Avian Responses to Post Oak Savanna Restoration in Eastern Texas

In response to the loss and degradation of oak savannas, associated wildlife populations have experienced long-term declines. For example, 70% of disturbance-dependent bird species in the United States have experienced declines with most of these species being associated with grasslands, oak savannas, and open forest communities. Few studies have documented the success of restoration in post oak savanna systems in regard to breeding bird assemblages. Our objective was to quantify avian abundance, density, species richness, and assemblage structure in restored post oak savannas at Gus Engeling Wildlife Management Area (GEWMA) in Eastern Texas. We conducted vegetation and avian transect surveys post-restoration (2016-2017) and compared our results to pre-restoration baseline surveys conducted in 2009. Restoration conducted in 2010 was partially successful, with vegetation changes that closely resemble historical characteristics. The avian assemblage also showed indications of successful restoration, with the appearance of obligate grassland species following restoration efforts. Specifically, pre-restoration, one dickcissel ( Spiza americana ) and no lark sparrows ( Chondestes grammacus ) were detected. By 2017, dickcissel density in the restored sites was similar to densities recorded on tallgrass prairie and other high-quality habitat in the southern portion of its range. Lark sparrows were also detected, but at low densities. We also observed the persistence and/or increase of several woodland and open woodland species over time. These patterns are likely attributed to the creation of a mosaic of suitable microhabitats preferred by these species such as the persistence of mottes as well as their increased edge-to-area ratios. Restoration sites that are larger in size and in closer proximity to other restored or remnant savannas should have a higher priority to increase their likelihood of recolonization by target species. Restoration efforts may still be successful in more isolated areas, such as GEWMA, but post-restoration monitoring should be conducted and reported to provide insights regarding site-specific restoration dynamics.

Thinning alters avian occupancy in piñon–juniper woodlands

ABSTRACT Natural resource managers are increasingly applying tree reduction treatments to piñon–juniper woodlands to meet a range of ecological, social, and economic goals. However, treatment effects on woodland-obligate bird species are not well understood. We measured multiscale avian occupancy on 29 paired (control/treatment) sites in piñon–juniper woodlands in central Colorado, USA. We conducted point counts at 232 stations, 3 times each season in 2014 and 2015. We used hierarchical multiscale modeling to obtain unbiased estimates of landscape and local occupancy (i.e. probability of use) in treated and untreated sites for 31 species. Treatments reduced the occupancy of conifer obligates, including Mountain Chickadee (Poecile gambeli), Clark’s Nutcracker (Nucifraga columbiana), and White-breasted Nuthatch (Sitta carolinensis), and increased occupancy of Lark Sparrow (Chondestes grammacus) and Mountain Bluebird (Sialia currucoides). Occupancy of Virginia’s Warbler (Oreothylpis virginiae) and Gray Flycatcher (Empidonax wrightii), two piñon–juniper specialists, decreased at the landscape scale in treated sites, and Pinyon Jay (Gymnorhinus cyanocephalus) occupancy decreased at the local scale. Tree reduction treatments in piñon–juniper woodlands have the potential to reduce habitat quality for a suite of bird species of conservation concern. We suggest that treatments designed to retain higher tree density and basal area will benefit conifer-obligate and piñon–juniper specialist bird species.