Field Work: Mating System

I am studying Muscovy ducks in the wild because they are allegedly promiscuous.  This is interesting because most waterfowl (ducks, geese, and swans) are monogamous, meaning that there is a pair bond between one male and one female (even though they may have "alternative reproductive strategies").  The objective of my field work is to determine whether the mating system of Muscovy ducks is in fact promiscuity, defined as the absence of pair bonds and the existence of multiple mating by individuals of both sexes.  Ultimately, I would like to figure out why Muscovy ducks might be an exception to the "rule" of monogamy in waterfowl.

My methods in the field include behavioral observations, nest searching and monitoring, and trapping:

---Behavior observations provide data on group size and composition, association patterns of individuals, activity time budgets, and interactions between males and females.  I will use these data to determine whether a social pair bond exists between males and females in this species, and if so, to characterize the relationship (e.g., how long does the bond last?  how many individuals are involved?  what are the costs and benefits of the bond to males and to females?)  I record behavior using a spotting scope, and I identify individuals by their unique facial markings.

 male Muscovy, "Patch," 
Poconé, Mato Grosso, Brazil

---I monitor nests to gather basic information on this little-studied species and to collect nest materials.  I can get a sample of the nesting female's DNA from feathers she leaves in the nest, and I can get duckling DNA from eggshell membranes after the eggs hatch.  By analyzing the DNA, I will learn how many fathers are represented in a given family.  This gives me a minimum estimate on the number of female mating partners.  Estimating the number of male mating partners is more difficult, as it requires getting DNA samples from males in the population and then being able to assign paternity of eggs in different clutches to the same male.  Because Muscovies usually nest in tree cavities, I use recreational tree climbing equipment to access nests.  Muscovy ducks will also use nest boxes.

tree climbing to access nests 

female Muscovy in nest box, 
Miranda, Mato Grosso do Sul, Brazil

---I capture individuals (or try to!) for several reasons.  First, I put aluminum bands on their leg as permanent identification.  Color bands allow me to identify individuals later when doing behavior observations, and a numbered band provides a record of the bird in case it is recaptured or recovered after death.  Second, I collect blood samples for DNA analysis.  In addition, I take measurements and photographs.  The birds are released as soon as these tasks are done.  So far only mist nets and nest traps have worked to catch these guys.  I haven't found success with decoy traps or bait traps, and other methods are out of my budget or aren't feasible at my field site.

me with "Patch" 

drawing blood from female Muscovy for DNA analysis
photo by John Harting