Introduced predators and nest competitors shape distribution and breeding performance of seabirds: feral pigeons as a new threat

Abstract

Petrels are particularly sensitive to predation by introduced species. Many populations have reduced their breeding ranges, currently mainly occupying predator-free sites. Breeding range reduction leads to interspecific competition for nesting sites, which can be detrimental to petrels. Here, we evaluate how the presence of introduced mammals (cats Felis catus and rats Rattus spp.) and potential competitors for nest sites (Cory’s shearwaters Calonectris borealis and feral rock pigeons Columba livia) shape the distribution, breeding density, and breeding performance of Bulwer’s petrel Bulweria bulwerii on Tenerife, the largest and most densely human populated of the Canary Islands. We estimated nest density, assessed the role of nest location and physical characteristics of nests on breeding success, and determined causes of breeding failure by introduced predators and competitors. Nest density was higher in predator-free colonies on marine rocks. Cat presence was the best predictor of nest density, but it was not correlated with either presence or abundance of competitors. Breeding success varied between years and colonies but was not related to nest characteristics. Pigeon competition for nests was the most frequent cause of breeding failure (7.3%), followed by rat predation (6.3%). We also compared petrel and pigeon nest cavities and found considerable overlap in the physical size of nest sites. Our study provides insights into an overlooked impact of the invasive rock pigeon: nest competition with small seabirds. We encourage more research on the effects of pigeons on nest density, as well as disease and pathogen transmission, and vegetation changes within seabird colonies.

Herpesviruses in migrating procellariforms, northeastern Brazil

“…Large interannual coastal strandings of seabirds (alive and/or dead) have been reported worldwide (Bugoni et of long-lived, pelagic species that spend most of their life cycle at sea (Stidworthy and Denk 2018). Due to these particular life history traits, procellariforms are amongst the most endangered threatened taxonomic groups (Croxall et al 2012), considered highly sensitive to anthropogenic activities (e.g., fisheries interaction, habitat degradation, climate change, invasive and non-native species) (Tavares et al 2019;Rodríguez et al 2022). Therefore, data on the infectious agents affecting Procellariiformes is pivotal for the conservation of this group.…”

Density and ecological drivers of free‐ranging cat abundance and activity in Madeira Island, Macaronesia

“…Free‐ranging insular cat populations are especially detrimental for seabirds (Dias et al, 2019; Medina et al, 2011; Nagata et al, 2022; Oliveira et al, 2022). A recent study by Rodríguez et al (2022) found that predation by cats and rats has shaped the current breeding distribution of petrel colonies in the Canary Islands, relegating them to isolated predator‐free areas. Similar findings have been reported in numerous other studies (e.g., Hervías et al, 2014), and likely explain the restricted breeding range of Manx shearwater in Madeira.…”