Artificial Perches as a Technique for Enhancing Tropical Forest Restoration: A Case Study From the Dominican Republic

Recovering secondary forests on degraded agricultural lands represents a promising opportunity to offset global carbon emissions as well as increasing local biodiversity and ecosystem services. In the insular tropical forests of the Caribbean, frugivorous birds are the primary seed dispersers for most native woody plants and have a large influence on regeneration dynamics during forest succession. In 2017, we initiated an experimental forest restoration program incorporating artificial perches on private farms within the Rio Yaque del Norte watershed in La Vega province, Dominican Republic. Five restoration plots (0.15–0.25 ha) were constructed in pastures near deforested streams. In each plot, 6-12 artificial perches, each 5 m in height, were constructed from bamboo poles fitted with crossbars. We remotely monitored perch use by birds using video cameras and evaluated the effects of perches on the establishment of woody plants in seedling quadrats both below perches and in open spaces. During the summer of 2019, we conducted a behavioral experiment using audio broadcasts of bird sound to test the effect of different avian taxa and feeding guilds on attracting seed dispersers. Eleven avian species were recorded visiting perches, with the most common being Northern Mockingbird and Gray Kingbird. Broadcasting bird sounds led to a significantly greater number of avian visits to the plot. We documented 1,171 seeds from 31 distinguishable species collected from seed traps below perches during the study. Most seedling regeneration in our plots was from exotic non-bird-dispersed taxa which grew equally in perches and control quadrats. Native plant seedlings were infrequent (i.e. beneath 4 of 36 perches) but grew exclusively beneath perches. We conclude that artificial perches are an effective method for augmenting the natural seed bank but are likely to be most effective when used in tandem with planting trees that readily grow to produce shade and litter.https://digitalcommons.odu.edu/gradposters2020_sciences/1004/thumbnail.jp

Local Avian Density Influences Risk of Mortality from Window Strikes

Up to a billion birds die per year in North America as a result of striking windows. Both transparent and reflective glass panes are a cause for concern, misleading birds by either acting as invisible, impenetrable barriers to desired resources, or reflecting those resources over a large surface area. A high number of window strikes occur during migration, but little is known about the factors of susceptibility, or whether particular avian taxa are more vulnerable than others. We report on a study of window strikes and mist-netting data at the Virginia Zoological Park (Norfolk, Virginia, USA), conducted in the autumn of 2013 and 2014. We focused on three factors likely to contribute to an individual\u27s predisposition to collide with windows: (i) taxonomic classification, (ii) age, and (iii) migrant vs. resident status. Thrushes, dominated by the partial migrant American Robin (Turdus migratorius), were significantly less likely to strike glass than be sampled in mist nets (χ2 = 9.21, p = 0.002), while wood-warblers (Parulidae) were more likely to strike than expected (χ2 = 13.55, p \u3c 0.001). The proportion of juveniles striking windows (45.4%) was not significantly different (χ2 = 0.05, p = 0.827) than the population of juvenile birds naturally occurring at the zoo (48.8%). Migrants, however, were significantly more susceptible to window strikes than residents (χ2 = 6.35, p = 0.012). Our results suggest that resident birds are able to learn to avoid and thus reduce their likelihood of striking windows; this intrinsic risk factor may help explain the apparent susceptibility of certain taxa to window strikes

Continent-wide analysis of how urbanization affects bird-window collision mortality in North America

Characteristics of buildings and land cover surrounding buildings influence the number of bird-window collisions, yet little is known about whether bird-window collisions are associated with urbanization at large spatial scales. We initiated a continent-wide study in North America to assess how bird-window collision mortality is influenced by building characteristics, landscaping around buildings, and regional urbanization. In autumn 2014, researchers at 40 sites (N = 281 buildings) used standardized protocols to document collision mortality of birds, evaluate building characteristics, and measure local land cover and regional urbanization. Overall, 324 bird carcasses were observed (range = 0–34 per site) representing 71 species. Consistent with previous studies, we found that building size had a strong positive effect on bird-window collision mortality, but the strength of the effect on mortality depended on regional urbanization. The positive relationship between collision mortality and building size was greatest at large buildings in regions of low urbanization, locally extensive lawns, and low-density structures. Collision mortality was consistently low for small buildings, regardless of large-scale urbanization. The mechanisms shaping broad-scale variation in collision mortality during seasonal migration may be related to habitat selection at a hierarchy of scales and behavioral divergence between urban and rural bird populations. These results suggest that collision prevention measures should be prioritized at large buildings in regions of low urbanization throughout North America