The Double-Edged Sword of Wildlife-Friendly Yards

CONDOR-16-26 Steve Hager

Hundreds of millions of birds are killed in collisions with windows each year in the U.S. alone, and although high-rise buildings tend to be the biggest individual culprits, the vast number of suburban homes across the continent means that even a few deaths per house add up fast. A new study in The Condor: Ornithological Applications examines the factors that affect window collision rates at homes and shows that yards that are more attractive to birds are also the sites of more collisions.

Working with Alberta homeowners who collectively contributed more than 34,000 days’ worth of collision data, Justine Kummer of the University of Alberta and her colleagues found that the presence of a bird feeder, whether a house was in an urban or rural area, and the height of the vegetation in the yard were the most important predictors of collisions. Of Alberta’s 421 bird species, 53 were represented in the data, mostly common urban species.

“Although each typical residential dwelling only causes one or a few bird–window collisions per year, the enormous number of these buildings means we are killing far more birds in our collective backyards than are dying at large office buildings and skyscrapers,” according to Scott Loss of Oklahoma State University, lead author of a landmark 2014 review on the subject. “Kummer et al. provide an excellent example of how the power of citizen scientists can be harnessed to address this major conservation issue.”

The data was collected through a citizen science project launched in 2013 that recruited homeowners in Alberta to walk the perimeters of their houses daily and report evidence of bird–window collisions. “Conducting a citizen science project had a number of challenges,” says Kummer. “Unlike some other projects, I didn’t spend my time collecting data; I spent it trying to recruit homeowners and educate the public about the issue.”

Most homeowners would not want to remove their feeders and wildlife-friendly vegetation. Instead, the authors suggest that mitigation efforts should focus on evaluating the effectiveness of products such as tape and film that can be applied to window panes to prevent collisions. “As homeowners don’t want to reduce the number of bird in their yards,” says Kummer, “I think the next step will be to determine the best window deterrents they can use at their homes.”

The use of citizen science to identify the factors affecting bird-window collision risk at houses is available at http://www.aoucospubs.org/doi/full/10.1650/CONDOR-16-26.1.

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology. It began in 1899 as the journal of the Cooper Ornithological Club, a group of ornithologists in California that became the Cooper Ornithological Society.

Habitat Needs of Nestling & Fledgling Songbirds

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A juvenile Acadian Flycatcher with a radio transmitter. Photo credit: J. Jenkins

Both before and after they leave the nest, baby birds face a host of challenges. A new study in The Condor: Ornithological Applications examining songbird survival in the nestling and fledgling stages finds that even in the same habitat, different species face different risks and survive at different rates.

Ovenbirds and Acadian Flycatchers are migratory songbirds that nest in similar habitats, but they have very different nesting and foraging strategies. Julianna Jenkins of the University of Missouri and her colleagues tracked the survival of young birds of both species before and after they fledged. They found that flycatcher survival at both stages was related to mature forest, while Ovenbirds did best in mature forest as nestlings but sought areas with dense understories after fledging. Post-fledging survival was lower for Ovenbirds than for Acadian Flycatchers, with more than half of the tracked Ovenbird fledglings dying within ten days of leaving the nest.

Habitat information like this can be crucial for conservation biologists trying to address songbird population declines, because they can take action through land management to boost birds’ survival at multiple life stages. “It is my hope that by investigating what affects both nesting and postfledging survival, we can make management decisions that are effective for the entire breeding season,” says Jenkins.

Jenkins and her colleagues monitored nests at three sites in central Missouri, fitting nestlings with radio transmitters shortly before they fledged so they could continue to track their survival. From 90 Ovenbird and 264 Acadian Flycatcher nests, they tracked 50 Ovenbird fledglings and 45 flycatcher fledglings. “Tracking radio-tagged fledglings was the highlight of my day,” says Jenkins. “Without transmitters, I doubt we could have relocated many fledglings, if any. I was amazed at how far from the nest newly fledged Ovenbirds could travel, even without the ability to fly.”

