The conservation of the Spotted Owl (Strix occidentalis) has been the center of a 40-yr conflict between those who wish to conserve owls and old growth forests and those who wish to log trees as commodities. Although the Spotted Owl conflict seems unique because it has lasted so long, it is no different than many other conservation conflicts in which many scientists—and raptor biologists specifically—might find themselves engaged. Therefore, I explore the commonality among conflicts, including specific details of the Spotted Owl case, to illustrate the problems inherent in conservation conflicts and why these disputes last so long. I suggest two general motivations that I believe capture the reasons behind people's willingness to engage in conflict: money and passion. Yet the specific motivations (e.g., economic well-being and ideology) nested within these general motivations are complex and interconnected. This complexity can lead to intractable situations, such as Spotted Owl conservation, which have been defined as “wicked problems” that cannot be resolved to the satisfaction of most. But understanding these broad motivations and identifying the wide variety of specific motivations nested within them may yield opportunities to manage—rather than resolve—a conservation conflict. Accordingly, I present a conceptual overview of the owl situation as a case study, along with some guidelines for raptor biologists working in conflict environments.

The identification of breeding habitat is essential for the implementation of conservation efforts for threatened species. Using seven natural and anthropogenic variables, and based on 27 nesting attempts over 17 yr, we created a species distribution model for Harpy Eagle (Harpia harpyja) breeding habitat across 5636 km² in the Pacific Region of Darien Province, Panama. Highly suitable habitat had high forest cover, low elevation, and a relatively low distance to rivers. We identified specific breeding habitat associations for Harpy Eagles and found that 34% of the area analyzed contained highly suitable breeding habitat. At the regional level, highly suitable habitat was found predominantly in the northern portion of the study area in the four watersheds occurring there, and along the Pacific Coast. The Juradó watershed in the south contained relatively little habitat, owing to a high amount of mountainous terrain. Among three protected areas in the region, Darien National Park contained an equal amount of habitat as the relatively smaller and neighboring Chepigana Forest Reserve and Serranía de Bagre Biological Corridor, a fact that highlights the importance of northern forests for the conservation of Harpy Eagles in Darien. Generally speaking, areas with the greatest amount of human influence were associated with greater forest loss and less suitable habitat. We therefore propose that community-based strategies for sustainable resource management are needed to mitigate forest disturbance levels in areas where the Harpy Eagle coexists with humans. Considering the high importance of the breeding habitat for the Harpy Eagle in the Serranía de Bagre Biological Corridor and Chepigana Forest Reserve, we recommend a revision of the legislation that governs the extractive use of the natural resources in these two protected areas.

La identificación del hábitat reproductivo es esencial para la implementación de esfuerzos de conservación en especies amenazadas. Usando siete variables naturales y antropogénicas y basados en 27 intentos de anidación a lo largo de 17 años, creamos un modelo de distribución de especies para el hábitat de cría de Harpia harpyja a través de 5636 km² en la Región del Pacífico de la Provincia de Darién, Panamá. El hábitat más adecuado tuvo una alta cobertura de bosque, una baja altitud y una proximidad relativamente cercana a ríos. Identificamos asociaciones de hábitat reproductivo específicas para H. harpyja y encontramos que el 34% del área analizada incluyó hábitat reproductivo muy adecuado. A escala regional, el hábitat más adecuado fue encontrado predominantemente en las cuatro cuencas presentes en la porción norte del área de estudio y también a lo largo de la costa del Pacífico. La cuenca del Juradó, en el sur, presentó relativamente poco hábitat adecuado, debido a una alta cantidad de terreno montañoso. De las tres áreas protegidas en la región, el Parque Nacional Darién incluyó una cantidad similar de hábitat comparada con las vecinas y relativamente menores Reserva Forestal Chepigana y Corredor Biológico Serranía de Bagre. Esto resalta la importancia de los bosques del norte para la conservación de H. harpyja en Darién. En términos generales, las áreas con mayor cantidad de influencia humana estuvieron asociadas con mayor pérdida de bosque y menos hábitat adecuado. Por ende, proponemos la necesidad de estrategias comunitarias para la gestión sostenible de los recursos y mitigar los niveles de disturbios forestales en áreas donde H. harpyja coexiste con humanos. Considerando la gran importancia del hábitat reproductivo para H. harpyja en el Corredor Biológico Serranía de Bagre y la Reserva Forestal Chepigana, recomendamos una revisión de la legislación que gobierna el uso extractivo de los recursos naturales en estas dos áreas protegidas.

