Researchers have discovered several bird species that host ticks carrying Lyme disease bacteria in northwestern California as well as another pathogen that causes chronic illness in humans.

“The role of birds in the maintenance of Lyme disease bacteria in California is poorly understood,” said Erica Newman in a release. Newman is a UC Berkeley Ph.D. student in the Energy and Resources Group at the University of California, Berkeley and lead author of a recently released study that “did a molecular study of bird blood, ticks present on the birds, and the associated species of bacteria that they were hosting.”

“This is the most extensive study of the role of birds in Lyme disease ecology in the western United States, and the first to consider the diversity of bird species, their behaviors and their habitats in identifying which birds are truly the most important as carriers.”

UC Berkeley researcher Erica Newman, pictured in front of chaparral, where she studies bird communities. Chaparral biodiversity, including bird communities, is largely understudied because of the difficulty of detecting wildlife in dense shrub habitats.
Image Credit: David Hembry

Using mist netting, Newman and others in the team trapped over 623 birds from 53 different species from 14 sites in the UC Hopland Research and Extension Center in northwestern California and took blood samples to analyze them for the presence of pathogens. More than 99 percent of the ticks discovered were western black-legged ticks (Ixodes pacificus). Of the birds, 23 species were found to be infected with Lyme bacteria, though a few species harbored more subtypes of the disease than others.

The teams study showed that the lesser goldfinch (Spinus psaltria), oak titmouse (Baeolophus inornatus) and the dark eyed junco (Junco hyemalis) were all competent hosts of Lyme disease bacteria (Borrelia burgdorferi) and harbored many more subtypes than other species. The golden crowned sparrow (Zonotrichia atricapilla) was found to be infected more frequently than other species. They also found, for the first time in the world according to Newman, that some bird species were hosting a related disease that humans can contract ­­— Borrelia bissetttii — which has infected people in Southern California and Europe.

But not all ecosystems showed an equal level of infection.

“The birds that were associated with dense oak woodlands in California had higher levels of Lyme disease bacteria in them,” Newman said. “Basically the different habitats and their associated birds really showed different levels of infection.”

While chaparral shrub ecosystems tend to have high biodiversity with many species endemic to California, birds in those areas weren’t found to host Lyme disease at any significant rate.

But the birds that were found to host the disease were coincidentally the same bird species that happened to benefit from suburbanization in California, meaning they spend more time around humans.

Newman said that the team’s findings could have implications for land development policies in California such as the way chaparral is currently cleared to reduce fire risks. The practice of clearing the land may favor birds hosting Lyme disease that move into areas once the chaparral is gone.

“We may be playing around with disease ecology by trying to manage the fire ecology of a region,” she said.

Researchers with South Dakota State University are finishing up a three-year study funded by the South Dakota Department of Fish, Game and Parks and the South Dakota Agricultural Experiment Station that will determine which fall cover crops lure deer away from livestock feed in South Dakota, particularly during the months of August and September.

The study is the first controlled experiment with fall cover crops, although some landowners experiment with cover crops and deer on their own, according to Jonathan Jenks, distinguished professor at the University’s Department of Natural Resource Management and lead researcher on the study. Landowners in the state are often faced with large herds of 100 to 200 deer eating their stored livestock feed including hay and distiller grains.

With limited information so far north in the Great Plains, South Dakota proved to be a good location for the study. Further, Jenks manages a captive deer herd of 50 white-tailed deer at the Wildlife and Fisheries Sciences Research Facility at South Dakota State University. “Because we have a captive deer herd at South Dakota State, there is more control when evaluating the deer rather than just planting crops and seeing what gets eaten,” Jenks said.

In response to SDFGP’s interest in forages that best attract deer, Jenks and graduate student Troy Weiberg put together a project evaluating a number of forages that had been used in other studies.

As part of the project, Jenks and Weiberg chose six cover crops based on previous literature from state biologists — purple top turnips, Daikon radishes, Austrian winter peas, winter rye, chicory and crimson clover — and planted them at the South Dakota State’s Wildlife and Fisheries Research Facility. Based on their data, they found that deer were particularly drawn to purple top turnips, Daikon radishes and Australian winter peas — likely because they are more digestible and have the highest protein content.

Jenks plans to provide wildlife officials with the results as soon as they are compiled. He hopes that his research will help provide wildlife officials recommendations in regards to which cover crops should be used to help manage South Dakota’s deer population.

Gull populations off Canada’s southwest coast have dropped by half since the 1980s, likely due to a decline in quality food, according to a new study.

But at the risk of crying wolf, researchers at the University of British Columbia looked at long-term data compiled about the Glaucous-winged Gulls (Larus glaucescens) over the past 150 years to make sure the 30-year trend isn’t a passing phase.

“The larger implications in part are to point out that using long-term information on population trends, diet and demography gives us a much richer picture of the factors potentially driving bird population trends, said Peter Arcese, the Forest Renewal British Columbia chair of conservation biology at UBC and coauthor of the study.

“The [gull] population increased into the 1980s, but that’s really only when people started monitoring birds systematically there.”

Arcese said the team focused their study on Mandarte Island — a small rocky outcropping in the Salish Sea near Vancouver Island. On that island, the population of birds had increased from 200 breeding pairs around the beginning of the 20^th century to about 2,500 breeding pairs in the 1980s. But he said this spike could be representative of the effects of the Migratory Bird Treaty Act of 1918. Prior to that, humans harvested gull eggs or hunted the birds and historical factors like the gold rushes of the 1800s could have affected populations.

The study found that even though gull populations started to recover throughout most of the 20^th century, egg clutch sizes tended to be small, and diet analysis showed a decline in food quality.

“Eventually the decline in diet reduced clutch size and began to impair the survival of young to the point that that increase could no longer be sustained,” Arcese said.

He also added that other factors like the recovery of bald eagles (Haliaeetus leucocephalus) that prey on gulls could have had an effect on the latter’s numbers. And the lack of food for gulls may only make it easier for the eagles to hunt them. “When food is short, predators are often more effective.”

A Gauge for Ecosystem Change

While Arcese said that many people often think about gulls as “garbage birds,” the birds didn’t always feed on human trash and leftovers. Much of their diet was based on so-called forage fish.

“This bird 150 years ago was a bird that fed almost exclusively on herring and other marine organisms,” Arcese said. But these fish stocks have declined drastically over the past 150 years due to human development and fishing.

“We think there needs to be focused attention on the recovery of forage fish stocks that sustain a whole host of marine organism and marine birds,” he said.

And it isn’t just gulls. The birds were chosen because their wide-ranging diet means their population dynamics are a good gauge for health of the ecosystem in general. “Because they’re generalists, and omnivores, they also tell us something about the foods available over the past 150 years,” Arcese said. “We think the gulls are riding on top of that long-term change.”

Arcese said the gull study is part of a larger work on the history of bird populations on the Salish Sea that sits roughly between Vancouver Island and the mainland of B.C. and Washington state. They have done other studies on Mandarte island looking at marbled murrelets (Brachyramphus marmoratus) and western grebes (Aechmophorus occidentalis), which have declined by 90 percent since the 1950s and 1970s, respectively. But while the historical information on the numbers of these birds is often fragmented, they have much better information on gulls. This is necessary, he stresses, because in order to create working conservation and management plans, it’s necessary for governments and conservationists to know what the situation was like in the past.

“It’s that long term perspective that we feel is essential if someone is going to be able to create a reliable and defensible long term conservation plan,” he said. “When we talk about restoring ecosystems, we need to know where we come from. You can’t know what’s going on by looking at the past 20 years.”