Links between fear of humans, stress and survival support a non-random distribution of birds among urban and rural habitats.
Urban endocrine ecology aims to understand how organisms cope with new sources of stress and maintain allostatic load to thrive in an increasingly urbanized world. Recent research efforts have yielded controversial results based on short-term measures of stress, without exploring its fitness effects. We measured feather corticosterone (CORTf, reflecting the duration and amplitude of glucocorticoid secretion over several weeks) and subsequent annual survival in urban and rural burrowing owls. This species shows high individual consistency in fear of humans (i.e., flight initiation distance, FID), allowing us to hypothesize that individuals distribute among habitats according to their tolerance to human disturbance. FIDs were shorter in urban than in rural birds, but CORTf levels did not differ, nor were correlated to FIDs. Survival was twice as high in urban as in rural birds and links with CORTf varied between habitats: while a quadratic relationship supports stabilizing selection in urban birds, high predation rates may have masked CORTf-survival relationship in rural ones. These results evidence that urban life does not constitute an additional source of stress for urban individuals, as shown by their near identical CORTf values compared with rural conspecifics supporting the non-random distribution of individuals among habitats according to their behavioural phenotypes.
Departamento de Ecología, Genética y Evolución &IEGEBA-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
Natalia
N
Rebolo-Ifrán
Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, Sevilla, Spain.|Department of Conservation Biology, Estación Biológica de Doñana, CSIC Sevilla, Spain.
Martina
M
Carrete
Department of Conservation Biology, Estación Biológica de Doñana, CSIC Sevilla, Spain.|Instituto Mediterráneo de Estudios Avanzados, IMEDEA (CSIC-UIB), Miquel Marqués 21, E-07190 Esporles, Islas Baleares, Spain.
Ana
A
Sanz-Aguilar
Department of Biology, Biochemistry and Pharmacy, Universidad Nacional del Sur, Bahía Blanca, Argentina.
Sol
S
Rodríguez-Martínez
Department of Conservation Biology, Estación Biológica de Doñana, CSIC Sevilla, Spain.
Sonia
S
Cabezas
Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, SK S7N 5E2, Canada.
Tracy A
TA
Marchant
Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, SK S7N 5E2, Canada.
Gary R
GR
Bortolotti
Department of Conservation Biology, Estación Biológica de Doñana, CSIC Sevilla, Spain.
José L
JL
Tella
D000818:Animals; D001717:Birds; D017753:Ecosystem; D005239:Fear; D006801:Humans; D008962:Models, Theoretical; D011157:Population Dynamics; D013312:Stress, Physiological; D013315:Stress, Psychological