Burrowing Owl Research Articles

Neotaphonomy of a rodent skeletal accumulation by Strigiformes in an Andean valley. Implications for taphonomy, archaeology and palaeontology

ABSTRACT Holocene accumulations of rodent bones digested by raptors have been found in El Bolsón, a high-altitude valley in Catamarca, Argentina. Yet, so far there were no relevant taphonomic frames of reference to account for them. We thus studied a modern accumulation in Los Viscos rockshelter from a taphonomic perspective. The rockshelter is used for roosting, and the surface is covered by rodent skeletal remains. The analysed sample (NISP = 421) is dominated by remains of Phyllotis vaccarum, and also comprises other cricetid species, cavids, ctenomids and abrocomids. The anatomical, breakage and digestion patterns were compared to data on different predators. The most probable predator related to this accumulation is a Strigiformes (Aves) species. Most variables, including digestion, suggest a low-intensity modifier, probably Tyto alba, an individual of which was spotted around. Although Athene cunicularia may produce similar bone breakage, the prey taxa are not compatible with its diet. Alternatively, intense fragmentation may relate to postdepositional processes such as trampling. We discuss the implications of these findings for understanding the formation of the zooarchaeological and palaeontological record in the area, as well as for helping assess the global variability of Tyto alba taphonomic signature.

Invertebrate-biased diet of burrowing owls in a newly-restored coastal grassland

Recovering biodiversity across trophic levels is a major challenge in restoration ecology. Specifically, predator population recovery depends on the timely re-establishment of their preferred prey species in restored habitats. Here, we evaluate potential dietary factors contributing to the loss of western burrowing owls (Athene cunicularia hypugaea (Bonaparte, 1825)) from a newly-restored coastal grassland. We examined owl pellets and found that burrowing owl diets were relatively low in vertebrate prey during their brief occupation of the restoration site (2.6% of prey items; found in 61.8% of sampled pellets). We suggest that preferred food limitation may have been one contributor to the loss of owls from the restoration site. These findings suggest the need to prioritise re-establishment of prey communities for effective long-term recovery of burrowing owls in restored landscapes.

Agricultural pesticides in feathers of the burrowing owl (Athene cunicularia) and its relationship to land-use in the argentinean pampas

The pampas of South America represent one of the most productive lands for agriculture in the world, and consequently this activity has expanded throughout the region, especially in Argentina. In this context, native fauna faces various risks associated with agriculture, with exposure to pesticides being one of the most dangerous and deadly. Assessing the impact of pesticides on wildlife becomes fundamental and the use of sentinel species emerges as an important tool to monitor environmental health. In this study, we determined pesticide levels in the burrowing owl Athene cunicularia nesting in both rural and urban areas of the argentinean pampas. We used a multiple scale approach to evaluate the influence of land-uses (urban, crops, and grazing fields) at the nesting site on the contaminant load of A. cunicularia individuals, and assessed the potential use of this owl as a sentinel species. From March 2018 to January 2020, A. cunicularia feathers were collected at their nest sites in one urban and two rural areas. These samples were analyzed for the presence of contaminants, including chlorpyrifos and 18 organochlorine pesticides. All the compounds analyzed were detected in A. cunicularia samples. The chlorpyrifos showed the highest frequency of occurrence and concentration, thus denoting the exposure of owls to current-use pesticides. ∑DDTs showed the highest occurrence among organochlorines, followed by ∑HCHs > ∑Endosulfans > ∑Heptachlors > ∑Drins = ∑Chlordanes > methoxychlor. Principal Component Analysis showed that most of the compounds found in A. cunicularia samples showed a positive association with grazing fields, suggesting that exposure to contaminants does not depend on specific habitat use at the local scale, but probably the regional scale. Our results evidenced the exposure of A. cunicularia individuals to past and current-use pesticides in the pampas of Argentina, and indicate that this owl would be useful as a sentinel species.

