Should Apprentice Falconers be Allowed to Fly American Kestrels?

(What the Data Says)


Matthew Mullenix &

Brian A. Millsap

 

Tiercel American Kestrel, photo by Craig Golden

 

INTRODUCTION
As falconers, we tend to develop opinions of the sport and our peers based on events and situations encountered in daily life. These experiences, or those lived vicariously through stories of others, mold our attitudes and beliefs about how falconry should be practiced. This process is an important part of the tradition of falconry and rightly shapes much of how the sport is practiced today. However, if based on a narrow range of experiences or faulty logic, these opinions can become millstones around our collective necks.
What choice do we have but to base our positions on personal or anecdotal experience? An obvious alternative is the use of data, i.e. information collected, recorded, and analyzed in an objective, systematic way. As falconers who have worked in a state wildlife agency that regulates falconry, we have witnessed instances where we believe the sport could have benefitted by a data-based view of an issue rather than the perspective afforded by individual experience. A recent example is the issue of whether apprentice falconers should fly American kestrels (Falco sparverius). Here we use this controversy to illustrate how data can help evaluate a real world falconry question in a more objective manner.
 
BACKGROUND
Kestrels, particularly the Eurasian kestrel (F. tinnunculus), have been long associated with the sport of falconry, serving as the traditional bird for novice practitioners (Ford 1992). During the sport's revival in the United States, the smaller American kestrel was considered an ideal analog of its Eurasian relative and was generally recommended for use by the apprentice (Beebe and Webster 1964). When the federal regulations regarding falconry were promulgated in 1976, American kestrels were listed as one of three species (along with redtail [Buteo jamaicensis] and red-shouldered [B. lineatus] hawks) allowed licensed apprentice falconers.
Since that time, concern has surfaced among some falconers that the diminutive size and relatively delicate nature of the American kestrel make it unsuitable for use by the novice. It is a common belief among falconers that the smaller the species flown, the smaller the margin of error becomes particularly with regard to the raptor's weight control and equipment design. Apprentice falconers are considered by some insufficiently experienced to maintain such a small bird in good health, particularly when the larger and presumably more robust redtail hawk is available.
This sentiment was shared by a number of experienced falconers practicing in Florida. Ultimately, based on the opinions of this group, the matter was brought to the attention of the Florida Game & Fresh Water Fish Commission in the form of a proposal to delete kestrels as legal birds for apprentice falconers. The FG&FWFC adopted this proposal at its March 1992 meeting, and the rule became effective April 14, 1992.
Our purpose here is not to chastise those falconers who encouraged the change in law. To the contrary, it is admirable that a group of falconers would care so much about the birds we fly that they would seek to impose restrictions upon themselves to protect that resource. What we are interested in, however, is the basis for the opinion that apprentice falconers lack sufficient skill to provide adequate care for small raptors and also discovering whether this use has any significant impact on the resource. With these objectives in mind, we set out to determine the facts.
 
DATA AND APPROACH
Whether kestrels suffer substantially greater mortality under falconry management than redtail hawks can be evaluated empirically using data provided through mandatory falconry reports. We reviewed published annual reports on harvest and disposition of raptors held for falconry in three active falconry states with good record keeping systems (Idaho, New Mexico, & California) between the years of 1971 and 1985. These are the only states where apprentice falconers may fly both species and for which we could find published harvest/disposition records. We incorporated in this analysis mortality rates of wild individuals of both species based on band recovery data from the published literature.
 
FINDINGS
Our analysis included information on the disposition of 1017 redtail hawks and American kestrels harvested for falconry (Table 1). Combined 445 (43.8%) individuals were lost or released to the wild, 50 (4.9%) died, and 522 (51.3%) were presumably maintained in captivity.
The raw mortality rate of American kestrels under falconry management (7.7%) was slightly higher than that for redtail hawks (4.3%). This difference was significant in that the probability of seeing a chance difference this great in a sample of this size drawn from two populations with equal mortality rates would be less than 7%. We conclude from this that the difference in mortality rates of redtail hawks and kestrels under falconry management was real and not an artifact of the analysis.
That said, there is still a matter of considering whether or not a 3.4% difference in survival between the two species in captivity is biologically meaningful. There is a general trend among raptors for smaller species to have higher annual mortality rates than larger species (Newton 1979). Indeed, analysis of band recovery data from throughout North America yielded estimates of first year mortality for wild American kestrels of 67% (Henny 1972) and for first year redtail hawks of 64% (Henny and Wright 1972). These authors used a life table method to calculate these mortality rate estimates, and this methodology can produce biased and misleading results (Anderson et al. 1981). For this reason, we are cautious about placing too much emphasis on the band recovery estimates, but they do support the general trend reported by Newton (1979). Taken together, we believe the available data supports a conclusion that the relative difference in mortality among first-year kestrels and redtail hawks is similar in both wild and captive populations.
 