[Traducción de los autores editada]

Like many raptors, Red-shouldered Hawks (Buteo lineatus) exhibit asynchronous hatching, which is thought to be a parental strategy for rearing the maximum number of offspring under conditions of unpredictable prey availability. Current knowledge of incubation patterns and the associated behavioral mechanisms by which asynchronous hatching occurs in raptors is limited, and few detailed quantitative studies are available for any species of Accipitriformes. We investigated the effects of egg-laying intervals and parental behavioral incubation patterns during egg-laying on hatching asynchrony in the Red-shouldered Hawk. We used 24-hr/d digital color/infrared video cameras at 15 Red-shouldered Hawk nests to record egg-laying and hatching, and to quantify the proportion of time parents spent incubating, standing, or absent from the nest. The mean egg-laying interval was 2.9 ± 0.1 d or 69.8 ± 2.2 hr (range = 65.8–74.2 hr), and the mean duration of incubation (from the onset of full incubation to hatch) for last-laid eggs was 33 d (32–34 d, n = 15). Red-shouldered Hawks exhibited partial incubation behavior, with the delay in the onset of full incubation varying by clutch size and among individuals; full incubation generally began with or just after the laying of the penultimate egg of the clutch. The mean interval between the hatching of the first and second egg was 0.56 ± 0.49 d; between the second and third eggs, 1.24 ± 0.71 d (P= 0.0215); and between the third and fourth eggs, 2.42 ± 0.38 d (P < 0.0004). The total amount of time parents at each nest spent incubating during the egg-laying period explained most of the variation in the amount of time between the hatching of their first and last egg (the hatching span; r² = 0.83, P < 0.0001). Hatching patterns were the result of both the egg-laying intervals and the pattern of partial incubation, which may represent an adaptive mechanism to reduce the hatching interval while maintaining the hatching asynchrony.

Parent-offspring conflicts arise through the competing efforts of the parents (to optimize their reproductive success) and the offspring (to secure maximum resources for themselves to enhance survival). Competition among siblings in a brood plays a key role in each nestling's relative fitness, particularly in avian species that hatch asynchronously. Previously published research has shown that the first-hatched nestling secures the most food, often at an energetic cost to its siblings. However, few researchers have simultaneously investigated competition and parental allocation behaviors to determine their effects on food distribution among raptor nestlings. We found that Ferruginous Hawk (Buteo regalis) parents delivered the same number of prey to nests, regardless of brood size. Contrary to our expectations, all nestlings consumed a similar amount of food within individual feeding events. Importantly, neither nestling competition nor parental allocation was the dominant process responsible for equal food distribution. Instead, the first-hatched and second-hatched nestling gained more food by competition, and the third-hatched nestling gained more food through parental allocation. Although each nestling attempted to optimize its food consumption relative to its siblings, resulting in unequal competitive outcomes, parents altered their allocation behavior to offset sibling competition. Ultimately parents provided the last-hatched nestling with more food, and thereby controlled food distribution to maximize their reproductive output. Future work should explore the role of nestling competition and parental allocation on food distribution using supplementation at nests when prey abundance in the environment is low.

The Northern Goshawk (Accipiter gentilis) is an apex predator occurring across North America and Eurasia. The species has received considerable conservation focus in late-seral conifer forests of western North America, where its habitat has been substantially reduced and altered by timber harvest and is increasingly at risk from high severity fire, drought, and forest pathogens. In the Sierra Nevada range of California, management and conservation of goshawks are hampered by a lack of knowledge of their basic space use and movement ecology. We used global positioning system (GPS) loggers to investigate space use of 20 resident, adult Northern Goshawks over 3 yr (2015–2018) in the Plumas National Forest, California. Median home range sizes of male goshawks were more than twice as large as those of females, and nonbreeding-season home ranges were three times larger than breeding-season home ranges. High resolution GPS data (location interval 1–6 min) allowed quantification of daily transit distances up to 60 km for individual goshawks and revealed long-distance forays into adjacent territories and surrounding areas. Four goshawks (three males, one female) undertook forays >8 km from their nest locations, with forays lasting up to 6 d; these forays occurred during both breeding and nonbreeding seasons for both sexes. Comparing our results to current conservation approaches, we determined that USDA Forest Service goshawk Protected Activity Centers protected <25% of both the roost locations and the area used during the daytime. Conservation efforts for Northern Goshawks in the Sierra Nevada would benefit from consideration of year-round habitat needs at larger scales than previously thought.