Burrowing Owls Require Mutualist Species and Ample Interior Habitat Space

Mitigating habitat loss of western burrowing owls (Athene cunicularia hypugaea) often involves relocation from California ground squirrel (Otospermophilus beecheyi) burrows to offsite nest boxes. Naval Air Station Lemoore (NASL), Kings and Fresno counties, California, initiated this approach to displace a regionally important population from airfield grasslands. We examined monitoring data of burrowing owls and fossorial mammals at NASL to assess mitigation options. Occupied nests increased by 33 (61%), with 47 nest box installations in 1997–2001, peaked at 87 in 1999, then declined by 50 through 2013. Although ≥13 nest boxes were occupied in 2000, none were occupied in 2003–2013. Within a 43.1 ha isolated grassland monitored for 13 years, nest site reuse in ground squirrel burrows averaged only 17% between any 2 consecutive years. Compared to the average density across grassland study areas, ground squirrel burrow systems/ha numbered 43% higher within 60 m of occupied nests and non-breeding-season burrows. Vegetation clearing to restore kangaroo rat (Dipodomys n. nitratoides) habitat preceded a 7.4-fold increase in ground squirrel burrow systems and a 4-fold increase in occupied nests, but drought-induced extirpation of ground squirrels eliminated occupied nests from the 43.1 ha grassland study area. Ground cover near occupied nests averaged 58% of the mean vegetation height and 67% of the mean percentage of bare ground in the field. Both nest sites and non-breeding-season burrows occurred >60 m interior to field edges 1.4 times more than expected. Non-breeding-season burrows averaged 328 m from same-year nest sites, and only 7% of non-breeding-season burrows were also used as nest sites. Mitigating habitat loss should be made more effective by fostering natural burrow construction by fossorial mammals on patches of short-stature vegetation that is sufficiently expansive to support breeding colonies of ≥12 pairs averaging ≥60 m from the field’s edge and a separation between non-breeding-season burrows and nest burrows minimally equal to mean nearest-neighbor distances among nests.

Predation of two species of Columbidae by the burrowing owl Athene cunicularia (Strigiformes, Strigidae) in urban environment

Predation of two species of Columbidae by the burrowing owl Athene cunicularia (Strigiformes, Strigidae) in urban environment

Anuran consumption by burrowing owl (Athene cunicularia Strigiformes) in lower Chubut river valley, Patagonia, Argentina

Anuran consumption by burrowing owl (Athene cunicularia Strigiformes) in lower Chubut river valley, Patagonia, Argentina

The behaviour of Athene cunicularia (Molina 1782) on the coast of Santa Catarina, Brazil, and the influence of urbanization on daily activity

The behaviour of Athene cunicularia (Molina 1782) on the coast of Santa Catarina, Brazil, and the influence of urbanization on daily activity

Sudden death and Haemoproteus infection in captivity Burrowing Owls (Athene cunicularia) from Brazil

The present study aims to report the sudden death of two captive individuals of the Burrowing Owl Athene cunicularia that coexisted in the same enclosure with other raptor birds in a Zoo of Brazil. Despite Haemoproteus infections generally being considered benign, they can lead to sudden death, particularly in stressful environments. Through hematological examinations and microscopic analyses, this article reports two cases of Haemoproteus in Burrowing Owls, suggesting a potential correlation between its presence and owl’s deaths. Also, discusses the prevalence of this infection in captive raptorial birds, emphasizing the significance of immunity and proper management to prevent infections and reveal the importance of early diagnosis for the preservation of the health of these captive birds.

Experimental changes in food and ectoparasites affect dispersal timing in juvenile burrowing owls.

Natal dispersal is a key demographic trait that affects population dynamics, and intraspecific variation in dispersal affects gene flow among populations and source-sink dynamics. However, relatively little is known about the selective pressures and trade-offs that animals face when departing their natal area due to the logistical difficulties associated with monitoring animals during this critical life stage. We used a randomized block design to examine the selective pressure that influence dispersal timing in juvenile burrowing owls (Athene cunicularia) by experimentally altering both food and ectoparasites at 135 nests. We also examined the effects of local food abundance, ectoparasite loads, and parental departure on natal dispersal timing. Juvenile burrowing owls varied widely in natal dispersal timing, and phenotypic plasticity in dispersal timing was evident in juvenile owls' response to our experimental treatments, local conditions, and their parents' departure from the natal area. Moreover, juveniles responded differently than their parents to experimental manipulation of food and ectoparasite loads. Juveniles typically dispersed shortly after their parents departed the natal area, but delayed dispersing more than 2 weeks after parental departure if they did not receive experimental food supplements during a low-food year. In contrast, the experimental food supplements did not affect the migratory departure decisions of adult owls in either year. Juveniles at nests treated for ectoparasites initiated dispersal at a younger age (and prior to adults in the high-food year) compared to juveniles at control nests. In contrast, parents at nests treated for ectoparasites departed later than parents at control nests. Our results suggest that unfavorable conditions (low food or high ectoparasite loads) caused juveniles to delay dispersal, but prompted adults to depart sooner. Our results highlight the extent of intraspecific variation in natal dispersal timing, and demonstrate that ecological conditions affect dispersal decisions of parents and offspring differently, which can create important trade-offs that likely affect life history strategies and responses to climatic changes.

