I 
 
 
X'l B R_AR.Y 
 
 OF THE 
 UNIVERSITY 
 or ILLINOIS 
 
 NATURAL HISTORY 
 SURVEY. 
 
STATE OF ILLINOIS 
 Adlai E. Stevenson, Governor 
 
 DEPARTMENT OF REGISTRATION AND EDUCATION 
 
 Noble J. Puffer, Director 
 
 POPULATION LOSSES IN THE MALLARD, 
 BLACK DUCK, AND BLUE-WINGED TEAL 
 
 Frank C. Bellrose 
 
 and 
 
 Elizabeth Brown Chase 
 
 
 Printed by Authority of the State of Illinois 
 
 NATURAL HISTORY SURVEY 
 
 Harlow B. Mills, Chief 
 Biological Notes No. 22 Urbana, Illinois January, 1950 
 
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POPULATION LOSSES IN THE MALLARD, 
 BLACK DUCK, AND BLUE-WINGED TEAL 
 
 Frank C. Bellrose 
 
 and 
 
 Elizabeth Brown Chase* 
 
 Up to about 15 years ago, few wildlife conservation agencies had a significant amoiont 
 of factual information on game populations and kill. Consequently most hunting regulations gov- 
 erning the take of game were based largely on opinions and more often than not were applied in 
 a hit-or-miss mcinner. Even though recent development of wildlife technology has given conser- 
 vation agencies increasingly large amounts of factual information on which to base game regula- 
 tions, most of the information obtained to the present time has been inadequate in that it has been 
 concerned mainly with censuses of the population and inventories of the hunter teike. 
 
 POPULATION MECHANICS AND MANAGEMENT 
 
 Officials engaged in drafting hunting regulations need to know more than trends in 
 game populations and kill; they need to know the maiximum proportion of a game population that 
 can be harvested without adversely affecting the future of that population. It is evident that a 
 large proportion of any game population will disappear each year from natural causes; it is a 
 responsibility of management to see that the greatest possible use is made by man of the annual 
 losses that normally occur. Shooting a v^ild duck in the autumn does not necessarily reduce the 
 total spring population by one duck, for many a game bird falling before sonae hunter's gun would 
 otherwise have died from natural causes before another breeding season rolled arotind. Para- 
 phrased from Elton (1942): A duck shot might have died in any case the next day or week in its 
 ordained place in the life curve. 
 
 In order to formulate the proper hunting regulations for a game species, we must first 
 measure the total annual loss that a population of that species undergoes, and we must measure 
 the influence of varying kill intensities on that loss. What effect does a moderate hunter-kill have 
 on the over-all annual mortality? How high can the kill rate go in a game species before it 
 reaches a point beyond which the productivity potential caruiot bring the population back to its 
 former level? 
 
 The year-to-year game-regulation "tactics" should come, as they often do now, from 
 up-to-the-minute census and kill information. The population information necessary to lay out 
 the general game-regulation "strategy" should develop from long-term band recovery data and 
 from age ratio data. Band recoveries furnish facts on population losses; age ratios supply facts 
 on productivity. 
 
 * Frank C. Bellrose, Associate Game Specialist, Illinois Natural History Survey; Dr. Eliza- 
 beth Brown Chase, 1945-48, Research Assistant, Illinois Natural History Survey. 
 
ANALYSIS OF BAND DATA 
 
 The use of band data in analyses of bird populations was pioneered by Nice (1937) in 
 her study of the song sparrow. Leopold et al. (1943) combined band and census data to deter- 
 mine mortality of ring-necked pheasants on the University of Wisconsin Arboretum refuge. On 
 the other side of the Atlantic, Lack (1943a, b, c) published studies, based entirely on band re- 
 covery figures, on the' survival of several English birds. 
 
 Recently Farner (1945), Buss (1946), Marshall (1947), and Hann (1948) have published 
 on the survival and mortality of, respectively, the robin, ring-necked pheasant, herring gull, 
 and oven-bird. Deevey (1947) presented a searching analysis and review of life tables as used 
 to determine survival of aninnals in nature. 
 
 The present study deals with the survival and mortality of the mallard, black duck, 
 and blue-winged teal in the Mississippi flyway as determined for the most part by means of 
 10,718 recoveries (bands recovered from ducks shot and bagged or ducks found dead) from 
 51,297 individuals banded by the Natural History Survey at the Chautauqua National Wildlife 
 Refuge, near Havana, Illinois, fig. 1 , or at McGinnis Slough, in and with the co-operation of the 
 Forest Preserve District of Cook County, near Orland Park, Illinois. The actual banding was 
 done during the fall months, 1939-1944, at Lake Chautauqua and, 1940-1945, at McGinnis Slough; 
 recovery data extend through 1946 for Lake Chautauqua and 1947 for McGinnis Slough. Inclu- 
 sion of the McGinnis Slough data in this report was made possible through the co-operation of 
 Roberts Mann, Dr. David H. Thompson, and John Jedlicka. 
 
 VALIDITY OF SHOT RECOVERIES. — Previous investigations indicate that satisfac- 
 tory appraisals of longevity can be made from band recoveries of shot birds. Paynter (1947) 
 found that there was no significant difference in mean length of life between herring gulls dy- 
 ing as a result of shooting, trapping, or other human interference and those dying as a result of 
 natural or unknown causes. Farner (1945) showed that, in robins, life-expectancy figures ob- 
 tained from the nunnber of birds shot and from the number killed by cats were similar to those 
 calculated from band recoveries representing the total population. 
 
 Band recoveries from shot ducks are many times as numerous as records of live re- 
 captures or other returns, and they provide the largest sampling on which to base life tables. 
 
