Banding programs allow biologists to track the movements of some individuals, to know their nesting and wintering grounds, to learn whether they are healthy and feeding well, to answer questions that are important to a refuge's management. Banding studies can answer questions that bear on the health of an entire population of birds.
500 ducks in a cannon net! (Photos by Narca)
This particular banding project started before dawn, when refuge staff baited a levee to attract the ducks, then fired off a cannon net to capture them. We arrived as the biologists, along with a group of students from Arizona State University, were wading in the icy water and quickly retrieving ducks from the net, in an effort to prevent any from drowning. They had caught far more ducks than expected, with perhaps as many as 500 in the single net! Some of those escaped, but by the end of the morning, 432 had been banded.
Rod is ready to open the cage for the next ducks to come.
Ducks retrieved from the net are put into plastic pens to await processing.
Too many ducks were caught to fit into the plastic pens, so the others were put into bags in the back of a pickup truck.
Other methods are often employed to trap ducks, including night-lighting to capture individuals and swim-in traps. Old-time waterfowl banders will generally employ cannon nets over dry land, not water, although no doubt the refuge staff had their reasons for handling it the way they did. The method they used certainly was effective at catching large numbers!
Each method has its pros and cons. One problem with using a net over water is that ducks can become soaked and be unable to fly until they dry off, cormorant-style. Getting that wet is stressful, and the drying ducks are temporarily vulnerable to predators like Coyotes.
Northern Pintail can, however, be wilier than Coyotes. Rod told us of his colleague working with nesting ducks in the prairie pothole region of North Dakota, who watched a Coyote trotting along with a female pintail in his mouth. The Coyote dug a hole and cached his prey, completely burying the duck. Soon after the Coyote left, the dirt started to move, and one bright eye peeked out and looked around. The pintail hen then emerged from the dirt and flew away! She had been playing dead.
A handsome drake Northern Pintail, ready for release
Most of the captured ducks were Northern Pintails, with a number of Green-winged Teal and a handful of Mallards, including this hybrid male Mallard x Mexican Duck. Hybrids of this mix are more often encountered here at the northern edge of the Mexican Duck's range than they are farther south in the bootheel of New Mexico, where green-headed Mallards only rarely breed.
A hybrid Mexican Duck x Mallard shows a gloss of green on his head.
Mexican Ducks are officially considered a subspecies of Mallard, probably based in large part on political ramifications. Hunting programs would be impacted if Mexican Ducks were given full species status, because they would have to be treated as endangered. See Richard Webster's assessment of the issue at http://www.azfo.org/journal/mottled_duck.html.
Rod bands a Northern Pintail drake
Rod is an old hand at banding ducks, geese and cranes. He much prefers to do it sitting in a chair, but the staff at Bosque didn't get that fancy in their set-up.
Here's a method of holding a band that is hard to do with songbird bands!
And what questions were answered by this day's banding?
To start with, refuge biologists saw that a few of the ducks were loaded with parasitic worms. The weight of many was lighter than expected, raising some concern about nutrition. But other questions will only be answered down the road, as band returns trickle in, or as birds return in future winters and are recaptured. For example, banding studies can clarify whether the problems in a declining bird population are occurring on the breeding grounds, on the wintering grounds, or in migration. Banders are a patient breed, and the questions that banding studies may eventually answer can't always be anticipated.