In addition to the difference in survival between the two species, fledglings’ success also varies between regions. According to the study’s authors, this highlights the need for tracking postfledging survival for a variety of species and landscapes rather than assuming that birds nesting in similar habitat face similar risks. “Jenkins and her colleagues provide insight into factors related to post-fledging survival and how those factors might influence population trajectory,” according to David Andersen of the University of Minnesota, an expert on bird population ecology who was not involved with the study. “Their results shed light on the complex interactions between fledgling songbirds, the landscapes in which they exist, and how this important life stage influences population dynamics.”

Contrasting patterns of nest survival and postfledging survival in Ovenbirds and Acadian Flycatchers in Missouri forest fragments is available at http://www.aoucospubs.org/doi/full/10.1650/CONDOR-16-30.1.

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology. It began in 1899 as the journal of the Cooper Ornithological Club, a group of ornithologists in California that became the Cooper Ornithological Society.

Alaska’s Shorebirds Exposed to Mercury

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A Pectoral Sandpiper, one of the shorebirds included in the study. Photo credit: B. Lagasse

Shorebirds breeding in Alaska are being exposed to mercury at levels that could put their populations at risk, according to new research from The Condor: Ornithological Applications.

Thanks to atmospheric circulation and other factors, the mercury that we deposit into the environment tends to accumulate in the Arctic. Mercury exposure can reduce birds’ reproductive success and sometimes even be lethal. Shorebirds may be particularly vulnerable because they forage in aquatic environments where mercury is converted into methylmercury, its most dangerous form. Marie Perkins of the Biodiversity Research Institute (BRI) and her colleagues investigated the level of mercury in Alaska’s shorebirds and found that some birds breeding near Barrow, at the state’s northern end, have mercury concentrations upwards of two micrograms per gram of blood.

“These species already face a lot of tough new challenges, from climate change to disappearing stop-over habitat, so throwing a neurotoxin in the mix that can reduce reproductive success is likely to harm their populations,” according to Dan Cristol of the College of William & Mary, an expert on mercury in birds who was not involved with the new study. “The mercury concentrations reported in this paper are likely to reduce reproduction, but not catastrophically, based on what we know from other species. What may be even worse, though, is that these mercury levels probably spike when they leave the breeding grounds and start burning their reserve fuel, making their already arduous continent-jumping trips even harder.”

To assess the birds’ mercury exposure, Perkins and her colleagues collected blood and feathers from nine shorebird species breeding and staging for their southward migration at sites throughout Alaska. In addition to the troubling results from birds breeding near Barrow, they found that mercury levels depended on a species’ foraging habits—shorebird species that foraged in upland areas, away from methylmercury-rich wetlands, had the lowest blood mercury concentrations.

More work is needed to determine how much mercury various shorebird species can handle before they suffer adverse effects. “These results have encouraged me to expand my research on mercury exposure in Arctic shorebirds,” says Perkins. “I am currently pursuing my PhD at McGill University, where I am working in collaboration with BRI and the Arctic Shorebird Demographics Network to closely examine mercury exposure in multiple shorebird species breeding across the North American Arctic.”

Mercury exposure and risk in breeding and staging Alaskan shorebirds is available at http://www.aoucospubs.org/doi/full/10.1650/CONDOR-16-36.1.

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology. It began in 1899 as the journal of the Cooper Ornithological Club, a group of ornithologists in California that became the Cooper Ornithological Society.

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Feather-Munching Bacteria Damage Wild Bird Plumage

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Carolina Chickadees were among the many species sampled for the study. Photo credit: C. Kent

A new study in The Auk: Ornithological Advances links feather-degrading bacteria to damaged plumage on wild birds for the first time, offering new insights into how birds’ ecology and behavior might affect their exposure to these little-studied microbes.

Scientists know surprisingly little about the diverse community of microbes that lives on bird feathers. A few of these species of bacteria can actually break down keratin, the material feathers are made of, but few studies have looked at how feather-degrading bacteria actually affect birds in the wild. Combining data from a decade’s worth of bird-banding studies, Cody Kent and Edward H. Burtt of Ohio Wesleyan University found that tail-feather wear was strongly correlated with the presence of feather-degrading bacteria—the first time this relationship has been demonstrated in live, wild birds.