 The number of band recoveries from ducks in a banding-class* shot in a particular 
 year following banding is dependent on two principal factors: (1) the number of ducks in the 
 bcinding-class left alive to be bagged and (2) the shooting pressure. If shooting pressure in 
 two specified years is equal, then the difference in the number of band recoveries in the two 
 years would be a measure of total population loss from the first year to that following. How- 
 ever, there has been a year-to-year variation in shooting pressures. In Chautauqua-banded 
 mallards the season-of-banding bag ranged from 6.7 to 14.9 per cent of birds banded, 1939- 
 1944, table 9. This year-to-year variation results in a sampling error when the population 
 loss is measured for any specified year considered separately. But because ducks of most 
 
 * Banding-class refers to the ducks banded in a specified year. 
 
year-classes* are represented in several calendar years, the year-to-year variation in recov- 
 ery data resulting from chauiges in shooting pressure has been minimized for each year-class 
 but that for 7-8, table 1. 
 
 After analyzing figures obtained from banded mallards that return to the traps in 
 subsequent years, we have concluded that these data do not allow for a valid interpretation of 
 population losses because of the small size of the sample and because of yearly variations in 
 rate of return of ducks to the same flyway resting or feeding grounds. Our band returns show 
 that, although in each year there is some degree of return by mallards to the same flyway rest 
 stops, the degree of return varies from year to year. 
 
 Because band recoveries from shot ducks representing the extensive areas over 
 which ducks fly are not only many times as numerous as records of live recaptures but are not 
 subject to yearly variations in the return to a single spot on the flyway, these band recoveries 
 were used in this study to measure population losses in the mallard, black duck, and blue- 
 winged teal. 
 
 YEAR-OF-BANDING RECOVERY CORRECTIONS. --In order to use recovery data ob- 
 tained the same year that mallards and black ducks were banded, we found it necessary to com- 
 pensate for the fact that banding was done south of the breeding grounds during the hunting sea- 
 son rather than on the breeding grounds immediately preceding the hunting season. To correct 
 for the chronological and geographical differences involving band recoveries in the season of 
 banding (part of hunting season and south half of flyway) and band recoveries in subsequent sea- 
 sons (entire hunting season and entire flyway), we used a simple ratio that involved the number 
 of days banded ducks were actually available for shooting and the number of days these banded 
 ducks would have been available if all had been banded before the beginning of the season. Cor- 
 rections were made separately for each calendar year and for each age and sex group. 
 
 The first step in making the corrections in year-of-banding data involved finding the 
 nximber of ducks banded in each autumn banding period and then locating for each period the 
 mean date of banding activities. This mean date assumes that all ducks were banded on a sin- 
 gle day a definite length of time after banding was begun and before it was ended. The next 
 step was to determine the number of days from the mean banding date to the end of banding. 
 
 The daily rate of mallard kill was found to be approximately the same before and af- 
 ter the mean banding date. This rate of kill was determined by tabulating returns through the 
 hunting season for mallards banded at least one year previously. Very few mallards were 
 killed in September, more in October, and most in November; then the kill declined through 
 December. So that the data would more nearly resemble a normal curve, the nxunber killed in 
 September was added to the number for October, and October 1 was assvimed in calculations to 
 -be the first day of bcinding. 
 
 * The ducks in a year-class are those killed in the year of banding or in a specified number 
 of years after being banded and are indicated in table 1 by the columns headed O-l corrected, 
 1-2, 2-3 , etc. Ducks in year-class 1-2 are those killed during the period between 1 and 2 
 years after being banded. 
 
The formula for deriving the corrected number of recoveries for the O-l year-class 
 to the end of the banding period is as follows: 
 
 Corrected number of 
 
 recoveries from Octo- Number of days from 
 
 be r 1 to end of banding October 1 to end of 
 
 period __ banding period 
 
 Actual number of re- Number of days from 
 
 coveries before end of mean banding date to end 
 
 banding period of banding period 
 
 Recoveries from the time banding is terminated until September 1 of the following 
 year are added to the corrected number of bands recovered up to the end of the banding period. 
 The result gives the corrected year-of-banding recovery data, which are roughly comparable 
 to recovery data for ducks banded on the breeding grounds before the beginning of the hunting 
 season. 
 
 Below is given an example of the use of the formula in correcting the year-of-band- 
 ing recovery data. Bands were recovered from 33 juvenile male mallards during the 1939 
 banding period and 16 after the end of this period but before the following September 1 — a total 
 of 49 recoveries, table 1. The number of days from October 1 to termination of banding in 1939 
 was 89. The number of days from mean banding date to end of the banding period was 28.2. 
 
 Substituting the appropriate figures in the formula gives the following equation: 
 
 X 
 
 = 
 
 89 
 
 33 
 
 28.2 
 
 X 
 
 — 
 
 89 X 33 
 
 28.2 
 
 X = 104 
 
 To 104, the corrected number of band recoveries before the end of the banding period, 
 are added the 16 recoveries after the end of this period, to give a total of 120, table 1. 
 
 Another method by which the corrected number of recoveries can be determined is 
 more nearly accurate for individual years, but it requires a good sample of recoveries for a 
 given year from prior bandings; it cannot be used for the year in which banding is first instituted! 
 
 This formula is as follows: 
 
 Corrected number of Total number of previously 
 
 recoveries from selected banded ducks recovered in 
 
 year of banding __ selected year 
 
 Actual number of recoveries Number of previously banded 
 
 from selected year of band- ducks recovered after mean 
 
 ing before end of banding selected-year banding date 
 
 period before end of banding period 
 
 In addition to these two formulas developed by the authors for correcting current- 
 year banding data on the flyways is still a third method, which was developed simultaneously 
 and independently by Thompson & Jedlicka (1948). 
 
 Year-of-banding band recoveries for the blue-winged teal, table 7, were not correctec 
 
as were year-of-banding mallard eind black duck recoveries, because most of the blue-wings 
 were banded before the hunting season opened, 
 
 LIFE TABLES AND TERMINOLOGY.— In the life tables presented here, mortality 
 figures and survival figures were derived from figures representing the number of bands re- 
 covered and the number of ducks banded in each of the various year-classes. Returns are com- 
 plete for the first three year-classes; so the percentage of return is based on the total number 
 of ducks banded, tables 1-7. For the fourth year-class (3-4), returns are lacking for 1 year 
 (banding-class); so only the number of birds banded prior to that year are considered. Each 
 succeeding year-class has returns for 1 year less; the 7-8 year-class has returns for only 1 
 year. 
 
