A group of scientists from Cardiff University, University of London, and Max Planck Institute for Ornithology have reported in PLoS ONE, for the first time, that when birds eat small invertebrates contaminated with environmental pollutants, significant changes occur in both the bird’s behavior and their brain. Surprisingly, male European starlings that have been exposed to higher levels of natural and synthetic estrogen, found in sewage effluent, sing longer and more complex songs than their controlled male counterparts. What is so unique about this research is that the group of scientists were able to show that the key brain area controlling male song complexity (HVC) was significantly enlarged due to the pollution. Not surprisingly, female songbirds prefer to mate with birds who sing songs which are stronger and go on for a longer period of time, and thus choose males with higher pollution levels.

Although this seems beneficial in reality more harm than good is happening to these hyped up polluted birds. As predicted by the scientists, the birds that have exposure to pollutants have suppressed cell-mediated and humoral immune functions. As a result, females choose to mate with polluted male birds despite their reduced immune functions. The scientists conclude that “[O]ur data suggest that female starlings would bias their choice towards exposed males, with possible consequences at the population level.” 

Although we feel troubled by the fact that these birds are negatively affected by the sewage waste, it is surprising that the pollution improves the songbirds song - a key evolutionary function in these birds. Yet, we remain hopeful that the reporting of the pollution problem will subsequently save these songbirds and other species from extinction.