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Investigating the causes of the decline of the urban House Sparrow (Passer domesticus) population in Britain Dr. KATE VINCENT (DE MONTFORT UNIVERSITY)

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Presentation on theme: "Investigating the causes of the decline of the urban House Sparrow (Passer domesticus) population in Britain Dr. KATE VINCENT (DE MONTFORT UNIVERSITY)"— Presentation transcript:

1 Investigating the causes of the decline of the urban House Sparrow (Passer domesticus) population in Britain Dr. KATE VINCENT (DE MONTFORT UNIVERSITY)

2 Outline of talk Background Fieldwork Key results Summary of findings

3 Why research on House Sparrows? Major declines in rural, urban and suburban habitats  65% decline between 1974-2000  Red data listed (RSPB)  decline in some European cities  London (-90%), Edinburgh (-80%), Hamburg (- 69%)  Oct 2000 Tony Blair - speech on the environment

4 There was no shortage of sparrows in London in the 1920’s

5 Possible causes of decline: theories put forward Predation Lack of nest sites Disease Lack of food (inverts in summer/seed in winter) possible link between pollution and invertebrate abundance



8 Methodology Nestboxes along urban gradient Record nesting success Investigate diet and invertebrate abundance L.C.C. - pollution data

9 Location of study sites

10 Fieldwork Census/survey at 9 study sites No. boxes used = 100 [500+ chicks ringed]  Monthly foraging obs. in 44 locations

11 Fieldwork Provisioning watches - 55 completed Habitat mapping around used boxes Aphid abundance in home ranges Over-winter survival

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

13 Provisioning watch methodology No. visits to box & food type fed Each watch lasted 1hr 30mins 55 watches completed

14 Foraging Observation methodology Does foraging change across season/area type? Initial visit recorded habitat type –using a 13 habitat category system

15 Foraging Observation methodology Made monthly visits to 44 transects Recorded no. of adults/juvs and habitat

16 Habitat Mapping methodology Compare habitat around all used boxes Used 13 habitat category system Took radius of 70m around each nest (80-100 gardens in suburbia)

17 Aphid abundance 0-50m & 50-100m from box randomly selected 20 shrubs, 20 trees, 15 veg, 30 flowers (in both areas) scoring system 0 to 3 (0 = no aphids, 3 = infested) sampled 10 points on shrub/tree to give average

18 Key Results Diet of nestlings Productivity/nesting success Chick condition Habitat utilisation/selection

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

20 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

21 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

22 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


24  = 70% : 14 day chick period     IIIIIIIIIIII  = 20% : 14 day chick period IIII

25 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

26 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

27 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


29 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%

30 Summary of key findings 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

31 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

32 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

33 For further information on all my research and findings & to download my thesis online visit:

34 A BIG THANKYOU TO RSPB, EN & DMU (for funding) 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 Denis Summers-Smith

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