 In the mortality* series, the percentage of the total nvimber of bands recovered is 
 given for each year-class, tables 1-7. The figure for any one year-class represents a per- 
 centage of the total number of recoveries. 
 
 The cumulative per cent of bajids recovered, as presented in tables 1-7, is found for 
 any one year-class by adding the mortality series figure for that year-class to the mortality 
 series figures for all previous year-classes. Figures in the survival series, the reverse of 
 the mortality series, are obtained for any one year-class by subtracting from 100 the number 
 representing the cunnulative per cent of bands recovered for that year-class. The mortality 
 rate, which measures the percentage of those birds alive at the start of a year that die in that 
 year, is found for any year-class by dividing the mortality series figure for that year-class by 
 the survival series figure for the previous year-class; for year-class O-l, the survival ser- 
 ies figure for the previous year-class is 100 per cent. 
 
 POPULATION LOSSES.- -Mortality and survival figures of a population of ducks of 
 known age are given in table 1. Banded as juveniles, the mallard drakes making up this popu- 
 lation probably rsinged in age from 3 to 7 months at time of banding at Leike Chautauqua. 
 
 Data in table 1 indicate that in this population of mallards banded as juveniles, and 
 therefore of known age throughout their history, for every 100 alive on October 1 of the year 
 of banding 55 (54.9 percent) died before the next 0<;tober 1. In the second year following band- 
 ing, 20 additional ducks died; in the third year 11; in the fourth year 6. By the end of the sixth 
 year, only 2 (1.9 per cent) were still alive. 
 
 Mortality and survival figures for a population of mallard drakes banded as adults 
 are given in table 2. The ages of the individuals were luiknown except that all were at least a 
 few months more than 1 year of age at the time of banding. Data in the table indicate that for 
 every 100 of these mallard drakes alive on October 1 of the year of banding 36 died before 
 October 1 of the following year; 25 died the second year, 15 the third year, and 11 (10.5 per 
 tent) the fourth year. By the end of the sixth year less than 3 (2.5 per cent) were still alive. 
 
 The principal difference in the mortality rates of the two groups of ducks, one band- 
 ed as juveniles and the other banded as adults, was in the greater year-of-banding losses in 
 
 * The term mortality as used in this paper includes death caused by hunters and by natural 
 forces; it is applied only to ducks that have reached flying stage. 
 
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 14 
 
the ducks banded as juveniles, tables 1 and 2. A comparison of mortality rates of the two groups 
 discloses that in the first 4 years after the year of banding the average yearly rate of loss was 
 42 per cent in the group bajided as juveniles (average of 43. 9i 43.1, 38.9, and 42.0), and 41 per 
 cent in the group banded as adults (average of 38.8, 37.6, 42.9, and 44.5). The significant fact 
 these figures reveal is that senescence is not an importeint mortality factor in wild mallard popu- 
 lations. Shooting, accidents, and predation are responsible for most of the deaths, and juveniles 
 are nnore subject to these causes of mortality than are older ducks. 
 
 The higher year-of-banding mortality rate in juvenile populations is partly, but not 
 entirely, the result of a higher proportion of juveniles taken by hunters. The mortality rate is 
 about 1-1/2 times as high for juveniles as for adults, tables 1 and 2, and the hunting vulnerabil- 
 ity* rate is approximately in the same proportion. Differences in the survival rates of mallard 
 drakes banded as adults and those banded as juveniles are presented graphically in fig. 2. 
 
 
 lOO-i 
 
 
 90- 
 
 
 80- 
 
 
 70- 
 
 llJ 
 
 
 > 
 
 60- 
 
 -J 
 
 
 < 
 
 
 1- 
 
 50- 
 
 z 
 
 
 Hi 
 
 o 
 
 40- 
 
 on 
 tlJ 
 
 30- 
 
 Q. 
 
 
 
 20- 
 
 ADULTS 
 JUVENILES 
 
 10- 
 
 12 3 4 5 
 
 YEARS FOLLOWING BANDING 
 
 Fig. 2. --Survival rates of mallard drakes banded at Lake Chautauqua, 
 1939-1944, one group banded as adults and the other banded as juveniles. 
 
 There was a higher rate of loss among mallard hens than among mallard drakes, as 
 shown by differences in the mortality rates, tables 3 and 4. This loss in hens occurred despite 
 the fact that current-season or year-class O-l band data derived from figures in tables 3 and 
 4 show that drakes in this year-class are 4 per cent more vulnerable to hunting than are hens. 
 It would appear, then, that the greater hen mortality occurs outside of the hunting season. 
 Field studies indicate that hens during the breeding season are subject to more hazards than 
 
 * The term vulnerability in this paper refers to the deaths of birds bagged b y hunters, whereas 
 mortality refers to deaths from all causes, including deaths resulting from crippling by hunters. 
 
 15 
 
are males. While the hens, incubating their eggs and caring for their young, are subject to high 
 mortality, the drakes gather in bands in large nnarshes or on extensive lakes where such deci- 
 mating factors as predation and drought apparently cause fewer losses. Differences in the sur- 
 vival rates of mallard drakes and hens are presented graphically in fig. 3. 
 
 DRAKES 
 
 YEARS FOLLOWING BANDING 
 
 Fig. 3. --Survival rates of mallard drakes and mallard hens banded at 
 Lake Chautauqua, 1939-1944. 
 
 Banding traps are selective in that in most situations they take a disproportionate 
 number of individuals in one or more of the various age and sex groups (usually the adult naale 
 group). Therefore, life tables based on banding data in which figures for all age and sex groups 
 are lumped together usually are not representative of the population involved. 
 
