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Reproductive success of house sparrows along an urban gradient. Kate Vincent (BSG), Will Peach (RSPB), Jim Fowler (DMU) & Phil Grice (NE). Methodology Fieldwork Key results Summary of findings. Study City - Leicester. City in the middle of England Population approx 285, 000

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Reproductive success of house sparrows along an urban gradient

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Reproductive success of house sparrows along an urban gradient l.jpg

Reproductive success of house sparrows along anurban gradient

Kate Vincent (BSG), Will Peach (RSPB), Jim Fowler (DMU) &

Phil Grice (NE)


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  • Methodology

  • Fieldwork

  • Key results

  • Summary of findings


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Study City - Leicester

City in the middle of England

Population approx 285, 000

10th largest city in England


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Methodology

  • Productivity along urban gradient

    (nest boxes; urban/suburban/rural)

  • Investigate diet and invertebrate abundance

  • Used local pollution data


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Fieldwork

  • 9 study sites (nest boxes/surveys)


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Fieldwork

  • Nestboxes used = 100 [500+ chicks ringed]

  • Monthly foraging observations in 44 locations – to establish habitat use


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Fieldwork

  • Habitat mapping around used boxes

  • Aphid abundance in home ranges

  • Over-winter survival – colour-ringed adult birds


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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/juveniles 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

  • Productivity/nesting success

  • Diet of nestlings

  • Chick condition


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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    

I

I

I

I

I

I

 = 20% : 14 day chick period

I

I


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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

  • NO2 levels =  brood mass at fledging

    •  post-fledging survival

    • fledging in  polluted areas = survival disadvantage


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Mean brood body mass at fledging against nitrogen dioxide in 2002 and 2003


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Relative abundance of aphids within 100m of nests during June and July 2003.

Aphid scores are grouped into four reflecting low (0) to high (3) relative abundance


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Summary

  • No. fledging & brood biomass  in home ranges with  grass/deciduous shrubs/trees

    • suggests invertebrate availability sensitive to habitat quality

  •  fledged from broods fed a plant-dominated diet

    • evidence linking vegetable dominated diet with complete brood failures

  •  chick starvation during June/July not been reported before

  •  NO2 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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