Urbanization is 
a familiar concept and in its most basic form urbanization is the congregation of a large number of people into one community. With urbanization comes the need for artificial lighting such as street lights and large stadium lights used to light up the field at a sporting event. These artificial lights cause anthropogenic light pollution (light pollution caused by humans). Organisms living in an ecosystem near to an urban area will inevitably come into contact with these artificial lights and these lights could potentially have an effect on these organisms. A study performed by Bart Kempenaers and his colleagues at the Max Planck Institute for Ornithology aimed to test the effects of these artificial lights on the dawn song of five song birds which yielded some pretty interesting results.
The study was performed by comparing three separate territories each of which contained the five species of songbirds. These territories included an edge territory (which is a territory on the edge of the urban interface) with no artificial light, an edge territory with artificial light (street lights) and a central territory (which is a natural territory in a forest away from the urban interface) with no artificial light. Of the five species of songbirds the males of four of these species near street lights began singing much earlier in the day as opposed to the males in ot
her territories. This observation of the males near the street lights singing earlier was much more apparent in the species of songbird that naturally prefer to sing earlier at dawn. The blue tit songbird was the species the study primarily focused on. The breeding habits of the blue tit songbird were compared between both edge territories containing and not containing artificial light and the central territories. This study would take place over the span of seven years.
After seven years of study a number of surprising results would be observed. The female blue tit songbirds who resided within the territory with street lights laid there eggs an average of one and a half days prior to species residing within other territories without the influence of street lights. Male blue tit songbirds living in an edge territory containing street lights had double the success of acquiring an extra-pair mate as opposed to other male blue tits living in edge territories without lights and in the central territories. This means that those males living near street lights were able to mate with more than one female allowing those males to be better able to spread their genes amongst the population. The males living near the street lights also started singing much earlier in the day and were observed to have doubled the success of acquiring an extra-pair mate. All of these factors put together leads to the observation that males living near street lights had greater reproductive success as opposed to those males living in other territories where there were no street lights. Since more females were breeding with the males living in territories where artificial light existed it implied that females were more attracted to the males who began singing earlier in the day.
So a false sense
of quality has been placed in the minds of the female birds living near the territory with the street lights. It has been observed that females prefer those males who sang earlier in the day. This observation can be used to show that artificial light has an effect on the breeding habits of the blue tit songbird by creating a quality-indicator trait within the female’s mind. This trait is that a male who starts to sing earlier in the day is of higher quality and that they must in turn be more suitable as a mate. It is still unclear as to whether or not artificial lighting will have a negative impact on the species due to females mating with males they would not otherwise mate with but it can be concluded that artificial lighting has an impact on the breeding habits of blue tit songbirds. The fact that males who sing earlier in the morning are more likely to find a mate alludes to the classical phrase “the early bird gets the worm” or in the case of the blue tit songbird “the early male gets the female.”
Bibliography
Bart Kempenaers, Pernilla Borgstrom, Peter Loes, Emmi Schlicht and Mihai Valcu (2010). Artificial Night Lighting Affects Dawn Song, Extra-Pair Siring Success, and Lay Date in Songbirds. Volume 20, Issue 19, 1735-1739. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VRT-511J7V4-3&_user=1067211&_coverDate=10%2F12%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000051237&_version=1&_urlVersion=0&_userid=1067211&md5=7073a8c754b1dec9723bf28275e3b58b&searchtype=a
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