posted on July 27, 2004 00:00
Prairie State Dove Hunting
There's a lot of research being done on the migratory mourning dove. You can judge for yourself on whether bird numbers are up or down this fall.
Photo by Marc Murrell
By Daniel D. Lamoreux
The echo of the approach of rolling thunder reverberated in the air. Dark clouds overhead pushed and shoved like stampeding cattle as they jockeyed for position before a hasty wind. With a deafening crack and a brilliant flash of light, a cloudburst cut loose to the west and raced in a great wall of water in my direction.
As a kid, I loved a great storm, and I still do. Racing from the porch and into the cold downpour, I realized this was like nothing I had ever seen. With the precision of a military maneuver, the squall forced its way down the south side of the street, pounding the houses with torrents of icy water. My neighbors across the street remained dry.
From curb to curb I ran back and forth across the street. Into the rain, out of the rain and back again. For all of 10 minutes I played in God's own sprinkler - laughing, screaming, enjoying the time of my life.
Then the storm moved on.
Who could have predicted an event like that?
It's been many years since I thought about that day, but researching this article brought it back to mind in living color. For all the years and dollars we have invested in meteorology, we still cannot predict the weather with precision. Forecasting dove populations is no less problematic.
John Schulz is a wildlife research biologist for the Missouri Department of Conservation and he has some information that affects Illinois dove hunters.
"Doves are habitat generalists," he said. "They use all major ecological habitats except wetlands and boreal forests. They can thrive just about anyplace with bare ground, seeds and a place to drop a couple of eggs. Habitat does not drive their populations. When we think about managing doves, we're basically managing by default. There's not much we can do other than through (management of) hunting."
David Dolton is a wildlife biologist and mourning dove specialist in the Division of Migratory Bird Management for the U.S. Fish and Wildlife Service (USFWS). During an interview, Dolton made this statement: Previous banding studies have shown that hunting is not detrimental to dove populations. We've seen declining populations and we think it is due to a number of things, most likely habitat-related."
While it may seem that these two gentlemen are in disagreement, the reality is that they are allies in the search for good information. Neither one is necessarily wrong. So, if both of the above statements are relatively true, what are the factors that could be root causes of population fluctuations?
"That's the $95 million question," Schulz said. "This is why I get paid for doing research, to basically answer that question."
A review of data provided by a number of agencies raises uncertainties regarding the reliability of dove research that has been done to date. The decision-making process that is conducted as a result of these studies must also, therefore, be examined.
The first question that must be asked is this: Are dove populations truly in decline? To answer that question, we need to understand how population surveys are conducted.
The study that is primarily used for estimating dove populations and thereafter for setting annual hunting regulations is the Mourning Dove Call-Count Survey (CCS). As the name implies, the CCS reports on the number of doves heard along selected survey routes.
There are over 1,000 routes that are covered nationwide, 16 of which are in Illinois. The USFWS report "Mourning Dove Population Status, 2002" describes the survey procedures in this way.
"Each call-count route is usually located on secondary roads and has 20 listening stations spaced at 1-mile intervals. At each stop, the number of doves heard calling, the number seen and the level of disturbance (noise) that impairs the observer's ability to hear doves are recorded. The number of doves seen between stops is also noted."
There are fundamental problems with this survey. First, the objective is not to count the number of calls heard but the number of birds that are actually calling. As one biologist adroitly explained, "That's darn near impossible to track in your head." While the number of doves seen is recorded, this information is kept separate and is used as supplemental data for comparison purposes only.
Second, counting calls provide a relative index of the population found along a route and may not necessarily reflect actual changes in population. For example, a research report written by Schulz indicated that the survey trends might instead represent "an index to unmated males in the breeding season" rather than trends in the population as a whole.
Third, it is necessary to return to the same spots year after year in order to ensure that the data is comparing "apples to apples." If different locations were used each year, it would be impossible to make reasonable comparisons.
The problem with this practice is that there is nothing to compensate for changes in the landscape along survey routes. Things like crop rotations, timber harvest, construction and many other factors may change the way in which doves use a particular survey route without impacting the actual size of the local population.
