You can’t fool a coot…American coots employ selective conspecific brood parasitism

With a name like the coot, which sounds slightly off-color, it is not surprising that Fulica americana has several unique characteristics, a few that immediately catch peoples’ attention as well as several unique behavioral traits. The common waterfowl isn’t actually a duck, despite what most people assume from its tendency to live in and around marshes and water.

It is instead a swimming rail, and it is related to the common moorhen. A few obvious differences between rails and their duck counterparts are their beak and their feet. The coot beak is short and broad, unlike the Anatidae family,which have broad bills, and their feet aren’t webbed, instead consisting of toes with lateral lobes. They have distinctive red eyes, and the juveniles have distinctive red heads lacking feathers. Their necks and upper torsos are covered in small, moist-looking yellow feathers. All in all, they are a bit grotesque to watch, and their transformation from chick to adult is a distinct (and in my opinion, positive) one.

Coots live in marshy wetlands where reeds and other aquatic plants, their preferred food source, are readily available. They interact with others of their species, in medium sized flocks. At Brazos Bend State Park, they were the most common water bird visible, with various groups hanging out in different areas of the water body, both in the middle and near the shoreline.

Within each group it seemed like there were smaller huddles of coots rooting around slightly apart from each other, yet they did not seem exclusive. In fact, apart from their obnoxious honking (which didn’t sound aggressive) all of the coots I observed seemed quite amenable towards the company of other species. Black-bellied whistling ducks and spoonbills were both paddling amidst them without disturbance.

Coots move almost constantly by gliding ungracefully across small portions of the area or by flying (almost flitting) around short distances in the given microhabitat. To do this, they have to scuttle along the water to prepare for takeoff, not unlike the rickety runway starts of small non-commercial aircraft piloted by novices.

Their main activity in the water seemed to be dabbling, and I watched them picking at submerged vegetation or other sources of food for almost half an hour without disturbance. Interestingly, it has also been found by the U.S. Fish & Wildlife Service that, when no other food is available, coots will resort to cannibalism, sometimes picking at carcasses and feathers of their dead companions.

Coots exhibit a bobbing neck motion to and fro (from anterior to posterior) while paddling. They tend to stay near reeds and other wetland monocots. Their honking squeak sounds like a whoopee cushion. The sounds they make are gratingly almost two-toned, but the cadences are somewhat slurred, producing a very distinctive chirping “pik” noise akin to a beep or what I thought was a farting noise. Brisbin and Mowbray have described their calls as “cackling, grunting, and croaking.”

When they submerge their heads to feed or scavenge under water, their feet show, as well as their lighter colored bottom. Coots will also spend time on land, where they look for food in a similar manner to the common moorhen. When they walk, their lighter under plumage is visible, and when they fly, they spread out their winds, neck, and legs, making their distinctive feet visible.

The American coot has become a model species for bird reproduction strategies because of the various thorough investigations of its reproductive behavior. For example, Dr. Bruce E. Lyon of the EEB Department of UC Santa Cruz studies parental care and avian nest parasitism behaviors of birds in the genus Fulica.

A primary examination of reproductive behavior in the early 1990s showed that parasitism was usually pursued as a less-productive complementary strategy for those females who were already territorial and had stable nesting practices. In this sense, its primary function as a behavioral characteristic is to provide flexibility to female coots.

One limiting factor on number of offspring is parental care, clearly indicating that parasitism is a viable way to propagate ones genes while avoiding the responsibility and energy commitment that is required of parents.

Another study Lyon pursued, in the last five years, examined the varying parenting strategies of American coot females in central British Columbia in Canada. The two reproductive tactics observed were nesting (the conventional technique employed by many birds) and laying parasitic eggs in the nests of other females of the same species (called conspecifics).

The purpose of his research was to reach an understanding as to why only 25% of the coots laid eggs in the nests of conspecifics. The three factors integral to his comprehension of this phenomenon were host availability, host nest accessibility, and variable benefit of laying parasitic eggs in comparison to nesting them.

An additional [more internal] constraint on parasitic behavior by females is their level of fecundity and egg-laying capability. Lyon found that parasitic broods were on average older than their non-parasitic counterparts. Not only this, but the former laid more total eggs (once parasitic females reached the age of 2, five or more parasitic eggs were seen to be laid versus less than four for those younger), leading to speculation as to the relationship between individual capacity for laying eggs and parasitism practices.

Interestingly, Lyon’s work from 2007 shows that females often use one of two methods of determining when their nest has been parasitized. These are “true recognition” and “minority recognition.” In the first method, ones own eggs are recognized as such, whereas in minority recognition, the parasite egg is singled out. Interestingly enough, though, sometimes coots will seem to recognize a foreign egg without rejecting it. In this case, is the coot just lazy? Unfortunately, I haven’t been able to see coots breeding, but it was quite entertaining to watch them bob and scurry around the water, honking raucously. I think it’s safe to say that there is more to a coot than meets the eye.

