East with the night: longitudinal migration of the Orinoco goose (Neochen jubata) between Manú National Park, Peru and the Llanos de Moxos, Bolivia

Abstract

We report on the intra-Amazonian migration of a pair of Orinoco Geese (Neochen jubata) from Manú National Park, Peru. The species is Critically Endangered in Peru, so a major aim of the study was to aid conservation planning by learning the wet season location of the country's last known breeding population. We captured a breeding pair on October 27, 2010, and fitted the birds with Microwave Telemetry, Inc. GPS/Argos satellite PTT's. The pair migrated ∼655 km from Manú National Park to the Llanos de Moxos, Bolivia (Dept. of Bení) in a predominantly longitudinal migration, reaching their final destination on December 23, 2010. Major movements (>5 km per time period) were almost exclusively at night and were undertaken with and without moonlight. Foraging areas used at stopovers in the Llanos de Moxos were remarkably limited, suggesting the importance of grazing lawns maintained by the geese and other herbivores, possibly including cattle. Orinoco Geese are resident in the Llanos de Moxos year-round, so the Manú geese represent a partial migration from the Bení region. We hypothesize that cavity nest limitation explains the partial migration of Orinoco Geese from the Llanos de Moxos.

Figure 1. Orinoco Goose Migration Route.

The complete migration (pink line) of the Orinoco Geese caught in Manú National Park, October 27, 2010. Locations denote date and local time for points discussed in the text. Google Earth accessed 19 April 2012 coordinates 13°14′33.19′′S; 68°35′31.77′′W.

Figure 2. Major Movements by Date, Time and Phase of the Moon.

Major Movements (>5 km per period) by Julian date, time, and phase of the moon between October 27 and December 31, 2010. For each day, shaded areas are times when the moon is not visible in the sky at the goose's location. Movements are diagrammed by date and time with red diamonds sized in relation to the log of the distance traveled (in km) during that period. Each movement is placed at the midpoint of the time period during which the goose traveled, which is typically within a 6 h period between 6 pm and midnight or midnight and 6 am. Vertical red lines on the furthest left points and one anomalous point at 07∶00 demonstrate these potential spreads in timing.

Figure 3. Stopover 1 50% MCP Core Foraging Area.

Daytime foraging area used by the Orinoco Geese at Stopover 1, December 2 to December 16. Inset map shows the foraging location with respect to the typical night-time roost about 10 km away and 95% Minimum Convex Polygon (MCP) of daytime and night-time locations. The underlying yellow polygon is the 50% MCP core area of use. Google Earth accessed 11 April 2012 coordinates 13°28′31.23′′S; 66°49′28.44′′W.

Figure 4. Final Destination Foraging Area.

Foraging area used by the Orinoco Geese at their final destination, December 23 to Feburary 4. The white polygon is the 95% Minimum Convex Polygon (MCP), and the underlying yellow polygon is the 50% MCP core area of use. Google Earth accessed 11 April 2012 coordinates 13°9′39.56′′S; 65°32′33.07′′W.