Identifying Potential Breeding Areas of Short-Eared Owls Prior to Nesting Using Roadside Surveys to Detect Courtship and Territoriality Behavior: A Comparison of Visual and Audio Techniques

We piloted a roadside survey technique for detecting Short-eared Owls during the courtship period in western Montana.  Thirty-five surveys were conducted between 2009 and 2012 and were timed to coincide with pair-formation and courtship behavior. Short-eared Owls perform courtship flights and vocalizations which can be observed and heard during the crepuscular period.  Surveys were designed to compare visual and audio survey techniques.  Visual surveys occurred during the crepuscular period at the end of civil twilight and were immediately followed by a nocturnal audio survey.  Visual survey techniques accounted for over 91% (N=240) of all detections.  Detections associated with audio survey techniques were almost always associated with survey points where at least one owl was detected during visual survey.  Nearly three-quarters of visual detections (N=220) occurred between 30 and 70 min before the end of civil twilight.  Over 75% of visual detections and 90% of nocturnal detections occurred in areas where vegetation was uncut and ungrazed and most frequently associated with vegetation heights greater than approximately 60cm.  Short-eared Owls were never detected in areas where livestock was present.  We recommend visual surveys during the courtship to identify potential breeding areas prior to the onset of incubation

Black Color Morph of the Brown Lemming, Lemmus trimucronatus = L. sibiricus

A black pelage Brown Lemming is reported from Barrow, Alaska. The occurrence of this black color morph appears to be rare. During twelve years of Snowy Owl research and lemming trapping, only one has been seen. Of 554 snap-trapped Brown Lemmings and 1649 Brown Lemmings found cached at owl nests, no black individuals were found. The pelage of the black morph is described using a Munsell Soil Color Chart

Dietary Overlap of American Barn Owl and Short-Eared Owl in the Mission Valley, Montana

The Mission Valley is home to many species of wildlife, including the Short-eared owl.  Over the last decade Barn Owl sightings have increased in the valley and nests have been discovered.  We analyzed food-niche overlap between American Barn Owls (Tyto furnata) and Short-eared Owls (Asio flammeus) over one year to determine whether prey competition from the local Barn Owl population will affect the Short-eared Owl population. A total of 325 prey items (11 different species) were identified from 152 pellets; 79 Barn Owl and 73 Short-eared Owl.  Diets of both species consisted primarily of Microtus species, although traces of additional food resources were present. Using Pianka’s index the food-niche overlap was 0.658, where Pianka’s index determines what proportion of the two owl species’ diets overlap with a value of 0 representing total separation and a value of 1 representing total overlap.  The results of this study showed a food niche overlap between the two owl species. We suggest, however, that the current population of Barn Owl in the Mission Valley is not directly competing with the established Short-eared Owl population in the Mission Valley, given th

Natural Nest-Site Characteristics of Two Small Forest Owls with Implications for Conservation and Management

Natural nest cavities of the Northern Saw-whet Owl (Aegolius acadicus) and the Northern Pygmy-Owl (Glacidium gnoma) were characterized using several variables measured from 79 nests. Northern Saw-whet Owls appear to prefer larger diameter trees, with larger cavity openings, and deeper cavities compared to the Northern Pygmy-Owls. Pygmy-owls also use a higher proportion of living trees with natural, i.e., not excavated, cavities compared to saw-whet owls. Tree height, nest height, and the number of cavities located on a snag were consistent between the two species. Internal examination of hundreds of cavities within owl territories shows that many cavities which appear appropriate for nesting owls are unusable. Leaving dead or dying trees for cavity nesting species is a common practice for forest managers in the West. However, criteria for “wildlife habitat” trees often adhere to a one-size-fits-all approach; retained cavities are selected based on external assessment alone. The dissimilarity in nest-site selection by these two species, and the fact that cavities show great variability in internal condition, underscore the need for forest managers to select a diverse array of trees for cavity nesting birds in western forests

Evidence That Mutation Is Universally Biased towards AT in Bacteria

Mutation is the engine that drives evolution and adaptation forward in that it generates the variation on which natural selection acts. Mutation is a random process that nevertheless occurs according to certain biases. Elucidating mutational biases and the way they vary across species and within genomes is crucial to understanding evolution and adaptation. Here we demonstrate that clonal pathogens that evolve under severely relaxed selection are uniquely suitable for studying mutational biases in bacteria. We estimate mutational patterns using sequence datasets from five such clonal pathogens belonging to four diverse bacterial clades that span most of the range of genomic nucleotide content. We demonstrate that across different types of sites and in all four clades mutation is consistently biased towards AT. This is true even in clades that have high genomic GC content. In all studied cases the mutational bias towards AT is primarily due to the high rate of C/G to T/A transitions. These results suggest that bacterial mutational biases are far less variable than previously thought. They further demonstrate that variation in nucleotide content cannot stem entirely from variation in mutational biases and that natural selection and/or a natural selection-like process such as biased gene conversion strongly affect nucleotide content

The genomic basis of parasitism in the Strongyloides clade of nematodes.

Soil-transmitted nematodes, including the Strongyloides genus, cause one of the most prevalent neglected tropical diseases. Here we compare the genomes of four Strongyloides species, including the human pathogen Strongyloides stercoralis, and their close relatives that are facultatively parasitic (Parastrongyloides trichosuri) and free-living (Rhabditophanes sp. KR3021). A significant paralogous expansion of key gene families--families encoding astacin-like and SCP/TAPS proteins--is associated with the evolution of parasitism in this clade. Exploiting the unique Strongyloides life cycle, we compare the transcriptomes of the parasitic and free-living stages and find that these same gene families are upregulated in the parasitic stages, underscoring their role in nematode parasitism

Trophic Niche of Nearctic Short-Eared Owls

Volume: 105Start Page: 497End Page: 50

Breeding Season Diet of Short-Eared Owls in Massachusetts

Volume: 105Start Page: 490End Page: 49