Meeting Abstract
More than half of the Earth’s human population lives within cities, which leads urban animals to come into frequent, direct contact with humans. Most considerations of human impacts on wildlife have focused on daytime hours, but after-dark human activity in cities may also serve as overlooked selection pressures (e.g. on metabolic rate, oxidative balance, disease resistance, body condition) to which urban organisms must acclimate or adapt. Thus, we hypothesized that urban animals might better cope with nighttime exposure to humans. In this experimental laboratory study, we exposed wild-caught urban and rural juvenile house finches (Haemorhous mexicanus) to repeated and randomized night-time intrusions by a human (i.e. who entered the darkened housing room and gently walked, while briefly rustling, the bird cages for 5 minutes). We predicted that urban birds would be resilient to the negative impacts on various physiological metrics, such as basal metabolic rate, plasma carotenoid levels (a dietary antioxidant), intestinal coccidian parasite (Isospora spp.) loads, and body condition. Our night disturbance treatment increased intestinal parasite loads relative to controls, but did not affect body condition. Additionally, the magnitude or presence of an effect did not appear to depend on whether the birds were caught from an urban or rural site. Despite nighttime disturbance having a possible disease-promoting effect on birds, from our results it does not appear that urban house finches have adapted to cope with this effect.