 However, at McGinnis Slough, trap selectivity was at a minimum because a relatively 
 low population density allowed the ducks there to feed into the traps in such a way that seldom 
 did an age or sex group dominate the situation, and the trapped population was fairly represen- 
 tative of the population using the area. Because of this relative lack of selectivity in trapping 
 euid because the number of ducks involved was small, the data on all age and sex groups of each 
 of the three species treated in this paper have been combined in determining mortality losses, 
 tables 5,6, cind 7. 
 
 Among McGinnis Slough mallards, the mortality losses for all age and sex groups, 
 table 5, approximated losses suffered by mallard hens banded at Lake Chautauqua, table 4, and 
 were slightly higher than mortality losses suffered by the entire mallard group banded at Lake 
 Chautauqua. 
 
 16 
 
Black ducks bcinded at McGinnis Slough, table 6, had mortality losses that totaled 94.2 
 per cent through year-class 3-4, while mallards banded there had losses amounting to 92.1 per 
 cent through the same year-clasa. The average of yearly mortality rates through year-class 4-5 
 was 53.7 per cent for the black duck, 46.4 per cent for the mallard. 
 
 Blue-winged teals beinded at McGinnis Slough, table 7, had higher mortality losses than 
 either mallards or black ducks banded there. T^e average of yearly mortality rates for the blue- 
 wings was 57.1 per cent, more than 3 per cent higher than for black ducks. Although there was 
 no well-defined yearly trend in the mortality rates of the mallards aJid black ducks, the mortality 
 rate of the blue-winged teals increased with each successive year-class. 
 
 3 
 
 LONGEVITY. --Longevity, as used here, is the life expectancy of a duck after banding. 
 Longevity research does not provide information essential for evaluating population mechanics, 
 but it may provide figures readily comprehended by the layman. Because some investigators 
 have used them, we include longevity figures for mallards for comparison with the figures for 
 other species. 
 
 There is a difference in longevity data as obtained by mean (average) and by median 
 (mid-point) figures, table 8. This difference occurs because a few individuals lived a dispropor- 
 
 Table, 8. --Expectation of further life after September 1 in year of banding by mallards 
 banded at Lake Chautauqua, 1939-1944, as determined from mean and median calculations. 
 
 
 Life Expectancy in Years 
 
 Statistic Used 
 
 Adult 
 Male 
 
 Juvenile 
 Male 
 
 Adult Male and 
 Juvenile Male 
 
 Female 
 
 
 1.79 
 1.04 
 
 1.27 
 0.23 
 
 1.56 
 0.52 
 
 1 38 
 
 Median (mid- 
 
 41 
 
 
 
 tionately large nunnber of years. Because the median figures are more precise measurements 
 of population longevity, we believe they should be used in measurements of longevity, particularly 
 in comparisons with other species. 
 
 According to figures presented by Addy (1945) the longevity of the black duck in New 
 England is slightly less thcin that of the mallard in Illinois. Addy found that the average life 
 span of black ducks cifter banding at three stations in Massachusetts was 1.17, 1.29, and 1.49 
 years. In Illinois the life span of mallard drakes averaged 1.56 years and that of hens 1.38 
 years in the years of this study. 
 
 YEARLY HUNTER-BAG. --Yearly hunter-bag losses for mallards are given in tables 
 9 and 10, for black ducks in table 11, and for blue-winged teals in table 12. These bag figures 
 involve only those ducks from which the bands were recovered in the year of banding. In the 
 case of mallards emd black ducks, the figures are corrected to compensate for bcinding during 
 the hvuiting season mid- way down the fly way. 
 
 17 
 
Table 9. --Per cent of mallards banded at I<al^e Chautauqua, 1939-1944, bagged in year 
 of banding, as determined by band recoveries. 
 
 Year of 
 Banding 
 
 Nximber of 
 Mallards Banded 
 
 Per Cent of Banded Mallards 
 Bagged in Year of Bcinding* 
 
 1939 
 
 3,474 
 
 8.6 
 
 1940 
 
 5.840 
 
 14.9 
 
 1941 
 
 4,834 
 
 6.7 
 
 1942 
 
 6,854 
 
 12.6 
 
 1943 
 
 6,445 
 
 10.2 
 
 1944 
 
 3,465 
 
 11.1 
 
 ♦ Corrected to compensate for time and place of banding: during the hunting season 
 and halfway down the flyway. Not corrected to compensate for bands not reported. 
 
 Of particular note is the finding that yearly variations in rate of mallard loss were 
 somewhat similar at the two banding stations, about 175 miles apart. There was also simi- 
 larity in trends in the year-to-year percentage losses in the mallard, the black duck, and even 
 in the early migrating blue-winged teal. 
 
 The lowest rates of hunter-bag losses in mallards occurred in 1939, 1941, 1943, and 
 1947. The highest were in 1940, 1942, 1944, 1945, and 1946. The bag in the period 1944-1947 
 averaged about 1.5 per cent more per year than it did in the period 1940-1943. 
 
 Table 10. — Per cent of mallards banded at McGinnis Slough, 1940-1947, bagged in 
 year of banding, as determined by band recoveries. 
 
 Year of 
 
 Number of 
 
 Per Cent of Banded Mallards 
 
 Banding 
 
 Mallards Banded 
 
 Bagged in Year of Banding* 
 
 1940 
 
 483 
 
 13.7 
 
 1941 
 
 312 
 
 8.3 
 
 1942 
 
 1,882 
 
 13.3 
 
 1943 
 
 3,009 
 
 8.8 
 
 1944 
 
 1,778 
 
 15.7 
 
 1945 
 
 2,287 
 
 14.7 
 
 1946 
 
 1,634 
 
 12.9 
 
 1947 
 
 973 
 
 6.2 
 
 ♦ Corrected to compensate for time and place of banding: during the hunting season 
 and halfway down the flyway. Not corrected to compensate for bands not reported. 
 
 18 
 
Table 11. — Per cent of black ducks bemded at McGinnis Slough, 1940-1945, bagged in 
 year of banding, as determined by band recoveries. 
 
