Reproductive success of house sparrows along anurban 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

10th largest city in England

Methodology

• Productivity along urban gradient

(nest boxes; urban/suburban/rural)

• Investigate diet and invertebrate abundance

• Used local pollution data

Fieldwork

• 9 study sites (nest boxes/surveys)

Fieldwork

• Nestboxes used = 100 [500+ chicks ringed]

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

Fieldwork

• Habitat mapping around used boxes

• Aphid abundance in home ranges

• Over-winter survival – colour-ringed adult birds

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/juveniles 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

• Productivity/nesting success

• Diet of nestlings

• Chick condition

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

0.09

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

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

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

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

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