North America’s rarest songbird is a phoenix from the flames

In 1755 curators at the Ashmolean museum in Oxford (UK) threw the last remaining tissue specimens of the dodo onto a fire. Unfortunately for this most hapless of flightless creatures, this means that we are still not entirely certain what this giant tropical pigeon truly looked like.

The dodo represents perhaps one of the most extreme examples of a population crash ever witnessed, slipping from discovery to extinction in only around 80 years. Of course the blame for this lies firmly in the hands—and stomachs—of humans, as hungry sailors devoured their way through the entire species when they set anchor in the Mauritius.

However, human activity can also have unintended consequences for vulnerable species.

Populations plummet

A century after the last remains of the Oxford dodo were salvaged from incineration, an innocuous little songbird called the Kirtland’s warbler was being described for the first time by its namesake, the naturalist and politician Jared P Kirtland.

At the time of its discovery, populations of the bird were already low, isolated in the lower peninsula of Michigan in the US. Here, they still occupy a specialised habitat of Jackpine forest that is almost totally reliant on large-scale wildfires to germinate new seedlings and open up hardy pine kernels for food.

However, reductions in logging practices and improved fire management over the last century has reduced the availability of this habitat, forcing populations of these birds to plummet to critically low levels. On top of this, predation by the brood parasitic brown-headed cowbird left the Kirtland’s warbler on the brink of extinction by the early 1970’s.

Fortunately, conservation awareness has improved since the 17th century, and wide scale changes in habitat management policies were enough to help the species recover to healthier, more sustainable levels.  

Genetic bottlenecks

In a new article published in BMC Ecology, Amy Wilson and colleagues from the Smithsonian Conservation Biology Institute describe changes in genetic diversity of this songbird throughout the period from discovery to recovery. Unlike their dodo cousins, intact historic specimens were thankfully still available from the University of Michigan archives, which could be compared directly with contemporary populations.

Analysis of such genetic changes in a species over time are a useful indicator of the robustness of populations to large-scale demographic fluctuations, and provide a good measure of how processes such as inbreeding depression can negatively affect vulnerable populations.

These indicators are critically important in guiding conservation efforts of endangered species, and are one of a number of criteria used by the International Union for Conservation of Nature (IUCN) to evaluate how vulnerable each species is to extinction.

In this instance, the researchers detected a signal of a genetic bottleneck in contemporary populations and warn that at the lower range of estimates, the current effective population size would not be sufficient to maintain long-term genetic viability.

Whilst conservation efforts have been remarkably successful in bringing the Kirtland’s warbler back from the brink of extinction, it seems they may not be quite out of the fire just yet.

 

Temporal patterns of genetic diversity in
Kirtland’s warblers (Dendroica kirtlandii), the rarest songbird in North
America

Amy S Wilson, Pete Marra and Rob C
Fleischer

BMC Ecology 2012, 12:8 

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