Just for the birds: Climate Change and Birds Part II – Idaho Press

Rock wren by Terry Rich.
White-throated Swift by Julio Mulero.
Pink-footed shearwater by Zak Pohlen.
Western gull by David Iliff.
Male peregrine falcon.

Rock wren by Terry Rich.
White-throated Swift by Julio Mulero.
Pink-footed shearwater by Zak Pohlen.
Western gull by David Iliff.
Male peregrine falcon.


In Climate Change and Birds Part I, I looked at the factors that affect how a bird species might respond over time to a major environmental perturbation, such as climate change. For example, species with large ranges, large clutch sizes, or long life spans are predicted to be more resilient than species with small ranges, small clutch sizes, or short life spans.
There are 10 such factors, and the predicted relationships are pretty intuitive. I used these factors in a vulnerability assessment of the entire North American avifauna (658 species). This sort of assessment is used to rank species from most in need of conservation attention to least in need.
I finished the last piece, pointing out that the taxonomic order Apodiformes (hummingbirds and swifts) ranked as more vulnerable than many other orders, and that we can do something to help hummingbirds right in our own yards. I could move on through the other orders and families, but it’s hard to keep track without the graphs and tables we use in scientific journal publications.
So, let me just mention one more result of looking at taxonomy. The least vulnerable family, according to my analysis, is the wrens. I love the scientific name for this family — Troglodytidae. Troglodyte brings to my mind images of cave-dwelling, semi-human apes, wielding clubs, and definitely to be avoided. Think, Lord of the Rings.
As far as I know, only one of the 86 species of wrens (10 in North America) lives in caves. The rock wren often nests in small caves or at least under little ledges, in rocky landscapes. But back to the point. Wrens are predicted to be better off than any other bird family in North America with global warming.
There are many other ways to look at the vulnerability of different species. For example, it seems logical that birds restricted to only a single type of breeding habitat might be more vulnerable than those who have less strict requirements. This turns out be consistent with my results. The order from least to most vulnerable is, four breeding habitats, three, two, and one. Much like species with large ranges, species using multiple habitat types are predicted to be better prepared to deal with environmental change.
Classifying habitats is a messy enterprise. Vegetation zones morph from one into the other along every gradient you can imagine — precipitation, elevation, latitude, soil type, and many others. I chose the habitat types used by the North American Bird Conservation Initiative (NABCI) in their State of the Birds reports. It would be fun to look at species according to other classifications to see how robust this relationship is.
So, species using only a single breeding habitat type are more vulnerable than those using more than one type. We can look at just the former species to discover which breeding habitat types have the most vulnerable species. And realize I am looking at the bird species in these habitats, not the habitats per se. Increases or decreases in the quantity and quality of the habitats themselves is another factor that heavily impacts the future of all species, including ours.
Oceanic (e.g., albatrosses and shearwaters) species come out worst, a result also found by The State of North America’s Birds report (NABCI, 2016) using somewhat different criteria. Coastal (e.g., shorebirds, gulls, and terns) were second in my analysis and third in NABCI’s. Next were species breeding in the Arctic. The Arctic group includes 62 species from a variety of different bird families. My results echo many other findings that these groups of birds are most at risk.
It turns out species using marshes are, on the whole, least vulnerable on this scale. Birds of “aridlands,” such as sagebrush, and those of “western forests” fall in the middle. Thus, for most of Idaho’s birds, they are neither best nor worst off going into the more unpredictable climate future.
We can also look at latitude of the breeding range. The most interesting result of that analysis was that species with broad latitudinal ranges were less vulnerable than other groups. This is consistent with the previous findings that species with large ranges and those using multiple breeding habitat types will be best off. This tells us species that are already pretty flexible will fair better in the future. This also makes a lot of sense.
I have compared a few of my results to those of NABCI, but it’s critical to compare these sort of results to those of other analyses. There are so many variables involved and so many assumptions, you can’t take it to the bank without many more comparisons.
Another sort of test is to look at how The International Union for Conservation of Nature (IUCN) Red List categories for species compare to my scores for the same birds. Their categories are, at decreasing levels of concern are: Critically Endangered, Endangered, Vulnerable, Near Threatened, and Least Concern. It turns out our results are similar to each other.
Another comparison was possible with an assessment of California “at-risk” species. Obviously, this applied to a much smaller geographic area and a smaller group of species. Plus, the methods were somewhat different. Nonetheless, our results again were reasonably consistent. A particularly useful result of this sort of comparison is to look at species we scored very differently, e.g., western gull. California ranked this species as much more vulnerable than I did. It would be a deep dive to tear this apart here, so I’ll spare you those details. And ultimately these are all just hypotheses. We won’t know who or what is correct until some future date.
In Nevada, a group of experts applied the NatureServe Climate Change Vulnerability Index to many species of several taxa, including 105 species of birds. As with the California assessment, the purposes and methods were somewhat different than mine. I found no difference in the average scores among the groups they defined: Highly Vulnerable, Moderately Vulnerable, Presumed Stable, and Increase Likely. Thus, our two approaches lead to very different conclusions for the same species. This comparison illustrates especially well how users must understand the purposes and methods of different vulnerability assessments.
Finally, I looked at species in The Climate Change Sensitivity Database. This is focused on species in the Pacific Northwest, but many of the species were assessed at the range-wide scale. Note that “sensitivity” has a particular meaning in the climate change literature and is technically only one component of vulnerability.
I found no significant among the three categories of sensitivity — Extremely High, High, and Medium — for 99 species of birds in this database. As with the previous comparison, such differences in outcomes require us to reexamine methods and assumptions.
As I mentioned, the purpose of these sorts of assessments is to rank species according to their need for conservation action. We wouldn’t have to rank species if conservationists had plenty of money. We don’t — not even close. Funding has always been limited, and the sad fact is threats to birds (and most other species on the planet) keep going up faster than funding. Sources of federal, state, and private funds are flat or decreasing more often that they are increasing. So, our limited resources have to be applied almost in the mode of triage.
But it’s not just money. We also have to understand what factors are impacting a given species. Then, we have to know where and when those impacts are happening. Once we have the money, and know where and when to take action, we need people to take those actions. This, too, can be a problem. Not every conservation organization has the capacity to do what’s needed.
In the end, it’s like a big jigsaw puzzle, say one with a million pieces, being assembled by hundreds of people. Pieces do fall into place, and those successes are both inspiring and instructive. The bald eagle, peregrine falcon, and Kirtland’s warbler are pieces we can celebrate. But as we continue to get pieces in place, it seems that the table is routinely jostled, and the puzzle keeps getting bigger.
You can reach Terry at terryrichbrd@gmail.com.
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