RACING PIGEONS â IMPACT OF RAPTOR PREDATION

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Estimates of potential peregrine kills of Scottish racing pigeons derived from the DFI-based calculations Of the eight parameters, four could be quantified with some accuracy (Table 3), while the remaining four could only be estimated within wide bounds (Table 4). For these latter four parameters, the probable upper and lower limits within which realistic values were likely to lie were estimated. Distributions based around these upper and lower limits were then used in a series of 375 simulations to examine the uncertainty inherent in using this approach to estimate loss. This analysis produced a very wide range of estimates for total loss but indicate that the figure is likely to lie between 7,820 (2.3%) and 117,581 (34.5%) Scottish racing pigeons. The distribution of the estimates is highly skewed to the left, i.e. toward lower numbers of potential kills (Figure 3). These estimates would also include stray birds. This analysis illustrates the high degree of uncertainty associated with the use of these figures. Given this high range of uncertainty we believe it would be unwise to attribute any significance to any specific values within the range of estimates derived. However, it may be possible to refine these parameter estimates in future to reduce the inherent uncertainty in this approach, and hence narrow the range of estimates produced. Table 3. Values for the four parameters which could be quantified with some accuracy used in a series of DFI-based simulations to estimate the potential number of Scottish racing pigeons killed by peregrines. Parameter Category Value Number of peregrines Breeding pairs 630 Non-breeding pairs 65 Single 348 Young (dependent) * 1390 Young (independent) ** 834 Daily food intake (g/day) of Adult 188 Young (dependent) 222 Young (independent) 188 Days present *** Adult 183 Young (dependent) 56 Young (independent) 85 Mean weight of domestic pigeon (g) 375 */** Assumes a mean of 2 young hatched per territorial pair and all surviving for 14 days but then numbers of young decreased through brood reduction to a mean of 1.2 young per territorial pair fledged. *** Number of days that adult and young peregrines are present during the 183 day racing pigeon season. 108
Table 4. Values for the four parameters whose accuracy was uncertain but nonetheless used in a series of DFI-based simulations to estimate the potential number of Scottish racing pigeons killed by peregrines. Parameter Values used in the analysis % peregrine diet that is pigeon derived from prey remains * 31, 45, 57, 65, 77 Correction factor for over-representation of pigeon in prey remains ** 0.60, 0.70, 0.83 % of all pigeons killed that are racing pigeons ** 50, 60, 70, 80, 92 % of all racing pigeons killed that are estimated to be Scottish birds * 37, 50, 63, 75, 88 * minimum and maximum value from empirical data ** maximum value only from empirical data Number of DFI-based estimates 90 80 70 60 50 40 30 20 10 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 Potential peregrine kills of Scottish racing pigeons (x10,000) Figure 3. Frequency distribution of the estimates derived from DFI-based calculations of the potential number of Scottish racing pigeons killed by peregrines throughout Britain during the racing pigeon season. 109
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RACING PIGEONS - IMPACT OF RAPTOR P
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CONTENTS PAGE 1. EXECUTIVE SUMMARY
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6.3 DETERRENTS USED IN OTHER CIRCUM
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OB=48). Collectively, however, the
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• The risk of sparrowhawk predati
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1.5 REVIEW OF DETERRENTS • A revi
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• Overall reported losses to spar
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2. INTRODUCTION 2.1 BACKGROUND Pere
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During the Second World War (1939-4
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Table 2.1. Changes in the peregrine
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website, 2002). In South Wales, Dix
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2.5.2 Sparrowhawk Diet Sparrowhawk
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In 1996 a total of 34,685 birds fro
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Dixon (2002) also estimated the num
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more likely to follow natural featu
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3. TOTAL REPORTED LOSSES FROM SCOTT
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3.3a). The circumstances of losses
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Figure 3.2. Location of lofts used
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Table 3.3 Regional comparison of ol
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would be expected as a consequence
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p>0.05), although at the Federation
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Ayrshire Loft 25 20 15 10 5 0 1981
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4. REPORTED LOSSES TO SPARROWHAWKS
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Table 4.1. Summary of reported loss
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Table 4.2. Comparison of reported l
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irds, a mean of 0.91 birds per loft
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5. LOSSES TO PEREGRINES AWAY FROM L
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Figure 5.1. Regional distribution o
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crags were also examined unless it
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also died between the time of the r
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5.2.3 Discussion It was always reco
Page 66 and 67: 5.4 ESTIMATE OF POTENTIAL STRAYS 5.
Page 68 and 69: Figure 5.5. Principal race routes f
Page 70 and 71: 5.4.3 Discussion The rate of potent
Page 72 and 73: These 86 questionnaire returns were
Page 74 and 75: Table 6.2. Frequency of multiple lo
Page 76 and 77: within the area of application. The
Page 78 and 79: Table 6.6. Management techniques wh
Page 80 and 81: 1986). Peregrines in Britain, likew
Page 82 and 83: pitched wail and may illuminate at
Page 84 and 85: development to ensure that the chem
Page 86 and 87: deterrents were regularly moved and
Page 88 and 89: located at another loft) and two un
Page 90 and 91: other stimuli. Essentially, the mor
Page 92 and 93: 7. FIELD TRIALS OF RACE DETERRENTS
Page 94 and 95: Table 7.1. Return rates of racing p
Page 96 and 97: 8. CONCLUSIONS AND RECOMMENDATIONS
Page 98 and 99: 9. FUTURE RESEARCH Accurate recordi
Page 100 and 101: Trials of loft-based deterrents The
Page 102 and 103: Conover, M.R. 1979. Response of bir
Page 104 and 105: Inglis, I.R. 1980. Visual bird scar
Page 106 and 107: Nicolaus, L.K., Herrera, J., Nicola
Page 108 and 109: Toyne, E.P. 1998. Breeding season d
Page 110 and 111: pigeons are available to peregrines
Page 112 and 113: Daily Food Intake (DFI) Redpath & T
Page 114 and 115: Reliability of the available data T
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