Assessing bird diversity in Neotropical rainforests: A comparative study of camera traps and mist nets reveals complementary sampling approaches

ABSTRACT Different sampling methods are used to study bird diversity in the tropics, mist nets being one of the most common approaches. However, camera traps have been used for this purpose in the last 20 years. We compared the performance of mist nets and camera traps in sampling the diversity of understory and sub-canopy birds in a Neotropical rainforest. Given its high biodiversity, obtaining accurate bird diversity estimates in these forests is a challenging task. We sampled secondary forest patches in the Colombian central Andes between 2019 and 2021. We compared the effectiveness of both methods based on six comparison criteria (body size, foraging stratum, detection difficulty, habitat specialization, population trend, and migratory status). We recorded a total of 99 bird species: 92 species were captured using mist nets and 37 species using camera traps; 30 species were detected using both methods (mainly generalist and abundant birds). Mist net's effectiveness was 83%, while camera trap effectiveness was 68%. Differences in sampling effectiveness were mainly determined by body size, as small birds were captured using mist nets, while camera traps often recorded large birds. However, detection difficulty and habitat specialization were also relevant. Camera traps effectively recorded ground-dwelling species that were not captured in mist nets. In contrast, those birds that forage in the sub-canopy stratum were mainly captured in the mist nets but not detected in camera traps. Although both methods detected different species, we found similar patterns regarding estimated species richness among different categories of body size, detection difficulty, population trend, and behavior, but not for habitat specialization. As both methods have advantages and limitations, using mist nets and camera traps together would improve bird diversity estimations. We urge investigators to explore canopy ecology with camera traps, as they provide long-term information that cannot be obtained with other methods. How to Cite Vargas-Daza, A. M., J. F. Betancurt-Grisales, L. J. Cardona-Salazar, Y. A. Benavides-Ossa, F. E. Fontúrbel, and G. J. Castaño-Villa (2023). Assessing bird diversity in Neotropical rainforests: A comparative study of camera traps and mist nets reveals complementary sampling approaches. Ornithological Applications 125:duad019. LAY SUMMARY Camera traps are often used for biodiversity inventories and population monitoring of terrestrial and understory birds in tropical forests. Their use has considerably increased in the last couple of decades. Assessing camera trap performance for bird sampling is key to improve bird monitoring in the tropics. Mist nets recorded more bird species than camera traps, as small birds that fly in the sub-canopy were captured by those nets but not detected by cameras. Conversely, camera traps recorded large ground-dwelling birds not captured in the mist nests, providing complementary information for bird surveys. Mist nets and camera traps detect different species, but estimated species richness patterns were similar for different categories of body size, detection difficulty, population trend, and behavior. Therefore, it is important to use them together. We encourage future research to investigate canopy ecology in tropical forests using camera traps, which may expand our understanding of bird community spatial and temporal variability. RESUMEN Diferentes métodos de muestreo se han usado para estudiar la diversidad de aves en los trópicos, siendo las redes de niebla uno de los más comunes. Sin embargo, las cámaras trampa se han usado para este propósito en las últimas dos décadas. Comparamos el desempeño de redes de niebla y cámaras trampa para el muestreo de la diversidad de aves de sotobosque y sub-dosel en un bosque lluvioso Neotropical. Dada su alta biodiversidad, obtener estimaciones precisas de diversidad es un desafío. Muestreamos bosques secundarios en los Andes centrales colombianos entre 2019 y 2021. Comparamos su efectividad de ambos métodos en función de seis criterios de comparación (tamaño corporal, estrato de alimentación, dificultad de detección, especialización del hábitat, tendencia poblacional y estado migratorio). Registramos un total de 99 especies de aves, de las cuales 92 especies se capturaron con redes de niebla y 37 especies usando cámaras trampa; 30 especies fueron detectadas por ambos métodos (mayormente especies abundantes y generalistas). La efectividad de las redes fue de 83%, mientras que la efectividad de las cámaras fue de 68%. Las especies registradas por ambos métodos fueron principalmente aves generalistas y abundantes. Las diferencias en efectividad se explican principalmente por el tamaño corporal, dado que aves pequeñas se capturan principalmente en las redes y aves grandes en las cámaras. Además, la dificultad de detección y la especialización del hábitat también influyeron en los resultados. Las cámaras trampa fueron muy efectivas en detectar aves terrestres de gran tamaño que no caen en las redes, mientras que las redes lo fueron para aves pequeñas del sub-dosel que no son detectadas por las cámaras. A pesar que estos métodos difieren en las especies detectadas, encontramos patrones similares de riqueza de especies entre categorías de tamaño, detección, tendencia poblacional y conducta, pero no para especialización del hábitat. Puesto que ambos métodos tienen ventajas y limitaciones, usarlos conjuntamente mejoraría las estimaciones de diversidad de aves. Instamos a los investigadores a explorar la ecología del dosel con cámaras trampa, ya que pueden proporcionar información complementaria a largo plazo que no se puede obtenerse con otros métodos.