Galapagos Finches Are Altering Behavior Because Of Us
Humans’ ever-spreading presence around the globe influences patterns of biological evolution in ways that we are just beginning to explore. Infrastructure development, introduction of exotic species and human food availability, all natural environment altering factors, are a direct impact of human disturbances via urbanization.
Meanwhile, in one of the most significantly biodiverse places in the world, the Galapagos, a body of evidence shows that the effect of our presence is increasing. This includes the near-extinction of the famous Mangrove finch, resulting from the introduction of a parasitic fly, and the collapse of multiple unique plant and animal species due to habitat modification and the introduction of alien species.
In this study, a group of scientists spent two years observing Darwin’s finches on the Galapagos islands in order to evaluate the exact effects our presence and foods have on their behavior. Throughout their work, the researchers sought answers to the following questions:
- Does novel human food availability in urban areas alter finch diets?
- If so, do finches in urban environments prefer human foods over natural foods?
- Do the birds respond differently to the presence of people?
- What are the consequences of finches’ use of human foods for their biodiversity?
They started by conducting feeding observations and field experiments on coexisting ground finch species at sites that span from non- to urban. Finch-human interaction experiments were employed to test whether and how finches respond to the presence of people.
Here, bird responses to visual (human presence) and audiovisual (human presence plus a noisy bag of chips) stimuli were recorded. To quantify finch feeding preferences, as well as measuring whether and how they varied with the degree of urbanization, “cafeteria” experiments were carried out – finches were presented with a selection of human and native food items.
They found that Darwin’s finches consumed human foods with increasing urbanization. Some human food items contributed disproportionately to the finch diet at urban sites, but almost never at non-urban sites. In fact, finches were observed feeding almost exclusively (79% of all observations) on human foods, including crackers, rice and introduced garden species, at the urban location.
In contrast, at the non-urban site, finches were seen feeding almost exclusively on native plant species. Interaction tests suggest that urban birds were more accustomed to the presence of humans. Finally, at all sites of regular human presence, finches preferentially consumed human foods over natural foods.
Coming back to the original questions, the main findings indicate that:
- Finch density was notably higher at urban sites.
- Food type availability and the diet of finches at urban sites was notably broader and included many human foods.
- Birds at sites frequented by people were willing to approach people and novel objects much more.
- The degree of urbanization and the presence of humans associate closely with strong preferences for human foods.
The researchers warn that exploiting urban environments might present additional challenges for organisms, including negative health and physiological effects brought on by the consumption of highly processed foods, potentially reducing life span and probabilities of survival. Furthermore, the year-round availability of soft and highly abundant human foods in urban environments might affect the very ecological and evolutionary processes that promoted species and phenotypic diversification. While the results clearly show a shift to human foods in urban sites, the adaptive significance of that shift is still an open question.
These findings also suggest that human behaviour, rather than human population density is the main driver of finch preference for human foods. The researchers propose a possibility that the effect of human behavior is facilitated by our tendency to feed birds, be it directly or inadvertently via food dropping or littering.
It seems vital to understand the unexpected consequences of urbanization on ecological niches, as such knowledge might spearhead strategies for preserving biodiversity and the processes that generate it. Animal advocates might want to remain cautious – though wildlife has evolved long enough to thrive in nature, offering processed foods might prove to be detrimental to their well-being in the long run.