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Reproductive success of house sparrows along an urban gradient

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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  1. Reproductive success of house sparrows along anurban gradient Kate Vincent (BSG), Will Peach (RSPB), Jim Fowler (DMU) & Phil Grice (NE)

  2. Methodology • Fieldwork • Key results • Summary of findings

  3. Study City - Leicester City in the middle of England Population approx 285, 000 10th largest city in England

  4. Methodology • Productivity along urban gradient (nest boxes; urban/suburban/rural) • Investigate diet and invertebrate abundance • Used local pollution data

  5. Fieldwork • 9 study sites (nest boxes/surveys)

  6. Fieldwork • Nestboxes used = 100 [500+ chicks ringed] • Monthly foraging observations in 44 locations – to establish habitat use

  7. Fieldwork • Habitat mapping around used boxes • Aphid abundance in home ranges • Over-winter survival – colour-ringed adult birds

  8. Biometrics/Nesting success • Weight • Tarsus length • Fat score • Muscle score • Faecal samples (400+) • Colour ringing

  9. 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

  10. 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)

  11. Aphid abundance • 0-50m & 50-100m from box • selected 20 shrubs, 20 trees, 15 veg, 30 flowers • scoring 0 to 3 (none to infested)

  12. Key Results • Productivity/nesting success • Diet of nestlings • Chick condition

  13. Diet composition (175 samples from 2001, 2002 & 2003) Thanks to Del Gruar for helping analyse samples

  14. 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

  15. 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

  16. 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

  17.  = 70% : 14 day chick period     I I I I I I  = 20% : 14 day chick period I I

  18. 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

  19. Productivity • Mean no. fledged per attempt • suburban = 1.98 BTO = 2.6 • rural = 2.37 BTO = 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

  20. 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

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

  22. 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

  23. 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

  24. 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

  25. 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

  26. 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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