Does Bird Feeding Positively Impact Songbird
Survival?
Dr. David Horn, Associate Professor of Biology, Millikin University
Dr. Travis Wilcoxen, Assistant Professor of Biology, Millikin University
Introduction
• Bird feeding is a popular pastime. In 2011, 53 million
Americans over 16 fed birds and other wildlife and spent
$5 billion on the hobby (USFWS 2012).
• The practice of bird feeding remains one of the least
studied wildlife-management issues in the United States
(Horn and Johansen 2013).
• Since 2005, the Wild Bird Feeding Industry Research
Foundation has been funding studies to answer some of
the hobby’s most important questions.
Introduction
Introduction
Introduction
Introduction
• While scientific studies on the impact of wild bird feeding
have been conducted, several fundamental questions about
the hobby remain.
• Few studies have examined how bird feeding influences
the health of individual birds and may change the overall
bird community (e.g., Brittingham and Temple 1988, Geis
and Pomeroy 1993).
Objective
• We examined how bird feeding impacts abundance of
individual species, bird visits to feeders, health of individual
birds, bird survival, and dependency of birds to feeders.
Study Sites
• The study took place from spring 2011 – spring 2014 at six
forested sites in central Illinois. Sites ranged in size from
120 – 1,500 acres.
• During spring 2011, no feeders were added to any sites to
get baseline estimates of population size and bird health.
After spring 2011, feeders were added to three of the sites,
while the remaining three sites served as controls. Feeders
were removed in summer 2013.
• The food blend used was 50% black-oil sunflower, 18%
white proso millet, 10% safflower, 9% whole peanuts, 7%
medium sunflower chips, and 6% red proso millet.
Study Sites – Fort Daniel Conservation Area
Study Sites – Robert Allerton Park
Methods – Bird Populations
• We conducted point counts to estimate the population size
of birds at forested sites with and without bird feeders.
Methods – Bird Health
• We captured birds in mist nets to examine how bird
feeding influences the health of individual birds.
Methods – Bird Health
• Six areas of bird health were assessed: body condition,
stress, antioxidant levels, nutritional condition, immune
function, and disease.
Methods – Bird Survival
• To assess survival and recruitment of offspring from the
previous summer, we compared recapture rates between
spring 2012 and spring 2013.
Methods – Impact of Removing Feeders
• To assess whether bird feeders promote dependency, we
compared health measures and recapture rates between
spring 2013 and spring 2014.
Results – Bird Populations
• 17 species were used in data analysis including 9 residents
and 8 migrants.
• Population trends of species at sites where bird food was
provided were similar to population trends of species at
sites for which no supplemental food was present.
Results – Seasonal population size estimates for
Tufted Titmouse
Results – Seasonal population size estimates for Bluegray Gnatcatchers
Results – Bird Health
• From spring 2011 – spring 2014, we captured 1,480 birds
from the six study sites combined with 401 (27%) of the
captures being recaptures from previous sampling periods.
Results – Body Condition
• We found that supplemental feeding improves the body
condition index of 5 species and fat stores in 10 species.
Results – Stress
Results – Antioxidant Levels
Results – Nutritional Condition
Results – Survival
• In spring 2012,
– 20% of captures at sites without feeders were recaptures
– 34% of captures at sites with feeders were recaptures
• In spring 2013,
– 8% of captures at sites without feeders were recaptures
– 49% of captures at sites with feeders were recaptures
• In spring 2014,
– 6% of captures at sites without feeders were recaptures
– 8% of captures at sites with feeders previously were
recaptures
Discussion
• The establishment of a feeding station at forested sites
resulted in limited changes in forest-wide population sizes.
• As a feeding station becomes more established, the
maximum number of birds visiting feeders increased until a
plateau was reached. Feeder visits than remained
equivalent in subsequent seasons.
Discussion
• Bird feeding is likely to have localized impacts to the bird
community immediately adjacent to a bird feeding station
as opposed to larger-scale, forest-wide changes.
• Birds from the forested site may use the bird feeders, but
continue to maintain territories/home ranges farther away
from feeders.
Discussion
• When compared to birds at sites without feeders, there are
consistent patterns of birds being in a greater overall
health state when feeders are present.
• Positive health effects include:
– Improved body condition
– Lower stress
– Greater antioxidant capacity
– Greater nutritional condition
– Greater immune function
Discussion
• Bird feeding appears to improve survival and recruitment.
– Feeder sites had increased recapture rates and increased
capture rates of second year birds compared to non-feeder
sites.
• Bird feeding does not appear to promote dependency.
– Health state and survival become equivalent to sites
without feeders after feeders are removed.
Discussion
• While some negative effects of bird feeding were also
found, these effects can be mitigated.
– Attraction of unwanted bird species may be mitigated by
switching food types.
– Increased disease prevalence may be mitigated by altering
feeder cleaning regime.
Importance of Study
• This study is the first to examine the effects of wild bird
feeding on bird populations, feeder visits, individual health,
survival, and dependency of a broad range of species
across multiple seasons.
• Studies such as this can and have been used to develop
scientifically-based recommendations that lead to a better
bird-feeding experience.
Acknowledgments
• Support for this study was provided by Wild Bird Feeding
Industry Research Foundation, The Scotts Company,
Siemer Enterprises, Millikin University, Decatur Audubon
Society, Illinois State Academy of Science, and Sigma Zeta.
• We thank Rebekah Carlson, Jared Cerny, Kelly Commons,
Mike Dixon, Joey Flamm, John Griesbaum, Danny Guerra,
Dave Herzog, Jim Hines, Brianna Hogan, Cody Hubble,
Sarah Huber, Steve Huss, Stacey Johansen, Madeline
Knott, Lisa Lundstrom, Paul Marien, Jim Nichols, Abby
Robertson, Faaria Salik, Sam Wassenhove, and Scott
Wiegel for their assistance with this study.
Questions
Dr. David J. Horn
Millikin University
217-424-6392, dhorn@millikin.edu
WBFI Research Foundation
Wild Bird Food & Feeder Test Site
Dr. David Horn, Associate Professor of Biology, Millikin University
Wild Bird Food & Feeder Test Site
• Food & Feeder Test Site would provide independent,
empirical testing of food and feeders for wild birds
– Test bird seed, seed blends, suet, seed blocks, etc.
– Test bird feeders
• Food & Feeder Test Site would conduct other research that
complements the site’s activities
– Does bird feeding positively impact survival?
Wild Bird Food & Feeder Test Site
• Compare company’s bird food/feeder products with others
– Each test would consist of up to 4 products simultaneously
– Each test would be a blind test
• Each test would include:
– Monitoring of the number of birds of each species that visit
each product during 30, 45-minute sessions
– Total food consumption of each product measured weekly
– Monitoring will take place at three locations in and around
Decatur, IL
Wild Bird Food & Feeder Test Site
• Testing is expected to be complete in 60 days
• A written report summarizing the results will be provided
– Report will include statistical analysis
– Report will include other comments
Wild Bird Food & Feeder Test Site
• Next step in wild bird feeding research
• May lead to creation of quality standards for seed blends
• Provides companies with valuable information prior to
product launch
Questions
Dr. David J. Horn
Millikin University
217-424-6392, dhorn@millikin.edu