WHAT DOES IT MEAN?
We conclude that there is no evidence of meaningfully higher mortality for American kestrels than for redtail hawks under falconry management, considering inherent differences that appear to exist in survival rates of these species in the wild. Additionally, mortality rates under falconry management appear to be substantially less than in the wild for both species.
We readily admit that this data might be flawed, particularly considering the small sample sizes, but the flaws do not necessarily invalidate our conclusions. First, the reports on mortality under falconry management might include improperly reported results and missing data. However, we see no reason why the effect of reporting errors would not be the same for both species, in which case the bias would be inconsequential. Second, we have no way of knowing how many of the American kestrels and redtail hawks included were held by apprentice falconers as opposed to falconers in other classes. We suspect that apprentices held many birds of both species, but again, any bias in this regard would likely apply equally to both species. Finally, as we have already acknowledged, the data on mortality rates in the wild are of questionable accuracy and precision. However, as we noted earlier, even if first-year mortality in the wild is equal between these two species, we question whether the observed difference in mortality under falconry management is of any real consequence.
Going into this analysis, we expected to find support for the position that kestrels were indeed more difficult birds to manage in falconry than redtail hawks and that this difficulty would be reflected in higher rates of captive mortality. Though we found some evidence to this effect, we do not believe the difference is significant in terms of practical falconry or resource management. One lesson this exercise has driven home to us is that it is risky to base regulatory decisions on personal opinions alone. This is particularly important when you consider that wildlife management agencies have little reason to regard the opinions of falconers over those of bird watchers, animal rights advocates, or gun hunters. The great equalizer in scientific debate is good information, and we cannot help but believe that falconry would benefit from increased application of the scientific method in its practice and regulation. To this end, we suggest that the falconry community support the collection of appropriate data that can be used to objectively evaluate such basic questions as the impact of wild harvest on raptor populations and post release survival rates of falconry birds. Our sport may well be the environmentally responsible, ecologically sound activity we claim it to be, but without the data to support this, ours is merely one opinion among many.
 
ACKNOWLEDGMENTS
We would like to thank Colonel Kent Carnie, Curator of the Archives of American Falconry, for his assistance in locating the published data used in this article. Jennifer Coulson, Tom Coulson, and Tim Breen made helpful comments on an earlier draft of this article.
 

Table 1. Disposition of American kestrels and redtail hawks taken for falconry in New Mexico (1971 - 1980), California (1978, 1980), and Idaho (1980 - 1985)

 Species - State  Number lost/released  Number died  Total in possession
 American kestrel
 New Mexico

9

3

14

 California

90

10

174

 Idaho

5

2

7

 Total

104 (53.3%)

15 (7.7)

195

 Redtail hawk
 New Mexico

18

6

30

 California

308

28

762

 Idaho

15

1

30

 Total

341 (41.5%)

35 (4.3%)

822

 
LITERATURE CITED
Anderson, D. R., A. P. Wywialowski, and K. P. Burnham. 1981. Tests of the assumptions underlying life table
methods for estimating parameters from cohort data. Ecology 62:1121-1124
Beebe, F. L., and H. M. Webster. 1964. North American Falconry and Hunting Hawks. 1st edition. Wingsong Press,
Denver, Colorado, USA.
Ford, E. 1992. Falconry Art and Practice. The Bath Press, London, England.
Henny, C. J. 1972. An analysis of the population dynamics of selected avian species. U.S. Department of the Interior,
Fish and Wildlife Service, Wildlife Research Report 1.
Henny, C. J., and H. M. Wight. 1972. Population ecology and environmental pollution: red-tailed and Cooper's
hawks. Pages 229-250 in Population ecology of migratory birds, a symposium. U.S. Department of the Interior,
Fish and Wildlife Service, Wildlife Research Report 2.
Newton, I. 1979. Population ecology of raptors. Buteo Books, Vermillion, SD, USA.
 
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