Urbanization, climate and ecological stress indicators in an endemic nectarivore, the Cape Sugarbird

Stress, as a temporary defense mechanism against specific stimuli, can place a bird in a state in which growth rates and resistance to diseases are diminished. The Cape Sugarbird Promerops cafer is an endemic specialist of the Cape Floristic Region (CFR) of South Africa that may be threatened by urbanization and climate change. Ecological stress due to urbanization and climate may result in disease and morphological abnormalities. We investigated the correlation between urbanization and climate and four ecological stress indicators (tarsal disease, fluctuating asymmetry, body condition and feather fault bars) in 1375 Cape Sugarbirds from 14 sites across the CFR. Sugarbirds at sites with warmer climates had a higher incidence of tarsal disease and fault bars. Birds closer to urban settlements had higher levels of fluctuating asymmetry and fault bars in feathers. There were no clear correlations among stress indicators. Cape Sugarbirds are subject to multiple stressors, and adequate monitoring of population health will require assessment of multiple rather than single stress responses.