Clint W. Boal

The Predicted Influence of Climate Change on Lesser Prairie-Chicken Reproductive Parameters

The Southern High Plains is anticipated to experience significant changes in temperature and precipitation due to climate change. These changes may influence the lesser prairie-chicken (Tympanuchus pallidicinctus) in positive or negative ways. We assessed the potential changes in clutch size, incubation start date, and nest survival for lesser prairie-chickens for the years 2050 and 2080 based on modeled predictions of climate change and reproductive data for lesser prairie-chickens from 2001–2011 on the Southern High Plains of Texas and New Mexico. We developed 9 a priori models to assess the relationship between reproductive parameters and biologically relevant weather conditions. We selected weather variable(s) with the most model support and then obtained future predicted values from climatewizard.org. We conducted 1,000 simulations using each reproductive parameter’s linear equation obtained from regression calculations, and the future predicted value for each weather variable to predict future reproductive parameter values for lesser prairie-chickens. There was a high degree of model uncertainty for each reproductive value. Winter temperature had the greatest effect size for all three parameters, suggesting a negative relationship between above-average winter temperature and reproductive output. The above-average winter temperatures are correlated to La Niña events, which negatively affect lesser prairie-chickens through resulting drought conditions. By 2050 and 2080, nest survival was predicted to be below levels considered viable for population persistence; however, our assessment did not consider annual survival of adults, chick survival, or the positive benefit of habitat management and conservation, which may ultimately offset the potentially negative effect of drought on nest survival.

Identifying habitat sinks: a case study of Cooper’s hawks in an urban environment

We studied a population of Cooper’s hawks (Accipiter cooperii) in Tucson, Arizona from 1994 to 2005. High rates of mortality of nestlings from an urban-related disease prompted speculation that the area represented an ecological trap and habitat sink for Cooper’s hawks. In this paper, we used estimates of survival and productivity from 11years of monitoring to develop an estimate of the rate of population change, λ, for Cooper’s hawks in the area. We used a Cormack–Jolly–Seber approach to estimate survival of breeding hawks, and a stochastic, stage-based matrix to estimate λ. Despite the urban-related disease, the estimate of λ indicated that the area does not function as a habitat sink for Cooper’s hawks (

Influence of Natal Experience on Nest-Site Selection by Urban-Nesting Cooper's Hawks

widehatlambda

FORAGING AND NESTING HABITAT OF BREEDING MALE NORTHERN GOSHAWKS IN THE LAURENTIAN MIXED FOREST PROVINCE, MINNESOTA

= 1.11 ± 0.047; P = 0.0073 for the null of λ ≤ 1). Because data required to reliably identify habitat sinks are extensive and difficult to acquire, we suggest that the concept of habitat sinks be applied cautiously until substantiated with reliable empirical evidence.

NONRANDOM MATING AND PRODUCTIVITY OF ADULT AND SUBADULT COOPER'S HAWKS

Abstract We collected diet data at 12 Ferruginous Hawk (Buteo regalis) and 14 Swainsons Hawk (B. swainsoni) nests in a short-grass prairie and agricultural community in the panhandle area of northwest Texas and southwest Oklahoma, and in northeastern New Mexico during the 2003–2004 breeding seasons. We documented 959 Ferruginous Hawk and 1,058 Swainsons Hawk prey deliveries during ∼5,618 hrs of video monitoring. Ferruginous Hawks delivered 10.0 ± 0.7 (x̄ ± SE) prey species per nest and typically larger prey. Swainsons Hawks delivered 13.4 ± 1.1 prey species per nest and typically smaller prey. There was a dietary overlap (Simplified Morisita Index [CH]) of 0.31 in prey species delivery frequency and 0.56 in prey species biomass. Ferruginous Hawks made 4.6 deliveries/day at 480 g/delivery whereas Swainsons Hawks delivered smaller prey items (147 g/delivery) but more frequently (7.0 deliveries/day). Deliveries/day and mass/day increased with increasing brood sizes of both species, but deliveries/day/nestling and mass/day/nestling decreased. Provisioning rates did not vary significantly over the nestling period. These data represent the most accurate diet quantification to date for Ferruginous and Swainsons hawks. Ferruginous Hawks used a larger array of prey types than shown in other studies based on indirect diet analysis methods. The low interspecific diet overlap suggests that prey is partitioned, which may facilitate the well-documented sympatric distribution of the two species.