 Year of 
 Banding 
 
 Number of Black 
 Ducks Banded 
 
 Per Cent of Black Ducks Bagged 
 in Year of Banding* 
 
 1940 
 
 123 
 
 12.2 
 
 1941 
 
 659 
 
 7.1 
 
 1942 
 
 1,069 
 
 12.5 
 
 1943 
 
 962 
 
 6.5 
 
 1944 
 
 852 
 
 16.9 
 
 1945 
 
 716 
 
 9.4 
 
 ♦Corrected to compensate for time and place of banding: during the hunting season and 
 halfway down the flyway. Not corrected to compensate for bands not reported. 
 
 Table 12. --Per cent of blue-winged teals banded at McGinnis Slough, 1940-1946, bag- 
 ged in year of banding, as determined by beind recoveries. 
 
 Year of 
 Banding 
 
 Number of Blue-Wings 
 Banded 
 
 Per Cent of Banded Blue-Wings 
 Bagged in Year of Banding* 
 
 1940 
 
 137 
 
 2.2 
 
 1941 
 
 1,233 
 
 1.4 
 
 1942 
 
 1,343 
 
 2.8 
 
 1943 
 
 976 
 
 1.8 
 
 1944 
 
 1,498 
 
 3.6 
 
 1945 
 
 1,065 
 
 2.9 
 
 *Not corrected to compensate for bands not reported. 
 
 EVALUATION OF POPULATION SURVIVAL AND LOSSES 
 
 Available records show that birds live longer in captivity than in the wild state. 
 Flower (1926) reported that the length of life of 20 pintails and widgeons in aviaries was 21 
 years and 5 months, and 5 of the 20 were still alive at the time of his report. Jean Delacour 
 of the American Museum of Natural History (letter, February, 1947) stated that in a well-run 
 aviary there is a yearly loss of 5 per cent of the ducks from illness and another 5 per cent 
 from accidents. The larger species of ducks begin to show signs of old age at 20 years. In 
 the wild, decimating factors are so great that few ducks ever reach senescence. Fronn the 
 tens of thousands of wild mallards banded, Cooke (1942, 1943) listed the length of life of the 
 four individuals living the longest from banding to reported death as 8,8, 10, and 14 years. 
 
 19 
 
Do Mississippi flyway mallards and black ducks lead a more hazardous life than other 
 birds? Mortality rates for several species recently studied are given in table 13. It is evident 
 
 Table 13. — Mortality rates for various bird populations as determined by recent 
 studies. 
 
 
 Mortality Rate, Per Cent 
 
 
 Bird Population 
 
 Year of Banding 
 
 Subsequent Years 
 
 All Years 
 
 Source** 
 
 Mallard (Chautauqua)* 
 
 55 
 
 39-44 
 
 -- 
 
 Table 1 
 
 Mallard (McGinnis)+ 
 
 -- 
 
 — 
 
 44-49 
 
 Table 5 
 
 
 88 
 
 65 
 
 
 Hohn (1948) 
 Table 6 
 
 Black duck (McGinnis) 
 
 
 
 48-66 
 
 Blue-winged teal (McGinnis)- 
 
 -- 
 
 — 
 
 51-67 
 
 Table 7 
 
 
 74 
 
 56-66 
 
 — 
 
 Hcinson & Smith 
 (1950) 
 
 
 
 -- 
 
 -- 
 
 50-58 
 
 Bump et al. 
 (1947) 
 
 
 Ring-necked pheasant 
 
 70 
 
 70 
 
 — - 
 
 Leopold et al. 
 (1943) 
 
 Ring-necked pheasant 
 
 74-81 
 
 56-65 
 
 — 
 
 Buss (1946) 
 
 
 60 
 
 29-48 
 
 — 
 
 Marshall (1947) 
 
 
 
 53 
 
 53 
 
 
 Farner (1945) 
 Hann (1948) 
 
 Oven-bird -- 
 
 45 
 
 46 
 
 — 
 
 ♦Juvenile males. +A11 ages and sexes. **Tables referred to are those in this 
 
 paper. 
 
 that these mallards and black ducks, even though experiencing heavy shooting pressure, do not 
 suffer from exceptionally high mortality rates, for the mortality rates are lower than for some 
 other game birds and not much higher than for the protected herring gull, the robin, or the 
 oven-bird. Mallards studied by Hohn (1948) in England had a much higher mortality rate than 
 that found in the present study, for North American mallards. The year-of-banding mortality 
 rate of 88 per cent in mallards banded as young in England was three-fifths greater thein that 
 of male mallards banded as juveniles at Lake Chautauqua. The mortality rate among adult- 
 banded mallards the year of banding in England was two-thirds greater than the mortality rate 
 among adult-banded male mallards the year of banding at Lake Chautauqua. 
 
 It is well recognized that blue-winged teals do not suffer as heavy hunting losses as 
 do Mississippi flyway mallards. Hiuiting seasons open so late in the United States that most of 
 these teals have departed for southern regions by the opening dates. Yet despite low gunning 
 losses, table 12, the blue-winged teal had higher annual mortality losses than the mallard. 
 Ring-necked pheasants (Leopold^ al. 1943, Buss 1946) that were fully or partially protected 
 from hunting had a higher mortality rate than shot mallard populations, table 13. Canada geese 
 in the Horseshoe Lake region of southern Illinois, 1940-1947, xinderwent higher losses than did 
 Chautauqua-banded mallards (Hanson & Smith 1950). However, this goose population was so 
 heavily shot that it was undergoing a decline at the time measurements were taken. 
 
 20 
 
The rviffed grouse survival rate from one September to the next averaged 49.8 per 
 cent, 1930-1941, at the Connecticut Hill study area and 42.1 per cent, 1931-1941, at the 
 Adirondack study area (Bump et al. 1947). Mallard males- banded as juveniles at Lake Chau- 
 tauqua had a first-year survival rate of 45 per cent and a subsequent-year survival rate for 
 the next 4 years of 56 to 61 per cent. Mallards of all ages and of all year-classes banded at 
 McGinnis Slough had a yearly survival rate of 51 to 56 per cent the first 5 years after band- 
 ing. 
 
