses that predicted differential shifting velocity based on ecological adaptability and climate change exposure. Contrary to our hypotheses, we found large differences between the observed and modeled shifts among all studied bird species and within specific ecological guilds. However, temperate migrants and habitat generalist species tended to have higher velocity of observed shifts than other species. Neotropical migratory and wetland birds also had significantly different observed velocities than their counterparts, which may be due to their climate change exposure. The velocity based on modeled bioclimatic suitability did not exhibit significant differences among most guilds. Boreal forest birds were the only guild with significantly faster modeled-shifts than the other groups, suggesting an elevated conservation risk for high latitude and altitude species. The highly idiosyncratic species responses to climate and the mismatch between shifts in modeled and observed distribution centroids highlight the challenge of predicting species distribution change based solely on climate suitability and the importance of non-climatic factors traits in shaping species distributions.

Interrelationships among feather mercury content, body condition and feather corticosterone in a Neotropical migratory bird, the Purple Martin (Progne subis subis)

Purple Martins (Progne subis) are migratory birds that breed in North America and overwinter and complete their molt in South America. Many of the breeding populations are declining. The eastern North American subspecies of Purple Martin (P. subis subis) comprises >90% of all Purple Martins. This subspecies overwinters and molts in the Amazon Basin, a region that is high in mercury (Hg) contamination, which raises the possibility that observed declines in Purple Martins could be linked to Hg exposure. Exposure to Hg results in numerous and systemic negative health outcomes, including endocrine disruption. Corticosterone (CORT) is a primary modulator of the stress and metabolic axes of vertebrates; thus, it is important in meeting metabolic and other challenges of migration. Because feathers accumulate Hg and hormones while growing, quantification of Hg and CORT in feathers provides an opportunity to retrospectively assess Hg exposure and adrenal activity of birds using minimally invasive methods. We evaluated interrelationships among concentrations of total Hg (THg) and CORT in feathers that grew in the Amazon Basin and body condition (mass, fat score) of these birds in North America. Concentrations of THg in Purple Martin feathers ranged from 1.103 to 8.740 μg/g dw, levels associated with negative physiological impacts in other avian species. Concentrations of CORT did not correlate with THg concentration at the time of feather growth. However, we found evidence that THg concentration may negatively impact the ability of Purple Martins to accumulate fat, which could impair migratory performance and survivorship due to the high energy requirements of migration. This finding suggests potential carryover effects of Hg contamination at the wintering grounds in the Amazon to the summer breeding grounds in North America.

Effects of Landscape Configuration on the Body Condition of Migratory and Resident Tropical Birds

Landscape structure and configuration may affect bird body condition, with contrasting effects on resident and migratory species. There is little empirical evidence to support this hypothesis in tropical regions, where land-use change poses a major threat to biodiversity. We aimed to assess the effects of landscape structure and configuration on the body condition of neotropical migrant and resident bird species. We compiled body condition data (using the scaled mass index) of nine bird species (five resident and four migratory). We characterized landscape structure and configuration at 26 localities. We evaluated the effects of landscape metrics on bird body condition using Bayesian linear mixed models. The landscapes in our study largely varied in forest, crop, and grassland cover, as well as in landscape metrics. When we examined migrant birds, we found a positive effect of landscape connectivity and crop cover on body condition. Similarly, body condition of resident birds was positively affected by connectivity and crop cover, but also by forest patch area and capture day. Changes in landscape structure and configuration may indirectly alter the access to resources, causing additional energy expenditures, leading to a deteriorated body condition. Conversely, landscape heterogeneity may have a positive effect on bird body condition. Therefore, we recommend maintaining connectivity and complementary resources in the landscape.

Neotropical Migratory Bird Conservation Act Grants (DOI)

Federal Grants & ContractsVolume 45, Issue 20 p. 4-4 Grants Alerts Neotropical Migratory Bird Conservation Act Grants (DOI) First published: 14 September 2021 https://doi.org/10.1002/fgc.31946Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume45, Issue2016 September 2021Pages 4-4 RelatedInformation

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.

Characterization of the Plasmodium and Haemoproteus parasite community in temperate-tropical birds during spring migration.

