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1. Avian use of avocado farms and intact forest in the northern Sierra de Bahoruco, Dominican Republic

   https://doi.org/10.55431/jco.2023.36.147-161  

   Young, Avery ; Aborn, David ; Latta, Steven C. ; Boyd, Jennifer Nagel ( February 2023 , Journal of Caribbean Ornithology)

   Abstract The Dominican Republic is experiencing increased forest loss due to the expansion of avocado farming. While agricultural lands can provide viable habitat for birds, knowledge of avian use of avocado farms relative to native forest is limited. We conducted surveys in fall 2021 to compare the bird communities and vegetation complexity of two avocado farm sites and two native dry forest sites in the northern Sierra de Bahoruco region of the Dominican Republic to assess avian habitat use. Overall, we found that habitat associations differed for bird species distinguished by contrasting geographic ranges. In particular, the abundance, richness, and diversity of bird species endemic to Hispaniola were significantly greater in forests than in farms, while non-endemic resident bird species had the opposite habitat associations. The abundance, richness, and diversity of Neotropical migrants exhibited fewer distinct differences between farm and forest sites. Vegetation structural complexity was reduced in avocado farms relative to forests and was positively associated with the abundance, richness, and diversity of endemic bird species but negatively associated with these community measures of non-endemic resident species. Collectively, our findings suggest that avocado farms could provide viable habitat for non-endemic resident and migrant bird species, but that endemic species could be negatively impacted by an increase in avocado farming in the region. We offer recommendations for forest preservation, farming practices, and future research that could help to inform the conservation of endemic species in the region. Keywords agriculture, avian conservation, Dominican Republic, endemic species, habitat use, land-use change, Neotropical migrants Resumen Uso de granjas de cultivo de aguacate y bosques nativos por parte de las aves en el norte de la Sierra de Bahoruco, República Dominica • La República Dominicana está experimentando una mayor pérdida de bosques nativos como consecuencia de la expansión de los cultivos de aguacate. Aunque las tierras agrícolas pueden proporcionar un hábitat propicio para algunas aves, el conocimiento sobre el uso que hacen de los cultivos de aguacate en comparación con las áreas forestales nativas es limitado. En otoño de 2021, realizamos muestreos en dos granjas de aguacate y dos bosques secos nativos en la región norte de la Sierra de Bahoruco (República Dominicana), y comparamos las comunidades de aves y la complejidad de la vegetación para evaluar el uso del hábitat que hacen las aves. En general, observamos diferencias entre las asociaciones de hábitats de las especies de aves con distribuciones geográficas distintas. En particular, la abundancia, riqueza y diversidad de especies de aves endémicas de La Española fueron significativamente mayores en los bosques que en las granjas; mientras que las especies de aves residentes no endémicas mostraron asociaciones de hábitat opuestas. La abundancia, riqueza y diversidad de las aves migratorias neotropicales exhibieron menos diferencias entre las granjas y los bosques. La complejidad estructural de la vegetación se redujo en las granjas de aguacate en relación con los bosques y tuvo una correlación positiva con la abundancia, riqueza y diversidad de aves endémicas, pero negativa con las mismas medidas comunitarias de especies residentes no endémicas. En conjunto, nuestros resultados sugieren que los cultivos de aguacate podrían proporcionar un hábitat adecuado para aves residentes no endémicas y migratorias; mientras que las especies endémicas podrían verse afectadas negativamente por un aumento de estos cultivos en la región. Por último, proporcionamos recomendaciones para la conservación de los bosques, prácticas agrícolas y futuras investigaciones que podrían contribuir a la conservación de las aves endémicas de esta región. Palabras clave agricultura, aves migratorias neotropicales, cambio de uso de suelo, conservación de aves, especies endémicas, República Dominicana, uso de hábitat Résumé Utilisation par les oiseaux des plantations d’avocatiers et des forêts non exploitées dans le nord de la Sierra de Bahoruco, en République dominicaine • En République dominicaine, la forêt indigène est en régression en raison de l’augmentation de la culture des avocatiers. Bien que les terres agricoles puissent fournir un habitat approprié à certains oiseaux, les connaissances sur l’utilisation des plantations d’avocatiers par rapport à celle des forêts indigènes sont limitées. Nous avons échantillonné deux plantations d’avocatiers et deux forêts sèches indigènes dans la Sierra de Bahoruco (République dominicaine) au cours de l’automne 2021, et nous avons comparé leurs communautés d’oiseaux et la complexité de leur végétation afin d’évaluer l’utilisation de ces deux habitats par les oiseaux. Dans l’ensemble, nous avons observé que les associations entre espèces d’oiseaux et habitats différaient en fonction de la répartition géographique des oiseaux. En particulier, l’abondance, la richesse et la diversité de l’avifaune endémique à Hispaniola étaient significativement plus fortes dans les forêts que dans les plantations, tandis que les espèces d’oiseaux sédentaires non endémiques étaient inversement associées à ces habitats. L’abondance, la richesse et la diversité des migrateurs néotropicaux présentaient moins de différences distinctes entre les milieux agricoles et forestiers. La complexité de la structure de la végétation était plus faible dans les plantations d’avocatiers que dans les forêts, et était positivement corrélée à l’abondance, à la richesse et à la diversité des espèces d’oiseaux endémiques, mais négativement corrélée à ces mesures pour les communautés d’espèces sédentaires non endémiques. Dans l’ensemble, nos résultats semblent indiquer que les plantations d’avocatiers pourraient constituer un habitat viable pour les espèces d’oiseaux sédentaires et migrateurs non endémiques, mais que les espèces endémiques pourraient être affectées négativement par une augmentation de ces cultures dans la région. Nous formulons des recommandations pour la préservation des forêts, les pratiques agricoles et les recherches futures qui pourraient contribuer à la conservation des espèces endémiques dans la région. Mots clés agriculture, changement d’affectation des terres, conservation de l’avifaune, espèces endémiques, migrateurs néotropicaux, République dominicaine, utilisation des habitats

