Does mercury contamination reduce body condition of endangered California clapper rails?

We examined mercury exposure in 133 endangered California clapper rails (Rallus longirostris obsoletus) within tidal marsh habitats of San Francisco Bay, California from 2006 to 2010. Mean total mercury concentrations were 0.56 µg/g ww in blood (range: 0.15-1.43), 9.87 µg/g fw in head feathers (3.37-22.0), 9.04 µg/g fw in breast feathers (3.68-20.2), and 0.57 µg/g fww in abandoned eggs (0.15-2.70). We recaptured 21 clapper rails and most had low within-individual variation in mercury. Differences in mercury concentrations were largely attributed to tidal marsh site, with some evidence for year and quadratic date effects. Mercury concentrations in feathers were correlated with blood, and slopes differed between sexes (R(2) = 0.58-0.76). Body condition was negatively related to mercury concentrations. Model averaged estimates indicated a potential decrease in body mass of 20-22 g (5-7%) over the observed range of mercury concentrations. Our results indicate the potential for detrimental effects of mercury contamination on endangered California clapper rails in tidal marsh habitats.

Mercury correlations among six tissues for four waterbird species breeding in San Francisco Bay, California, USA.

Despite a large body of research concerning mercury (Hg) in birds, no single tissue has been used consistently to assess Hg exposure, and this has hampered comparisons across studies. We evaluated the relationships of Hg concentrations among tissues in four species of waterbirds (American avocets [Recurvirostra americana], black-necked stilts [Himantopus mexicanus], Caspian terns [Hydroprogne caspia; formerly Sterna caspia], and Forster's terns [Sterna forsteri]) and across three life stages (prebreeding adults, breeding adults, and chicks) in San Francisco Bay, California, USA. Across species and life stages, Hg concentrations (least square mean +/- standard error) were highest in head feathers (6.45 +/- 0.31 microg/g dry wt) and breast feathers (5.76 +/- 0.28 microg/g dry wt), followed by kidney (4.54 +/- 0.22 microg/g dry wt), liver (4.43 +/- 0.21 microg/g dry wt), blood (3.10 +/- 0.15 microg/g dry wt), and muscle (1.67 +/- 0.08 microg/g dry wt). Relative Hg distribution among tissues, however, differed by species and life stage. Mercury concentrations were highly correlated among internal tissues (r2 > or = 0.89). Conversely, the relationships between Hg in feathers and internal tissues were substantially weaker (r2 < or = 0.42). Regression slopes sometimes differed among species and life stages, indicating that care must be used when predicting Hg concentrations in one tissue based on those in another. However, we found good agreement between predictions made using a general tissue-prediction equation and more specific equations developed for each species and life stage. Finally, our results suggest that blood is an excellent, nonlethal predictor of Hg concentrations in internal tissues but that feathers are relatively poor indicators of Hg concentrations in internal tissues.

Why birdsong is sometimes like music.

The sounds and songs of birds have inspired the musical compositions of numerous cultures throughout the globe. This article examines a variety of compositions from Western music that feature birdsong and explores the concept of birds as both vocalists and instrumentalists. The concept of birds as composers is then developed-how they use rhythmic variations, pitch relationships, and combinations of notes similar to those found in music-and the theory that birds create variation in their songs partially to avoid monotony is considered. Various families of birds that borrow sounds from other species are surveyed, in particular the European starling (Sturnus vulgaris), which may have inspired a Mozart composition. We conclude that the fusion of avian bioacoustics and the study of birdsong in music may function as a conservation tool, raising the awareness of humans and stimulating future generations to save for posterity what remains of the natural world.