Discoveries from 2020 Nest Search Expedition Guide Next Steps for Blue-throated Macaw Research and Conservation

Breeding Blue-throated Macaws posed playfully on dead Moriche palm nest
(Photo: Tjalle Boorsma – Asociacion Armonia).

2020 Blue-throated Macaw rainy season search expedition results: 

10 Blue-throated Macaw nests discovered in the northwestern subpopulation
3 unknown Blue-throated Macaw breeding sites discovered
Approximately 100 Blue-throated Macaws observed in Llanos de Moxos during rainy season
Northwestern subpopulation breeding requirements unraveled
~307 km2 surveyed of 566 km on horseback through flooded savanna

Armonía’s latest expeditions to study the Bolivian endemic Blue-throated Macaw have produced important discoveries about behavior and ecology due to two differences from previous studies: they followed the northwestern subpopulation of Blue-throated Macaws, and they were conducted during the rainy season. Only between 312 and 455 Blue-throated Macaws remain in the wild (full article) dispersed over three separate subpopulations and need to be protected urgently.

The macaws at Armonía’s Barba Azul Nature Reserve are part of the northwestern subpopulation, one of three separate subpopulations of Blue-throated Macaws. The northeastern subpopulation inhabits areas east of the large Mamoré river, while the southern subpopulation is found near Loreto and Armonía’s Laney Rickman Blue-throated Macaw Reserve. Most of what was previously known about the Blue-throated Macaws was based on observations of the northeastern and southern subpopulations only. 

At Barba Azul the macaws migrate, spending the dry season in the reserve and then leaving at the start of the rainy season in the months of October and November when they are ready to breed. Monitoring of the macaws at Barba Azul resulted in the largest ever single high count of 155 Blue-throated Macaws in 2017 (see post), and similarly impressive highest counts in subsequent years: 130 individuals in 2018, and 131 in 2019, indicating a healthy and growing subpopulation.

All early observations of the northwestern subpopulation were necessarily from the dry season, as the savannas are usually flooded and inaccessible in the rainy season. Inaccessibility of the savannas during the macaws breeding season maintained the mystery of their unknown breeding grounds. Armonía unraveled this mystery.

Open Moriche palm savanna, used as breeding habitat for Blue-throated Macaws.
(Photo: Tjalle Boorsma – Asociacion Armonia).

Since the earliest observations in the Barba Azul Nature Reserve in 2007, the leading question has been where the macaw’s breeding grounds are located. In 2016 anecdotal leads from ranchers who said they had nesting macaws on their properties prompted a 3-day expedition. The first ever rainy season Blue-throated Macaw roost was discovered. This information then justified an expedition for 2017 to find breeding macaws, with support from the American Bird Conservancy and The Cincinnati Zoo.  The first ever 5 nests for the northwestern subpopulation were discovered!

The standout information from the 2017 search was that three of the nests observed were located in Moriche palms (Mauritia flexuosa). Barba Azul’s habitat consists of several types of palms, including Motacú (Attalea princeps) palms, the fruit of which is one important food source for the macaws, but no Moriche palms. Could the macaws be migrating in search of Moriche? Locating and searching in large Moriche forests left the trail cold. No macaws were sighted in these single-species forests.

Reorganization of efforts led to Toyota Environmental Activities Grants (through Birdlife Tokyo) and Vogelbescherming Nederland funding two years of expeditions. Though expectations were high for the 2019 search, an abundant rainy season resulted in severe flooding. Flooded savannas were inaccessible. This seasonal flooding, typical of the Llanos de Moxos ecosystem, is the reason data is limited for the northwestern macaws in the rainy season.  With the searches cancelled, all resources for the two years then went to the 2020 expedition.

Local cowboy guiding research teams through flooded savanna, typical of Llanos de Moxos
(Photo: Tjalle Boorsma – Asociacion Armonia).

Thankfully, the weather cooperated in early 2020 and networking paid off. Three search teams went on horseback surveying 5 different sites visiting 26 ranches. Armonía is extremely grateful to all the ranchers who willingly collaborated in the form of lodging, participation of staff as local guides, and use of their horses. The teams covered 566 km total on horseback, surveying an area of 307 km2. They searched through a large belt of Motacú and Moriche mixed-palm forest in the northern Llanos de Moxos. 

