2009 State of the Birds: Climate Change and Birds

National Audubon Society Releases Report on Climate Change Impacts on North American Bird Species

The northward and inland movement of North American birds, confirmed by thousands of citizen-observations, provides new and powerful evidence that global warming is having a serious and measurable impact on North American bird species, according to new analyses by Audubon scientists. 

Analyses of citizen-gathered data from the past 40 years of Audubon’s Christmas Bird Count (CBC) reveal that 177 (58 percent) of the 305 widespread species that winter on the continent shifted significantly north since 1968, some by hundreds of miles. 140 of these species are found in Oregon. Movement was detected among species of every type, including more than 70 percent of highly adaptable forest and feeder birds.

Population shifts among individual species are common, fluctuate, and can have many causes.  However, Audubon scientists say the ongoing trend of movement by some 177 species—closely correlated to long-term winter temperature increases—reveals a strong correlation to the changing climate.

Report Summary | Table of Species Analyzed (by species) | Table of Species Analyzed (by state)

How You Can Help

• Support Portland Audubon's efforts to promote policies and actions to combat global climate change including responsible development of renewable energy resources and strategic protection of wildlife habitat to allow species to adapt to the changing climate.  Get involved by joining FAUNA (Friends and Advocates for Urban Natural Areas), which focuses on conservation issues in the Portland Metro Region. To join contact Jim Labbe.
• Help support birds in your backyard and neighborhood. Go to http://www.audubonportland.org/backyardwildlife/brochures/protectingbirds to learn more about backyard conservation, or participate in Audubon's backyard habitat certification program.
• Participate in Citizen Science efforts that help scientists identify long-term bird population trends.

Birds and Climate Change Q&A

Q-What’s so new about this research? Hasn’t it been done before?
A-This is most certainly the most comprehensive look at the data on bird movements over the past forty years and what they reveal about the response to climate change. It tells us that those who think climate change impacts will be felt far from home and far off in the future had better think again. There are impacts being seen here and now. We must act immediately to stem the causes of global warming to reduce the severity of its impacts AND to employ habitat and species conservation action to help where changes can’t be avoided.  

Q-Your list shows that birds moved into or out of my area. What does that mean?
A-It shows us that climate change is having a serious and pervasive impact on our country and the natural world right now. What we’ve detected is a response from birds—at least in part—to the disruption by climate change of healthy, functioning ecosystems. It’s an uncontrolled experiment that is being conducted on birds, other wildlife, their habitats and ours; and we can’t really know the long term harm that can be done. The best we can do is to fight hard to curb climate change and minimize its worst effects, and to take science-based conservation action to help species and habitats weather the changes we can’t avoid.  

Q-Don’t bird ranges change all the time?
A- Birds alter their ranges for a variety of reasons, including: successful reintroductions, habitat loss, recovery from DDT, loss of food supplies, etc. However, the large number and array of species moving north is consistent with increasing winter temperatures. Similarly, many birds are moving away from coastal areas, where oceans help moderate temperatures, and are being seen farther inland – as temperatures rise. In both cases, they are following the biological imperative to move into areas with suitable climate—and providing compelling evidence that we are seeing the impact of climate change play out across the continent.

Q-How can you be sure that this is a climate caused movement?
A-There is a strong correlation between shifting ranges and winter temperature trends; this relationship explains some of the widespread and directionally consistent movements seen among U.S. bird species. Specifically, annual latitudinal distributions of birds are correlated with annual temperatures; in other words, birds are found further north in warmer winters than they are in colder winters. 

B. Among all the species in our study, twice as many bird species moved north as south; twice as many species moved inland as moved coastally. Both of these directional movements are consistent with a climate change model. 

C. An equal number of birds moved east as moved west. This is also consistent with a global warming model - movements away from the Atlantic and Pacific should be about equal, with no other expectation of differences in east-west movement.

D. There is a high correlation between the rate of winter population change for species in states, and the rate of winter temperature change in those states – and this is the case regardless of state or province latitude.

E. While birds found only in a few southern states were not included in the main part of this study, they have been observed in increasing numbers, suggesting that they have moved north from south of the United States. 

Q-Didn’t some species fare really well over the past 40 years (even showing population increases)?
A-Yes, many of the species that moved north and inland increased in population at the same time. But it would be short-sighted to focus on what may appear to be short-term gains. We’re concerned because the movements indicate that ecological disruption is underway. Where food or habitat is available, species may do well in the short term, but ultimately the need to adjust to changing climate conditions can put species in peril in a variety of ways. Some will move into areas where an unusually harsh winter will still bring conditions they cannot survive. Others may be unable to find food or suitable habitat (especially if the healthy habitats they need, like grasslands) are already being decimated by overuse, pollution, and other threats. Even species that fare well amid the changes are likely to force out other, less adaptable birds, taking a long-term toll on ecological health and all it supports. 