    

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2. Bird communities in African cocoa agroforestry are diverse but lack specialized insectivores

   https://doi.org/10.1111/1365-2664.13864  

   Jarrett, Crinan ; Smith, Thomas B. ; Claire, Tabe T. R. ; Ferreira, Diogo F. ; Tchoumbou, Melanie ; Elikwo, Malange N. F. ; Wolfe, Jared ; Brzeski, Kristin ; Welch, Andreanna J. ; Hanna, Rachid ; et al ( March 2021 , Journal of Applied Ecology)

   Forests are being converted to agriculture throughout the Afrotropics, driving declines in sensitive rainforest taxa such as understorey birds. The ongoing expansion of cocoa agriculture, a common small‐scale farming commodity, has contributed to the loss of 80% rainforest cover in some African countries. African cocoa farms may provide habitat for biodiversity, yet little is known about their suitability for vertebrate fauna, or the effect of farm management on animal communities.

   Here, we report the first in‐depth investigation into avian diversity and community composition in African cocoa, by assembling a dataset of 9,566 individual birds caught across 83 sites over 30 years in Southern Cameroon. We compared bird diversity in mature forest and cocoa using measures of alpha, beta and gamma diversity, and we investigated the effect of cocoa farm shade and forest cover on bird communities.

   Gamma diversity was higher in cocoa than forest, though alpha diversity was similar, indicating a higher dissimilarity (beta diversity) between cocoa farms. Cocoa farms differed from forest in community composition, with a distinctive decrease in relative abundance of insectivores, forest specialists and ant‐followers and an increase in frugivores.

   Within cocoa farms, we found that farms with high shade cover in forested landscapes resulted in higher relative abundance and richness of sensitive forest species; shady farms contained up to five times the proportion of forest specialists than sunny farms.

   Synthesis and applications. Sunny African cocoa farms were less able to support sensitive bird guilds compared with shaded farms in forested landscapes. Our findings support the notion that certain ecological and dietary guilds, such as ant‐followers and forest specialists are disproportionately affected by land‐use change. In light of the current push to increase cocoa production in sub‐Saharan Africa, our results provide policymakers opportunities for more wildlife‐friendly cocoa schemes that maximize avian diversity.

    

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3. The effect of shade tree species on bird communities in central Kenyan coffee farms

   Kammerichs-Berke, D ( October 2021 , Bird conservation international)

   Atkinson, Phil (Ed.)

   Shade coffee is a well-studied cultivation strategy that creates habitat for tropical birds while also maintaining agricultural yield. Although there is a general consensus that shade coffee is more “bird-friendly” than a sun coffee monoculture, little work has investigated the effects of specific shade tree species on insectivorous bird diversity. This study involved avian foraging observations, mist netting data, temperature loggers, and arthropod sampling to investigate bottom-up effects of two shade tree taxa - native Cordia sp. and introduced Grevillea robusta - on insectivorous bird communities in central Kenya. Results indicate that foliage-dwelling arthropod abundance, and the richness and overall abundance of foraging birds were all higher on Cordia than on Grevillea. Furthermore, multivariate analyses of the bird community indicate a significant difference in community composition between the canopies of the two tree species, though the communities of birds using the coffee understory under these shade trees were similar. In addition, both shade trees buffered temperatures in coffee, and temperatures under Cordia were marginally cooler than under Grevillea. These results suggest that native Cordia trees on East African shade coffee farms may be better at mitigating habitat loss and attracting insectivorous birds that could promote ecosystem services. Identifying differences in prey abundance and preferences in bird foraging behavior not only fills basic gaps in our understanding of the ecology of East African coffee farms, it also aids in developing region-specific information to optimize functional diversity, ecosystem services, and the conservation of birds in agricultural landscapes. 

