Intensity of Nest Defense of White-Winged Choughs () in Urban Versus Natural Habitats.

Nesting birds face significant risks of predation, prompting parents to invest in nest defense. However, not all environments are the same, and parental investment may vary across different environments. Urbanization often leads to habitat changes and an increase in generalist nest predators, potentially driving a higher risk of reproductive failure for birds. This may require urban-breeding birds to invest more time and energy in nest defense, in addition to balancing other essential activities, such as incubation, foraging, and feeding their young. Here, we assess the impact of urbanization on nest defense by white-winged choughs (). We predicted that (1) urban habitats have a greater abundance of nest predators compared to natural habitats, and that (2) nest defense would correspondingly be higher in urban-breeding white-winged choughs. We also predicted that (3) nest defense in the white-winged choughs would increase with the age of the brood, in accordance with the nest defense theory, irrespective of their habitat. Our results confirm a significantly greater abundance of avian nest predators in urban areas, and that nest defense is significantly higher in urban groups compared to groups in natural habitats. However, we found no significant increase in nest defense with the age of the brood. Our study confirms that the increase in nest predator abundance can cause urban birds to face different trade-offs, and have to invest more in nest defense. This reflects one effect of urbanization on the composition and behavior of urban wildlife.