Linking Behavioral States to Landscape Features for Improved Conservation Management

A central theme for conservation is understanding how animals differentially use, and are affected by change in, the landscapes they inhabit. However, it has been challenging to develop conservation schemes for habitat-specific behaviors. Here we use behavioral change point analysis to identify behavioral states of golden eagles (Aquila chrysaetos) in the Sonoran and Mojave Deserts of the southwestern United States, and we identify, for each behavioral state, conservation-relevant habitat associations. We modeled behavior using 186,859 GPS points from 48 eagles and identified 2,851 distinct segments comprising four behavioral states. Altitude above ground level (AGL) best differentiated behavioral states, with two clusters of short-distance movement behaviors characterized by low AGL (state 1 AGL = 14 m (median); state 2 AGL = 11 m) and two associated with longer-distance movement behaviors and characterized by higher AGL (state 3 AGL = 108 m; state 4 AGL = 450 m). Behaviors such as perching and low-altitude hunting were associated with short-distance movements in updraft-poor environments, at higher elevations, and over steeper and more north-facing terrain. In contrast, medium-distance movements such as hunting and transiting were over gentle and south-facing slopes. Long-distance transiting occurred over the desert habitats that generate the best updraft. This information can guide management of this species, and our approach provides a template for behavior-specific habitat associations for other species of management concern

Barn Owl Roadway Mortality: Understanding Why More Females Than Males are Involved

Barn owls (Tyto alba) are the most widespread of the owl species as they are found worldwide. They play an important role in monitoring rodent populations and they serve as good indicators of a healthy environment with a large biodiversity. Roadways are a relatively new addition to the landscape and though the full impact on wildlife is not fully known, recent data suggests that roadways are negatively impacting many wildlife populations- including barn owls. Roadways drastically change the landscape by damaging wildlife habitats, increasing habitat fragmentation, aiding in the dispersal of invasive plants, and directly colliding with animals. To better understand this phenomenon, we studied how roadways impact the movement and flight behavior of Barn Owls (Tyto alba) in Southern Idaho. Animals that have adapted to avoid oncoming traffic are impacted less. Barn owls however have been known to not react to roads. This means that historically they have not been found to recognize roadways and vehicles as a threat and therefore do not frequently avoid them. This results in a high roadway mortality rate. We fitted 27 barn owls in Southwest Idaho with GPS data loggers that collected data on the owl\u27s location, flight speed, and altitude. Data was collected for multiple nights in December 2019 and 2020. It was found that males are more likely to cross roadways within those months. However, the current literature suggests that females have a higher rate of roadway mortality regardless of the time of year (Boves and Belthoff, 2012). It was concluded that male barn owls travel more per night than females and subsequently cross more roads than females. However, males and females did not have significant differences in roads crossed per km traveled. There is also no significant difference between the distance from roads- males do not seem to be avoiding roads more than females. It’s possible that males are avoiding oncoming traffic because they are more agile due to their smaller size. It is also possible that there are more females on the landscape making it appear that there is higher mortality of females because there are more females available

Breeding Schedules of Burrowing Owls in Idaho: Have Nest Initiation Dates Changed with an Evolving Climate?

Climate change is causing bird distributions to change, shifts in migration times, and a mismatch between the behavior of some birds and their primary prey. In certain species, migration distances are predicted to increase by thousands of kilometers, whereas in others migration distances may diminish. Another prominent effect on birds is earlier breeding; clutch initiation dates have advanced by almost a month in some species of raptors. Burrowing Owls (Athene cunicularia) are a species of conservation concern in North America in which weather affects reproductive biology. For example, extreme rainfall events substantially reduce Burrowing Owl productivity. Understanding the potential effects of a changing climate on Burrowing Owls is therefore important for conservation and management of this species. We made use of long-term data (1997 – 2019) collected from Burrowing Owls breeding in the Morley Nelson Snake River Birds of Prey National Conservation Area (NCA) to explore temporal changes in breeding phenology and analyze how annual variability in weather influenced clutch initiation dates. We also investigated how climate change effects differed between human-modified agricultural lands and more natural shrub-steppe areas, as Burrowing Owls breed in both types of environments in the NCA

