We have studied Acorn Woodpeckers at Hastings Reserve in Carmel Valley, California since 11 April 1968. We have focused on a variety of topics over the past 55+ years, including:
- The evolution of cooperative breeding;
- The relationship between acorn woodpeckers and California oaks;
- Social networks and movement patterns of acorn woodpeckers;
- The role of ecological constraints in the environment as a predictor of group living;
The mating system of the acorn woodpecker (Melanerpes formicivorus) is among the most complex of any vertebrate, with groups consisting of a breeding core of up to seven cobreeding males and three joint-nesting females mating together (cooperative polygynandry) in combination with a variable number of nonbreeding helpers that are offspring from prior years and that have delayed dispersal to remain on their natal territory.
Males compete to mate and females lay their eggs communally in the same nest. Cobreeders of the same sex are almost always close relatives, either siblings or parents and offspring.
The project tests experimentally the role of roosting / nesting cavities and of storage facilities in which groups store acorns as ecological constraints leading to delayed dispersal by offspring and cooperative polygamy by same-sex coalitions of relatives. The project also involves a study of reproductive skew among cobreeding males. Previous work revealed that joint-nesting groups of females, unlike males, share parentage equally. Through experiments, behavioral observations, and genetic analyses; we are attempting to determine the factors that influence reproductive sharing in acorn woodpecker societies.
A primary goal of our work is to understand the fitness consequences of cooperative breeding and to integrate findings into the larger questions of the evolution and ecology of group living in highly social species like acorn woodpeckers and humans.
We welcome collaborative projects that could benefit from our long-term data.
We have devoted much effort to understanding the complex social environment that birds experience. In particular, we have examined a number of important questions with our acorn woodpecker population:
- What role do social interactions play in determining coalition formation, dispersal, or movement patterns?
- Can acorn woodpeckers recognize individuals from other social groups, and can they infer relationships among non-kin?
- What role does fire play in disrupting social networks?
- What factors determine where birds foray as they move across the landscape?
Walters Lab alum, Spencer Schubert, is studying seed dispersal (the movement of seeds away from the parent plant) within tropical forests of the Dominican Republic. Several fruiting species produce a crop multiple times per year and Spencer is trying to determine why such a strategy has evolved. He is also examining the network of frugivore mutualists and their role in determining the biodiversity of wet forests in the region.
Walters Lab alum, Nick Flanders, is examining the role of frugivorous birds in the dispersal and distribution of oak mistletoe (Phoradendron leucarpum). Through this project, Nick aims to further develop his understanding of plant ecology, interactions between birds and plants in the southeastern US, and the use of occupancy models to estimate bird distributions.
Avian hosts likely play an important role in tick dispersal. Several species of ticks in eastern Virginia have shown sudden and dramatic range shifts. These tick species act as vectors of human disease and thus a complete understanding of the role that avian hosts play in these range shifts is of critical importance. Our research examines how both resident and migratory avian species act as hosts to different tick life stages at various times of year. Our sampling occurs at several key locations in Virginia to map the progression of new tick species and the pathogens they carry as they move deeper into Virginia.
Since 1997, Eric Walters has been working with utility organizations and companies throughout the United States and Canada to examine factors influencing wildlife – utility structure interactions. The focus of his work has been on determining the extent to which woodpeckers damage utility structures and evaluating potential preventative and mitigative measures.
Eric Walters has served as an expert witness in cases where woodpecker activity has led to catastrophic failure of utility poles, resulting in wildlfires and loss of life and property.
Our research has found that most woodpeckers are using wood utility structures for either nesting or foraging activities. Ways of preventing such damage depend upon the species involved, geographic location, nearby habitat structure, integrity of the pole, chemical treatment of the pole, previous mitigation measures, and many other factors. Each case of damage must be examined on an individual basis – there are no general trends that allow companies to predict utility structure susceptibility to damage. A field visit (supplemented with historical information) is usually necessary so that recommendations can be made to prevent, reduce, or repair woodpecker damage.
Graduate student Ella DiPetto is studying oyster-based living shorelines, a method of shoreline protection that seeks to facilitate natural ecosystem functions and provide coastal protection. Ella is addressing the need for a scientifically based monitoring approach. She is attempting to review existing oyster-based living shoreline projects, evaluate vertebrate habitat provisioning, potential for oyster enhancement, and protection from erosion. Her project evaluates the potential for a practitioner-focused monitoring framework. She hopes to advance the science behind living shorelines as coastal protection.
- Habitat benefits of living shorelines;
- Pre- and post-monitoring of erosion and oyster enhancement;
- Synthesize monitoring methodology and results to create guidance for monitoring protocols
Ella conducts her research in Hampton Roads, Virginia, an area prone to some of the highest sea level rise in the United States. Sea levels have risen >35 cm since 1950. This is the second largest population center, next to New Orleans, at risk from sea level rise in the United States.
Graduate student Oleksii Dubovyk is studying functional diversity and rarity among North American bird taxa. Using both Breeding Bird Survey and eBird data, Oleksii is asking a number of questions:
- How do functional traits relate to environmental filtering along urban gradients?
- Can one predict avian communities associated with urban environments based on functional traits?
Understanding the role of urban fragmentation on wildlife movement patterns is critical to long-term conservation of species using such areas. One of North America’s most important migration routes, the Atlantic Flyway, follows a path directly over an urban area of 1.6 million people. Hampton Roads, the 2nd largest port in North America, provides important stopover habitat to millions of birds each year. Fragmented patches of protected habitat are critically important to many migratory species. Our work examines the role that these habitat patches play for both resident and migratory species within the urban matrix. The project also involves a significant public outreach component whereby members of the public get to experience bird banding up close and get a better understanding of the suite of species that rely on these remnants of habitat within a large major city.
Walters Lab alum, Chance Hines, was studying the role of hackberry (Celtis occidentalis) as a keystone resource within migrant songbird stopover habitat. Through a mutualism with hackberry gall psyllids, hackberry trees indirectly create species-rich patches of fruiting plants that are used by migrant songbirds during stopovers in the autumn.
Eric Walters has been studying cavity-nesting birds (47 species) and mammals since 1990. He has worked on 19 of the 22 species of woodpeckers found in North America and has conducted field work in Arizona, British Columbia, California, and Florida.
Walters is considered a leading expert on Acorn Woodpeckers, Red-breasted Sapsuckers, Red-naped Sapsuckers, and Yellow-bellied Sapsuckers. He has coauthored the Birds of the World accounts for each of these species.