References

Lyon, B. E. 1993. Conspecific brood parasitism as a flexible female reproductive tactic in American coots. Animal Behavior., 46:91-928. doi: 10.1006/anbe.1993.1273

Lyon, B. E. 2003. Ecological and social constraints on conspecific brood parasitism by nesting female American coots (Fulica americana). Journal of Animal Ecology., 72:47-60. doi: 10.1046/j.1365-2656.2003.00674.x

Lyon, B. E. 2007. Mechanism of egg recognition in defenses against conspecific brood parasitism: American coots (Fulica americana) know their own eggs. Behavioral Ecology & Sociobiology 61:455–463. doi: 10.1007/s00265-006-0273-2

These papers outline the practice of conspecific brood parasitism and the resultant defensive strategy employed by coots to lower the likelihood of such parasitism.

Brisbin, I. L., Jr., H. D. Pratt, and T. B. Mobray. 2002. American Coot (Fulica americana) and Hawaiian Coot (Fulica alai). In The Birds of North America, No. 697 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.

Brisbin, Jr., I. Lehr and Thomas B. Mowbray. 2002. American Coot (Fulica americana), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America. doi:10.2173/bna.697a

These sites contain pertinent characteristics of the coot that allow for easy identification.

Paullin, D. G. 1987. Cannibalism in American Coots induced by severe spring weather and avian cholera. Condor 89:442-443. doi: 10.1111/j.1474-919X.

This article described cannibalistic practices in American coots during and after a very harsh winter.

Figures

Photograph 1. American coot with young, the adult sporting a noticeable frontal shield while the juveniles show off their garish autumn colors. This photograph was originally posted to Flickr by mikebaird at http://flickr.com/photos/72825507@N00/530921201.

Photograph 1. American coot with young, the adult sporting a noticeable frontal shield while the juveniles show off their garish autumn colors.

This photograph was originally posted to Flickr by mikebaird at http://flickr.com/photos/72825507@N00/530921201.

Photograph 2. An American coot with lighter under feathers shown as well as the white back feathers and strange lobed feet. Photo provided by Terry Sohl.

Photograph 2. An American coot with lighter under feathers shown as well as the white back feathers and strange lobed feet.

Photo provided by Terry Sohl
Photograph 3. Typical reedy marshy habitat of American coots. This photograph was originally posted to Flickr by SeattleYogi at http://www.flickr.com/photos/seattleyogi/2384740456/.

Photograph 3. Typical reedy marshy habitat of American coots. This photograph was originally posted to Flickr by SeattleYogi at http://www.flickr.com/photos/seattleyogi/2384740456/.

Figure 1. The affect of host availability on percentage of broods that also lay parasitic eggs. There is a clear positive correlation between number of potential hosts and the frequency of brood parasitism. (Lyon, 2003)

Figure 1. The affect of host availability on percentage of broods that also lay parasitic eggs. There is a clear positive correlation between number of potential hosts and the frequency of brood parasitism. (Lyon, 2003)

Figure 2. Comparison of (a) the total fecundity of eggs laid in the individual’s nest to (b) to the aggregate clutch size of their own plus parasitically laid eggs. Each filled bar shows the fecundity for parasitic females and each white bar represents non-parasitic females. Each set of bars is taken from a different wetland. (Lyon, 1993)

Figure 2. Comparison of (a) the total fecundity of eggs laid in the individual’s nest to (b) to the aggregate clutch size of their own plus parasitically laid eggs. Each filled bar shows the fecundity for parasitic females and each white bar represents non-parasitic females. Each set of bars is taken from a different wetland. (Lyon, 1993)

Graph 1. Graph of the common distribution of <em>Fulica Americana</em> based on breeding patterns and migration routes.

Graph 1. Graph of the common distribution of Fulica Americana based on breeding patterns and migration routes.

Range map information from Ridgely, R.S., Allnutt, T.F., Brooks, T., McNicol, D.K., Mehlman, D.W., Young, B.E., and Zook, J.R. 2003.

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2 Responses to You can’t fool a coot…American coots employ selective conspecific brood parasitism

  1. Shannon says:

    I live in the Netherlands and have been watching a family of coots outside my office over the past several weeks. What I’ve seen has been extremely odd:

    In May, there were 2 parents and 2 chicks. The parents were actively feeding them, and all seemed quite “normal”… although I did notice that the parents continued to mate, despite having two small chicks.

    I went on holiday for 2 weeks and when I returned, the parents had rebuilt their nest, and were sitting on it in shifts so I assume there are eggs. The 2 chicks, which are still small but seem OK, are on their own in the pond. They are eating, diving, and swimming about, and keep their distance from the parents, who seem to want nothing to do with them.

    Would this be an example of “parasitic” egg laying, or is it a known behavior of Coots to have offspring and then another brood shortly after?

    While the babies do seem to be fine on thier own, they seem too young to have been cast out of the nest or away from the parents.

    I’ve been really curious and haven’t foudn much information online so I’d be interested in someone else’s feedback!

  2. xalamanderx says:

    I believe parasitic egg laying refers to the phenomenon of females adding eggs to others’ broods, which is hard to determine without research. In your case, perhaps the earlier brood was made up entirely of conspecifics, causing the parents to “abandon” the chicks, but more likely they were simply starting a second brood (if there were indeed eggs). Also, are you sure they are the same pair of birds?

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