AUTHOR BLOG: Do Burrowing Owls aid in the long-distance dispersal of plague-infected fleas?

Kara Navock and Jim Belthoff

Linked paper: Investigation of the geographic origin of burrowing owl fleas with implications for the ecology of plague by K.A. Navock, D.H. Johnson, S. Evans, M.J. Kohn, and J.R. Belthoff, The Auk: Ornithological Advances 136:1, January 2019.

nestling
Collecting samples from a Burrowing Owl nestling. Photo by John Kelly, Boise State University.

Western Burrowing Owls (Athene cunicularia hypugaea) and Pulex irritans, the so-called human flea, have a curious host-parasite relationship. Although we’ve known about it for some time, many details of their connection remain unclear, including why it appears mainly in the northwestern portion of the Burrowing Owl’s range despite the fact that both species have much broader geographic distributions. We were interested in the potential interplay among the migratory movements of Burrowing Owls, the potential for dispersal of P. irritans through its affiliation with owls, and Yersinia pestis—the zoonotic (animal-transmitted) bacteria infamous for causing bubonic plague.

Outbreaks of plague continue to occur sporadically throughout western North America, and it is typically transmitted among susceptible rodent hosts via flea bites. Birds are generally thought to not be vulnerable to plague, but some researchers have suggested that birds of prey could move infected rodents between sites, thus contributing to the disease’s spread. We wondered if birds such as Burrowing Owls could instead be directly aiding dispersal of fleas, which could happen over much longer distances, perhaps even from plague-infected areas in the owls’ wintering range to their breeding grounds. Although P. irritans is not necessarily the key player in plague outbreaks in western North America, it is a possible vector, so a better understanding of the extent to which birds of prey facilitate its dispersal is important.

To help clarify the geographic origins of the fleas on Burrowing Owls, and therefore the potential for long-distance flea dispersal facilitated by migratory owls, we collected feathers, portions of toenails, and fleas from adults and nestlings in two breeding populations of owls in Idaho and Oregon. We then analyzed stable isotopes of hydrogen to decipher whether the fleas on owls had isotopic signatures reflective of owl breeding or wintering grounds. These isotope ratios vary predictably across the latitudinal gradient, providing a geographic map to help understand where our samples originated.

adult
An adult Burrowing Owl ready for sampling. Personal photo, Belthoff lab.

Our analysis was based on three assumptions: (1) adult owl feathers would show the isotopic signatures of the owls’ breeding grounds, because of the timing of feather growth, and (2) nestling toenails would have local breeding-ground hydrogen isotope ratios, but (3) adult toenails would reflect the isotope ratios of the owls’ wintering grounds, as toenails grow continuously and adults just arriving on the breeding grounds would have toenails recently grown in wintering areas. We reasoned that if the fleas we collected had hydrogen isotope ratios most like those of adult owl toenails, then they must have started out on the owls’ wintering grounds and hitched long-distance rides.

Assessing the hydrogen isotope ratios in over 250 fleas, we found that they were markedly different from the ratios in adult toenail samples, but they frequently matched those of the feathers and toenails of nestlings. This implies a breeding ground origin rather than a wintering ground origin for the fleas infesting the Burrowing Owls. Fleas from adult owls in the Idaho population however had a slightly more southern hydrogen isotope signature, which could mean that the owls were moving fleas over short distances, such as between recent migration stopovers and breeding grounds. However, we found no evidence of long-distance dispersal of fleas between the owls’ wintering and breeding grounds.

This lack of pronounced continent-level movement of fleas suggests that even during outbreaks of plague among wildlife, the chance of long-distance dispersal of fleas carrying plague bacteria is low, despite that Burrowing Owls in portions of their breeding grounds might be regularly “bugged” by P. irritans.

During completion of this research, Kara Navock was an undergraduate researcher participating in Boise State University’s REU Site in Raptor Research, funded by the National Science Foundation (REU Site Award; DBI 1263167 to JB) and Boise State University. In addition to authoring this manuscript, Kara was awarded a William C. Andersen Award for best student poster for her presentation at the 2017 annual meeting of the Raptor Research Foundation. As of January 2019, she is continuing her studies at Boise State University at the graduate level. Research into the ecology of Burrowing Owls and their host-parasite relationship with P. irritans continues in the Belthoff lab at Boise State University and through the Global Owl Project.

Crystal Ruiz Earns Certified Association Executive Credential

Crystal RuizCrystal Ruiz, AOS Director of Operations and Administration, has earned the Certified Association Executive (CAE) designation. The CAE is the highest professional credential in the association industry.

