does bird feeding positively impact songbird survival? dr. david horn, associate professor of...

Does Bird Feeding Positively Impact Songbird Survival?

Dr. David Horn, Associate Professor of Biology, Millikin UniversityDr. 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 Blue-gray 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. HornMillikin University

217-424-6392, dhorn@millikin.edu

WBFI Research FoundationWild 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. HornMillikin University

217-424-6392, dhorn@millikin.edu