Finally, the number of routes that are surveyed is insufficient. Illinois is representative of this problem. The total landmass of the state is 55,593 square miles, but data is collected from no more than 320 listening stations in our entire state.
There are other types of surveys that are used in a variety of jurisdictions, but unfortunately they are no more exacting. One of these alternatives is the North American Breeding Bird Survey (BBS). Data is collected in essentially the same manner as with the CCS, excepting that the BBS data for doves heard and seen are combined for analysis. The BBS also uses 50-stop routes, which increases the sample size. But the survey is taken later than CCS and the timing prevents the use of this data for regulation development during the year of the survey.
Some individual states also conduct harvest surveys to obtain rough estimates of the number of dove hunters and the total number of doves killed. This information also has its limitations. Quoting again from the USFWS population status report:
"Attempts to use state harvest surveys to obtain coordinated national and regional estimates have been unsuccessful because sample frames and survey methodologies vary widely among states." Translation: the states conduct their surveys in different ways and therefore the surveys may not reflect comparable information.
John Cole from the Illinois Department of Natural Resources explained the harvest survey conducted in this state.
"At the end of the year we collect the stubs from sales of licenses and Habitat Stamps," Cole said. "From those we draw a random sample of 3,000 to 4,000 hunters statewide and send out a questionnaire."
The results of those questionnaires are then used as a basis for calculating the number of hunters and their relative success for the entire state.
While a variety of corrections are built into the formula used in making these estimates, there are certainly some assumptions that must be made if this data is to be accepted as reliable. The number of respondents who hunt doves should represent a reasonable percentage of those who hunt doves statewide, their success should be typical of dove hunters on the whole, and they must be honest in their answers about participation and success.
In addition to these surveys, the USFWS also has initiated collection of dove harvest information through the Harvest Information Program (HIP). This system has proved inadequate thus far for collecting waterfowl harvest information, primarily because of a lack of hunter participation. Information collected regarding dove harvest can be no more reliable.
Despite the imperfections, wildlife management agencies are using the only tools they currently possess.
"The USFWS and the states manage migratory birds with the best available information," Schulz explained. "Even if the best available isn't necessarily the best."
So what do these surveys tell us?
For the sake of simplicity, let's look at only those numbers being provided for Illinois and the Eastern Management Unit (EMU), of which this state is a part.
According to the CCS, there were no significant changes detected for the unit as a whole, but the population increased significantly in Michigan and the New England states while it decreased in Delaware/Maryland and Mississippi. The average number of doves heard per route increased 2.1 percent. The data is not yet available from the BBS studies for this time period to compare their most recent results.
Looking at data over a 10-year period, the CCS indicated a significant decline in doves heard in those states within the EMU that hunt doves. The BBS indicated no trend. In the non-hunting states, the CCS showed no trend while the BBS showed a significant population increase.
Over a 36-year period of time, CCS analysis indicated a population decline in the hunting states, while the BBS indicated no trend. In the non-hunting states the CCS showed no trend while the BBS data indicated a significant population increase.
The Illinois harvest report has indicated significant declines since 1989, with harvest estimates dropping from 1,612,706 to 1,061,801. However, during this same time period they also estimate that hunter numbers have declined by approximately 24 percent.
The HIP program shows yet another picture. Preliminary results of the total estimated harvest for the 2000-01 season indicate an 8 percent increase. This figure is followed by an explanation that reads, in part, "If a state's sample frame does not include all migratory bird hunters in that state, the survey results underestimate hunter activity and harvest for the state."
So, in summary, we have four different surveys that have produced four different sets of results. Nonetheless, migratory bird managers are convinced that dove numbers are in decline.
WHAT DOES IT ALL MEAN?
If we accept the premise that dove numbers are falling, the reasonable question is, Why? That brings us right back to the place where Schulz and Dolton have differing opinions about habitat vs. hunting.
The fact is there are a huge number of variables that may contribute to fluctuations in dove populations. The short answer is that nobody knows what has created the problem, if it even exists, but a theory has emerged that has prompted a few biologists to ask some important questions.
