Use of communal roosts by Andean Condors in northwest Patagonia, Argentina

Abstract

Andean Condors (Vultur gryphus) are endangered in the northern portion of their South American range, but populations are larger further south. However, throughout their range, little is known about current population sizes and dynamics. Andean Condors use cliffs with shelves as communal roosts and, from 1999 to 2001, we surveyed three of these roosts in northwestern Patagonia, Argentina, to estimate population sizes and trends. The minimum population of Andean Condors in our study area was 196, one of the highest populations recorded for this species. The maximum number of condors observed increased during our 3‐yr study. However, there was a strong seasonal pattern in roost use and use also varied among roosts, possibly due to differences in their environmental characteristics, size, and room available for roosting, as well as proximity to nest sites and stage of the breeding season. In 1999 and 2000, more adults were observed than juveniles, but proportions were similar in 2001. Because we observed differential use of roosts among age classes, spatial segregation seems probable. We conclude that intensive censuses of communal roosts can provide useful information about the size, status, and dynamics of local populations. However, the large aggregations we observed may represent a potential risk for the conservation of the species because a single threat could affect multiple individuals. We suggest that a suitable conservation strategy for condors must involve the design and protection of a network of communal roosts.

Winners and losers in human‐made habitats: interspecific competition outcomes in two Neotropical vultures

“…Andean condors were once widely distributed along the Cordilleran range from Venezuela to Tierra del Fuego. Currently, the species is threatened mostly in the northern parts of its range, but is still relatively abundant in the south (BirdLife International, 2008b;Lambertucci, J´acome & Trejo, 2008). Conversely, black vultures have a large global population size, and the species is evaluated as of Least Concern (BirdLife International, 2008a).…”

“…In the mountains (up to 3600 m a.s.l. ), there are many Andean condor roosts and breeding areas (Don´azar et al, 1999;Lambertucci et al, 2008), and human disturbance is very low, with some isolated human settlements and a few unpaved roads. In contrast, Andean condors are less abundant in plains (between 500 and 900 m a.s.l.…”

Cliffs Used as Communal Roosts by Andean Condors Protect the Birds from Weather and Predators

“…Hence, cliffs can be useful to analyse other potential advantages of communal roosting behaviour beyond its association with feeding habits. In particular, Andean condors ( Vultur gryphus ) roost communally in cliffs different from those in which they choose to nest (more detailed information is given in Methods, Study species) [16], [17].…”

“…The distribution and the aggregation patterns of condors in roosting places might be limited by the occurrence of roosts offering sun or protection, among other characteristics [16], [18]. Here, we proposed that communal roosts may serve as refuges from adverse weather conditions (“Climate Refuge Hypothesis”, CRH).…”

Factors influencing the selection of communal roost sites by the Black Vulture Coragyps atratus (Aves: Cathartidae) in an urban area in Central Amazon

“…Communal roosts are complex and comprise a series of spatially closed roosts used by a local population of vultures that alternates among such roosts in a given area, forming a roosting system (STOLEN & TAYLOR 2003). These complex communal roosts have been the subject of several studies that address habitat characteristics, social behavior, movements between roosts, seasonal and daily use patterns, and population dynamics (RABENOLD 1986, 1987, WRIGHT et al 1986, THOMPSON et al 1990, BUCKLEY 1998, STOLEN & TAYLOR 2003, EVANS & SORDAHL 2009, MCVEY et al 2008, LAMBERTUCCI et al 2008. However, one key question remains poorly investigated: what drives the selection of communal roosting sites by urban Black Vultures at the landscape scale?…”