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

Outline of talk Background Fieldwork Key results Summary of findings

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

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

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

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

Location of study sites

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

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

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

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

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

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

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

Aphid abundance 0-50m & m 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

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

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

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

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

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

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

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

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

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

Habitat utilisation/selection 227 transects 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%

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

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

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 (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