No abstract

Ten polymorphic microsatellite loci were isolated and characterized for the ferruginous pygmy owl (Glaucidium brasilianum). Observed and expected heterozygosity were 0.07–0.85 and 0.1–0.88, respectively. Allele numbers ranged from five to 16 per locus.

Northern saw-whet owls (Aegolius acadicus) are known for their unique asymmetrical ear structure and ability to localize prey acoustically, yet few attempts have been made to explore the auditory capabilities of this species. In this study, we evoked auditory brainstem responses (ABRs) with tonebursts to assess three main hypotheses regarding the evolution of auditory sensitivity: sender-receiver matching, ecological constraints, and phylogenetic/morphological constraints. We found that ABR amplitude increased with increasing stimulus level, which is consistent with results in other avian species. ABR amplitudes, latencies, and thresholds indicate that the hearing range of Northern saw-whet owls extends from 0.7 to 8.6 kHz, with an extended frequency range of best sensitivity between 1.6 and 7.1 kHz. Sensitivity fell off rapidly above and below these frequencies. The average audiogram was structurally similar to those found in other species of owls, suggesting that phylogeny or morphology may be constraining the frequency range of auditory sensitivity. However, ABR thresholds were 10-25 dB lower than those of Eastern screech-owls (Megascops asio), with thresholds below 0 dB SPL in some individuals. The lowest thresholds were at frequencies not found in the vocalizations of Northern saw-whet owls, suggesting ecological constraints rather than conspecific vocalizations are driving absolute sensitivity.

Sequences from the mitochondrial cytochrome b gene were used to examine patterns of variation within and among populations of the ferruginous pygmy-owl (Glaucidium brasilianum) from both North America (including populations from Mexico) and South America. As currently conceived, G. brasilianum is paraphyletic, with North American and South American clades representing two distinct groups that should be recognized as the distinct species G. ridgwayi and G. brasilianum, respectively. Within the G. ridgwayi clade, populations from Arizona, Sonora, and Sinaloa are genetically distinct and share no mitochondrial haplotypes with populations occurring in Texas and other regions of Mexico. According to nested clade analysis this separation may be the consequence of past fragmentation that predates the origin of the Sonora desert. In addition, gene flow between the Arizona/Sonora/Sinaloa populations and the Texas/other Mexico populations is practically nonexistent, with estimates being approximately one individual every 10 generations. Collectively, these data suggest that the Arizona/Sonora/Sinaloa clade should be recognized as either a distinct subspecies or phylospecies from the group containing populations in Texas and the remainder of Mexico. These data should be used as guidelines for pygmy-owl recovery and conservation, as they meet the recommendations of task 3 of the pygmy-owl recovery plan that lists genetic data as essential information for pygmy-owl management.

Diverse biomarkers including stable isotope, hormonal, and ecoimmunological assays are powerful tools to assess animal condition. However, an integrative approach is necessary to provide the context essential to understanding how biomarkers reveal animal health in varied ecological conditions. A barrier to such integration is a general lack of awareness of how shared extraction methods from across fields can provide material from the same animal tissues for diverse biomarker assays. In addition, the use of shared methods for extracting differing tissue fractions can also provide biomarkers for how animal health varies across time. Specifically, no study has explicitly illustrated the depth and breadth of spacial and temporal information that can be derived from coupled biomarker assessments on two easily collected tissues: blood and feathers or hair. This study used integrated measures of glucocorticoids, stable isotopes, and parasite loads in the feathers and blood of fall-migrating Northern saw-whet owls (Aegolius acadicus) to illustrate the wealth of knowledge about animal health and ecology across both time and space. In feathers, we assayed deuterium (δD) isotope and corticosterone (CORT) profiles, while in blood we measured CORT and blood parasite levels. We found that while earlier migrating owls had elevated CORT levels relative to later migrating birds, there was also a disassociation between plasma and feather CORT, and blood parasite loads. These results demonstrate how these tissues integrate time periods from weeks to seasons and reflect energetic demands during differing life stages. Taken together, these findings illustrate the potential for integrating diverse biomarkers to assess interactions between environmental factors and animal health across varied time periods without the necessity of continually recapturing and tracking individuals. Combining biomarkers from diverse research fields into an integrated framework hold great promise for advancing our understanding of environmental effects on animal health.