Nocturnal noise and habitat homogeneity limit species richness of owls in an urban environment

Abstract

Habitat loss and fragmentation are listed among the most significant effects of urbanization, which is regarded as an important threat to wildlife. Owls are the top predators in most terrestrial habitats, and their presence is a reliable indicator of ecosystem quality and complexity. However, influence of urbanization on owl communities, anthropogenic noise in particular, has not been investigated so far. The aim of this study was to identify the role of noise and landcover heterogeneity in the species richness of owl assemblage in the urban ecosystem. Owls were surveyed in the city of Kraków (southern Poland) on 65 randomly selected sample plots (1 km 2 ). The area of main landcover types, landcover diversity index, mean size of landcover patch, and nocturnal noise level were defined within the sample plots and correlated with owl species richness. Five owl species were recorded in the study area with forests as the dominant landcover type for Tawny and Ural owls, grasslands for Long-eared and Barn owls, and gardens for Little owls. In total, 52% of sample plots were occupied by at least one species (1–3 species per plot). The number of owl species was positively correlated with landcover diversity index and negatively correlated with nocturnal noise emission. This study demonstrates that species richness of owls in urban areas may be shaped by landcover heterogeneity and limited by noise intensity. This indicates that noise changes top predator assemblage, which in consequence may disturb predator-prey interactions within human-transformed habitats.

Nightlife in the city: drivers of the occurrence and vocal activity of a tropical owl

“…Our findings also show that the Mottled Owl tends to be in less noisy sites across the city. These results agree with the growing body of evidence of the negative impacts of noise on habitat occupation and life history of birds in urban settings (Francis et al 2009;Patón et al 2012;Luther and Gentry 2013;Slabbekoorn 2013), as well as recent studies suggesting decreases of owl species richness with high nocturnal noise levels (Fröhlich and Ciach 2019). Given that most birds depend on the acoustic channel for communication, anthropogenic noise acts as an environmental filter by limiting species presence according to their tolerance to noise (González-Oreja 2017; Manzanares Mena and Macías Garcia 2018).…”

“…In comparison to diurnal species, the ecological response of nocturnal birds to urbanization has not been well studied because of their low density and detectability (Weaving et al 2011;Isaac et al 2013;Fröhlich and Ciach 2019). Among nocturnal birds, owls are particularly interesting given their role as top predators in most terrestrial habitats, with their presence often being related to ecosystem quality (Isaac et al 2013;Fröhlich and Ciach 2019). Actually, in some urban areas owls have been identified as important biological control agents of rodent pests (Saufi et al 2020).…”

“…Recent studies on nocturnal birds suggest that anthropogenic noise can have little impact on their habitat occupation (Shonfield and Bayne 2017), while others have shown negative impacts on their foraging efficiency (Mason et al 2016;Senzaki et al 2016), decreases of habitat occupation Ciach 2017, 2018), and reduction of their species richness in urban settings (Fröhlich and Ciach 2019). Albeit several species can take advantage of ALAN (e.g., diurnal raptors and waders that can increase their foraging efficiency in light polluted sites; Debrot 2014), it is unclear how ALAN may shape the distribution of nocturnal raptors, as well as its influence on nighttime vocal activity (Gorenzel and Salmon 1995;Longcore and Rich 2004;Canário et al 2012;Gaston and Bennie 2014;Scobie et al 2016).…”

Evolution and Ecology of Silent Flight in Owls and Other Flying Vertebrates

“…Their methods did not test whether prey, once detected, are made easier to catch by the elevated background sound, as predicted by the stealth hypothesis. Some ecological studies found a negative correlation between owl diversity and abundance in habitats with high levels of anthropogenic sound ( Fröhlich and Ciach 2018 , 2019 ), implying owls avoid noisy environments, as predicted by the self-masking model but not the stealth model; but others have not found this pattern ( Shonfield and Bayne 2017 ).…”

Living in the concrete jungle: a review and socio-ecological perspective of urban raptor habitat quality in Europe

“…2). While indicating the sites' importance to breeding raptors, it potentially reflects a bias in sampling effort arising from their accessibility to the researchers and public as most of the studies required either physical inspection of the nest sites or for observations to be made from accessible locations (Rutz 2008;Sumasgutner et al 2014b;Fröhlich and Ciach 2019). Raptors nesting around areas highly frequented by people, whether they are in green spaces or "out of place", are likely to draw citizens' attention (Philo and Wolch 1998;Khoo and Lee 2020), making them vulnerable to human disturbance (Chace and Walsh 2006;Sorace and Gustin 2010).…”