Geology topics

Christopher Dodge

Publications and source records attributed to Christopher Dodge.

3 recordsLinked to original sources

USGS2026

Bird guilds exhibit varied responses to floodplain forest restoration in the Colorado River delta, Mexico

Grouping species into guilds can be useful to inform management decisions locally and at broader scales because guilds lack species-specificity. We investigated the response of five breeding bird guilds to riparian habitat restoration in the arid Colorado River delta, based on two decades of bird detections (2002–2021) at 230 bird count stations across 7 routes in actively revegetated (“restored”) sites, and 20 routes in non-actively revegetated (“control”) sites. We used guilds based on habitat associations. We also described changes in vegetation and explored their influence on bird species detections and guild dynamics. Riparian forest bird specialists responded positively to active revegetation, but this positive response was delayed and weaker in a river reach where restoration began later and featured less typical riparian vegetation. Birds associated with wetland habitat showed a positive response to restoration in the wettest reach, which had a baseline of high abundance of wetland birds in control sites and relatively abundant macrophyte cover. Conversely, the abundance of desert scrub bird specialists was highest in the driest and least vegetated restored reach. Generalists only exhibited decreased detections in the wettest restored reach. All this occurred while declines of riparian forest, wetland, desert scrub, and generalist bird species observed over a decade prior to restoration had stabilized in control sites. Detections of birds associated with agricultural fields increased in the study area, irrespective of restoration efforts. Our study demonstrates that the choice of bird guilds as ecological indicators can significantly influence the interpretation of restoration outcomes.

Arizona↗

USGS2024

Avian communities respond to plant and landscape composition in actively revegetated floodplains of the Colorado River delta in Mexico

We examined the influence of local habitat factors such as plant community composition and species cover, and landscape habitat factors (e.g., land cover types) on the composition of the avian community in an arid-region large river delta (Colorado River). This 106 river km-long study area has experienced restoration through environmental water deliveries and active management of vegetation for ca. 10 years after decades of degradation. Variation partitioning and spatial models (Moran Eigenvector Maps) showed that plant communities and land cover combined explained 29.3% of the variability of 115 bird species, with a high overlap of 13.1% as vegetation and landscape factors were partially confounded and spatially correlated. Redundancy analyses showed that a higher cover of native riparian trees and shrubs and a larger amount of land covered by forests, typical characteristics of revegetated sites, favored bird species with affinity for riparian forests. Marshland and open water landscape features and high cover of macrophytes (which were common in the wettest river reach among the five included in the study), irrespective of active revegetation, were associated with a higher prevalence of wetland birds. Dominance by the non-native shrub Tamarix spp. and, especially, barren areas were detrimental to most bird species. The proportion of agricultural lands around the study sites was related to high abundance of generalists and some non-native species. Overall, our study showed that both local (vegetation) and landscape (land use) factors are important considerations for restoration of riparian bird communities.

Ecological Engineering↗

USGS2024

Bird community response to one decade of riparian restoration along the Colorado River delta in Mexico

We assessed the response of breeding birds to one decade of riparian restoration in the Colorado River delta including active vegetation management since 2010 and various environmental water deliveries since 2014. Bird surveys were conducted from 2002 to 2021 at 230 bird count stations distributed along five river reaches with different hydrogeomorphic characteristics, across 7 routes in actively revegetated (“restored”) sites, and 20 routes in non-actively revegetated (“control”) sites. Both restored and control sites could be affected by environmental flows/water deliveries. We examined the temporal trajectories of four community-aggregated metrics for 53 breeding species, and the number of detections (counts) for the 30 most frequently detected among the 53 species at the restored and control sites, using generalized linear mixed-effects models. Diversity and richness of the 53 breeding species were highest in the wettest river reach, but higher than in control sites in only one restored site within one of the driest river reaches. The avian community was recovering in control sites, ameliorating a long-term declining trend, perhaps indicating indirect positive effects of active restoration. The response to restoration of the 30 most common species was species-specific. Ten of the 16 riparian forest specialist species had more detections in restored sites of the wettest reach (vs. only two in the driest reach). Species with preference for agricultural fields and generalists had the highest counts along the entire delta. Generalists generally decreased following revegetation, which was another positive restoration effect. Our results will be used to help guide future restoration efforts.

Ecological Engineering↗