F. Hernán Vargas

Nesting Density of Harpy Eagles in Darien with Population Size Estimates for Panama

Abstract Between October 2000 and December 2006, we located 30 nests of 25 breeding pairs of Harpy Eagle (Harpia harpyja) in the province of Darien, Panama. Most nests were in primary tropical rain forest at a mean altitude of 132 m (range  =  50–305 m). Applying the Polygon and the Maximum Packed Nest Density (MPN) methods, we estimated nest densities of 4 and 6 nests/100 km2, with each breeding pair occupying 24 and 16 km2 of forest, respectively. This nesting density is the highest reported for the species throughout its breeding range. Although most nests (n  =  25) were in primary forest, the average distance from small parcels (<2 ha) of agricultural fields was 2.5 km. By extrapolating the nesting density results from the selected study area in Darien to the entire area of Panama with suitable forest cover at altitudes below 350 m, we estimated that the Harpy Eagle population size could range between 806 and 1208 pairs. Greater conservation effort should be placed on potentially suitable Harpy Eagle habitat. We also suggest that educational outreach measures should be an important part of conservation efforts throughout Panama.

Effect of Sex and Age at Release on the Independence of Hacked Harpy Eagles

Abstract Release methods used in species restoration can affect the success of establishment and survival of released animals. We evaluated the effect of age at release and sex on the length of the dependence period of hacked captive-bred juvenile Harpy Eagles (Harpia harpyja). Between 2002 and 2007, we released 34 (19 males and 15 females) young eagles in Panama and Belize. To test the effect of age, these eagles were divided into two age classes: younger age class 1 (5–7 mo old) and older age class 2 (18–22 mo old). Survival (hacking success) was lower for the younger release age (70%) compared to the older release age (100%; Z  =  −2.05, P  =  0.040). This difference in hacking success was attributed to the extended period of dependence on provisioned food by the younger (18.9 ± 1.3 mo [SE]) compared to older eagles (1.5 ± 0.8 mo). Between-sex comparisons showed that the average length of the dependence period was longer for males of age class 1 (males  =  21.8 mo vs. females  =  14.3 mo) and for females of age class 2 (females  =  2.7 mo vs. males  =  0 mo). Cox regression models indicated that the interaction of age at release and sex had a significant effect on the dependence period, and that age at release was the most influential variable. Eagles released at 18 mo or older showed increased survival and shorter dependence periods. Hacking can be used to successfully release captive-bred Harpy Eagles into the wild, but this technique was more efficient when delayed from fledging age (when falconers traditionally hack falcons) to nearer the Harpy Eagles age of independence.

From the Vagile to the Sedentary: Disease Implications and New Host Relationships on Islands

How species come to be established on islands and their consequent adaptations and evolution are subjects that lie at the heart of much of ecology and evolutionary and conservation biology. On islands, small populations, limited gene diversity and flow, and simpler ecosystems facilitate our understanding of how species arrive and then adapt and evolve in new locations. One component of this is understanding how the transition from arrival to establishment may affect species and their parasites and diseases. Colonizing species may arrive without the full burdens of parasites weighing on their source populations, allowing them to reduce their energetic investments in immune defenses. However, reduced genetic diversity may also reduce populations through inbreeding depression or diminish capacity to evolve. Loss of genes and adaptation to novel environments may over time reduce the capacity of insular species to deal with new parasites or old ones that “catch up.” With increasing anthropogenic introduction of novel biotas, including parasites, to islands, the conservation of insular biodiversity becomes increasingly challenging, which in turn reduces our ability to study and understand both islands and diseases.

Observations of a Tree-cavity Nest of the Rufous-legged Owl and Predation of an Owl Nestling by a Chimango Caracara in Andean Temperate Forests

Andean temperate ecosystems have lower avian species richness than other temperate, subtropical, and Andean forest types, but they contain many endemic species (e.g., 41% for birds; Vuilleumier 1985). Because of its high concentration of endemism and exceptional loss of native forest habitat (approximately 70%), the Andean temperate ecosystem is classified as a Global Biodiversity Hotspot (Myers et al. 2000). The Rufous-legged Owl (Strix rufipes) is an endemic forest-specialist raptor once considered one of the least-known owls in South America; this species has declining populations because of increasing habitat loss (Martı́nez and Jaksic 1996). Recent studies have shown that this species tolerates some habitat disturbance, but still requires a complex forest-stand structure comprising large, decaying trees, dead standing trees (snags), and a dense understory (Ibarra et al. 2014b, Ibarra and Martin 2015). Rufous-legged Owls in temperate forests are sit-and-wait predators with a diet composed mainly of arboreal and scansorial small mammals, but also smaller proportions of forest passerines and invertebrates (Martı́nez 1993, Martı́nez and Jaksic 1997, Figueroa et al. 2006, 2016). The few reported nests described for Rufous-legged Owls include one likely unusual nest on the ground in a pine (Pinus radiata) plantation (Estades 1998), and six cavity nests in large, decaying native trees (Vukasovic et al. 2006, Wallace 2010, Beaudoin and Ojeda 2011). In all these cases, however, information on Rufous-legged Owl nesting activity (e.g., incubation period, adult parental behavior, prey consumption) and nest fate was lacking. Secondary Andean temperate forests and open areas are readily utilized by the Chimango Caracara (Milvago chimango), a common, yet poorly studied raptor (Figueroa 2015). This habitat generalist raptor feeds on carrion, human rubbish, invertebrates, lizards, small mammals, and 1 Email address: jtibarra@uc.cl