Body Condition and Chronic stress in Urban and Rural Noisy Miners

ABSTRACT

Cities are potentially stressful environments for birds for numerous reasons, including their high volumes of pedestrian and vehicular traffic. Native birds inhabiting cities tolerate such human disturbance, but may still potentially incur some cost that is reflected in body condition and the level of chronic stress experienced, unless they are inherently relatively insensitive to urban stressors. We compared body mass and condition, three erythrocyte variables and heterophil: lymphocyte ratios (HL) of adult Noisy miners (Manorina melanocephala) in urban Melbourne, Australia and its rural hinterland. Urban individuals had a significantly higher HL (mean 0.995) than rural con-specifics (0.719), suggesting that they may have been experiencing higher chronic stress levels. Body condition (mass-size residuals) and haematocrit were similar in urban and rural individuals, but urban individuals were a little heavier (~ 1%) and rural individuals had a 0.6 g dl^-1 higher whole blood haemoglobin concentration. There were no significant relationships between body condition indices and blood variables of the kind demonstrated in some bird species; their absence in Noisy miners may either reflect a lack of winter fattening or confirm that the occurrence of these relationships is species-specific.

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