American Birding Podcast



Open Mic – The Endangered Species Act and Birds: A Wild Success?

At the Mic: Jason A. Crotty

The Endangered Species Act (ESA) is difficult to evaluate, as its success is tough to define. Should the criteria be avoiding extinction, avoiding further decline, increasing population by some specific amount, achieving a complete recovery, or something else? Moreover, a species is only listed when it is already in danger of becoming extinct, a challenging starting point for any program. Putting aside these challenges, there have been few studies that focus on outcomes for birds.

The Center for Biological Diversity has attempted to analyze ESA as it applies to specifically birds in a recent report entitled “A Wild Success: A Systematic Review of Bird Recovery under the Endangered Species Act.”  The press release is here.

As the title suggests, the authors conclude that ESA has been “extraordinarily successful in recovering imperiled birds.” Its principal conclusions are that 85% of species either increased or stabilized after listing and that the average population increase after listing has been a robust 624%. The report also compares population trends for listed birds and unlisted birds, finding that listed birds increased while unlisted birds declined.

Of course, the Center for Biological Diversity is an advocacy group focused on ESA and it is a frequent litigant on ESA issues. It has a special interest in the actual and perceived efficacy of ESA. That said, there are few reports like it and it sets forth its methodology and data sources. Moreover, it includes a Appendix showing the underlying population trends for every listed bird included in the report.

How did the report arrive at these findings?

The report states that there have been 120 bird species listed under ESA and species that were likely extinct at listing or were removed from the list because of taxonomic changes or court order were excluded from the analysis.  The report also excluded species that had been listed for less than a decade, on the basis that there was not sufficient time to implement a recovery plan or data to properly assess the impact of ESA on those species. That left 97 species and data existed for 93. That group constitutes the ESA-listed bird species used for analysis in the report.


Hawaii has been the site of a great many extinctions in the last century, but the Nene has generally bucked that trend. Photo: Jason A. Crotty.

For all listed birds, population trends were generally negative 3-5 years after listing, flattened out during years 5-8, and turned positive after years 8-10. There were exceptions, of course, but the impact of the management and protections provided by ESA listing appears modest initially and strongly positive as time passes, i.e., once ESA recovery plans are issued and/or ESA management is implemented.

The authors also attempted to compare ESA-listed birds with non-listed but nonetheless sensitive birds, finding that populations of listed birds were more likely to have stabilized or increased. For listed birds, 84% of species stabilized or increased compared to 50% for unlisted birds.

The non-listed group consisted of sensitive habitat-obligate birds as determined by the North American Bird Conservation Initiative in its State of the Birds reports. Although it is far from clear that ESA listing is the only meaningful variable that impacts these two populations, it does not appear to be a wildly inappropriate comparison. This analysis also suggests that ESA is meaningful to listed birds.

However, the fact that positive population trends and ESA listing are correlated does not necessarily mean that there is a causal relationship. Among other things, some listed birds may have disproportionally benefited from other federal environmental laws and regulations passed since the 1970s.

For example, the Clean Water Act (1972) and Clean Air Act (1973) have significantly improved the nation’s water and air quality. The National Environmental Policy Act (NEPA) was passed in 1970. The National Wildlife Refuge System has been vastly expanded since the 1970s (particularly in Alaska) and the Refuge System was finally given an formal conservation mandate in 1997. The Environmental Protection Agency (established in the 1970) banned the pesticide DDT in 1972.


Isolating the impact of ESA is difficult, particularly since many of these laws complement each other. For example, a federal agency considering a project must generally prepare an environmental impact statement under NEPA and consult with the U.S. Fish & Wildlife Service regarding species listed under ESA.

There may be other confounding variables as well but the report does not discuss that possibility or attempt to account for any such variables. For example, the State of the Birds report separately analyzed birds of different habitats and found substantial variations. But this report does not analyze listed vs. unlisted seabirds, and so forth.

Nevertheless, even allowing for possible shortcomings in the data or methodological quibbles, the analysis suggests that the impact of the ESA on birds has been positive and significant. Simply put, there appears to be a strong correlation between bird population trends and formal ESA listing. Given the resources dedicated to ESA and the protections it provides, the analysis also seems intuitively sound.

For birders, the entire overall report is well worth reading.


Jason A. Crotty is a birder and a lawyer living in Portland, Oregon. He wrote about volunteering in National Wildlife Refuges in the most recent issue of Birder’s Guide. His next for for the ABA – about the U.S. Endangered Species Act as it applies to birds, with examples drawn from the Red-cockaded Woodpecker, and photos by Tana Tanaka – will appear in the August issue of  Birding.