Food affects the colour of male house finches

Male house finches photographed 1 day apart in Kelowna - diet is responsible for colour differences.

As a rule, animals cannot produce carotenoids.  These are important chemicals found in plants and are responsible for the bright colours you see in carrots, fall leaves, and berries.  There are over 600 types of carotenoids.  They range in colour from red through orange to yellow.  They are important to health as they are powerful antioxidants and some get repurposed into other chemicals such as Vitamin A.

It turns out that many birds are affected by carotenoids in that they affect feather colour.  For some, such as house finches, the male's colour can be red, orangish, or even yellow depending upon what foods are eaten.  The pigments end up in feathers as they are growing and eventually displayed after a molt.  Once the feather has formed no new pigments are added; the colour remains the same regardless of what is eaten.

The spring-like weather in Kelowna has enticed me to take up my birding camera and so I have been out photographing my avian friends in earnest.  Friday found me shooting near the lake and Saturday's excursion took me to a mountain pond.  I found male house sparrows in both places.  What was amazing was the difference in colouration.  

The above-left photo shows a typical male boasting a vibrant red cap, cheek, and bib.  The male on the right shows only a faint representation; there is hardly any colouration at all.  This can be explained by considering the bird's diet.  The one on the left was eating highly coloured mountain ash berried while the one on the right could have been visiting a nearby community where bird-feeding stations were abundant.  Seeds found in many feeders do not have the pigments fruits do, and so the forming feathers would not have the associated colours.

Females tend to be more interested in males with brighter hues and so, if left to choose between the two above, a female would likely pick the bird on the left.  

To some extent, the adage, you are what you eat, seems to be true.

Thanks for reading.

Eric Svendsen     www.ericspix.com