Nathan Troyan has spent the summer in the field in Colorado providing hands on research on our waterfowl and migratory birds. We asked him to share with our readers a bit about the work he is doing in the field to give hunters an in depth look at the field work he is doing.
Brief Background
Monitoring wildlife’s movements and patterns by means of tagging is by far one of the most often used methods in gaining an in depth understanding of a particular species habits and patterns. Once the particular species of interest is tagged by whichever means that may be, animals day to day activities can be tracked, monitored and thereafter studied. Upon being analyzed, a detailed picture into the actual ecology and behavior of the species can be determined. Tracking movements can offer information such as feeding habits, ranges, and migration patterns. From this type of particular research biologist and field technicians such as myself can set forth and suggest new and improved management practices based on conclusions drawn from the data collected.
The tracking of migratory species of birds is no exception to this matter. Waterfowl in particular travel vast distances to and from wintering, breeding and nesting grounds while stopping at many places in between. Sometimes these migrations dodge storms and adverse weather conditions, maybe oceans and sometimes the occasional hunters for that matter. However one important thing to remember is that without affixing means of visual or radio identification to these migrating individuals, how could anyone know where their travels lead them? Banding and VHF radio telemetry are the two most common methods of tracking waterfowl and as of recently using newer GPS equipped satellite transmitters that operate on solar energy. Though these are only a few of the actual methods used to actually study waterfowl, I hope to better inform you of the benefits and types of research being conducted on our countries waterfowl.
Avian Research Goals
Here in Colorado’s San Luis Valley as a Wildlife Research Technician, I’m taking part in a waterfowl nesting ecology study being performed by the Colorado Division of Wildlife. Situated at just under 8,000ft elevation in the North end of the valley, a high desert waterfowl oasis area called Russell Lakes WMA lies lush and full of water. Approximately 4,000 acres of prime wetlands and nesting habitat is available for waterfowl migrating back south along the Rocky Mountains from Canada. It is here that the CODOW tends to further grasp an understanding of nesting ecology and in particular habitat selection as it correlates to nest success and or failure. Species of particular interest for the monitoring portion of study are the Mallard, Gadwall and Teal varieties however all other nests found are recorded also.
Nesting success in particular is a key factor in sustaining viable waterfowl populations. It is noted that at least a 20-30% rebirthing success rate is needed to maintain a stable population. Often susceptible to predation due to ground nesting behavior, waterfowl and ducks nest in particular fall victim to a variety of predators. Here in the San Louis Valley desert ecosystem, a healthy population of coyote and raven do the most nest raiding. A constant threat from other species such as blackbirds, skunks and weasel also stack the odds against the nesting females. It is from our nest habitat selection observations that we can determine such things as nest success and depredation rates based solely on habitat choice alone. The amounts of available nesting cover and vegetation litter are also key elements in determining whether a female duck will initiate nesting. Too little over head cover and the areas are deemed no good and would prove highly detectable. Nest success is highly determined by habitat selection and each individual species does seem to have a desired species of vegetation choice. Species of vegetation highly favored are in this area are, Bulrush, Baltic Rush, Spike Rush, Cattail and Grease bush. Areas where two or more species converge are highly favored and likely nesting areas.
Method of Nest Detection
To locate nest, researchers use a method known as nest dragging. Here two or more individuals stretch out a specified length of rope between them. Attached to the rope or often used chain between two ATV’s, noise making devices such as aluminum cans with gravel inside are linked in spaced intervals approximately 10ft apart. This insures that while dragging a particular nesting location in grids, usually upland vegetation located near water, females will flush from the actual nest location therefore revealing its presence. Sometimes dependant on vegetation type’s available, females will nest over water in a suspended bowl. Locating a nesting female duck otherwise is nearly impossible and by random occurrence without using a technique such as this. Using flagging and GPS equipment we are able to cover every square foot of available habitat within particular units and impoundments. This method is used in the prairies covering vast land areas often as mentioned with ATV’s however works well on foot covering areas ranging from acres to several miles of marsh.
Upon Nest Detection
Once a female is flushed and the species correctly identified, the nest will be found and given an identification number also marked with GPS coordinates. Biological measurements are then taken on the eggs present. We record length and width measurements in millimeters of (3) separate eggs to gather a representative average for that particular species. The number of eggs present helps to determine species fertilization rates and potentially from that population trends. We then use a method called “egg candling” to visually inspect the inside of the egg through the shell and access the incubation stage of the embryos development. To do this we simply use a piece of black rubber tubing held up to our eye with the egg placed against the opposite end and aligned with the sun or available light source. From this inspection based on incubation rates known for each particular species, we can determine approximate egg laying dates as well for future research. This information alone can assist waterfowl and wetland managers additionally in determining when to manipulate habitat and draw down water levels to maximize available habitat. Along with egg data collection, surrounding habitat type/s, distance to water, litter depth, and region within study area are recorded. Each found nest is then monitored once weekly to make note of predation, abandonment or successful hatching.
Monitoring Efforts
In addition to nest and egg related research, physically capturing and marking waterfowl is another part of our study design. Females in the last week of their incubation stages right before “pipping” or egg hatching are captured using dip nets and hoop traps while on the nest. Upon successful capture of the incubating female, a numbered U.S. Fish and Wildlife Service identification band is placed on the right ankle. This number is intended to serve as a means of tracking movements spatially throughout the ducks lifetime and is intended to be visually noted or gathered via hunter harvest. In addition to the leg band two more methods of tracking movements are affixed. A less often used method known as nasal disk tagging is also done. This involves placing a small wire through the nares of the bill and placing (2) plastic disk labeled with a unique single letter and (2) digit number combination on either side. The wire is then crimped on the ends much like that of a rivet and fastened in place. This is more intended to be visually seen using optics or via hunter harvest. This method was used during the prior year’s research efforts and is also being used to determine return rates of females to this particular area. As another responsibility of mine I conduct observational studies for the presence of these disks as well.
In addition to these two methods, affixing VHF radio transmitters with subcutaneous anchors to the duck are also used. Of the many transmitter attachment techniques used for birds, subcutaneous anchors provide secure attachment offering relatively little secondary side affects. A unique frequency is associated with the transmitter and the signal can be located up to several miles dependant on habit density and terrain. From this transmitter attachment, the division and local marsh managers hope to track brood rearing females and their habitat selection preference for raising young. This data will then be transformed and applied to managing favorable marsh and upland habitat desired for successful brood rearing.
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