A ruddy-headed goose with an Argos PTT (Antonella Gorosábel)
17.08.2020 Animal tracking applications

Ruddy-headed geese, endangered sheldgeese on South American continent

Ruddy-headed goose is considered regionally endangered in Argentina and Chile, since recent estimates indicate that population size is less than 800 individuals. Ruddy-headed geese were tracked back and forth during their migrations over the South American continent to better understand how to protect them there.

Photo: a ruddy-headed goose with an Argos PTT (Antonella Gorosábel)

 

An endangered migratory South-American continental population

Ruddy-headed goose (Chloephaga rubidiceps) is the smallest of the five South American sheldgeese . Two separate populations exist. One sedentary in the Malvinas Islands, is considered as “least concern” by IUCN. The other, migratory on the South American continent, which is critically endangered in Argentina and Chile. Only 800 individuals are reported nowadays, i.e., 10 % of the population estimated around 1900. Recent decrease has been attributed to invasive predators, degradation of breeding areas due to livestock, and illegal hunting. Habitat change and degradation at stopover sites along migration flyways are also suspected.

The continental ruddy-headed goose population overwinters in the Pampas region of Argentina, and breeds in Southern Patagonia (Argentina and Chile), before going back to their wintering grounds. However, the details of those annual migrations were poorly known, with questions on identification of stop-over, breeding and wintering sites, and migration timing during spring and autumn migration.

 

Tracked from their wintering grounds to their breeding sites

Six ruddy-headed geese males were equipped with Argos satellite telemetry tags in their wintering area in July- August 2015 and 2016. They were tracked from their wintering grounds in the Pampas region, Argentina, to their breeding sites in Southern Patagonia and back. All of them returned to the areas where they were captured one year before.

Tracked birds left their wintering sites in the second half of August and migrated in less than two weeks about 2,400 km on average, mainly over land, to their breeding grounds. The geese remained there, in southern Patagonia in the Magallanes region (Chile) during summer for at least seven months. It must be noticed that the ruddy-headed geese revisited the same breeding grounds in following years. The six birds migrated during austral autumn leaving end of May and in June, travelling only slightly less kilometres (about 2,350) in more than one month, mostly spending more time at stopovers. For that migration, geese moved along the Atlantic coastline, over the sea or close to the coastline. Maybe due to the prevailing weather conditions. The telemetry data show that the two migrations are similar in distance, speed when flying and in the number of stopovers, but not in their locations and in the time spent there.

Migration pathways of ruddy-headed geese tracked in 2015–2018. Grey (blue) indicates spring migration and black (red) autumn migration. Circles show stopovers during spring migration and autumn migration. Black points indicate wintering grounds in Buenos Aires province and specified breeding grounds in Patagonia. (From [Pedrana et al., 2020])
Migration pathways of ruddy-headed geese tracked in 2015–2018. Grey (blue) indicates spring migration and black (red) autumn migration. Circles show stopovers during spring migration and autumn migration. Black points indicate wintering grounds in Buenos Aires province and specified breeding grounds in Patagonia. (From [Pedrana et al., 2020])

Ruddy-headed geese conservation

Understanding migration timing and stopover sites is critical to propose any conservation plan for a species. This study shows for the first time the complete migration cycle of the ruddy-headed goose by using satellite transmitters. Among the conservation actions which could be led following this novel information, implementing feeding areas along ruddy-headed goose stopover sites would be foremost. This would create disturbance-free zones with food and protective vegetation cover, with control of introduced carnivores and of illegal hunting.

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