Archbold Biological Station, Biennial Report 1997-1998

 
Hugh Ellis (L) and Reed Bowman with a suburban scrub-jay; photo by  Nancy Deyrup

 

       Accomplishments 1997-98
  • Published 1 paper and 5 abstracts in peer-reviewed journals or symposium proceedings. Submitted 5 additional manuscripts for publications in journals or books. Submitted a monograph entitled "Population dynamics, demography, and contributions to metapopulation dynamics by suburban populations of the Florida scrub-jay" based on 6 years of our suburban jay research. This research continues into its 8th year.
  • Continued U.S. Department of Defense-funded research on the population dynamics of Florida scrub-jays and red-cockaded woodpeckers at Avon Park Air Force Range. Submitted reports summarizing 5 years of demographic data for both species.
  • Initiated a new U.S. Fish and Wildlife Service-funded project using radio-telemetry to study the natal dispersal and non-dispersal forays of Florida scrub-jays in heterogeneous landscapes.
  • Served as major advisor for 2 Master’s students and served on the graduate committees of 4 other students from 2 universities.

  P9sjmap.jpg
Florida Scrub-Jay centroids (.) are plotted against contours of human housing density (houses/40 ha) in a residential subdivision in Lake Placid, Florida. Map by Reed Bowman.


Applied Avian Ecology

 

Project Director: Reed Bowman
Post-doctoral Associates: David A. Aborn, Ernest (Ted) E. Stevens
Research Assistants: Leslie K. Backus, Patricia M. Barber, Geoff M. Carter, Nathalie J. Hamel, Stephanie A. Legare, David L. Leonard, Allison R. Mains, Lawrence A. Riopelle, Sean Rowe, Diana Swan
Graduate Interns: Barbara J. Beckford, Michelle L. Dent, Arthur L. Fleischer, Matthew D. Shawkey
Outside Collaborators: David R. Breininger, Dynamac Inc., NASA; Robert L. Curry and Lee W. Walton, Villanova University; Hugh I. Ellis, University of San Diego; John W. Fitzpatrick, Cornell University; Stephan J. Schoech, Indiana University; Bradley M. Stith, University of Florida

[Biennial Contents | Biennial 95-96

Human disturbance of natural habitats is ubiquitous. These disturbances are numerous and varied and their effects on birds are immense, but our understanding of these effects is still rudimentary. Long-term research in the Applied Avian Ecology Lab combines an observational and experimental approach to examine the effects of human disturbance on birds. We examine these effects at different ecological scales, such as impacts on individuals (behavior and physiology), populations (demography), and communities (structure and composition). In particular, our research has focused on the effects of urbanization on the demography and social biology of the Florida scrub-jay (Aphelocoma coerulescens) and on the effects of multiple resource management (grazing, forestry, human recreation, military training, and endangered species management) on both Florida scrub-jays and red-cockaded woodpeckers (Picoides borealis), both federally-listed species.

     Florida Scrub-Jays. Our research emphasizes population- specific demographic and life history patterns, dispersal patterns, and immigration and emigration rates in suburban habitats and focuses on developing individual and spatially-explicit population models that reflect habitat-specific life-history parameters. Since 1992, Reed Bowman and many interns and graduate students, have studied a banded population of scrub-jays in a suburban setting near Archbold Biological Station. Here, we are attempting to identify distinct ecological and demographic patterns that differ across a gradient of increasing suburbanization (see map, page 9, and map [c], page 29) and between our suburban study site and the jay population studied by Glen Woolfenden and colleagues at Archbold. At the recent XXII International Ornithological Congress, in Durban, South Africa, four papers (see Appendix F), one of which was invited, presented comparative results from these two jay populations.

     Among many patterns, two particularly robust ones have emerged in which suburban jay populations differ from jay populations in natural habitats. Several collaborative and student projects seek the mechanisms underlying these patterns. First, jays in suburban areas begin nesting earlier and show little between-year variation in their timing of breeding. Artie Fleischer demonstrated that the pre-breeding time budgets of females differ between the suburbs and Archbold, suggesting that access to supplemental food may allow females in suburban habitats to conserve energy prior to breeding. With Hugh Ellis, we are using doubly-labeled water to determine the daily energy budgets of jays in both habitats. With Stephan Schoech, we have examined how access to supplemental food influences blood plasma levels of protein, lipids, and calcium of females prior to breeding and the seasonal chronology of hormone profiles. We are seeking correlates between food, physiological condition, endocrinological patterns and the timing of breeding.

     Extremely low juvenile recruitment in the suburban population is the second robust pattern. Path analyses of the effects of different demographic attributes on recruitment suggest that low recruitment is strongly influenced by high rates of brood reduction and post-fledging mortality. These patterns implicate food and predation as important factors influencing recruitment rates in the suburbs. Several student projects (see Student Research) are examining the proximate causes of brood reduction and post-fledging mortality in the suburbs.

     Understanding the dispersal ecology of Florida scrub-jays has become an increasingly important research focus in the Applied Avian Ecology Lab. During autumn of 1997 and 1998, Fleischer and Bowman banded over 500 birds in southern Highlands County with population-specific color band combinations. Each fall, we conduct surveys of scrub-jays throughout the county to determine population and group size changes, recruitment of independent young, and movement of banded birds between populations. In 1998, we began a radio-telemetry project to examine how landscape characteristics influences the frequency and duration of off-territory forays made by non-breeding scrub-jays. Bowman, David Aborn, Geoff Carter, and several interns track non-breeders whenever they move off their natal territory recording the frequency, duration, and path of these movements relative to the landscape mosaic in which they occur. At Avon Park Air Force Range (APAFR), in Polk and Highlands counties, Bowman, Nathalie Hamel, Larry Riopelle, and Sean Rowe have recorded 133 natal dispersals; movements from natal to breeding site. We are examining gap characteristics and comparing the movement data from this fragmented landscape with dispersal patterns at Archbold.

     Also at APAFR, we are developing management recommendations for scrub-jays. We submitted recommendations for logging and prescribed fire, consistent with multiple resource management goals at APAFR, that also will significantly benefit jays and other scrub organisms. At Cape Canaveral Air Force Station (Brevard Co., Fla.), Ted Stevens and Stephanie Legare are examining scrub-jay demography and behavior in response to long-term fire suppression and a variety of different habitat restoration techniques. Together, these studies provide data on how scrub-jay populations respond to a variety of different human disturbances and insights into effective management.

     Red-cockaded Woodpeckers. Red-cockaded woodpecker (RCW) populations in south peninsular Florida occur in a very different landscape than populations elsewhere. Longleaf pine forests here are very open with relatively low pine densities. Our work on RCWs, led by Bowman, David Leonard, Leslie Backus, Patty Barber, Allison Mains, and Diana Swan, examines how landscape characteristics effect the demographic attributes of RCWs at APAFR. High annual survival of breeding adults in this population ensures limited breeding opportunities for non-breeding males. In our color-marked population, the age at first reproduction for males is later than in other populations. However, rather than remain as helpers, many of these older birds disperse and "float" through the population. In other populations, "floaters" tend to be limited to one-year old males. We are amassing enough data to begin to examine the fitness consequences of these alternative strategies and how landscape characteristics influence these demographic and social characteristics.

     Although survival of breeding adults in this population is high, recruitment of local females is so low that the population would decline without regular immigration. We are experimenting with different management techniques such as provisioning artificial nesting cavities and translocating females from within the population and from other populations. Recently, three females from Apalachicola National Forest were introduced at APAFR and all three paired with single males.

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Archbold Biological Station, 3 April 2000
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