Barn Owl Roadway Mortality: Understanding Why More Females Than Males are Involved

Wildlife-vehicle collisions (WVC) kill billions of animals every year. Among birds, WVC is particularly high for Barn Owls (Tyto alba) throughout their widespread range, especially during the nonbreeding season. One common pattern is that female Barn Owls outnumber males in WVC. For instance, Boves and Belthoff (2012) reported 1.4 times more roadkilled females than males in Idaho, and Moore and Mangel (1996) found dead females 2.8 times more frequently than males in California. Reasons for this disparity remain poorly understood. We evaluated the hypothesis that female-biased mortality is caused by wider-ranging behavior, more frequent road crossings, and greater proximity to roads by females. We tracked male and female Barn Owls with GPS data loggers during two winters (2019 and 2020) in southern Idaho, U.S.A., where high rates of road mortality are reported. Male Barn Owls traveled farther per night and crossed more roads than females and, when standardized to road crossings per km traveled, there was no difference in crossing rate between males and females. Finally, there was no difference in proximity to roads between males and females. Thus, there was no evidence that females encountered, crossed, or stayed in proximity to roads more than males. Indeed, males ranged more widely and crossed more roads per night than females. Thus, we are able to reject the hypothesis that female-biased road mortality is related to higher rates of road crossings for females. Instead, it is possible that when females do cross roads they are more susceptible to WVC because of their larger size and/or lower agility than males. Or perhaps higher numbers of WVC in females reflect a population sex ratio biased toward females

Integrated Pest Management in Idaho: Discovering the Diet of Idaho Barn Owls

Farmers in Idaho’s canyon county have a pest problem: gophers (Thomomys townsendii). These agricultural pests eat or otherwise damage crops and dig holes that disrupt fields and irrigation canals. To reduce the number of gophers without the use of harmful rodenticides, which have the potential to poison secondary wildlife, Canyon County Weed and Gopher Control has developed an integrated pest management program. This program included installing barn owl (Tyto alba) nesting boxes with the intention of attracting barn owls that would reduce gopher numbers through predation. But do barn owls actually prey on gophers? To find out, we collected regurgitated owl pellets found in and around nest boxes that were analyzed for prey contents. Based on analysis of 1,552 pellets from 47 nest box sites, we found 24 different prey species. The main staple of an Idaho barn owl’s diet was the mountain vole (Microtus montanus). The mountain vole made up 67.6% of the prey items found in the pellets analyzed. Only a small percentage of prey items were gophers (2.3%). Although gophers make up a small percentage of barn owl diet, the boxes have still been somewhat effective in controlling the gopher and other rodent populations based on our prey analysis and comments from local landowners about observed declines in gopher damage in fields. Thus, integrated pest management with barn owls is a viable option compared to labor intensive gopher trapping or the use of pesticides

Examination of Climate Effects on Host-Parasite Dynamics in Burrowing Owls and Fleas

Ectoparasites of raptors include lice, ticks, flies, and fleas. One interesting host-parasite relationship occurs between Western Burrowing Owls (Athene cunicularia hypugaea) and Pulex irritans (Family Pulidae), the so-called human flea. Fleas are hematophagous insects that sometimes infest birds, but this particular association is unusual because P. irritans typically parasitizes mammals such as carnivores, ungulates, and rodents. Moreover, the association between Burrowing Owls and P. irritans occurs only in the Pacific Northwest of the United States, even though both species have broader distributions. Molecular studies have confirmed that P. irritans feeds from Burrowing Owls, so owls are not simply a phoretic host for P. irritans. Factors that influence spatial and temporal variation in flea prevalence and intensity including climate effects have rarely been examined. Because fleas are susceptible to dessication, are there more fleas present in years with higher rates of precipitation and in years with cooler temperatures? And does climate affect host-parasite relationships similarly in human-modified landscapes as in non-agricultural lands? Our poster explores these questions and others using long-term data about flea prevalence and intensity collected between 1997-2019 from a population of Burrowing Owls breeding in Southern Idaho

