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An investigation in to the breeding biology and nestling diet of the House Sparrow in urban Britain Dr Kate Vincent, Dr Will Peach and Dr Jim Fowler
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Methodology Fieldwork Key results Summary of findings
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Methodology Record nesting success along gradient Investigate diet and invert. abundance L.C.C. - pollution data
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Fieldwork Census/survey at 9 study sites No. boxes used = 100 [500+ chicks ringed] Monthly foraging obs. in 44 locations Provisioning watches - 55 completed Habitat mapping around used boxes Aphid abundance in home ranges Over-winter survival
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Biometrics/Nesting success Weight Tarsus length Fat score Muscle score Faecal samples (400+) Colour ringing
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Foraging Observations Does foraging change across season/area type? Initial visit recorded habitat type Made monthly visits to 44 transects Recorded no. of adults/juvs and habitat
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Habitat Mapping Compare habitat around all used boxes Used 13 habitat category system Took radius of 70m around each nest (80-100 gardens in suburbia)
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Aphid abundance 0-50m & 50-100m from box selected 20 shrubs, 20 trees, 15 veg, 30 flowers scoring 0 to 3 (none to infested)
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Key Results Diet of nestlings Productivity/nesting success Chick condition Habitat utilisation/selection
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Diet composition (175 samples from 2001, 2002 & 2003) Thanks to Del Gruar for helping analyse samples
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Nestling Diet Spiders, Aphids, Diptera & Beetles = 80% of all remains Beetles & Diptera prominent in April/May Aphids most prominent in June Ants most prominent in July/August
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Nestling Diet Aphids - urban>suburban>rural broods Diptera - rural>suburban>urban broods ants in broods that died plant material during July/August & in broods that died
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Productivity/nesting success No. fledged late summer No. fledged in home ranges with grass/deciduous shrubs/trees & concrete. No. fledged from broods fed a plant-dominated diet High rate of chick starvation in June/July
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= 70% : 14 day chick period IIIIIIIIIIII = 20% : 14 day chick period IIII
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Brood survival Suburban nests = 75% (whole nest period) Rural nests = 78% All habitats BTO (2002) = 96.5% Lack of food causing complete or partial brood failure –inadequate provision of food poor quality habitat –provision of unsuitable food nutritional deficiency/starvation
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Productivity Mean no. fledged per attempt –suburban = 1.98BTO = 2.6 –rural = 2.37BTO = 2.9 Seasonal Productivity –4.21 young per year (suburban) –4.67 young per year (rural) –Oxford 1990s study = 5.68 productivity in this study is low due to high complete/partial brood failures
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Chick condition chicks fed beetle had higher body condition indices grass, deciduous shrubs & trees, concrete = brood biomass invert availability is sensitive to the habitat quality around nest NO 2 levels = brood mass at fledging – post-fledging survival –fledging in polluted areas = survival disadvantage
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Habitat utilisation/selection 227 transects - 4555 foraging observations most used = deciduous shrub least = evergreen/ornamental shrub Key habitats = deciduous shrubs, tilled land, grassy areas & trees Monthly effects grass being intensively used in May but less in July In July: urban areas; concrete = 50%
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Summary No. fledging & brood biomass in home ranges with grass/deciduous shrubs/trees suggests invert. availability sensitive to habitat quality fledged from broods fed a plant-dominated diet evidence linking veg. dominated diet with complete brood failures chick starvation during June/July not been reported before NO 2 levels = lower brood mass at fledging
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Conclusions nestling survival rate & no. young fledging are low links between; –poor habitat quality/insect availability/nestling diet/brood condition indicates direct effect of food limitation during the breeding season causing productivity in suburbia
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Conclusions productivity demographic mechanism causing decline demographic model - test if productivity levels are low enough to cause declines incorporated suburban & rural productivity levels and known survival rates (adult, first- year, post-fledge) showed suburban productivity is low enough to cause 10% decline p.a
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A BIG THANKYOU TO RSPB, EN & DMU Dr Will Peach & Dr Jim Fowler Derek Gruar (RSPB) Phil Grice (EN) All RSPB research assistants CJ Wildbird Foods (nestboxes) Householders that have nestboxes Denis Summers-Smith Ken Goodrich & LROS Leicester City Council My website: www.katevincent.org
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