Secret of the Stripes

Have you ever seen a White-throated Sparrow? White-throated Sparrows spend the winter in forested areas throughout many parts of the the United States in the winter. They are large gray-brown sparrows with long tails, yellow near their eyes, and head stripes. They seem like fairly simple birds, but did you know that their head stripes hold the key to their personalities?

I recently read an interesting article by author/naturalist Kenn Kaufman on Audubon’s website about the White-throats complex sex life. There are 2 morphs of White-throats: ones with white/black head stripes and ones with tan/dark brown stripes. (From this point forward I will refer to them as “white-striped” and “tan-striped”.) For many years scientists thought that the tan-striped birds were juveniles, but later learned that they are one of two permanent morphs.

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White-morph White-throated Sparrow at Boundary Creek (Image by BirdNation)

A lot of birds species have different morphs. Who cares, right? Well after much research (that is still ongoing), scientists have learned that these morphs determine a White-throat’s personality and their mating choices.

It may sound like a generalization, but tan-striped sparrows tend to more nurturing and white-striped tend to be more aggressive. Kaufman points out that these broad-sounding conclusions were made after numerous years of involved research. He sites multiple examples, such as white-striped of both sexes tend to sing more with a higher pitch, while tan-striped sing less often. Tan-striped live in denser forests and are not as aggressive with their territories, while white-striped live in more open woodlands and actively chase intruders.

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Tan-striped White-throated Sparrow morph (Image by Greg Lavaty via houstonaudubon.org)

Each morph is split pretty close to 50% male/female. Like they say with human relationships, opposites seem to attract in the White-throated Sparrow world. Studies found that pairs tend to consist of one of each morph. White-striped males with usually pair with tan-striped females, and tan-striped males with white-striped females.

Even though these pairings are common, White-throated Sparrows still have their own personal preferences. Females of both morphs prefer tan-striped males, and the more aggressive white-striped female tends to snag the tan males quicker. Males of both morphs prefer white-striped females. Tan-striped birds seem to stay monogamous longer, but white-striped may possibly be promiscuous.

Do the same morphs ever mate together? Studies find that around 95% of mating pairs will be these opposite morph pairs. More studies are needed to find out the results of same morph pairs, but there are some hypotheses of what might happen. It’s likely that a tan-striped nests could fail because of issues with defending their territories. White-striped nests could fail due to too much fighting with each other.

Studies on White-throated Sparrows are still ongoing, but the information we currently know about their complex social lives is fascinating. A bird species, such as White-throated Sparrows, may seem common, but many aspects of their lives are still packed with secrets that scientists are only starting to reveal.

If you’d like to read Kenn Kaufman’s article that was published on March 29, 2017 on the National Audubon’s Society website you can click on this link: The Fascinating and Complex Sex Lives of White-throated Sparrows

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Author: BirdNation

I am an avid birder, teacher, and nature lover. I primarily birdwatch throughout New Jersey and Eastern Pennsylvania.

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