 NATURAL VERSUS SHOOTING LOSSES. --Shooting losses as measured by band 
 recoveries reported from shot ducks furnish worthwhile figures on year-to-year hunting bags, 
 but additional information is needed before these losses can be used as a measure of the total 
 mortality caused by hunting. 
 
 It is evident that a large number of hunters shooting banded ducks fail to report the 
 bands. At the time he wrote, Mcllhenny (1934) believed that "fully 50 per cent" of the banded 
 ducks shot were reported. Leopold (1933) polled a number of game managers and officiails as 
 to their estimate of the percentage of banded ducks taken but not reported; the estimates were 
 as follows: the Carolinas, 80 per cent; Connecticut, 50 per cent; Memphis area (at clubs) 5 per 
 cent, (elsewhere) 10 per cent; Arkansas, 60 per cent. A questionnaire study made in Illinois 
 (Bellrose 1945) indicated that about 25 per cent of the duck bands taken in the state were not 
 reported. 
 
 During the 1948 hunting season the United States Fish and Wildlife Service issued 
 special "reward" bands. These bands, issued for use on mallards and black ducks, were simi- 
 lar to other bands except that they carried a notation of a reward if sent to the Service, We 
 placed 200 "reward" bands alternately with 242 other bands on 442 nnallards at the Spring Lake 
 Wildlife Refuge, Saveinna, Illinois, during late October and early November, 1948. Of 71 re- 
 turns received up to May 1, 1949, 50 were from reward bands. Reward bands were reported 
 about 2.9 times as frequently in proportion to the numbers applied as were non-reward bands. 
 
 Probably not all reward bands taken from shot ducks were reported. However, since 
 the reward bands provide the most nearly accurate figure yet available relative to bands re- 
 ported by hunters, we have used this figure as a correcting factor in some of our calculations. 
 
 Year-of-banding recoveries, corrected for banding during the hunting season, from 
 Illinois -banded mallards ranged fronn 6 to 16 per cent, tables 9 and 10, and averaged about 
 11 per cent. Allowing an additional 190 per cent for bands from mallards bagged but not 
 reported would raise the proportion of the mallard population taken home by hunters to about 
 32 per cent. It should be kept in mind that this correction is based on the 442 birds banded 
 at Savanna, Illinois, and not on the complete recovery list of reward bands issued by the Fish 
 and Wildlife Service to all co-operators. 
 
 Losses through crippling are 2in additional shooting drain that must be reckoned with. 
 Records obtained from interviewing hunters at clubs and public shooting grounds in Illinois, 
 table 14, show a crippling loss that ranges between 18 and 41 per cent of the ducks bagged, de- 
 pending upon the type of shooting. An over-all appraisal of hunters' reports indicates that in 
 
 21 
 
Illinois the knocked-down cripple loss is about 30 per cent of the number of ducks bagged, or 
 about 9 per cent of the total population. It is known that at least a small proportion of these 
 cripples recover; it is also known that, of the ducks shot at but apparently unharmed, many are 
 
 Table 14. --Ratio of cripple loss to bag loss in ducks shot at private hunting clubs and 
 at public shooting grounds in Illinois, 1938-1945. 
 
 Place of Hunting 
 
 Year 
 
 Number Bagged 
 
 Number Crippled 
 
 Ratio of Cripple Loss 
 to Bag Loss 
 
 Private hunting clubs - 
 
 Public shooting 
 grounds- - - - - — - 
 
 1938 
 1941 
 
 1944 
 1945 
 
 3,226 
 2,028 
 
 1,475 
 1,510 
 
 568 
 369 
 
 556 
 612 
 
 17.6:100 
 18.2:100 
 
 37.7:100 
 40.5:100 
 
 so severely wounded that they soon die. These two factors tend to counterbalance each other, 
 cind, in the absence of nnore detailed inforniation, the cripple mortality rate used is that ob- 
 tained by appraising the reports of hunters. The cripple loss of 9 per cent added to the pro- 
 portion of mallards bagged, 32"per cent, brings the calculated total jinnual shooting losses of 
 Mississippi flyway mallards up to 41 per cent of the population in the period 1939-1947. 
 
 The annual mortality rate of five year-classes of mallard drakes banded as adults 
 at Lake Chautauqua averaged about 40 per cent, table 2. The year-of -banding mortality rate 
 for males banded as juveniles was about 55 per cent, table 1. Since age ratios of mjile mallards 
 in the Mississippi flyway, 1939-1947, show that juveniles comprise about half of the male fsill 
 popxilation, then the annual mortality loss in the male population would be about 48 per cent. 
 The mortalities in the female population ajid the entire population would be somewhat higher. 
 
 If shooting losses annually account for 41 per cent of the mallard population, and 
 if the annual mortality is 48 per cent of this population, then natural losses would amount to 
 only 7 per cent. Man is responsible for part of the losses usueilly classed as natural. Inves- 
 tigations on lead poisoning of ducks by James S. Jordan and the senior author, both of the 
 Naturcil History Survey, tentatively indicate that annually 6 per cent of the mallard population 
 in the Mississippi flyway die from this cause. Thus, man appears to be directly or indirectly 
 responsible for most of the yearly mortality losses among Mississippi flyway mallards. 
 
 Our hunting-loss calculations have produced a maiximum figure that is probably too 
 high. An upward distortion in this figure could well have resulted from the high compensation 
 figure (for non-report of bands) in deriving it. 
 
 The black duck has relatively lower hiinting losses but higher total annual mortality 
 rates than the mallard. Calculations based upon the same crippling rate aind the same band-re- 
 turn rate for the black duck as for the mallard show that annual shooting losses for the black 
 duck averaged about 34 per cent and natural losses about 20 per cent of this population. 
 
 From duck species that undergo above-average shooting losses, we turn for com- 
 parison of natural versus hunting losses in the blue-winged teal, a species that probably has 
 smaller h\mting losses thatn any other popular game duck. 
 
