Physiological effects of toxic elements on a wild nightjar species

Nightjars are considered human-tolerant species due to the population densities reached in strongly managed landscapes. However, no studies have been done evaluating metal-related effects on physiology, condition or fitness in any nightjar species. The main aim of this study was to evaluate how metal exposure affects physiology and condition in red-necked nightjar (Caprimulgus ruficollis) populations inhabiting three different environments in southeastern Spain: agricultural-urban area (n = 15 individuals), mining area (n = 17) and control area (n = 16). Increased plasma mineral levels (magnesium and calcium) and alkaline phosphatase (ALP) activity were observed in breeding females, and ALP was significantly higher in young birds due to bone growth and development. In the mining-impacted environment, nightjars showed decreased retinol (17.3 and 23.6 μM in the mining area and control area), uric acid (28.8 and 48.6 mg/dl in the mining area and control area) and albumin (16.2 and 19.6 g/l in the mining area and control area), probably impaired by a combination of toxic metal exposure and low prey quantity/quality in that area. Moreover, they showed increased plasma tocopherol levels (53.4 and 38.6 μM in the mining area and control area) which may be a response to cope with metal-induced oxidative stress and lipid peroxidation. Blood concentrations of toxic metals (As, Pb, Cd and Hg) were negatively associated with calcium, phosphorus, magnesium, ALP, total proteins and body condition index. This could lead to metal-related disorders in mineral metabolism and ALP activity that may potentially increase the risk of skeletal pathologies and consequent risk of fractures in the long term, compromising the survival of individuals. Further studies need to be carried out to evaluate potential metal-related effects on the antioxidant status and bone mineralization of nightjars inhabiting mining environments.This work was supported by the Fundación Séneca - Agencia de Ciencia y Tecnología de la Región de Murcia (20031/SF/16 to S.E.). S. Espín was financially supported by Fundación Séneca (Saavedra-Fajardo Project 20031/SF/16) and by Ministerio de Ciencia, Innovación y Universidades (Juan de la Cierva-Incorporación contract, IJCI-2017-34653). The analysis of vitamins was funded by University of Castilla-La Mancha with project CGT13-0183. P. R. Camarero benefited from a contract financed by the Spanish Ministry of Economy and Innovation and CSIC (PTA2017-14583-I).Peer reviewe