The Tawny Owl (Strix aluco) is the most abundant nocturnal raptor in Europe. It has been thoroughly studied in various regions, but its habitat preferences in Mediterranean environments remain poorly understood. With the aim to present novel information about this aspect of the ecology of the Tawny Owl, we established 115 survey stations in the Special Conservancy Area “Sierras de Talayuelas y Aliaguilla” (Castilla–La Mancha region, eastern Spain) and carried out nocturnal surveys by recording spontaneous calls and vocal responses to call playbacks. We then assessed environmental characteristics (vegetation types, soil type, altitude, potential competitors, and anthropic disturbance) in areas where owls were detected or not detected during the breeding season. Overall, we detected 60 responding owls at 49 survey stations during breeding season in the study area (i.e., density 1.22 owls/km²). We found that Tawny Owls preferred lower altitudes and patchy heterogeneous areas. Owls seemed to avoid natural grasslands and areas characterized by limestone soils and associated vegetation, and preferred areas characterized by clay soils and associated vegetation. Interestingly, we did not detect owls close to wind farms, which seem to create a buffer effect on owls’ occurrence. The noise generated by the turbines might be a limiting factor that could account for this avoidance. Our multivariate results showed that Tawny Owls preferred heterogeneous patchy habitat but avoided non-irrigated arable land. Tawny Owls inhabit Mediterranean landscapes where conditions are favorable, but human activities such as wind farms may limit their distribution. Additional research is needed to determine the drivers of this avoidance and whether Tawny Owls also avoid wind farms in other regions of their range.

Coastal raptors in urban landscapes face multiple threats. Australia's coastal raptors (Osprey [Pandion haliaetus cristatus], White-bellied Sea-Eagle [Haliaeetus leucogaster], Brahminy Kite [Haliastur indus], and Whistling Kite [Haliastur sphenurus]) are all found in the urban region of South East Queensland/northern New South Wales, and have varying sensitivities to urbanization. To assess some of the effects of urbanization on these species on Australia's mid-east coast, we reviewed Currumbin Wildlife Hospital Foundation admissions data from July 1998 to February 2020. Overall, more birds were admitted because of anthropogenic causes than natural causes, and the hospital had high treatment success, with most patients surviving their injuries to be released to the wild. The most significant identifiable impact was fishing equipment entanglement, accounting for 21% of raptors for which we could determine the cause of admission, followed by bird attack (20%), and vehicle strike (19%). To our knowledge, this is the first assessment to show fishing activities to be a significant cause of injury for coastal raptors. Understanding the causes of injury and mortality to these birds, including especially anthropogenic causes, is critically important for species management and conservation. As recreational fishing is a popular practice in this region, it is important to continue to provide education about the threats fishing can cause, and disposal bins for fishing tackle in popular fishing areas to reduce the number of coastal raptors affected.

Feeding strategies, including cannibalism (in which an individual eats a member of the same species), are an important aspect of predator ecology. Cannibalism comprises five forms in raptors: siblicide, filicide, non-parental infanticide, conspecific strife, and conspecific scavenging. Cannibalism by raptors has been documented opportunistically for over a century, but it is unknown how frequent or widespread the behavior is. We performed the first systematic literature review and meta-analyses of the studies documenting filicide, non-parental infanticide, conspecific strife, and conspecific scavenging by raptors. We found 29 reports of these types of cannibalism; we did not review reports of siblicide due to the high frequency of the behavior, making it nearly ubiquitous among raptors. Filicide had nearly twice as many reports (n = 11, 37.9%) as any other type of cannibalism. Most reports were direct observations (n = 23, 79.3%), and nearly half the reports came from North America (n = 14, 48.3%) and approximately a third from Europe (n = 10, 34.5%). The 29 reports involved 25 raptor species from four families, with those from Accipitridae most common (n = 19, 65.5%). Cannibalism in raptors varies but most involves nestlings, which are easier to kill than adults, possibly because brood reduction can help the stronger young survive. Documented reports of cannibalism are increasing, possibly due to recent technological advancements that have increased our ability to document cannibalism and other ecological processes. Nevertheless, we encourage future reports of cannibalism from under-represented locations and for taxa that are less well studied.

