posted on September 24, 2004 00:00
DOUG LEIER COLUMN: Fall boosts interest in game numbers
Getting out in the field still the best way to gauge abundance
In coming weeks, we'll be flooded with news about upcoming hunting season projections. Fall flight forecasts for waterfowl and results from upland game brood surveys will pique the interest of hunters and wildlife managers alike.
Along the way, from crow season, which began in mid-August, to the close of turkey season in mid-January, there'll be no shortage of questions about wildlife populations.
For starters, there is a difference between how we try to estimate human and wildlife populations. Every 10 years, the United States carries out a census during which an attempt is made to count every person in the country. This is not the case with most wildlife surveys.
For example, an accurate census or actual count of sharp-tailed grouse in North Dakota is virtually impossible, because of their high numbers and broad range. Besides, it's probably not necessary to know if we have 500,000 sharptails or 612,576.
For effective wildlife management, however, it is important to know some things about populations. Instead of an actual count, wildlife surveys typically provide a population index. For instance, the spring mule deer index is mule deer per square mile surveyed. The pheasant brood index is broods per mile of survey route. One fish population index is fish per net hour.
By themselves, these indexes don't mean much, but when survey results from year to year are compared, trends start to develop. Biologists then can say certain populations are up or down from last year and higher or lower than a long-term average.
An index is a statistically accepted method as long as the survey is similar from year to year. That's why the spring pheasant crowing count, for example, takes place during the same time frame and along the same routes every year. If the routes changed from year to year, and one year surveyors started each route at sunrise and the next year they all started their routes at noon, the results would not be comparable.
Many species have spring and summer or fall surveys. In addition, last year's hunter harvest surveys also can factor in to this year's predictions.
Conducting surveys and compiling their related indexes is a science, but that doesn't mean that all hunters will experience season results that are in line with survey results. After all the numbers are crunched, wildlife populations still may vary depending on locale and species.
Take the spring crowing counts for pheasants. The statewide index, which includes the average of all survey routes, increased 21 percent from 2003. That doesn't mean pheasant hunters will shoot 21 percent more roosters this fall.
Remember that the statewide index is an average. Winter in northwestern North Dakota was worse than in the rest of the state. The spring pheasant index in that part of the state was down from last year. The big picture also will contain many other small areas where local weather conditions or habitat changes will yield a bird population - some lower, some higher - that is not in line with statewide predictions.
It's that unknown variable that makes hunting so interesting.
Waterfowl populations, because of their migratory nature, are a culmination of state and federal surveys. While North Dakota summer brood surveys provide an index of bird numbers produced in the state, federal surveys cover a much larger area and yield an overall fall flight estimate.
Based on the Game and Fish summer duck brood survey, North Dakota's contribution to the overall fall flight is expected to be down 40 percent from last year. However, there may be other ducks nesting elsewhere that will migrate through North Dakota, to make up for fewer birds produced in the state this year.
Again, the variable in your own back yard will come into play. Some areas will have more local ducks than last year. Because of habitat variations, some areas will attract more migrating ducks. Some areas will attract fewer ducks.
Even the record allotment of deer licenses can be deceiving if you only take the big picture into account. While many units, especially in the eastern part of the state, have many more whitetail doe licenses available than last year, some units in the west, because of previous disease problems or hard winters, have about the same or even fewer licenses.
Biological surveys give us a pretty good idea of what to expect, and overall, North Dakota hunters can look forward to a good fall. But individual success, as always, depends on when and where and the amount of effort invested.
The only way to find out is to take to the field in the coming months and, for most of us, that's a sure thing.
Leier is a biologist with the Game and Fish Department in West Fargo, N.D. Contact him at firstname.lastname@example.org.