This is a continuation of a 2010 CREOi-funded project. The hooded grebe (Podiceps gallardoi), discovered in 1974, has experienced a precipitous decline over the past 40 years, prompting its status to be revised from species of least concern to critically endangered. CREOi-supported research over the past three years has provided important information on the locations of breeding colonies, reproductive biology of the species, factors that affect breeding success, and threats to the population. This work has led to reclassification of the species by the IUCN from data-deficient to critically endangered, leveraging additional resources and attention for conservation of this grebe.
The most recent award supported continuing population and breeding surveys, including 185 lakes in 11 mesa plateaus in southwestern Argentina, covering the entire known breeding range of the hooded grebe. A total of 714 individuals were sighted, which represents almost 90% of the total population estimated for this species. There were 11 breeding colonies, although only two were successful, with a total of 64 juveniles fledging.
During the chick-rearing season the researchers conducted a pilot project by placing a human observer to protect nesting colonies from attacks by kelp gulls. The effort resulted in 67% chick survival in the protected colony, more than the 20-50% recorded previously. The presence of a “guardian” at the colonies not only buffered the kelp gull threat, but also decreased attacks by other aquatic bird species such as coots, ducks and swans, given that these species are less tolerant of human presence than the hooded grebe (which lacks a fear of humans).
The project also investigated the effects of introduced, stocked trout on habitat quality for hooded grebes and other aquatic birds. The aquatic plant “vinagrilla” provides grebes with nest building material and is home to many grebe prey items. The researchers discovered that in lagoons where trout were present, vinagrilla was absent and so were grebes and many other aquatic birds. The team is working on an eradication plan for trout, with studies of trout removals in several small lagoons to test the conservation strategy. Ultimately, the aim is to remove trout in several key lagoons such a Laguna de Islote, where grebes once numbered over 1,000, but have been absent since the introduction of trout.
Extending the effort to directly understand and manage threats to the hooded grebe population, the researchers also embarked on a study of the American mink, which was discovered as an introduced predator under the previous CREO award. The region was surveyed with a specialist in introduced mammals of Patagonia, revealing fairly small but more widespread populations than expected among the mesa plateaus. Much higher densities were discovered in the lower river drainages from the plateaus, and researchers will be focusing intensive monitoring of key lagoons that should be protected from mink invasions.
The hooded grebe project has garnered international and national attention, and partnerships with Aves Argentinas and BirdLife International have helped to expand both the research and outreach programming. A recent highlight of these efforts was the production of a documentary, available in Spanish and English, on the hooded grebe with narration (for the Spanish version) and music by Oscar-winning Argentine celebrities. This attention has also provided traction for the current effort to establish a national park encompassing key habitat for hooded grebes as well as other important species such as guanacos, foxes and various birdlife. ($7,925)