Geology topics

Ty Matthews

Publications and source records attributed to Ty Matthews.

4 recordsLinked to original sources

USGS2025

Water depth, position within the nesting colony, and nearest neighbor density affect nest survival in Aechmophorus occidentalis (Western Grebe)

Aechmophorus occidentalis (Western Grebe) are colonial nesting waterbirds that have experienced population declines. We located and monitored 709 grebe nests using a drone within Lake Cascade, the largest grebe breeding colony in Idaho. We conducted 6 flights between June 20, 2018 and July 11, 2018 and used the photographs from each flight to create an orthomosaic image that we then digitized and georeferenced. The resolution of the images allowed for visualization of each nest, nest contents, and adult grebes on each flight. Using the georeferenced images, we created nest histories and estimated nest fate for the 709 grebe nests. We also collected data on the following covariates to assess whether any of them affected nest survival: distance of the nest to the center of the colony; distance of the nest to the edge of the colony; distance of the nest to deep water habitat; water depth at the nest; nearest neighbor distance, and an aggregation index (mean distance to the 5 nearest nests). The orthomosaics from repeated drone flights allowed us to estimate nesting success without disturbing the colony; 51.2% of nests survived until hatching. The daily survival probability of grebe nests was positively correlated with the aggregation index and water depth at the nest (albeit only slightly). Daily survival probabilities were negatively correlated with distance between the nest and the colony center and distance to deep water (i.e., foraging habitat). The results of this study can be used to inform conservation efforts by identifying areas of the Lake Cascade grebe colony that are most vulnerable to nest failures and formulating explicit management actions that could be implemented to increase nest survival such as changes in timing of water drawdowns and habitat management to ensure habitat suitable for grebe nesting is in close proximity to deep water foraging areas. Moreover, grebes are not the only waterbird that makes use of managed reservoirs; other waterbirds may benefit from the findings of this study to implement more informed management practices.

Idaho↗

USGS2025

Patchy response of cheatgrass and nontarget vegetation to indaziflam and imazapic applied after wildfire in sagebrush steppe

Control of nonnative grasses is needed where they are altering fire regimes and degrading rangelands, such as cheatgrass ( Bromus tectorum ) invasion of perennial sagebrush-steppe communities. Aerial broadcast of the pre-emergent and postemergent herbicide imazapic has been used for decades over vast areas to control cheatgrass after fire. Recent small-scale studies indicate that the pre-emergent herbicide indaziflam may provide more enduring cheatgrass control. We evaluated landscape-level vegetation responses to indaziflam sprayed in replicated areas at 66.7 g · ai · ha −1 , with and without imazapic (66.1 g · ai · ha −1 ) over almost 500 ha of sagebrush steppe. Herbicides were strip-sprayed by helicopter in the fall of 2019 in subregions that either 1) had burned in the summer of 2019 and had moderate background cheatgrass invasion, 2) had burned in 2011 and became heavily invaded, or 3) were burned in both 2011 and 2019 and had intermediate invasion. Tarps were temporarily deployed to intercept herbicides and create untreated controls. Overall, indaziflam + imazapic had greater initial control of cheatgrass, but by 2023, both treatments led to similar ∼17 percentage-point reductions in cheatgrass cover. Cheatgrass individuals that “escaped” the herbicide treatment grew exceptionally large and fecund. There were no reductions in cover in any native vegetation type, including biocrusts, and nontarget increases in cover were observed for 1) deep-rooted perennial grasses treated with indaziflam + imazapic in the 2011 burn subregion and 2) the shallow-rooted Sandberg bluegrass ( Poa secunda ) treated with either herbicide in the 2011 or 2011 + 2019 burn subregions. Consideration of burn legacies, pretreatment landscape condition, and evenness of treatment application may improve restoration outcomes and help prioritize management allocation, timing, and treatment expectations.

Idaho↗

USGS2022

Drones and bathymetry show the importance of optimal water depth for nest placement within breeding colonies of Western and Clark’s grebes

Habitat selection involves a series of decisions that are arguably the most important decisions that animals make and these decisions occur at multiple hierarchical spatial scales. Colonial-nesting birds face a unique challenge when selecting a nest site because each bird’s choices are severely constrained by other birds within their breeding colony. Individuals must seek out optimum nesting locations within the constraint of the colony’s geographic location. We investigated how water depth and proximity to open water affected 4th-order nest-site selection of Western and Clark’s Grebes ( Aechmophorus occidentalis, Aechmophorus clarkii ), colonial nesting waterbirds that have declined in abundance across their range. We used an orthomosiac that we created from ~ 500 aerial drone images of a large breeding colony to construct a Resource Selection Function to describe microhabitat features that influence nest-site placement within the colony footprint. Grebes preferred to nest in portions of the colony with intermediate water depths (40-80 cm during nest construction) and they preferred to nest in portions of the colony furthest from open water. Understanding how individual birds make use of available microhabitat features within the footprint of their breeding colony can help inform conservation efforts of colonial-nesting birds, particularly for species that nest in wetland habitats whose water levels are managed for human use.

Idaho↗

USGS2020

Drones provide a better method to find nests and estimate nest survival for colonial waterbirds: A demonstration with Western Grebes

Drone use in wildlife biology has greatly increased as they become cheaper and easier to deploy in the field. In this paper we describe a less invasive method of using drones and exploring their limitations for studying colonial nesting waterbirds. Western Grebes, like most colonial nesting waterbirds, can be very sensitive to human interaction. Using a 3DR Solo quad copter equipped with a high-resolution digital camera we were able to effectively map and monitor a Western Grebe breeding colony throughout the nesting period with a series of 6 flights. We were able to use drone collected aerial imagery to model nest survival while minimizing disturbance to the birds. However, we were not able to deploy the drone at all of our study sites. Our ability to effectively deploy the drone was hindered by the environmental and vegetation characteristics of a site. Drone technology can be a useful tool, especially when studying a species sensitive to human interaction. However, there researchers should carefully consider their species and study site to evaluate if a drone is the proper tool to meet their objectives.

Idaho↗