Fragmented Riverine Habitats in Taiwan Have Spatio-Temporal Consequences, Re-Distributing Caprimulgus affinis into Urban Areas Leading to a Human–Wildlife Conflict

Abstract

Caprimulgus affinis is an endemic species commonly known as the Taiwan nighthawk, forest nighthawk, or South Asian nighthawk. In recent years, the C. affinis population has gradually moved outward from river habitats into the metropolitan areas of Taiwan. Because male birds’ booming sounds at night can reach up to 90 dB or higher and they can be intermittently tweeting for more than 10 hours, they often disturb the sleep of urban residents and can even cause nightmares. In this study, we analyzed long-term survey data to assess the distribution history of C. affinis in Taiwan. By using 1738 entries of observation data collected from 1999 to 2014, a model of C. affinis distribution was constructed, and a geostatistical method was used to improve the accuracy of the model estimate. In addition, the Mann–Kendall trend test was applied to predict future C. affinis distribution. Based on the results, four variables were selected to construct the C. affinis distribution matrix. Urban population, coastal proximity, and distance to upstream river location represented positive driving forces, whereas city elevation was a negative driving force. C. affinis is currently distributed on the plains of central and southern Taiwan and in eastern Taiwan. The C. affinis emergence trend diagram was plotted using the time–space trend diagram, which showed yearly increases in the C. affinis populations in urban and settled areas including central, western, northeastern, and southeastern Taiwan and yearly decreases in the populations in rural areas including northern and southern Taiwan, especially in fragmented riverine habitats. Regression kriging can correctly describe the distribution of the entire C. affinis population, which leads to the correct understanding of the biological corridor of C. affinis in their migration through the graphical contours in GIS. The analytic model in this study contributes to the establishment of the time–space trend diagram.

Biometrics, distribution, and breeding notes of Savanna Nightjar (Caprimulgus affinis) in several islands of Indonesia

“…Previously, this species tends to occupy natural habitats like savannah and river areas around forest. Yet, the rapid development of semi-natural ecosystems in the middle of urban areas has attracted this species to populate urban areas by nesting on tall buildings' roofs (Cheng et al 2019). For example, Iswandaru et al (2020) reported on the existence of Savanna Nightjar around the University of Lampung, Indonesia.…”

Predicting spatio‐temporal distributions of migratory populations using Gaussian process modelling

“…Previously, a variety of methods have been used to analyse species' spatial and/or temporal distributions with citizen science data. These methods include GLMs (Cheng et al, 2019), occupancy models (Altwegg & Nichols, 2019), maximum entropy models (Phillips et al, 2006) and generalized additive models (GAMs) typically using splines as basis functions (Bird et al, 2014). Tree‐based models have also been used, in particular random forests (Prasad et al, 2006) and gradient boosted trees (Elith et al, 2008).…”

Acoustic preadaptation to transmit vocal individuality of savanna nightjars in noisy urban environments

“…Increasing numbers of bird species have been observed to survive successfully in urban environments 36 , 37 . In Taiwan, the savanna nightjar has become one of the most successful urban residents 38 . To better understand their acoustic adaptation to noisy urban environments, we investigated the acoustic structures of individual males’ territorial calls using two proposed hypotheses (see “ Introduction ” for details): no frequency shifting and transmission efficacy of vocal individuality.…”