"In support of the USFWS, the CCS (an index of dove population trends since 1966) is the best and only available nationwide data," Schulz explained. "If we ignore potential errors with the survey and the resulting data, we have to ask, What is special about 1966 population levels? Could the survey have been established when populations were at all-time highs? The data from two independent surveys in Missouri may support this hypothesis."
The independent surveys Schulz referred to include the CCS, which was started in 1966, and a state survey known as the Roadside Dove Survey (RDS), which contains usable data going back to 1948. The RDS is also based upon driving standardized routes throughout the state, but it provides an index of birds seen rather than birds heard.
In the report titled "2002 Mourning Dove Population And Research Status Report," written by Schulz and Ronald Reitz (a research survey coordinator with the Missouri Department of Conservation), the following explanation was offered:
"Long-term mourning dove trends from both RDS and CCS surveys provide an interesting picture. Since 1966, both surveys show a strong relationship; a stronger relationship exists for the RDS and the North American Breeding Bird Survey (BBS) index of mourning doves. If we assume that these two (or three) surveys are tracking similar aspects of the mourning dove population, we see three things. First, we see that although population trends have declined since 1966, the trend has been relatively stable in the last 10 years. Second, we see that although trends are lower today than during the late 1960s, RDS trends are near levels similar to the late 1940s and early 1950s. Third, we see that some phenomena occurred during the late 1950s and early 1960s that caused dove trends to climb rapidly. Regionally, we can speculate that some beneficial and broad-scale land-use changes occurred during the late 1950s and early 1960s."
Dolton is familiar with Schulz's report and is, at the least, considering the plausibility of this theory.
"It is possible that the (CCS) surveys were started at the peak of dove populations," he said. "There have been a lot of changes - in habitat, in food supply . . . it's hard to figure out. Something may have happened in the '50s to create a peak, and doves may just be equalizing to where they were."
"We must be careful to avoid the application of rhetoric and hyperbole," Schulz said. "Our understanding of harvest effects on dove populations is far from certain, but in general we know that if harvest was having large negative impacts we would have observed much more obvious declines in a wide range of metrics.
"Also, implying that dove population trends are related to habitat changes is weak thinking and assumes that we understand what constitutes dove habitat," Schultz continued. "Although many have tried to define dove habitat, they have failed. Not only are ecosystems more complicated than we think they are, but they are also more complicated than we can think.
"Common sense would agree that dove populations may have declined since 1966, but we must acknowledge that that may not be a completely deleterious phenomenon," Schulz added. "What has caused the declines is uncertain, but dove populations appear to be 'healthy' when all available information is evaluated."
So what does this mean for dove hunters, particularly in the Prairie State?
Cole indicated that dove populations in Illinois appear to be basically stable overall. The state experienced a fairly mild winter this last year and, in fact, it appears that there may be more doves wintering here than in the past. Hunters can expect to see harvest numbers reasonably consistent with recent experience.
For the future, however, there needs to be change in our management structure.
"There is tremendous uncertainty in the mourning dove harvest management decision-making process," Schulz explained. "One of the first steps is to reach an agreement that the status quo is not working and that uncertainty will always exist in our knowledge base."
"Doves haven't gotten the attention they deserve," Cole said. "This is a national problem. We need more data."
Schulz and Dolton agree.
"For mourning doves, this means population models that incorporate estimates of annual survival rates, recruitment rates and harvest rates," Schulz explained. "Of the three areas of information needed, harvest rates are the most easily obtained."
As a community, sportsmen and sportswomen need to answer a few questions of our own. If we expect the kind of information that wildlife managers are currently trying to gather, we have to ask ourselves if we are willing to pay for it. Funding is always the greatest limiting factor. Priorities need to be established and existing priorities may need to be adjusted or changed.
Second, we have to decide whether or not we are going to be willing participants in these endeavors. As has been expressed, harvest information is a crucial part of the management decision-making process. If we don't cooperate, the numbers will never reflect reality.
Finally, we must decide whether or not we are willing to live with the results of all this research. If we can't accept the answers, we shouldn't ask the questions.
It is an accepted fact that the current data contains many inconsistencies. We know that our existing process is flawed. Where we go from here is really our decision.
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