Q-Many species moved south, what does that say about your conclusions?
A-Yes, about one-quarter of the species moved south. Birds frequently alter their ranges due to many factors, especially habitat changes and interactions with other species. Audubon does not suggest that all the birds that moved north or inland did so in response to climate change; a wide variety of other factors play a contributing role and explain why a minority of species showed no movement or even shifted southward.

Q-Couldn’t you make the opposite case about acting on climate change given the same findings?
A-What we’re finding is that birds are moving very rapidly. However, many other organisms can’t move as rapidly as birds can. Thus, many, many species will find themselves living in areas that are inappropriate. Rapid change also allows invasive, non-native species to move into new areas before native species are able to make the move. The result is ecological disruption that is bad for native species, bad for ecosystems, and bad for human health and welfare. 

Q-What groups of birds are at greatest risk?
A-Tundra species such as Snowy Owl and American Golden-Plover simply can’t go much farther north. Grassland species are also at particular risk because their habitats have been so decimated by human over-use that they have few other places to go to find more suitable climate—indeed that’s why many did not show much movement in our study. 

Coastal species face two major issues. Many will lose their habitats due to sea-level rise. Others will lose their food supply because of the disruption of ocean currents that bring their foods near to the ocean surface where they can be caught by birds.

Q-What birds are likely to be forced toward extinction?
A-We are concerned about ice-loving birds such as Ivory and Ross’s Gulls that share habitat with polar bears and Arctic-breeding shorebirds such as American Golden-Plover and Buff-breasted Sandpiper. We are very concerned about coastal birds such as Piping Plover and Saltmarsh Sparrow and coastal seabirds like Kittlitz’s Murrelet and Ashy Storm-Petrel. We are also concerned about mountaintop birds such as Brown-capped and Black Rosy-Finches and Bicknell’s Thrush.

Q-Doesn’t this prove that nature is adaptable?
A-Some birds are among the most adaptable creatures on earth, and they’re warning us about just how much movement may be needed—not just by birds but by all kinds of wildlife. Unfortunately, many species will not have the ability to make the moves the climate requires—their habitats or their own numbers or their sedentary nature or the necessary corridors may be too limited. They may face too much competition, or they could be decimated by sudden changes in weather that defy the long-term trends. Even though many species can adapt to change, we have to be careful about creating change that is beyond what they—and we—can handle.

Q-Wouldn’t birds have moved north in the absence of climate change?
A-Many would, because there are lots of factors that can lead to range shifts. But the number of species moving north vs. south and inland instead of towards the coast all point to climate factors at work. When you correlate the movements with the change in average temperatures over the period, the evidence of a climate response is indisputable.

Q-Isn’t it possible that for a given species, the cause was not climate?
A-There are many reasons that species will shift their ranges…and it’s impossible to be certain in determining how much of a role climate change played in any specific case. But the evidence is clear that climate change is playing a role in the movements of the vast majority of birds. And it is equally clear that climate change will affect their future…and ours. It’s only common sense to take action now to help lessen the impacts and to help deal with those we can’t avoid. 

Q-How do the California findings fit in with Audubon’s larger study of bird movements?
A-Our main study allows us to look back on how birds have moved over the past 40 years and to correlate those movements with climate change. California’s work allows us to look forward towards what will happen if the climate continues to change. It reinforces several key take-away points from our larger research:

• That habitat will be lost, putting birds—and ecological services—at risk, if climate change continues; 
• That the extent of change can be limited if there is immediate and widespread action to control global emission of global warming pollutants; and
• That addressing climate change is not enough to safeguard birds and ecological health. We must take immediate, science-guided action to restore and protect both habitats and species if we want them to be able to weather the effects of climate change.

The California research and similar studies can help us understand where our conservation investments can do the most good amid a changing climate. 

Q-This has been one of the coldest winters in memory in many parts of the country. Doesn’t this create some doubt about your claims of harm from global warming?
A- There is no evidence that this winter is anything but an aberration in the long-term warming of our climate. All along we have experienced year-to-year variability during the long-term trend towards warmer winters.

However, this cold winter is showing us what can happen when birds follow the longer-term warming trend further north. Already this winter, we have had a die-off of Brown Pelicans along the Pacific Coast that is being attributed to a big snowstorm off the coast of Oregon and Washington. This is a region where pelicans were never found until recently. So, one of the concerns about global warming is that it allows birds to move north, but there still will be hard winter storms that will catch birds that are ill-equipped to survive them.

Q-Christmas Bird Count data come from amateurs.  Is the information really scientifically valid?
A-Extremely.  While most “counters” are not professional scientists, they follow a carefully-developed and reporting protocol developed by Audubon scientists to ensure the quality of the data, which are also analyzed by professional scientists and statisticians.  The headline of a January, 2009 editorial in the authoritative journal, Nature, proclaimed: 

“The Christmas Bird Count is a model to be emulated in distributed, volunteer science.”  The editorial noted that “[CBC] data have informed reams of peer-reviewed work…”  Indeed, more than 200 scientific papers have been based on its well-respected data since the CBC began in 1900, serving as a vital foundation for conservation planning and policy development.