Effects of Human Land Use on Western Burrowing Owl Foraging and Activity Budgets

Abstract Exposure to environmental features early in life potentially can influence the kinds of places animals select to live later in life. We examined whether there is evidence that Coopers hawks (Accipiter cooperii) hatched in an urban environment choose sites with features similar to their natal areas when they nest for the first time. The features we examined were the nest tree species and the level of development surrounding the nest tree. We banded nestling and fledgling Coopers hawks in Tucson, Arizona, USA, from 1994 to 2004. We then monitored nests in Tucson to identify hawks that had been hatched in the city and eventually secured a breeding site. Percent cover of buildings around first breeding nests was not related to percent cover of buildings around natal nests for either sex. There was some evidence that being hatched in a particular tree species influenced choice of tree species at first breeding sites for males, but the influence was weak. In contrast, tree species in which first-time breeders built their nests, and the sites where the trees were located relative to development, were proportional to what was available in the Tucson metropolitan area. Our data suggest that natal experience played a limited role in nest-site selection by Coopers hawks in Tucson for the features we examined. If learning occurred, it could have been for the general structure of natal sites. Thus, any small grove of large trees planted in Tucson could be used as a nest site by Coopers hawks regardless of the level of development surrounding the nest.

Grassland bird associations with introduced and native grass Conservation Reserve Program fields in the Southern High Plains

Traditional subspecies classifications may suggest phylogenetic relationships that are discordant with evolutionary history and mislead evolutionary inference. To more accurately describe evolutionary relationships and inform conservation efforts, we investigated the genetic relationships and demographic histories of Buteo lineatus subspecies in eastern and western North America using 21 nuclear microsatellite loci and 375-base pairs of mitochondrial control region sequence. Frequency based analyses of mitochondrial sequence data support significant population distinction between eastern (B. l. lineatus/alleni/texanus) and western (B. l.elegans) subspecies of B. lineatus. This distinction was further supported by frequency and Bayesian analyses of the microsatellite data. We found evidence of differing demographic histories between regions; among eastern sites, mitochondrial data suggested that rapid population expansion occurred following the end of the last glacial maximum, with B. l. texanus population expansion preceding that of B. l. lineatus/alleni. No evidence of post-glacial population expansion was detected among western samples (B. l.elegans). Rather, microsatellite data suggest that the western population has experienced a recent bottleneck, presumably associated with extensive anthropogenic habitat loss during the 19th and 20th centuries. Our data indicate that eastern and western populations of B. lineatus are genetically distinct lineages, have experienced very different demographic histories, and suggest management as separate conservation units may be warranted.

Effects of Radiotransmitter Necklaces on Behaviors of Adult Male Western Burrowing Owls

Abstract We used radiotelemetry to examine foraging habitat preferences of 17 breeding, male northern goshawks (Accipiter gentilis) in Minnesota from 1998–2000. We assessed habitat preference using radio relocation points and 50-m radius buffers of radio relocation points. Our data suggested that foraging male goshawks used early-successional upland conifer stands (≥25 yrs old), early-successional upland deciduous stands (≥50 yrs old), late-successional upland conifer stands (≥50 yrs old), and late-successional upland deciduous stands (≥50 yrs old) more frequently than expected based on the abundance of these vegetation types in the landscape. The 2 most available stand types, early-successional upland deciduous (<25 yrs old) and all ages of late-successional lowland conifer stands, were used less than expected by foraging goshawks. Late-successional lowland deciduous stands (≥50 yrs old) were used in proportion to availability. Although analysis of relocation points suggested early-successional upland deciduous stands (25–49 yrs old) and late-successional upland conifer stands (≥50 yrs old) were used in proportion to availability, analysis of buffers around relocation points indicated that these stand types were also used more than expected by foraging goshawks. Regardless of vegetation community type, stands used by goshawks were structurally similar with high canopy and understory stem densities, high canopy closure, substantial shrub cover, and large amounts of woody debris. Nest stands consisted of taller and larger diameter canopy trees and fewer understory trees than foraging stands, but stands were otherwise similar in structural features, suggesting goshawks used similar stands for nesting and foraging but that they tended to select the most mature stands for nesting. A commonality among nesting and foraging stands was the presence of open spaces between the canopy and understory foliage, and between understory and shrub layer foliage. In our study area, these spaces may have served as relatively unobstructed flight paths where foraging and nesting stands possessed stem densities at the upper end of that reported for goshawk habitat.