Respiratory Infection by Cyathostoma (Hovorkonema) americana in a Population of Burrowing Owls (Athene cunicularia)—A Potential Case of Zoo–Wildlife Cross-Transmission

A population of burrowing owls (Athene cunicularia) under professional care at Zoomarine Portugal presented with sudden respiratory clinical signs. Clinical management included a thorough diagnosis plan, including in-house fecal analysis that revealed the presence of ovoid unioperculate eggs. In the postmortem examination of one hyperacute dyspneic specimen, adult nematode parasites were collected and identified based on their morphology as Cyathostoma (Hovorkonema) americana. Even after a broad-spectrum deworming protocol as part of the treatment and metaphylaxis approach, the incidence of parasitic reinfection was high. The complete clinical resolution was only accomplished after the identification and management of the possible focus of infection, a wild population of cattle egrets (Bubulcus ibis) that frequently congregated above the owls’ habitat. To the authors’ best knowledge, this is the first report of infection by Cyathostoma (Hovorkonema) americana in burrowing owls. Although nematodes of the family Syngamidae are not commonly included in the differential diagnosis of infectious respiratory agents of birds of the order Strigiformes, this report highlights the possibility of opportunistic parasitism in a zoological context, especially where there is a continued proximity to free-ranging avifauna.

Genetic and environmental drivers of migratory behavior in western burrowing owls and implications for conservation and management.

Migration is driven by a combination of environmental and genetic factors, but many questions remain about those drivers. Potential interactions between genetic and environmental variants associated with different migratory phenotypes are rarely the focus of study. We pair low coverage whole genome resequencing with a de novo genome assembly to examine population structure, inbreeding, and the environmental factors associated with genetic differentiation between migratory and resident breeding phenotypes in a species of conservation concern, the western burrowing owl (Athene cunicularia hypugaea). Our analyses reveal a dichotomy in gene flow depending on whether the population is resident or migratory, with the former being genetically structured and the latter exhibiting no signs of structure. Among resident populations, we observed significantly higher genetic differentiation, significant isolation-by-distance, and significantly elevated inbreeding. Among migratory breeding groups, on the other hand, we observed lower genetic differentiation, no isolation-by-distance, and substantially lower inbreeding. Using genotype-environment association analysis, we find significant evidence for relationships between migratory phenotypes (i.e., migrant versus resident) and environmental variation associated with cold temperatures during the winter and barren, open habitats. In the regions of the genome most differentiated between migrants and residents, we find significant enrichment for genes associated with the metabolism of fats. This may be linked to the increased pressure on migrants to process and store fats more efficiently in preparation for and during migration. Our results provide a significant contribution toward understanding the evolution of migratory behavior and vital insight into ongoing conservation and management efforts for the western burrowing owl.

New overwintering location of Burrowing Owl, Athene cunicularia hypugaea (Molina, 1782) (Strigidae) in Tennessee, USA, with diet assessed through pellets

Reporting new occurrence records of organisms is key to overcome the Wallacean shortfall. Here, we report the first sighting of a Burrowing Owl, Athene cunicularia (Molina, 1782), overwintering on a peninsula in the Tennessee River in Tennessee, USA, during boreal winters 2020–2022. Pellets from this bird showed combination of six species. This is the first record for the species in the Interior Plateau of the USA. Conditions supporting this bird and evidence of it overwintering bear to explore the environmental conditions that support this species in novel areas.

The owls are coming: positive effects of climate change in Northern ecosystems depend on grassland protection