 22 
 
Year-of -banding recoveries of blue-winged teals ranged from 1.4 to 3.6 per cent, 
 table 12, and averaged about 2.45 per cent. Since many band recoveries frona shot ducks come 
 from south of the United States, where the incentive to turn in bands is probably not so great as 
 in the United States, the proportion of bands not reported is probably higher in the blue -winged 
 teal than in the mallard. However, lacking specific data, we have used the sanne correcting 
 factor as was used for the mallard--190 per cent.' This brings the yearly hunter-bag of blue- 
 winged teals up to about 7 per cent of the total population of this species. The calculated 
 cripple loss, 30 per cent of the number of blue-wings bagged, or 2 per cent of the total popula- 
 tion, would increase the total annual shooting loss to 9 per cent. 
 
 The yearly mortality rates for the first 5 years following banding averaged about 57 
 per cent for blue-wings, table 7. The shooting mortality accounted for only 9 per cent of the 
 population, leaving 48 per cent of the blue -wings' annuzil mortality to be accoxmted for by 
 natural causes. Although the shooting mortality rate is considerably lower in the blue -wing 
 than in the mallard, the over-all mortality rate is higher in the teal. 
 
 It seems significant that, although the shooting mortality rate is lower in the black 
 duck and the blue -winged teal thain in the mallard, the over-all mortality loss is greatest in the 
 blue-winged teal, next so in the black duck, cuid least in the mallard. It is apparent that shoot- 
 ing losses do not accovmt for all the differences in mortality rates among the three species 
 of ducks. 
 
 Could the mallard ever have had an appreciably lower total mortaility rate than it had 
 for the period 1939-1947? No wild game bird species so far studied has such a low total mor- 
 tality rate, even ring-necked pheasant populations, completely or partially protected. Song 
 birds, much less productive than the m.allard, have comparable annual mortality losses. 
 
 What has enabled the mallard to luidergo heavy shooting losses without suffering 
 higher over-adl mortality rates? 
 
 Every wildlife population lives in an environment of limited carrying capacity. If 
 hunters take the excess population, then the lower population density that results makes the re- 
 maining individuals less subject to predation, disease, food shortages, and other factors that 
 contribute to natural losses. 
 
 It seems reasonable to us to assume that, in the mallard, heavy shooting losses 
 have largely replaced natural losses that would otherwise have occurred to enable the popula- 
 tion to live within the limitations of its environment. The mcillard population has an internal 
 elasticity that allows most of its components, including those that make up natural loss and 
 shooting loss, considerable stretch or shrinkage. But the extent of stretch or shrinkage is 
 limited, and the natural loss can never shrink to zero. Some natural loss nnust be expected, 
 and the shooting loss cannot entirely replace the natural loss. 
 
 The conjecture that game bird populations possess internal elasticity is substcintiated 
 by Bump et al. (1947), who found that although hunting took 17 per cent of the ruffed grouse fall 
 popiilation in New York study areas, the gun increased the total mortality rate by only about 8 
 
 23 
 
per cent, indicating that about half of the number of birds shot would have died before spring 
 from natural causes, if the areas had not been opened to hunting. 
 
 In the 1939-1947 period, the natural loss in the mallard population migrating through 
 Illinois was so small that any marked increase in the kill would undoubtedly have resulted in a 
 proportionate rise in the total mortality. The natural loss had contracted to the point where a 
 stretching of the hunting loss might have had disastrous results. 
 
 If this line of reasoning is valid, the blue-winged tesil and perhaps the black duck 
 could xindergo greater hunting losses without raising their total mortality rates. In this con- 
 nection, it is necessary to consider that the potentizil stretch gind contraction, or "give sind 
 take," between natural mortality and shooting mortality differs in various species of ducks. 
 
 Several wild game species are known to possess a flexible productivity potential of 
 such a nature that they respond to increased mortality with an increase in productivity. 
 
 Bvimp et al. (1947) found that, although hunting increased the mortality rate of 
 ruffed grouse, the flexibility of- the productivity potential tended to overcome this added loss. 
 They found from a correlation of population data between protected and hunted populations that 
 there was a distinct tendency for greater relative increases of young to be associated with lower 
 breeding populations; thus, there was an inverse relationship between the number of grouse in 
 the spring and the proportion of juveniles in the fall population. This population phenomenon has 
 also been demonstrated by Errington (1945) to occur in bobwhites aind by Allen (1943) in fox 
 squirrels. Its wide occurrence in small gajne populations would lead us to suspect that it is 
 present also in waterfowl populations. 
 
 To what extent the flexibility of the mallard's productivity potential could overcome 
 increased mortality in Mississippi flyway populations is at present conjectural. 
 
 The mallard has a high reproductive potential eind appears to be capable of maintain- 
 ing its population under conditions of at least moderately high mortality losses. On the other 
 hztnd, its breeding potential' in the north may be affected by drastic annueil fluctuations in breed- 
 ing habitat, and in certain years, despite the excellent reproductive potential of this species, 
 total numbers may be ciffected by the area available for expression of this potential. 
 
 This paper only opens the door to the subject of population losses in waterfowl. Even 
 where the conclusions appear final, they may be only temporarily so. Future, more extensive 
 studies may reveal, for example, that hunters report more or fewer bands, or that the loss 
 from crippling is greater or less. 
 
 24 
 
SUMMARY 
 
 1. This study of mallard, black duck, and blu6 -winged teal population losses in the 
 Mississippi flyway is based on 10 ,7 18 of these ducks shot and recovered from 51,297 ducks 
 banded at the Chautauqua National Wildlife Refuge or at McGinnis Slough in Illinois. 
 
 2. Because the banding of mallards and black ducks was done during the hunting 
 season and about half way down the flyway, a correction of year -of -banding return- data was 
 made for these species so that the data would be comparable to the return figures in subse- 
 quent years. As most of the blue -winged teals were banded before the hunting season opened, 
 no correction of year-of-bcunding returns was made for these ducks. 
 
