American Coot Species Getting Bigger?

In nature, any trait that confers a significant survival advantage generally tends to become more prevalent in the species over time. If that’s the case, then the American Coot (Fulica americana) is in the process of becoming a larger bird, or at least a bird that produces larger eggs and has larger offspring.

A joint study by researchers at North Dakota State University and Iowa State University found that female American Coots give preference to larger eggs in the nest. Wendy Reed, Mark Clark and Carol Vleck teamed up to study survival rates of American Coot chicks over the course of two breeding seasons. Their findings which can be read in their entirety in the November issue of The American Naturalist, showed that chicks from the largest eggs received a greater allocation of maternal care than their siblings, they said.

While there isn’t any data to suggest that larger eggs and larger chicks turn into larger adults, the higher survival rate of the largest eggs in any given clutch should result in coots that, as a species, lay larger and larger eggs over time. The researchers concluded that maternal care preference for certain characteristics in offspring can be a strong factor in the development of a species over time. If being hatched from a larger egg means that the mother apportions more food, and more nurturing to one of her chicks, then that becomes a survival trait, and larger American Coot eggs should be a continuing trend.

It is interesting to note that the size of the eggs was relative. In other words, the American Coot mother gave preference to the largest egg in the clutch without regard to objective size. Whether the egg measures 1.9 inches or 2 inches didn’t matter so long as it was the biggest of those in the nest at the time.

Sources:

http://www.newswise.com/articles/mom-likes-me-best-egg-size-predicts-offspring-survival

“Maternal Effects Increase Within-Family Variation in Offspring Survival”
The American Naturalist, Nov. 2009, Vol. 175, No. 5, pp.685-695
http://www.journals.uchicago.edu/doi/abs/10.1086/605962

-----------

Become a fan of the Manchester Bird Watching Examiner on Facebook to see additional photos, videos, and to join in the discussions.

Follow the Manchester Bird Watching Examiner on Twitter.

You might also enjoy these:

• Kevalr covered, high tech vessel takes aim at Japanese whaling fleet
• Undercover video from inside an egg production facility shows cruel and unsanitary conditions
• Complete index page of birdwatching slideshows
• Is your birdfeeder killing songbirds?
• Find out why birds sing
• the giant Haast's eagle may have eaten humans
• Birdwatching binocular basics: how to choose a good pair of birdwatching binoculars
• Common New Hampshire Woodpeckers: identification guide
• Birdwatching locations in New Hampshire: hawks at Blue Job Mountain
• Birdwatching is big businessin NH and ME
• Gull swallows Tern whole- amazing photo slideshow
• Help identify New Hampshire's Important Birding Areas
• Birdcams and backyard feeders
• Crow hunting season details and recipes