An Unusual Host-Parasite Relationship: Factors Affecting the Rate at Which Burrowing Owls are Bugged by Fleas

An interesting host-parasite relationship occurs between Western Burrowing Owls (Athene cunicularia hypugaea) and Pulex irritans (Siphonaptera: Family Pulidae), commonly named the “human flea.” P. irritans is a cosmopolitan species of flea that typically parasitizes mammals, which makes its association with Burrowing Owls remarkable. Moreover, the association between P. irritans and Burrowing Owls essentially occurs only in the Pacific Northwest region of the United States, even though both species have broader distributions. Molecular studies confirm that P. irritans feed from Burrowing Owls, so these fleas are truly parasitic on owls, and that Burrowing Owls are not simply phoretic hosts. Although this association was first reported in the early 1900s, most aspects remain poorly understood. We were interested in understanding factors underlying spatial and temporal variation in fleas on Burrowing Owls. Using long-term data (1997 - 2023, \u3e 900 nests) we explored patterns in P. irritans abundance on Burrowing Owl nestlings in the Morley Nelson Snake River Birds of Prey National Conservation Area, located in southwestern Idaho, U.S.A. We found that fleas declined over this time period, winter precipitation and summer temperature affected flea abundance, individual nest sites varied across time in flea abundance, and flea abundance did not differ for sites in agricultural and non-agricultural settings. Our poster explores these and other relationships about factors affecting distribution and abundance of P. irritans on Burrowing Owl nestlings

Patterns of Occupancy, Productivity, Site Tenure, and Recruitment in a Population of Burrowing Owls in Idaho, USA

Western Burrowing Owls (Athene cunicularia hypugaea) are ground-dwelling owls of western and central North America that breed in abandoned mammal burrows. The species is of conservation concern throughout portions of its range, so understanding population dynamics, fitness outcomes, and attributes of the most productive breeding sites are important for management, conservation, and the understanding of life history. Between 1997-2021, a mark-recapture approach was used to monitor a nesting population of Burrowing Owls making use of artificial burrows in the Morley Nelson Snake River Birds of Prey National Conservation Area, ID, USA. The study area is predominantly shrub steppe and disturbed grasslands but has a small percentage of irrigated agriculture, and Burrowing Owls breed in both settings. Using data from this 25-yr timespan, our objective was to assess attributes of the most productive and the most frequently occupied artificial burrow sites. We also were interested in deciphering patterns of tenure and turnover of individuals among sites, as well as locations of sites that were sources of recruits to the breeding population. We analyzed data from approximately 4900 individually marked owls from approximately 950 nests, including 800 nesting adult females, 400 adult males, and almost 4000 nestlings. We identified sites with the greatest occupancy, productivity, and number of recruits, assessed land cover characteristics at each, and analyzed relationships with occupancy, productivity, tenure, and recruitment. Finally, we evaluated if patterns were similar between agricultural areas and grasslands/shrublands

Associations Between Burrowing Owls and Common Ravens in the Morley Nelson Snake River Birds of Prey National Conservation Area, Idaho

Common ravens (Corvus corax) are generalist predators that present an increasing threat for a number of avian species of conservation concern. Often in association with anthropogenic changes, common raven abundance has increased in western landscapes. For example, energy infrastructure including power transmission line towers provide perching and nesting sites for ravens in areas previously devoid of natural substrates, allowing populations to grow. Some raven populations have increased 11-fold since the 1960s. We are interested in the potential effects of common ravens on burrowing owls (Athene cunicularia), which are a species of conservation concern in the U.S., Canada, and Mexico, as ravens prey on owl nestlings and scavenge food from owl nests. Thus, we examined patterns of co-occurrence of common ravens and burrowing owls along 21 standardized point-count survey routes throughout the Morley Nelson Snake River Birds of Prey National Conservation Area during 2017 and quantified raven visits at owl nests using a series of trail cameras. Our poster describes factors associated with raven-owl co-occurrence and the nature of their interactions at owl nests, and results will be useful for understanding potential paths to help mitigate negative effects of ravens on owls and other raptors