Does urban life change blood oxidative status in birds?

Cities may expose wild animals to new types of selection pressures, potentially leading to differentiation among urban and rural populations. One cellular mechanism likely important in determining the viability of vertebrate populations is resistance to oxidative stress, as tissue degradation resulting from oxidative stress may decrease reproductive performance and survival. We hypothesized that city-thriving Eurasian blackbirds (Turdus merula) would be more resistant to oxidative stress when exposed to stressful conditions than rural conspecifics. Hand-raised city and rural blackbirds kept under common garden conditions indeed differed in blood oxidative status when exposed to chronic stress: city birds had lower oxidative damage during stressful conditions compared with rural birds, but also tended to generally maintain lower levels of non-enzymatic and enzymatic antioxidants than rural birds. These findings show that individuals from urban and rural areas differ intrinsically in their blood oxidative status physiology, possibly as an adaptation to city life.