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4. Continental‐scale biomass redistribution by migratory birds in response to seasonal variation in productivity

   https://doi.org/10.1111/geb.13460  

   Ng, Wee Hao ; Fink, Daniel ; La Sorte, Frank A. ; Auer, Tom ; Hochachka, Wesley M. ; Johnston, Alison ; Dokter, Adriaan M. ; Storch, ed., David ( February 2022 , Global Ecology and Biogeography)

   Animal migration is often explained as the result of resource tracking in seasonally dynamic environments. Therefore, resource availability should influence both the distributions of migratory animals and their seasonal abundance. We examined the relationship between primary productivity and the spatio‐temporal distributions of migratory birds to assess the role of energy availability in avian migration.

   North America.

   Full annual cycle, 2011–2016.

   Nocturnally migrating landbirds.

   We used observations of nocturnally migrating landbirds from the eBird community‐science programme to estimate weekly spatial distributions of total biomass, abundance and species richness. We related these patterns to primary productivity and seasonal productivity surplus estimated using a remotely sensed measure of vegetation greenness.

   All three avian metrics showed positive spatial associations with primary productivity, and this was more pronounced with seasonal productivity surplus. Surprisingly, biomass showed a weaker association than did abundance and richness, despite being a better indicator of energetic requirements. The strength of associations varied across seasons, being the weakest during migration. During spring migration, avian biomass increased ahead of vegetation green‐up in temperate regions, a pattern also previously described for herbivorous waterfowl. In the south‐eastern USA, spring green‐up was instead associated with a net decrease in biomass, and winter biomass greatly exceeded that of summer, highlighting the region as a winter refuge for short‐distance migrants.

   Although instantaneous energy availability is important in shaping the distribution of migratory birds, the stronger association of productivity with abundance and richness than with biomass suggests the role of additional drivers unrelated to energetic requirements that are nonetheless correlated with productivity. Given recent reports of widespread North American avifaunal declines, including many common species that winter in the south‐eastern USA, understanding how anthropogenic activities are impacting winter bird populations in the region should be a research priority.

    

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5. Predation, parasitism, and drought counteract the benefits of patch-burn grazing for the reproductive success of grassland songbirds

   https://doi.org/10.1093/ornithapp/duab066  

   Verheijen, Bram H. F. ; Erickson, Amy N. ; Boyle, W. Alice ; Leveritte, Kiana S. ; Sojka, Jennifer L. ; Spahr, Lauren A. ; Williams, Emily J. ; Winnicki, Sarah K. ; Sandercock, Brett K. ( January 2022 , Ornithological Applications)

   Intensification of livestock production has reduced heterogeneity in vegetative structure in managed grasslands, which has been linked to widespread declines in grassland songbird populations throughout North America. Patch-burn grazing management aims to restore some of that heterogeneity in vegetative structure by burning discrete pasture sections, so that cattle preferentially graze in recently burned areas. Although patch-burn grazing can increase reproductive success of grassland songbirds, we know little about possible interactions with regional variation in predator communities or brood parasite abundance, or annual variation in weather conditions. Using six years of data from two tallgrass prairie sites in eastern Kansas, USA, we tested effects of patch-burn grazing on the rates of brood parasitism, clutch size, nest survival, and fledging success of three common grassland songbirds, Dickcissels (Spiza americana), Eastern Meadowlarks (Sturnella magna), and Grasshopper Sparrows (Ammodramus savannarum), among pastures managed with patch-burn grazing versus pastures that were annually burned and either grazed or ungrazed. Dickcissel nests experienced lower parasitism (72.8 ± 4.6% SE vs. 89.1 ± 2.2%) and Eastern Meadowlarks had higher nest survival (63.2 ± 20.5% vs. 16.5 ± 3.5%) in annually burned and ungrazed pastures than pastures managed with patch-burn grazing. However, average number of host fledglings per nesting attempt did not differ among management treatments for any species. Annual variation in weather conditions had a large effect on vegetation structure, but not on reproductive success. Probability of brood parasitism was consistently high (25.5‒84.7%) and nest survival was consistently low (9.9–16.9%) for all species pooled across treatments, sites, and years, indicating that combined effects of predation, parasitism and drought can offset potential benefits of patch-burn grazing management previously found in tallgrass prairies. Although differences in reproductive success among management treatments were minimal, patch-burn grazing management could still benefit population dynamics of grassland songbirds in areas where nest predators and brood parasites are locally abundant by providing suitable nesting habitat for bird species that require greater amounts of vegetation cover and litter, generally not present in burned pastures.

    

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