Viera Masked Duck Age and Sex

By David Simpson

I had read many references to the "female" Masked Duck that was spotted at Viera in November. Before I had the chance to observe the bird I had seen the excellent photos posted by Thomas Dunkerton and Brad Martin. I was curious as to how the bird was determined to be a female. The sexes are not diagnostically different in basic (non-breeding) plumage. In November, one would expect three plumage options for Masked duck: Adult male eclipse (non-breeding) Adult female basic (non-breeding) and Juvenile. According to Sibley's Guide, Masked ducks stay in juvenile plumage from August to February.

I did some research in the printed guides and came up with a few possible ID points. According to the Waterfowl book by Steve Madge and Hillary Burn, males tend to have a buffier head and more strongly mottled flanks and a larger white wing patch than females. Illustrations in this book and the National Geographic Guide show the lower stripe on the face is broader and enlarged toward the rear. According to the Waterfowl book, the juvenile plumage is similar to female but with a "more spiked" tail.

Photos of the bird in Viera show a fairly narrow line below the eye which seems good for female. The tail in Brad's photos seems "more spiked." My question is, "more spiked than what?" The only other Masked duck I have seen was a stunning breeding male in Pembroke Pines five and half years ago. Most of us Florida birders don't get to see Masked ducks on a regular basis. When we do, most of us don't concern ourselves with trivialities like whether it is adult female or juvenile. So why do I wonder about this? I just find it interesting. Maybe someone out there on the internet can enlighten us all on this ID problem. For all I know this discussion may already be taking place on Frontiers of ID. In the mean time, here are some links to Masked duck photos I found in the web.

• http://www.narba.org/galleryimages/masked_duck_matherly_1_cr.jpg
• http://www.mbr-pwrc.usgs.gov/id/framlst/i1680id.html
• http://www.texasbirds.org/tbrc/maskduck.htm
• http://avesphoto.com/website/NA/species/DUCMSK-3.htm
• http://www.greglasley.net/maskduck.html
• http://www.mangoverde.com/wbg/picpages/pic27-151-1.html
• http://www.fotosaves.com.ar/Anseriformes/FotosAnseriformes.html

After having seen the photos, the next morning I had a chance to observe the masked duck at Viera from 0630 to about 1100. There was a constant stream of people, some new and some old friends, during this time. The bird never took cover during the time I was there. It occasionally went behind a clump of Duck potato, but did not actually hide amongst the vegetation. It did fly back and forth from some more open water about 30m west a couple of times. It dove a couple times and fended off a few attacks from a pair of coots. Most of the time it sat in the water and eyed it's observers. The interesting thing is that it seemed the bird didn't move far from it's coot tormentors and even seemed to follow their movements. Near the time that I left, the bird moved back into the open water and began actively diving (feeding?)

During the time I was able to observe the bird I tried to access the condition of the feathers on the back and wings. Theoretically, fresh plumage would indicate an adult bird and worn feathers would indicate a juvenile. This is based on the assumption that adults would have recently molted into non-breeding plumage (Sibley indicates non-breeding plumage starting in October) and juveniles would be a few months old (Sibley gives a range of Aug-Feb for Juvenile plumage). The scapulars and back feathers showed distinct buffy tips. I could not tell whether they were worn or not, even zoomed in at 50X from 15m away. Someone with more experience handling or observing birds could probably access this better than me. The tail feathers seemed a bit ragged. They did not seem worn but more like they had not been preened recently. I don't know much about accessing age by the length of tail feathers.

So I still don't know whether it is adult or juvenile. I was leaning toward adult female, based on the paltry information I was able to gather. What is the significance of the bird's age? An adult female Masked duck was photographed in the Viera Wetlands in spring of 2005. If the recent bird is an adult, maybe it is the same bird that came back out of hiding. If it is a juvenile, maybe it is an offspring? If the bird is indeed a juvenile, it raises more questions, as all good investigations do. Do juvenile Masked ducks disperse from their natal grounds? If so, when? If not, does this indicate breeding in Viera? Breeding of Masked ducks in Florida has been suspected in the past, but never confirmed. The secretive nature of Masked ducks and the dense vegetation of their habitat makes their possible breeding a tantalizing possibility.

That's about all I have for now. I look forward to more information and opinions in the future.