Climate-driven migrations towards Northern latitudes are expected to reorganize biotic communities as result of range shift dynamics. However, the establishment of healthy populations of migrating species depends on habitat provision by receptor landscapes. Here, we ask if the rising temperatures and changes in precipitation regimes in western North America are likely to lead to an expansion of warm and dry-affiliated species, using the burrowing owl (Athene cunicularia) as a study case. This migratory species depends on grassland habitats for nesting and breeding, so we test for the effect of the lack of grasslands on the occupancy of future suitable environments. To estimate the burrowing owl's potential distribution, we used ecological niche models (ENMs) calibrated with climate and soil information and projected onto future scenarios of climate change (low versus high greenhouse gas emission). Then, we simulated environmental sorting using habitat filter masks derived from information on habitat use and forecasts of future land use change, focusing on grasslands as nesting and breeding habitat. We found that the burrowing owl could expand its geographic distribution by 3 to 10-fold towards Northern latitudes, especially under high-emission scenarios of climate change. However, nearly half of the suitable environments (up to 53,593 km2 of locations with suitable climate and soil) might not be covered by grasslands, due to conversion to agriculture and other human land uses which may prevent the establishment of breeding populations. Our results shed light on the pervasive effects of neglecting the preservation of grasslands across western North America, which could provide critically needed habitat for migrating species from lower latitudes. Enhancing and facilitating the colonization of novel species is a shift in the static paradigm of biodiversity conservation and a proactive measure for climate change adaptation.

Nesting innovations in neotropical parrots associated to anthropogenic environmental changes.

Parrots are among the most diverse and widely distributed groups of birds and one of the most threatened bird orders mainly due to habitat loss and illegal poaching. Most parrots are obligate cavity nesters, so the logging of mature trees and the transformation of natural cliffs represent important threats to their conservation. Here, we report novel observations of Neotropical parrots nesting in previously unrecorded substrates. We show the first documented case of the cliff-nesting burrowing parrots trying to breed at ground level in an abandoned burrowing owl cavity. Additionally, we provide the first documented observations of this species attempting to nest in building cavities in three urbanized areas of Argentina. Moreover, we report data from four countries of 148 pairs of eight species typically breeding in tree cavity using palm tree bracts as nest sites. Behavioral plasticity in nest sites may allow parrots to maximize their nesting success by exploiting alternative breeding substrates. Moreover, these novelties could contribute to cope with habitat loss and further transformation. However, further research is needed to assess the consequences of these nesting innovations in terms of individual fitness and population dynamics as well as potential factors promoting their appearance.

Analysis of clinical and hematological characteristics and search for hemoparasites in owls (Strigiformes: ‎Strigidae) seized or rescued from the Atlantic Forest biome of the Rio de Janeiro (southeastern Brazil)

Hemoparasitism is known to vary according to the presence of vectors and hosts, and hematological examination can be a useful tool for early diagnosis in avian medicine, contributing to monitoring and conservation of bird populations. In this context, we aimed to analyze the clinical and hematological aspects of free-ranging owls seized or rescued from the Atlantic Forest biome of Rio de Janeiro, Brazil. The animals, with or without clinical signs of diseases, were studied regardless of their age, sex, and physical status. Blood samples were collected and complete blood counts were carried out. Five different species were obtained in this study. These species were Megascops choliba (50%), Asio clamator (18.75%), Athene cunicularia (18.75%), Pulsatrix koeniswaldiana (6.25%), and Strix huhula (6.25%). Orphaned birds and traumatic injuries were the causes of admission to the wildlife rehabilitation facility. The search for hemoparasites revealed infection by protozoa of the genera Haemoproteus, Plasmodium, and Trypanosoma. We concluded that hematological findings in seized or rescued owls predominantly suggested the presence of stress or inflammation resulting from post-traumatic situations. The causes of admission were mostly due to human interference, which demonstrates to have a negative impact on the health aspect of owl populations in urban centers, such as Rio de Janeiro. Blood protozoa are circulating among the different populations of owls and although infection by Haemoproteus spp. and Trypanosoma spp. seems to trigger a low pathogenic potential, Plasmodium infection may indicate unfavorable prognosis, endangering wild species.

Investing in a nest egg: intraspecific variation in the timing of egg laying across a latitudinal gradient.

Avian reproductive strategies vary widely, and many studies of life-history variation have focused on the incubation and hatching stages of nesting. Birds make proximate decisions regarding reproductive investment during the laying stage, and these decisions likely constrain and tradeoff with other traits and subsequent behaviors. However, we know relatively little about egg-laying stage behaviors given the difficulty of locating and monitoring nest sites from the onset of laying. We used non-invasive continuous video recording to quantify variation in the egg-laying behaviors of burrowing owls (Athene cunicularia) along a 1400-km latitudinal gradient in western North America. Burrowing owls laid eggs disproportionately in the morning hours, and that tendency was strongest among first eggs in a clutch. However, selection appeared to act more strongly on laying intervals (the time between laying of consecutive eggs) than on the diel time of laying, and laying intervals varied widely among and within clutches. Laying intervals declined seasonally and with increasing clutch size but increased with increasing burrow temperature and as a function of laying stage nest attentiveness, which may be a strategy to preserve egg viability. Laying interval was positively correlated with the duration of hatching intervals, suggesting that laying interval duration is one mechanism (along with timing of incubation onset) that generates variation in hatching asynchrony. Our results lend support to two general hypotheses to explain laying schedules; selection favors laying eggs in the morning, but other selective pressures may override that pattern. These conclusions indicate that allocation decisions during laying are an important part of avian life-history strategies which are subject to energetic constraints and tradeoffs with other traits.