2020 Discoveries

The findings from this 2020 search were impressive. Between 93 and 104 individual Blue-throated Macaws were observed at 14 out of the 26 ranches visited. Ten nests were found: 9 were in Moriche palms and 1 was in a Motacú. The “two-palm hypothesis” was confirmed: that mixed Motacú/Moriche forest is key to the macaws’ migrations. The Motacú palms are important in both seasons for foraging, while the Moriche are sought for breeding purposes. The use of these tree species by the northwestern subpopulation was especially interesting in light of what was already known from the other two subpopulations of macaws. Blue-throated Macaws in the south and the northeast use a variety of palm and hardwood tree species for nest-building, but the Moriche palm isn’t known to be one of them; it isn’t even present in the habitat of the southern subpopulation. 

Blue-throated Macaws on nest at top of dead Moriche palm snag
(Photo: Teodoro Camacho – Asociacion Armonia).

Accepted range limits for the Blue-throated Macaw were expanded with a 2017 sighting of 10 birds in a location 40 km north of the previously accepted limits. In this same location, the 2020 expedition documented 56 birds. This site had no breeding birds when it was discovered; this year 2 nests were found in the area. Due to distance, it would technically be possible for macaws from Barba Azul to migrate to this location. Future expeditions will be focusing on answering the question of whether this group is a separate population. 

More questions raised

Another question raised in 2020 was whether the field techniques are successfully finding all nests passed. The technique used for 2020 was to walk through Moriche palm savanna paying attention to dead snags. Any time macaws were seen on dead Moriche snags, the location was observed, noted, and revisited the following day. If macaws were present on day 2, the snag was considered to be a confirmed nest. If no macaws were observed, the snag was discarded as not being a nesting site. The question came about due to a snag that had been confirmed as a nest on day 2. No birds were seen or heard on day three. One of the cowboys knocked on the post as he went by and was surprised to have a macaw come out. Its mate also called from a short distance away. This unexpected response left the researchers wondering how many nests had been overlooked due to the use of least-invasive techniques. 

Small, erect yellow cheek feathers observed in breeding macaws
(Tjalle Boormsa – Asociacion Armonia)

A feather pattern never seen before got the attention of the researchers in 2020. Adult breeding pairs were noted to have small yellow cheek feathers, present in both adults. Follow-up questions are whether these feathers indicate breeding, and whether they are present in the other subpopulations but have escaped notice to date.

Action plan for the future

The discoveries and ongoing questions provide direction for planning strategies to protect the Blue-throated Macaw. A total of 14 ranches have been confirmed as having Blue-throated Macaw presence in the rainy season, with 11 having confirmed nests. These 14 ranches will be the focus of relationship building, educational programs, and coordination of activities, made possible with funding from Future For Nature. The ranches have already received posters to raise awareness of conservation needs, presentations, and a handbook on Sustainable Ranching with benefits for both ranching and macaws. Further educational focus will be placed on the importance of leaving nests undisturbed, as ranchers have indicated there is some amount of animal trafficking pressure, and protecting roosting and breeding territories. Fire breaks have and will continue to be implemented in coordinated efforts with ranchers to protect vital habitat. 

Monitoring programs will be designed for the ranches, including the placement of nest boxes. The design that is showing promise for the northern subpopulation is the Penthouse Nest Box, as it mimics the higher location of natural nests due to the tall stature of the Moriche palm when compared to nests in the northeast and south. One hypothesis is that if the macaws become accustomed to using nest boxes at their breeding grounds, the potential for them to nest in boxes within the protected limits of Barba Azul will rise. 

This image has an empty alt attribute; its file name is TjalleBoorsma_Mayo2019-17-3-1024x683.jpg

Blue-throated Macaws on Penthouse nest boxes.
(Tjalle Boorsma – Asociación Armonía)

“We are extremely grateful to all the ranchers and cowboys throughout the study area for their incredible support and hospitality during our fieldwork.”

Tjalle Boorsma with cowboys who assisted Research Team
(Roberto Charbel Rescala)

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