Animal movements, especially avian migration, can be a mechanism for the large-scale dispersal and geographic range expansion of parasites. The host-parasite relationships among birds during migration have yet to be fully explored. We characterized the haemosporidian parasite lineages in passerines during spring migration on the Texas coast of the Gulf of Mexico, and identified associations among wintering origin (US, Central America, South America) and foraging height (canopy, understory, ground) and infection status. We examined 743 samples representing 52 species of 10 families over six years, 2014–2019. We used PCR and DNA sequencing of the haemosporidian cytB gene from avian blood samples to determine infection status with the genera Plasmodium and Haemoproteus and characterize the lineages of blood parasites. We found an overall haemosporidian infection prevalence of 48.4% among neotropical migrant and Texas wintering birds. Among families, Icterids had the highest prevalence (75%, 24 individuals, 4 species sampled) whereas Parulids had the lowest prevalence (38.4%, 177 individuals, 18 species sampled). Among infected birds, Plasmodium spp. infections were more common than Haemoproteus spp. infections in species that winter in Central America compared to those that winter in the US or South America. Similarly, among infected birds, Plasmodium spp. infections were more common than Haemoproteus spp. infections in species that forage on the ground or in the understory compared to those that forage in the canopy. Infected birds harbored 65 different haemosporidian lineages (71% Plasmodium; 29% Haemoproteus) of which 17 lineages have never previously been reported and six lineages were documented for the first time in North America, having been previously detected only in Central or South America. These data are consistent with the premise that intercontinental parasite dispersal may be facilitated by passerine birds. Future studies focused on surveillance, the probability of establishment of parasite lineages, and the use of individual bird tracking methods to understand infection dispersion over time will allow a more comprehensive understanding of changing avian host-haemosporidian relationships.

Predicting Bird Guilds Using Vegetation Composition and Structure on a Wild and Scenic River in Arizona

Riparian areas are among the most ecologically diverse terrestrial ecosystems but make up <2% of landscape area in southwestern USA. Many species of resident and neotropical migratory birds utilize riparian habitats for breeding, foraging, and nesting. We quantified vegetation composition and structure to predict bird guilds on Wild and Scenic portions of the Verde River, Arizona. We grouped plant species into guilds based on similar functional traits to describe composition. We surveyed birds during the breeding and migrating season to determine abundance and categorized species into guilds using preferences of breeding habitat, foraging substrate, and nest placement. Riparian obligate and facultative breeding guilds were most common. Both vegetation composition and structure were useful predictors of birds. Vegetation structure was most complex in gallery riparian forest. Abundance of riparian-obligate birds in the breeding guild were positively associated with vegetation structure of dense, multi-canopy canopy and tall trees. Abundance of most bird guilds were positively associated with composition of tall trees (Populus fremontii, Salix gooddingii) and drought tolerant shrubs (Prosopis velutina, Celtis reticulata). Our findings show complex riparian habitat important to wildlife is created by both composition and structure of near-stream vegetation that is tied to hydrology and sensitive to flow change.

Satellite tracking reveals age and origin differences in migration ecology of two populations of Broad-winged Hawks (Buteo platypterus)

Recent conservation plans for long-distance Neotropical migrant birds have emphasized the importance of understanding the ecology and threats facing a species throughout its life cycle, including migration and overwintering periods. To better understand the ecology of Broad-winged Hawks (Buteo platypterus) during the nonbreeding period, we followed the movements of 14 hawks from 2 breeding populations during July 2014–April 2019 to their overwintering sites. Three juvenile and 8 adult female Broad-winged Hawks were satellite-tracked from Pennsylvania, USA, and 3 adults (2 females and 1 male) were tracked from Alberta, Canada. We documented pre-migratory movements (post-breeding) of 4 of the 14 individuals. Adults initiated fall migration on x = 25 August ± 16.38 d and 2 of the 3 juveniles began fall migration on x = 20 August ± 2 d. Adults had 1–12 (x = 5.0 ± 3.5) stopovers in autumn that lasted for 1–24 d and juveniles had 2–5 (x = 3.0 ± 1.7) stopovers that lasted 2–51 d. Adults from Pennsylvania spent the overwintering period in Nicaragua, Brazil, Peru, and Colombia (n = 8) whereas those from Alberta wintered in Suriname, Venezuela, and Bolivia (n = 3). The distance traveled on autumn migration was greater for Alberta birds (x = 10,021 ± 866 km, n = 3) than for Pennsylvania birds (x = 7,925 ± 1,631 km, n = 8). Migration distance and overwintering region varied by geographic origin with age but with some overlap between the 2 distinct geographic breeding populations. Broad-winged Hawks appear to follow a hybrid time–energy minimization strategy during fall and spring migrations with (1) energy minimization in North America, and (2) time minimization in Mexico and Central America. Stopover frequency, duration, and migration rate support this hypothesis.