Electrical pylons are frequently used by birds for perching, roosting, and nesting. These behaviors can lead to electrocutions, particularly when pylons are constructed of grounded concrete and steel crossarms, as they were in our study area near Arak, Iran. To address electrocutions of Eurasian Kestrels (Falco tinnunculus) and a variety of passerines nesting on a 20-kV distribution line, we documented construction and use of nests on pylons on a 34-km segment of power line in 2018. Following removal of nests by the electric utility operating the line, we installed nest boxes on pylons that previously supported nests, and in 2019 we documented use of those nest boxes. We predicted that after installation of nest boxes, numbers of Eurasian Kestrel nests would increase, and numbers of nests outside of nest boxes, avian electrocutions, and faults (electric current arcing from conductors to pylons) would decrease. All four predictions were validated. We documented 31 nests in 2018, including 3 Eurasian Kestrel nests. In 2019, we documented 6 nests outside of nest boxes, and 31 nests in nest boxes, including 16 Eurasian Kestrel nests. In 2018, we found 1 electrocuted Eurasian Kestrel, and 39 electrocuted passerines. In 2019, we found 3 electrocuted Eurasian Kestrels, 11 passerines, 2 Eurasian Eagle-Owls (Bubo bubo), and 1 Steppe Eagle (Aquila nipalensis). The rate of electrocutions per nest for Eurasian Kestrels decreased from 0.33 to 0.19, and the electrocution count for all birds decreased by 57.5%. Electrical faults, an indirect measure of potential avian electrocutions, decreased from 173 in 2018 to 120 in 2019. Although there is some risk that nest boxes on power poles could create ecological traps, our results suggest that in this study electrocutions and electrical faults were reduced, supporting conservation goals and electric power reliability goals while simultaneously reducing electric utilities' maintenance obligations.

Interspecific competition plays a central role in structuring ecological communities and is a particularly strong force among avian scavengers. Niche partitioning among scavengers has been thoroughly investigated for Old World vultures (family Accipitridae), yet we know much less about its effect on the structure and functioning of the complex scavenger guilds of the New World (family Cathartidae). We studied how niche partitioning differed between ecosystems featuring species-poor and species-rich guilds of avian scavengers in South America. We compared dietary overlap between avian scavenger assemblages at two sites in Argentina where Andean Condors (Vultur gryphus) reside: Patagonia, featuring a rich guild of five main avian scavengers, and the High Andes, with only two main species of avian scavengers. We compared the δ¹³C and δ¹⁵N isotopic signatures, proxies for animal diets, of molted feathers to quantify niche breadth for individual species, and niche overlap between species. We found greater isotopic overlap between species and a smaller niche breadth for Andean Condors in Patagonia, where the richest assemblage of scavengers exists. These site-level differences in niche size and overlap are likely a result of greater isotopic diversity of ungulate prey around our sampling area in the High Andes, and future research should test this potential mechanism. The smaller niche breadth and greater isotopic overlap for the Andean Condor in Patagonia could signify competitive interactions with other scavengers and negative population-level effects for this species of conservation concern.

In Argentina, the Variable Hawk (Geranoaetus polyosoma) inhabits the northwestern, central, and southern parts of the country, but current information on its breeding distribution and conservation status for most Argentine provinces is lacking. Raptor nest surveys in Santa Cruz Province (southern Argentine Patagonia) during the breeding seasons of 1980–1981 and 2008–2011, revealed six active nests (one in 1980, two in 2008, and three in 2010), plus one additional nest (in 2011) showing evidence of use earlier in the breeding season. Additional ornithological surveys in Santa Cruz Province between 1994 and 2018 revealed two more nests (one each in 2002 and 2004). Results of these combined surveys suggest that the Variable Hawk breeds in very low numbers in the southern continental Patagonian steppes, grasslands, and coastal biomes of Santa Cruz Province. This low density substantiates previous reports on the rarity of the species in this province and contrasts with findings from northeastern Patagonia, where it breeds at high densities. Low Variable Hawk breeding abundance in southern continental Argentine Patagonia is likely related to low prey diversity and abundance as well as anthropogenic activities. We recommend surveys be conducted of this hawk and its prey in different biomes throughout Patagonia.

Birds are infected by several genera of blood parasites in the phylum Apicomplexa, Order Haemosporidia: Haemoproteus, Plasmodium, and Leucocytozoon. This broadly distributed and diverse group of parasites greatly influences many aspects of the hosts' lifecycle and can cause diseases and even mortality in birds under natural and captive conditions. We determined the prevalence of haemosporidian blood parasites in raptors in Iran by examining blood samples from 62 raptors (13 species from three families: Accipitridae, Falconidae and Strigidae). We documented the first known report in Iran of haemosporidian infection for several raptor species, including eight novel host records for Haemoproteus and two novel host records for Leucocytozoon. Raptors were infected by Haemoproteus spp. (24% of 62 individuals), Leucocytozoon spp. (3% of individuals), and microfilaria (58% of individuals). Such new information from less-studied countries such as Iran can potentially be used to address conservation and management questions in epidemiological studies of wildlife diseases, veterinary medical treatment of captive birds, and in the investigation of host–parasite relationships.