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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
• 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
0.09
0 0.2 0.4 0.6 0.8 1proportion of plant material in diet
pre
dic
ted
da
ily w
ho
le n
est
failu
re r
ate
2002 2003
= 70% : 14 day chick period I
I
I
I
I
I
= 20% : 14 day chick period
I
I
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
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