A genoscape-network model for conservation prioritization in a migratory bird.

Migratory animals are declining worldwide and coordinated conservation efforts are needed to reverse current trends. We devised a novel genoscape-network model that combines genetic analyses with species distribution modeling and demographic data to overcome challenges with conceptualizing alternative risk factors in migratory species across their full annual cycle. We applied our method to the long distance, Neotropical migratory bird, Wilson's Warbler (Cardellina pusilla). Despite a lack of data from some wintering locations, we demonstrated how the results can be used to help prioritize conservation of breeding and wintering areas. For example, we showed that when genetic, demographic, and network modeling results were considered together it became clear that conservation recommendations will differ depending on whether the goal is to preserve unique genetic lineages or the largest number of birds per unit area. More specifically, if preservation of genetic lineages is the goal, then limited resources should be focused on preserving habitat in the California Sierra, Basin Rockies, or Coastal California, where the 3 most vulnerable genetic lineages breed, or in western Mexico, where 2 of the 3 most vulnerable lineages overwinter. Alternatively, if preservation of the largest number of individuals per unit area is the goal, then limited conservation dollars should be placed in the Pacific Northwest or Central America, where densities are estimated to be the highest. Overall, our results demonstrated the utility of adopting a genetically based network model for integrating multiple types of data across vast geographic scales and better inform conservation decision-making for migratory animals.

Defining catchment origins of a geographical bottleneck: Implications of population mixing and phenological overlap for the conservation of Neotropical migratory birds

Abstract Migratory bottlenecks concentrate individuals and populations of Nearctic–Neotropical migrants from across vast breeding areas. The extent to which such concentrations occur has important ramifications for interpreting migratory connectivity and for the vulnerability of populations throughout the annual cycle but investigations of such phenomena are rare. We inferred breeding origins of 11 species of Nearctic–Neotropical migrants captured during fall migration in the Darién region, northwestern Colombia, using feather stable-hydrogen isotope values (δ 2Hf). Our objectives were to determine (1) the extent to which this region acts as a catchment for individuals from across a species’ breeding range, (2) if temporal patterns of arrival arise as a function of migration distance inferred from δ 2Hf, and (3) if phenological differences among species segregate populations. The Darién concentrated populations of 6 species, with individuals potentially derived from 78% to 94% of their respective North American breeding ranges. The catchment area for the remaining 5 species covered 40–72% of breeding ranges, with a bias in origin from the west (e.g., Northern Waterthrush [Parkesia noveboracensis], Swainson’s Thrush [Catharus ustulatus]), north or center (Yellow Warbler [Setophaga petechia]) of their range. Differential timing in the migration of populations occurred in 6 species, generating a degree of temporal segregation. In contrast, peak migration for all species occurred in October, resulting in high overlap among species in their use of the Darién. Overall, our results describe high mixing of populations in the Darién for several species, which, given the region’s highly restricted geographic extent, suggests that a bottleneck effect occurs; however, comparisons with other regions in Central America and northern South America are required. The combination of extensive population mixing and limited temporal segregation over a narrow geographical area suggests that long-distance migrants may be especially vulnerable to events occurring in such regions, including adverse weather conditions and anthropogenic land cover change.

Neotropical migratory and resident birds occurring in sympatry during winter have distinct haemosporidian parasite assemblages

AbstractAimWe compared the parasite assemblages of over‐wintering migratory birds and permanent residents on the wintering grounds. We determined whether parasite sharing between migratory and resident birds is influenced by host phylogenetic relatedness. We then inferred whether migratory birds transport haemosporidian parasite lineages between the breeding and wintering grounds.LocationSierra de Bahoruco National Park, Dominican Republic, Hispaniola.TaxaMigratory and resident birds (primarily Aves: Passeriformes) and their haemosporidian parasites (order Haemosporida, Plasmodium, Haemoproteus and Parahaemoproteus).MethodsWe used mist nets to capture birds in thorn scrub, broadleaf dry forests and pine forests during midwinter. We used molecular methods to recognize haemosporidian parasites in blood samples, and genotyped infections based on the nucleotide differences in a region of the parasite cytochrome b gene.Results and Main ConclusionWe identified 505 infections by 32 haemosporidian parasite lineages in 1,780 blood samples from 37 resident species, and in 901 blood samples from 14 overwintering migratory species, over five years at the same sites. Infection prevalence varied among migratory species from zero to 13%, whereas infection prevalence among resident species ranged up to 77%. Host relatedness did not predict parasite assemblage similarity. We discuss four hypotheses for the rarity of haemosporidian infections in migratory birds during winter, and for the infrequency of parasite sharing between migratory and resident birds: (a) relative abundance and host preferences of dipteran vectors lower parasite transmission to migratory birds; (b) parasite lineages adapted to infect endemic Caribbean hosts are unable to infect migratory species; (c) the physiology of migratory birds after migration and during winter reduces parasite survival; and (d) infected individuals suffer more pronounced mortality rates during migration. We highlight the link between host–parasite coevolution and the physiological adaptations associated with avian seasonal migration.