Evaluating captive-release strategies for the Western Burrowing Owl ( Athene cunicularia hypugaea )

Evaluating captive-release strategies for the Western Burrowing Owl ( Athene cunicularia hypugaea )

Additions and updates to the list of specimens of Imperial Woodpecker Campephilus imperialis (Gould, 1832), including genetic analysis of a putative clutch of eggs

We present an addendum to the list of known specimens of Imperial Woodpecker Campephilus imperialis published by Brown & Clark in 2009. The addendum adds a total of 31 specimens, comprising 15 mounts, ten study skins, three skeletons, two skulls and one not extant specimen, bringing the total number to 189 specimens. It also offers clarification of some of the records presented in Brown & Clark, as well as revisions of several specimens previously registered as C. imperialis but later found to be of other species. The latter includes a putative clutch of Imperial Woodpecker eggs, which was found via genetic analysis to belong to Burrowing Owl Athene cunicularia.

An evaluation of translocation as a tool to reduce burrowing owl collisions at airports

AbstractBird strikes at airports pose a human‐wildlife conflict (HWC) present in the world's major cities. Conflict mitigation frequently encompasses translocation, but its effectiveness in resolving HWCs is unclear. Here, we used the Burrowing Owl (Athene cunicularia) as a model species to test the effectiveness of translocation in reducing the number of bird strikes, the primary HWC at airports. We explored the translocation process, focusing on 3 aspects: 1) the influence of landscape structure on the persistence time of translocated animals at the released sites, 2) the influence of the release distance from the source on the return of translocated animals, and 3) the strike rate involving the species at the capture site at Brasília International Airport (BSB). Our results did not support burrowing owl translocation as a management option for solving the HWC at the BSB. We also found that the landscape composition did not guarantee individual persistence since the animals did not remain at release sites, regardless of the spatial configuration. Release distance did not explain the frequency of return of translocated animals to the capture site. Finally, we registered a higher number of collisions during translocation management. Thus, we believe that wildlife management programs must monitor translocated animals assessing if translocations are suited for the context.

Melanopsin expression in the retinas of owls with different daily activity patterns

Melanopsin is a photopigment found in a subset of retinal ganglion cells that is responsible for generating a series of responses to light in organisms, such as circadian rhythm regulation, pupillary light reflex, and body temperature control. The role of each melanopsin gene in the vertebrate retina is still not fully elucidated and a diversity of expression patterns of this photopigment can be observed in retinas of different vertebrate species. Owls are an excellent model for studying the role of melanopsin due to the diversity of species, which may present diurnal, nocturnal, or cathemeral habits. The purpose of this study was to characterize the expression of melanopsin genes in the retina of four different owl species from the Strigidae family (Athene cunicularia, Asio clamator, Glaucidium brasilianum, and Megascops choliba) through genetic and phylogenetic analysis. The specimens were euthanized, and the retinas were collected for RNA extraction and cDNA transcription. cDNA was used in the polymerase chain reaction (PCR) with subsequent sequencing to identify melanopsin genes expressed in the retina of owls. For the quantitative analysis of gene expression, real-time PCR was performed. The phylogenetic reconstruction was obtained by the maximum likelihood. The results showed that owls express both melanopsin genes, Opn4x and Opn4m, with different patterns of expression among the species. The expression of the Opn4x gene was two times higher in Asio clamator (nocturnal) compared to A. cunicularia (cathemeral), Glaucidium brasilianum (diurnal), and Megascops choliba (nocturnal). On the other hand, the expression of Opn4m was about two times lower in the cathemeral, A. cunicularia compared to the other three species. These results might indicate functional differences of the Opn4x and Opn4m genes among species, related to circadian rhythm regulation. Further investigation in owls at other times of the day will bring light to the circadian pattern of melanopsin expression in these species and its correlation with the different patterns of daily activity.