Kent and Burtt’s dataset included more than 3,500 birds from 154 different species captured between 1996 and 2005, in locations ranging from a rural Ohio backyard to Canada’s Bay of Fundy to a Louisiana bayou. Researchers carefully wiped each bird’s plumage across petri dishes containing a growth medium to culture any microorganisms living in the feathers. Ground-foraging, aerial-foraging, and fly-catching birds had a higher prevalence of feather-degrading bacteria, while nectivorous, tree-probing, and marine-foraging birds were less likely to harbor the microbes.

“In vitro work has shown that many organisms are capable of breaking down bird feathers, and several studies have linked bacterial load to factors with evolutionary implications, such as breeding success and survival,” says Kent, now a PhD student at Tulane University. “However, we have little knowledge on what factors actually influence bacterial load on wild birds or even clear evidence that feather-degrading bacteria actually break down feathers in live, wild birds. These are important factors to understand before we can make strong arguments for their evolutionary importance, and this paper begins to answer these questions.”

“Kent and Burtt’s new study is a tour de force,” says Dale Clayton, a University of Utah ornithologist who was not involved with the study. “It underscores the potential importance of feather-degrading bacteria as selective agents that may influence the evolution of birds in important ways. Tragically, Jed Burtt passed away prior to final publication of the paper, which is a fitting tribute to his lifelong love of birds and his pioneering work on the creatures that live on them.”

Feather-degrading bacilli in the plumage of wild birds: Prevalence and relation to feather wear is available at http://www.aoucospubs.org/doi/full/10.1642/AUK-16-39.1.

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology that began in 1884 as the official publication of the American Ornithologists’ Union. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.

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Campgrounds Alter Jay Behavior

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A Steller’s Jay steals a peanut from a campground. Photo credit: W. Goldenberg

Anyone who’s gone camping has seen birds foraging for picnic crumbs, and according to new research in The Condor: Ornithological Applications, the availability of food in campgrounds significantly alters jays’ behavior and may even change how they interact with other bird species.

Steller’s Jays are intelligent, adaptable birds, and in California’s Redwood National and State Parks, the ready availability of food draws them to campgrounds. Tracking the behavior of jays near living near campgrounds and comparing it with jays living in more natural areas of the same parks, Will Goldenberg of Humboldt State University and his colleagues found that having easy access to food made jays living near campgrounds less territorial. Campground jays spent less time foraging and more time near the ground than their counterparts without access to campgrounds.

A federally threatened seabird, the Marbled Murrelet, nests in the highest canopy old-growth redwood forest, and jays are known to eat murrelet eggs when they encounter their nests. Though jays living in campgrounds spent more time on the ground, 40 meters below where murrelets nest, Goldenberg and his colleagues still worry that the concentrated foraging activity of jays could put murrelets near campgrounds at risk. “The results of our study should give researchers and conservationists new tools to make informed decisions regarding corvid management,” according to Goldenberg.

They carried out the study in 2010 and 2011 by capturing and radio-tagging jays to follow their habits. “Working with Steller’s Jays in campgrounds really keeps you on your toes. Individual jays were quick to learn our trapping techniques and would avoid any traps that they had previously experienced,” says Goldenberg. “In addition, our study sites contained the tallest trees on the planet and more above ground biomass than any other forest, making our radio tracking efforts an extreme challenge.”

“This study by Goldenberg et al. breaks new ground by providing detailed observations of Steller’s Jay behavior in and out of campgrounds,” according to John Marzluff of the University of Washington, an expert on corvid behavior. “Though Steller’s Jays still pose a serious threat to sensitive species that nest well above ground, such as the Marbled Murrelet, their use of anthropogenic foods that occur most frequently at ground level in camps may reduce chance encounters between jays and murrelets within the camp proper.”

Steller’s Jay (Cyanocitta stelleri) space use and behavior in campground and non-campground sites in coastal redwood forests is available at http://www.aoucospubs.org/doi/full/10.1650/CONDOR-15-187.1.

About the journal: The Condor: Ornithological Applications is a peer-reviewed, international journal of ornithology. It began in 1899 as the journal of the Cooper Ornithological Club, a group of ornithologists in California that became the Cooper Ornithological Society.