Prioritize diversity or declining species? Trade-offs and synergies in spatial planning for the conservation of migratory birds in the face of land cover change

Stemming biodiversity loss requires strategic conservation guided by well articulated targets, whether they be proactive (e.g., protect biodiverse areas) or reactive (e.g., protect threatened species). Both types of targets can be effective, but there are trade-offs, especially for broadly distributed taxa such as migratory species, a group for which conservation has been challenged by limited knowledge of distributions throughout the annual cycle. We combined spatiotemporal distribution models with population trend data to first examine focal areas for the conservation of Neotropical migratory birds (n=112 species) during the non-breeding period in the Western Hemisphere, based on a proactive approach (highest diversity) versus a reactive approach (strongest declines). For focal areas, we then assessed the extent of recent anthropogenic impact, protected area status, and projected changes in land cover using shared socioeconomic pathways. Spatial priorities for high diversity emphasized southern Mexico and northern Central America, and were strikingly different from areas with species in stronger decline, emphasizing the Andean cordilleras. Only 1.4% of the non-breeding region met targets for diversity and decline, mostly in southern Central America. Areas prioritized to conserve high species diversity have experienced less recent anthropogenic impact than areas prioritized for species in decline but are predicted to experience more rapid land conversion to less suitable agricultural landscapes in the next three decades. Our findings indicate how efficient conservation efforts will depend on the careful consideration of desired targets combined with reliable predictions about the locations and types of land cover change under alternative socioeconomic futures.

Neotropical Migratory Bird Conservation Act Grants (DOI)

Federal Grants & ContractsVolume 43, Issue 20 p. 3-3 Grant Alerts Neotropical Migratory Bird Conservation Act Grants (DOI) First published: 17 September 2019 https://doi.org/10.1002/fgc.30648Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume43, Issue2019 September 2019Pages 3-3 RelatedInformation

Habitat selection and habitat quality for wintering wood thrushes in a coffee growing region in Honduras

Most Neotropical migrant birds spend the majority of the annual cycle in the tropics, and the continued population declines of some species is attributed at least in part to habitat degradation and destruction on the tropical wintering grounds. Many Neotropical migrants have been observed to use a range of disturbed, agricultural, and primary forest habitats on the wintering grounds, and this habitat-use information helps us better understand the potential effects of land use in the tropics on their populations as well as to develop programs and strategies to conserve these species. Although indices and estimates of habitat-specific abundance can be informative, some wintering migrants are reported to occur in similar or even greater numbers in marginal habitats due to despotic interactions with conspecifics. Thus, investigations of habitat-specific survival and other metrics potentially related to survival are a valuable supplement, and provide a more refined indicator of habitat quality. The wood thrush is a Neotropical migrant bird that has been undergoing range-wide population declines for the past half century or more, and although their numbers appear to be greater in disturbed habitats on the wintering grounds, they are reported to experience higher survival in primary forest. We captured and tracked wintering wood thrushes with radio-telemetry in a coffee growing region in Honduras, Central America, to evaluate habitat selection in this species, as well as to determine the habitat types and microhabitat characteristics associated with survival, movement metrics, and body condition. We found that wood thrushes preferred heavily-shaded coffee over forest and open agricultural habitats, although the probability of survival and of exhibiting stationary behavior was lower in heavily-shaded coffee compared to forest, especially at higher elevations. Our findings illustrate the hazards in assuming the presence of a species in a given habitat actually reflects habitat quality, as well as the importance of conserving forest within coffee producing landscapes.

