Rute A. Costa

This study evaluated the effects of environmental pollution on decreasing great tit (Parus major) breeding parameters in an industrial area in the west coast of Portugal. Several great tit breeding parameters were monitored in the industrial area, as well as in a rural area not affected by industrial emissions. Low levels of air pollution in both industrial and rural areas were confirmed by assessing trace element concentrations in pine needles. Concentrations of Cd and Hg in pine needles from the industrial area (Cd = 0.05 ppm; Hg = 0.005 ppm) were significantly lower than those found in needles collected from the reference area (Cd = 0.07 ppm; Hg = 0.007 ppm). Additionally, the breeding success of great tits increased in the industrial area in comparison to the reference area (0.93 ± 0.08 and 0.62 ± 0.22, respectively). The changes on great tit breeding parameters were probably related with changes in the breeding density of other competitive species, together with a decreasing frass-fall biomass. Further long-term ecological studies in industrial areas are necessary to understand the changing breeding performance and strategies used by great tits in response to pollution shifts in the environment.

Passerine species have been increasingly used as bioindicators of metal bioaccumulation especially by taking benefit of non-invasive procedures, such as collecting feathers and excrements. In 2009, metal (As, Cd, Cu, Hg, Ni, Pb, Se and Zn) concentrations were determined in feathers and excrements of nestling and adult female great tits (Parus major) in industrial (a paper mill) and rural sites in maritime pine forests on the west coast of Portugal. The aim of this study was to compare the levels of metals between the areas but also between sampling methods (feather vs. excrement) and age classes (nestling vs. adult). Although excrements and feathers of nestling great tits showed different concentrations, similar patterns of accumulation were detected in both study areas. There was a significantly higher concentration of mercury in the industrial area and significantly higher concentrations of arsenic in the rural area in both sample types. Metal levels in adult females had quite different results when compared to nestlings, and only nickel presented significantly higher levels near the paper mill. Since metal levels showed a consistent pattern in feathers and excrements of nestling great tits, we conclude that both represent good and non-invasive methods for the evaluation of these elements in polluted areas.

This long-term study (2003–2010) compared the breeding parameters of great tits living in a paper-and-pulp–industry area to those of great tits living in a rural area on the west coast of Portugal. We also measured the abundance of caterpillar biomass, an important food source and determinant of breeding success for tits. In 2009, we further analysed trace metal [arsenic (As), calcium (Ca), cadmium, copper, mercury (Hg), nickel, lead, selenium, and zinc] as well as Ca concentrations in excrement of 15-day-old great tit nestlings. Generally, for most trace metals, fecal concentrations were similar at both sites. Nonetheless, greater Hg levels and lower As levels were detected in the industrial area. Great tits laid more eggs and produced more fledglings in the industrial area than in the rural area. Caterpillar biomass was also greater in the industrial area, which likely explains the better breeding success. Our results suggest that there are no direct effects of emissions on the studied species.