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of young kestrels
Results summary - 1979-2003
kestrel summaries - Scotland
Summary of 25 years of Ayrshire Data
Based upon 660
breeding records where the outcome was known.
- Nesting territory
occupancy ranged annually from 44 to 85%.
- Productivity was
high in line with other small/medium sized raptors but there was considerable
annual variation in output.
- Clutch sizes
ranged from 3 to 8, the vast majority being in the 4 – 6 bracket with rarely
7s and one . In 533 clutches the average clutch size was 5 eggs.
- 87% of the nest
failures occurred at the pre laying and clutch stage, mostly due to desertion.
- The kestrel was
single brooded but occasionally a pair relayed a clutch of eggs if the failure
was at an early stage of the incubation period.
- The earliest egg
laying date recorded was 17 March but normally very few hens laid in that
month. The majority of first egg laying dates were in the second half of
April. Few clutches were started after mid-May.
- 74% of eggs laid
- Brood survival in
the nest is exceptionally high ranging from 73 – 100% annually. Average 88%.
- Early breeders
produce larger clutches and rear more young than pairs which begin the nesting
- Over the period
the average young produced per nesting attempt (including failures) was 2.9%
of nesting attempts failed.
- Consistent spells
of good or bad weather had a major effect on productivity.
- In upland areas
there was a direct correlation between low vole years and lower production of
fledged young and peak vole years when productivity was high.
DISPERSAL & MIGRATION