To be designated as a Certified Association Executive, an applicant must have a minimum of three years experience with nonprofit organization management, complete a minimum of 100 hours of specialized professional development, pass a stringent examination in association management, and pledge to uphold a code of ethics. To maintain the certification, individuals must undertake ongoing professional development and activities in association and nonprofit management. More than 4,300 association professionals currently hold the CAE credential. The CAE Program is accredited but he National Commission for Certifying Agencies (NCCA).

Crystal was hired by AOS in February 2015. “We are absolutely thrilled for Crystal,” says AOS Executive Director Melinda Pruett-Jones. “The CAE certification signifies her commitment to provide the highest quality service in all dimensions of the society’s management. Crystal is a consummate professional whose training and advancement will permit her to contribute to AOS in broad, strategic ways in the years to come.”

ASAE is a membership organization for more than 44,000 association executives and industry partners representing 7,400 organizations. Its members lead, manage, and work in or partner with organizations in more than a dozen association management disciplines, from executive management to finance to technology. Together, they create a vibrant community that makes the world smarter, safer and better every day. With support for the ASAE Foundation, a separate nonprofit entity, ASAE is the premier source of learning, knowledge, and future-oriented research for the association and nonprofit profession and provides resources, education, ideas, and advocacy to enhance the power and performance of the association and nonprofit community. Visit ASAE at asaecenter.org.

NSF rescinds proposal submission limit for 2019

In October, the American Ornithological Society co-signed a letter opposing changes to National Science Foundation policy that would have limited the number of funding proposals that could be submitted to a given division annually by a PI or co-PI. We are pleased to learn that the NSF has listened to the concerns of the scientific community and rescinded the planned change. Full details can be found on the NSF BIO blog.

It’s go time for Hawaiian bird conservation, and luckily there’s a playbook

Condor-18-25_'I'iwi_Lucas Behnke
‘I’iwi (Photo credit: Lucas Behnke)

A new study in The Condor: Ornithological Applications presents some of the best guidance to date on the priorities and actions that can be taken to help Hawaii’s endemic birds. Hawaii’s ecosystems, including its native bird populations, are struggling. Of the 21 species of forest birds left on the islands, almost two thirds (12 species) of are endangered or threatened. The current conservation status of the wildlife and vegetation on the island is almost entirely attributable to humans. The actions needed to stabilize or reverse these trends need stronger support and coordination, however funding and resources are limited. This new paper lays out a plan to better guide and empower conservation efforts for Hawaiian birds.

Eben Paxton of USGS Pacific Island Ecosystems Research Center and colleagues synthesized the key points that came out of a collaboration of more than 60 stakeholders in Hawaiian bird conservation. The focus is on actionable research and management approaches that can be employed today. Habitat loss, invasive plants, non-native predators, and introduced diseases were identified as the largest threats to Hawaiian birds. Climate change is projected to exacerbate all threats. Given limited resources, the stakeholders decided on eight main priorities as well as several actions specific to the island of Kauai. In addition to helping Hawaii and its birds directly, the goal of this collaborative report is to make Hawaii a model for other areas of the world, especially islands, that are in need of strong conservation efforts.

Lead author, Eben Paxton comments, “Our challenge in Hawaii is how do we conserve forest birds from multiple threats with just a fraction of the resources needed to fully address all the threats. Our solution was to bring researchers and managers together to share ideas, and as a community, identify priority research and management needs necessary to save these unique species. We believe these priorities will help focus resources where most needed and bring together different organizations to work together for the maximum benefit of the birds.”

“New Technology is being proposed to help stem the tide of extinctions in Hawaiian native birds. Eben Paxton and his co-authors recognize that all the native birds in Hawaii are Conservation Reliant Species and propose utilizing new technologies to assist with the preservation of this unique island avifauna,” adds Charles van Riper III, a ST Research Ecologist and Professor Emeritus, USGS and SNRE, University of Arizona. “This very complete paper also recommends enhancing Citizen Science and captive breeding in the Islands, along with continued monitoring and translocations to unoccupied habitat. The immediate target for this plan are the birds on Kauai – the authors feel that the native avifauna on this island is rapidly approaching extinction, and time will tell how successful this proposed plan is in implementing conservation actions in time to save these unique birds.”

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Research and management priorities for Hawai’i forest birds is available at http://www.bioone.org/doi/full/10.1650/CONDOR-18-25.1.
Research contact: Eben Paxton, epaxton@usgs.gov

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology published by the American Ornithological Society. The journal began in 1899, and in 2016 The Condor had the number one impact factor among 24 ornithology journals.