How much habitat is enough for endangered birds?

The Pale-headed Goldfinch was rediscovered in west-central Ecuador almost 25 years ago, after three decades without any trace of the species. The expedition to find this “lost” bird was led by the Fundación de Conservación Jocotoco with support from the American Bird Conservancy (ABC). Unfortunately, at the time, the species only numbered around fifteen pairs. And as far as we know, the pale-headed goldfinch only occurred on about 60 acres, an area equivalent to one or two high school campuses in the United States.

Jocotoco and ABC immediately began their conservation efforts by acquiring, protecting, and then improving goldfinch habitat. Over the past decades, the bird’s story has become a shining example of how, even in a small area, a species can be saved from extinction by following a clear-eyed strategy based on solid research.

In 2021, the total population was estimated at around 240 individuals, with 112 known territories. In total, Jocotoco and ABC, along with Rainforest Trust, have protected approximately 485 acres of goldfinch habitat. As a result of these actions, the species was downgraded from “critically endangered” to “endangered” on the International Union for Conservation of Nature’s red list. It appears that for the pale-headed goldfinch, an area of 485 acres was enough to prevent its extinction.

But some birds need much more space to thrive. How do biologists know how much habitat is enough? Obviously, this must be enough to provide space for an adequate population of the species to thrive. A rule of thumb that conservationists have long used is a minimum population of 500 individuals. This number is thought to provide enough genetic diversity to avoid inbreeding and provide a buffer for the population to survive loss in bad years.

Scientists are currently performing these habitat calculations with the pallid goldfinch’s cousin, the Antioquian goldfinch. This songbird was rediscovered near Medellín, Colombia, in 2018 and is now considered critically endangered. Field research has revealed that Antioquian goldfinches survive in natural shrubby habitats. The next conservation challenge is determining the bird’s potential range and applying the “500” rule of thumb to determine how much land needs to be protected to ensure its survival.