 3. The mortality rate in a known age group, mallard drakes banded in the fall as 
 juveniles, amounted to 55 out of 100 birds the first year, or year of banding, 20 the second 
 year, 11 the third year, and 6 the fourth year. By the end of the sixth year, less than 3 of the 
 original 100 were still alive. 
 
 4. The only marked differences in mortality rates among year-classes of mallards 
 was between juveniles and adults. Mallard mortality was about 1-1/2 times as great for juve- 
 nile birds as for older ones; much of the difference resulted because juveniles are more vul- 
 nerable to shooting. 
 
 5. There was a higher mortality rate among mallard hens than among drakes. This 
 higher rate apparently was not caused by hunting; it may have occurred because of natural 
 disasters on the breeding grounds. 
 
 6. Of three species of ducks, mallard, black duck, and blue -winged tecil, banded at 
 McGinnis Slough, the mallard had the lowest mortality rate; it was followed in order by the 
 black duck and the blue -winged teal. 
 
 7. The yearly hunter-bag rates followed a similar pattern for the three species. 
 There was no consistent yearly trend in the hunter-bags, but the annual bag in the period 
 1944-1947 averaged about 1.5 per cent more per year than it did in the period 1940-1943. 
 
 8. Compared to other birds that have been studied for population mortzility, mal- 
 lards have a low rate of mortality. Although the blue -winged teal does not suffer the shoot- 
 ing losses that mallards do, its mortality rate is higher. 
 
 9. Band recovery data, corrected for proportion of bands unreported by hunters, 
 and with estinnated crippling losses included, indicate that hunters accounted for about 41 per 
 cent of the 48 per cent annual mortality among Chautauqua-banded mallards, 1939-1947. 
 
 10. The high shooting-loss component in the mallard's annual nnortality loss is in- 
 dicative that, during the 1939-1947 period as a whole, the shooting losses probably absorbed a 
 large part of the losses that would have been "natural" in an unshot population. However, be- 
 cause of the small part of the mortality loss left to be absorbed by natural losses, ciny marked 
 increase in the shooting pressure over that occurring during the 1939-1947 period would un- 
 doubtedly have raised the mortality rate. 
 
 25 
 
LITERATURE CITED 
 
 Addy, C. E. 
 
 1945. Massachusetts waterfowl survey. Progress report of P.-R. Project 4-R. 
 
 Mass. Dept. Conservation. 21 pp. 
 
 Allen, Durward L. 
 
 1943 Michigan fox squirrel management. Mich. State Dept. Cons. Game Div. 
 
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 1945. Ratio of reported to unreported duck bands in Illinois. Jour. Wildlife Mgt. 
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 Bump, Gardiner, Robert W. Darrow, Frank C, Edminster, and Walter F. Crissey 
 
 1947. The ruffed grouse. N.Y. State Cons. Dept. 915 pp. 
 
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 1946. Wisconsin pheasant popvilation. Wis. Cons. Dept. Pub. 326, A-46. 184 pp. 
 
 Cooke, May Thatcher 
 
 1942. Returns from banded birds: some longevity records of wild birds. Bird- 
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 1943. Returns from banded birds: some miscellaneous recoveries of interest. 
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 Deevey, Edward S., Jr. 
 
 1947. Life tables for natural poptilations of animals. Quart. Rev. Biol. 22:4, 
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 Errington, Paul L. 
 
 1945. Some contributions of a fifteen-year local study of the northern bobwhite to 
 
 a knowledge of population phenomena. Ecol. Monog. 15:1-34. 
 
 Elton, Charles 
 
 1942. Voles, mice and lemmings. Oxford. 496 pp. 
 
 Farner, Donald S. 
 
 1945. Age groups and longevity in the American robin. Wilson Bui. 57:56-74. 
 
 Flower, Stanley S. 
 
 1926. Contributions to our knowledge of the duration of life in vertebrate animals. 
 
 IV, Birds. Zool. Soc. London Proc. 1925: 1365-1422. 
 
 Hann, Harry W. 
 
 1948. Longevity of the oven-bird. Bird-Banding 19:5-12. 
 
 Hanson, Harold C, and Robert H. Smith 
 
 1950. Canada geese of the Mississippi flyway, with special reference to an Illinois 
 
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 Hohn, E. O. 
 
 1948. Mortality of adult and young naallards. Brit. Birds 41:233-5. 
 
 Lack, David 
 
 1943a. The age of the blackbird. Brit. Birds 36:166-75. 
 
 1943b. The age of sonne more British birds. Brit. Birds 36:193-7. 
 
 1943c^. The age of some more British birds. Brit. Birds 36:214-21. 
 
 Leopold, Aldo 
 
 1933. Game management. Charles Scribner's Sons, New York. 481 pp. 
 
 26 
 
Leopold, Aldo, Theodore M. Sperry, William S. Feeney, and J. S. Catenhousen 
 
 1943. Population turnover on a Wisconsin pheasant refuge. Jour. Wildlife Mgt. 
 
 7:383-94. 
 
 Marshall, Hubert 
 
 1947. Longevity of the American herring gull. Auk 64:188-98. 
 
 Mcllhenny, E. A. 
 
 1934. Twenty-two years of bcinding migratory wild fowl at Avery Island, Louisiana. 
 
 Auk 51:328-37. 
 
 Nice, M. M. 
 
 1937. Studies on the life history of the song sparrow. Vol. 1. A population study of 
 
 the song sparrow. Linn. Soc. N. Y. Trans. 4. 247 pp. 
 
 Paynter, Raymond A., Jr. 
 
 1947. The fate of banded Kent Island herring gulls. Bird-Banding 18:156-70. 
 
 Thompson, David H., and John Jedlicka 
 
 1948. A method for correcting kill estimates from waterfowl banded during the hunt- 
 ing season. Jour. Wildlife Mgt. 12:433-6. 
 
 27 
 
Mi 
 
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