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

• Methodology

• Fieldwork

• Key results

• Summary of findings

Methodology

• Record nesting success along gradient

• Investigate diet and invert. abundance

• L.C.C. - pollution data

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

Biometrics/Nesting success

• Weight • Tarsus length• Fat score • Muscle score• Faecal samples (400+) • Colour ringing

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

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)

Aphid abundance

• 0-50m & 50-100m from box

• selected 20 shrubs, 20 trees, 15 veg, 30 flowers

• scoring 0 to 3 (none to infested)

Key Results

• Diet of nestlings

• Productivity/nesting success

• Chick condition

• Habitat utilisation/selection

Diet composition (175 samples from 2001, 2002 & 2003)

Others5%

Larvae 5%

Flies14%

Spiders11%

Ants8%

Hymenoptera2%

Aphids35%

Beetles20%

Thanks to Del Gruar for helping analyse samples

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

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

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

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

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0 0.2 0.4 0.6 0.8 1proportion of plant material in diet

pre

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ate

2002 2003

= 70% : 14 day chick period I

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= 20% : 14 day chick period

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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

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

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

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%

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

NO2 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

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