Movement patterns and habitat preference of Oilbirds (Steatornis caripensis) in the southern Andes of Colombia

Abstract

Habitat use and movement patterns in animals are usually determined by the availability of food, morphological and physiological traits, social systems, and safe sites to complete vital cycles. The objective of this study was to estimate the home-range area, daily traveled distance, and patterns of space use by Oilbirds (Steatornis caripensis), and the factors that can affect them in Cueva de Los Guacharos National Park (Huila, Colombia). We attached GPS devices to five individuals and recovered information from three. Home ranges were estimated by minimum convex polygon (MCP), 95 and 50% kernel methods. Traveled distances were estimated as the sum of the linear distances between sampling points (every 30 min), and patterns of habitat use were evaluated through ecologicalniche factor analysis (ENFA), including forest cover, altitude, and degree of fragmentation. Analysis of habitat preference was done using 25 vegetation plots established in frequently used areas and species richness, and the proportion of consumed plants was compared with other locations within their distribution range. Home-range area was estimated to be 4517 km², possibly an underestimation due to reduced sample size. The average traveled distance per night was 55 km (range: 0-112 km). Analyses of habitat use showed a clear preference for areas with higher forest cover. Height above sea level was also largely associated with frequencies of habitat use, indicating a low use of areas above 3000 m, while the degree of fragmentation was not a strong predictor of habitat use. Finally, vegetation plots in frequently used areas showed a higher abundance of fruiting trees consumed by Oilbirds than control plots. Overall, Oilbirds have amazing movement capacity, being able to use distant landscape elements, and showing a clear preference for areas with forest cover, lower altitude, and areas with a high representation of the plant species they consume.

Oilbirds disperse large seeds at longer distance than extinct megafauna

“…However, a breakthrough occurred when Holland and collaborators 28 found, with the use of GPS tracking devices, that oilbirds do not return every day to caves, and may spend several days foraging and dispersing seeds outside from their resting caves. Actually, the use of GPS devices allowed us to track oilbirds through the landscape and start to infer their role as seed dispersers 31,32 . Major findings include that the fruits they consume belong to forest plants, and when leaving the caves oilbirds travel on average 55 km (range 0-112 km, Fig.…”

“…Major findings include that the fruits they consume belong to forest plants, and when leaving the caves oilbirds travel on average 55 km (range 0-112 km, Fig. 1C), preferring forested areas (though they can fly over deforested lands), and avoiding the highest altitudes 31 . In addition, they disperse seeds of lowland and mountain species, and for a set of nine species, it was found that 48% of the seeds were estimated to reach suitable areas for establishment, and these estimates were higher during the non-nesting season 32 .…”

“…1C), preferring forested areas (though they can fly over deforested lands), and avoiding the highest altitudes 31 . In addition, they disperse seeds of lowland and mountain species, and for a set of nine species, it was found that 48% of the seeds were estimated to reach suitable areas for establishment, and these estimates were higher during the non-nesting season 32 . Therefore, oilbirds may positively affect plant fitness from both quantitative and qualitative components.…”

“…The park has several caves commonly used by oilbirds, but we focused on the main cave 26 . There are at least 74 plant families of woody plants in the park 50 , and the home range of three oilbirds with GPS devices was estimated to be at least 4517 km 2 (minimum convex polygon), then this colony has access to plants in a large area surrounding the cave 31 . We monitored seeds dispersed by oilbirds using six nylon traps (each ca.…”

“…To estimate seed dispersal kernels, we used seed retention times in the gut of oilbirds 51 and movement patterns (from GPS tracking devices attached to three birds) (see details in 31 ). Devices were set to provide instantaneous locations every 30 min.…”