Why Population Estimate Studies are Important: Summary of the Blue-throated Macaw Study

To prevent extinction of species and protect a population, it helps to know how many individuals actually exist. Over the past few years, different estimates of the Blue-throated Macaw population have been suggested, but in the first-ever systematic survey, we have determined the population to be larger than any of the previous estimates figures: the encouraging result of around 425 individuals in the wild.

The Blue-throated Macaw is classified as Critically Endangered, the category of threatened species closest to going extinct. Categories are determined by considering how many individuals exist, the size of the range they live in, the quality of their habitat, and the factors contributing to population decline. Population decline in the case of the Blue-throated Macaw came about due to the trapping of individuals from the wild for the illegal bird trade (mostly in the 1970s-80s) and due to habitat loss from unsustainable cattle ranching. These factors have been largely addressed through educational programs, and efforts to help the species recover have been underway for fifteen years.

The Blue-throated Macaw finds its home in the Beni savannas of Bolivia. These savannas flood for eight months of each year. This flooding makes getting to and from the area difficult, dangerous, and expensive. Accepted ways of counting the existing population size don’t work since the area has limited road infrastructure and travel from one point to another often isn’t direct or even possible. Traditional techniques are also not realistic because the macaws fly long distances and are not easily found.

These macaws are known to rely on four of the habitats within the Beni savannas: raised islands of Motacu palm forest, grasslands dotted with palms, swamps with Moriche palms, and occasionally river-edge forests with palms. Why palms everywhere? The macaws mainly eat the pulp of the Motacu fruits and mostly nest in holes in dead Moriche, Motacu, or Grugru (Totai) palms. 

There are three separate Blue-throated Macaw groups, or subpopulations. They may not ever come in contact with each other at this time, though the continuation of current conservation measures may lead to the eventual reconnection of these subpopulations. The area covered by each group is not heavily populated, but each year there are population gains that are observable in nest box fledglings and in larger flocks observed and recorded.   

So how DO we count the macaws?

Armonia’s study was carried out in 11 chosen sites plus two known roosting sites in the 2015 dry season. One survey team was assigned to each subpopulation and visited the sites in their area over 12 days. Then they went back to the beginning and did the same surveys in the same order over the next 12 days. Researchers traveled by foot or on horseback noting all Blue-throated Macaws detected and identified with certainty. Other details collected were time of day, type of habitat, tree species where perched or direction of flight, behavior, and other birds nearby.

For each of the 11 survey sites, two numbers were calculated. The first was the highest number of individual Blue-throated Macaws seen at once. The second was a conservative estimate of the total number of macaws in that site, which was calculated based on all of the details collected and was designed to assure that each bird was counted once and only once. These numbers were then used to calculate the total estimated population overall by taking into account how much suitable habitat exists and how densely the macaw generally group within given habitats. The numbers were similar enough in the two repetitions of the study that scientists are confident that the study design allowed for an accurate count.

This study now estimates the total population of Blue-throated Macaws to be between 312-455 individuals, occupying a range of around 11,000 km2 (about 4250 square miles). This total is higher than any previous population estimates, which gives us confidence that the current efforts such as the nest box program, protection of key habitat, and educational programs are increasing the likelihood of a positive future for the species. More information will continue to be collected, especially in terms of breeding habits and success and studies in the harder-to-reach areas of the range, in order to consider a change from Critically Endangered status. 

This is a summary for the general public of information presented in the following publication:  https://www.cambridge.org/core/journals/bird-conservation-international/article/abs/first-systematic-sampling-approach-to-estimating-the-global-population-size-of-the-critically-endangered-bluethroated-macaw-ara-glaucogularis/9EC8457A1ABE7844C7453B61632DCCAB#. Please refer to the publication for more specific information.

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