Reporte de la Bijirita de Connecticut (Oporornis agilis; Aves: Parulidae) en el oriente de Cuba

La Bijirita de Connecticut (Oporornis agilis) es una especie de ave migratoria neotropical. La literatura y los mapas de distribución publicados por eBird sugieren que la especie utiliza la región del Caribe durante la migración otoñal y primaveral. La isla de Cuba solo posee un reporte de la especie en la cayería norte de Ciego de Ávila y Camagüey. Fue capturado un individuo macho en redes de niebla pertenecientes a la Estación de Anillamiento Permanente Juan Christoph Gundlach, ubicada en la Reserva Ecológica Siboney Juticí, del municipio de Santiago de Cuba, provincia Santiago de Cuba. Este constituye el primer reporte de la especie en la zona oriental de Cuba. La falta de avistamientos de Bijirita de Connecticut en Cuba puede estar condicionada por dos factores principalmente: la baja densidad de individuos en la isla durante la migración o la posible confusión de los ornitólogos cubanos con especies similares.

Beyond canaries in coal mines: Co-occurrence of Andean mining concessions and migratory birds

Spatial planning and decision-support tools facilitate the consideration of socioecological tradeoffs associated with extractive activities, but insufficient data resources often limit their application. Focusing on birds and mining concessions in the Northern Andes, we illustrate how publicly-available data can be used in spatial prioritization tools to identify where concessions have the potential to impact 22 species of Neotropical migratory birds. Concessions covered 11% of the land area of Colombia, Ecuador, and Peru, and disproportionately occurred within important areas for migratory birds in Colombia and Ecuador, but not Peru. eBird data showed that one-quarter of avian species, including the Olive-sided Flycatcher, Cerulean Warbler, and Canada Warbler, had >10% of their global populations on concession land during the non-breeding season. More worrisome, species of greater conservation importance and with larger population declines (1974–2014) were most likely to co-occur with mining. Our approach highlights how public biodiversity data can be used to predict, avoid, or mitigate potential ecological impacts from extractive activities.

Optimizing the conservation of migratory species over their full annual cycle

Limited knowledge of the distribution, abundance, and habitat associations of migratory species hinders effective conservation actions. We use Neotropical migratory birds as a model group to compare approaches to prioritize land conservation needed to support ≥30% of the global abundances of 117 species. Specifically, we compare scenarios from spatial optimization models to achieve conservation targets by: 1) area requirements for conserving >30% abundance of each species for each week of the year independently vs. combined; 2) including vs. ignoring spatial clustering of species abundance; and 3) incorporating vs. avoiding human-dominated landscapes. Solutions integrating information across the year require 56% less area than those integrating weekly abundances, with additional reductions when shared-use landscapes are included. Although incorporating spatial population structure requires more area, geographical representation among priority sites improves substantially. These findings illustrate that globally-sourced citizen science data can elucidate key trade-offs among opportunity costs and spatiotemporal representation of conservation efforts.

Conservation of Neotropical migratory birds in tropical hardwood and oil palm plantations.

Tropical forests in the Americas are undergoing rapid conversion to commercial agriculture, and many migratory bird species that use these forests have experienced corresponding populations declines. Conservation research for migratory birds in the tropics has focused overwhelmingly on shade coffee plantations and adjacent forest, but both cover types are now in decline, creating an urgent need to evaluate conservation opportunities in other agricultural systems. Here we compare how a community of 42 Neotropical migratory bird species and a subset of five conservation-priority species differ in usage and habitat associations among a secondary forest baseline and four expanding commercial plantation systems in Guatemala: African oil palm, teak, rubber, and mixed-native hardwoods. We found that mixed-native hardwood plantations supported the highest richness and diversity of all migrants and that the three hardwood plantation types generally outperformed oil palm in richness and diversity metrics. Despite this, oil palm supported high abundance of several common and widespread species also experiencing range-wide population declines and may therefore play an important role in conserving common species. Mature secondary forest hosted low abundance and diversity of the full migratory community, but high abundance and richness of conservation priority migrants along with native hardwood and teak plantations. Likewise, the percentage of forest cover on the landscape was positively associated with priority migrant abundance and richness but negatively associated with the abundance of migrants in general, highlighting how individual species within the broad group of Neotropical migratory landbirds respond differently to anthropogenic changes in land use. Across all cover types, the retention of tall overstory trees increased the abundance, richness, and diversity of all migrants, which indicates that vertical structural diversity and remnant trees are important habitat features for birds in agricultural landscapes. Our findings show that conservation opportunities exist in hardwood and oil palm plantations, though the species likely to benefit from conservation action will vary among plantation types. For the subset of conservation priority migrants, our results suggest that conservation efforts should combine strategies that retain and restore secondary forest, promote the adoption of native hardwood and teak plantations, and promote the retention of tall, remnant trees in agricultural landscapes.