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Condor’s Top Cited, #1: Birds vs. Windows

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A Swainson’s Thrush killed by colliding with the window of a low-rise office building. Photo credit: Scott Loss

This week marks the end of our series of blog post highlighting both our journals’ top cited articles from 2014 and 2015. After counting down from number ten, today we reveal that The Condor‘s most cited paper from this time period was…

Bird–building collisions in the United States: Estimates of annual mortality and species vulnerability by S.R. Loss, T. Will, S.S. Loss, and P.P. Marra, from the February 2014 issue of The Condor: Ornithological Advances.

Loss and his colleagues reviewed the published literature and acquired unpublished datasets to systematically estimate annual bird mortality from window collisions in the U.S. and identify particularly vulnerable species. They found that 365–988 million birds are killed in such collisions each year, supporting the conclusion that building collision mortality is one of the top sources of human-caused bird mortality in the U.S. A large proportion of all mortality occurs at structures like houses that kill small numbers of birds on a per-building basis but make up a high percentage of all buildings, which suggests that achieving a large overall reduction in mortality will require mitigation measures to be applied across a large number of structures (not just high-rises).

For some species, including Golden-winged Warblers, Painted Buntings, Kentucky Warblers, and Canada Warblers, building collision mortality appears substantial enough to contribute to or exacerbate ongoing population declines. The authors suggest that a feasible long-term approach to reducing mortality would be the continued adaptation of Green Building certification standards to include bird collision risks.

Read the full paper at http://www.aoucospubs.org/doi/full/10.1650/CONDOR-13-090.1.

Early Arrival Gives Bluebirds an Edge in Keeping Nest Sites

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A Mountain Bluebird pair at a nest box. Image credit: S. & R. Proulx

Finders, keepers: Mountain Bluebirds are more likely to defend nest cavities against competition from other birds such as swallows if they get there first, but climate change may disrupt the migratory timing that lets them beat their rivals to the punch, according to new research in The Auk: Ornithological Advances.

The outcomes of interspecies battles for nest sites depend on a number of factors—while some species are inherently better competitors than others, the one that claims a site first also can have an advantage. To test what happens when Tree Swallows and Mountain Bluebirds compete for nest sites, Karen Wiebe of the University of Saskatchewan set up side-by-side pairs of nest boxes in grassland habitat in central British Columbia. When bluebird and swallow pairs moved in next door to each other, she would either block the entrance to one box and let the two pairs of birds compete for the one that remained, or remove both boxes and replace them with a fresh one.

Wiebe found that when Tree Swallows were defending their previously owned box or when the two species were competing over a new box, Tree Swallows won 65–70% of the time. Bluebirds got a boost when they defended a box they already occupied, however, fending off swallows 77% of the time. Mountain Bluebirds typically arrive on their breeding grounds earlier than Tree Swallows, giving them a chance to secure nesting locations before their competitors. However, climate change is moving up the timing of swallows’ spring migration, which may bring the two species into direct competition more often and reduce bluebirds’ ability to claim and defend nest sites.

“I became interested in this topic after watching many competitive interactions over natural tree holes during a long-term study of Northern Flickers in central British Columbia,” says Wiebe. “In early spring when the birds are trying to claim a nest site, these disputes can be intense and really grab your attention. Because bluebirds and swallows readily use nest boxes, I was motivated to try some experiments in a system where I could have more control over the spacing of nests and settlement patterns of the birds.”

“This is a nice set of clever and simple experiments that show that species are not the same when it comes to the importance of being the first one to occupy a nest site,” according to ecologist Hanna Kokko of the University of Zurich, an expert on interspecies competition in birds. “The one that currently tends to arrive first, the bluebird, relies more on this, which could easily cause problems if the arrival order changes on a changing planet.”

Interspecific competition for nests: Prior ownership trumps resource holding potential for Mountain Bluebird competing with Tree Swallow is available at http://www.aoucospubs.org/doi/full/10.1642/AUK-16-25.1.

About the journal: The Auk: Ornithological Advances is a peer-reviewed, international journal of ornithology that began in 1884 as the official publication of the American Ornithologists’ Union. In 2009, The Auk was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.

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