Karl L. Kosciuch

COWBIRD REMOVALS UNEXPECTEDLY INCREASE PRODUCTIVITY OF A BROOD PARASITE AND THE SONGBIRD HOST

Generalist brood parasites reduce productivity and population growth of avian hosts and have been implicated in population declines of several songbirds of conservation concern. To estimate the demographic effects of brood parasitism on Bells Vireos (Vireo bellii), we removed Brown-headed Cowbirds (Molothrus ater) in a replicated switchback experimental design. Cowbird removals decreased parasitism frequency from 77% and 85% at unmanipulated plots to 58% and 47% at removal plots in 2004 and 2005, respectively. Vireo productivity per pair was higher at cowbird removal plots when years were pooled (mean = 2.6 +/- 0.2 [SE] young per pair) compared to unmanipulated plots (1.2 +/- 0.1). Nest desertion frequency was lower at cowbird removal plots (35% of parasitized nests) compared to unmanipulated plots (69%) because removal of host eggs was the proximate cue for nest desertion, and vireos experienced lower rates of egg loss at cowbird removal plots. Nest success was higher among unparasitized than parasitized nests, and parasitized nests at cowbird removal plots had a higher probability of success than parasitized nests at unmanipulated plots. Unexpectedly, cowbird productivity from vireo pairs was higher at cowbird removal plots (mean = 0.3 +/- 0.06 young per pair) than at unmanipulated plots (0.1 +/- 0.03) because fewer parasitized nests were deserted and the probability of nest success was higher. Our study provides the first evidence that increases in cowbird productivity may be an unintended consequence of cowbird control programs, especially during the initial years of trapping when parasitism may only be moderately reduced. Thus, understanding the demographic impacts of cowbird removals requires an informed understanding of the behavioral ecology of host-parasite interactions.

Community-Level Patterns of Host Use by the Brown-Headed Cowbird (Molothrus ater), a Generalist Brood Parasite

ABSTRACT. Quantifying community-level host use by generalist brood parasites is important because it provides a measure of the resources that parasites need for reproduction. During the 2002–2007 breeding seasons, we quantified host use by the Brown-headed Cowbird (Molothrus ater) at Konza Prairie Biological Station in northeast Kansas. Overall, 54.4% of nests (n = 2,621) of 22 passerine host species that typically accept parasitic eggs were parasitized, and parasitized nests contained an average of 1.9 ± 1.03 (SD) Brown-headed Cowbird eggs, nestlings, or both. Multiple parasitism was common on the study site in all years: 55.7% of parasitized nests (n = 1,425) received ≥2 Brown-headed Cowbird eggs. The Bells Vireo (Vireo bellii; 70.5%) and the Dickcissel (Spiza americana; 69.6%) were parasitized at a significantly greater rate than the Red-winged Blackbird (Agelaius phoeniceus, 21.9%); collectively, these three species represented 85.8% of potential host nests found in all years. The host preference of Brown-headed Cowbirds did not appear to shift among the three species and instead they exhibited a consistent preference for Dickcissel nests over the course of the breeding season and among years. Both the rate and the intensity of parasitism on Dickcissels were significantly lower during the present study than in one conducted several decades earlier at the same site. Our results indicate that cowbirds in northeast Kansas differentially parasitize hosts, that most cowbird eggs are laid in the nests of a small number of host species, and that the Dickcissel appears to be preferred over other hosts.

Effects of Experimental Cowbird Removals on Brood Parasitism and Nest Predation in a Grassland Songbird

Abstract Brood parasitism and predation are two factors that limit seasonal fecundity in grassland songbirds. We removed Brown-headed Cowbirds (Molothrus ater) in a switchback experiment to examine the effects of brood parasitism and nest predation on the productivity of Dickcissels (Spiza americana). Nesting Dickcissels were monitored at four study plots in northeast Kansas in a two-year study. Brown-headed Cowbirds were captured with drop-in traps at two removal plots, two unmanipulated plots were reference plots, and treatments were reversed between years. To evaluate the effect of Brown-headed Cowbird removals, we compared the percentage of nests parasitized, rates of multiple parasitism, clutch size, daily nest survival rates, and overall productivity per nest between removal and reference plots. Removals of Brown-headed Cowbirds successfully reduced the probability of parasitism and rates of multiple parasitism, but only in one of two years. Brown-headed Cowbirds did not appear to contribute to nest losses, given that few nests were abandoned because of cowbird activity and that the probabilities of nest parasitism and nest survival declined simultaneously over the breeding season. Overall, nest productivity showed no difference between treatments in either year, despite reduced rates of parasitism at removal plots in 2004. High rates of nest predation minimized the potential benefits of Brown-headed Cowbird removals for increasing productivity of Dickcissels. Our results demonstrate that removals can reduce parasitism levels but that the success of removal programs may vary annually, particularly in regions where Brown-headed Cowbirds and nest predators are abundant. Management actions that minimize parasitism and predation by modifying habitat structure may provide better alternatives to programs based on removals.

EVOLUTION OF COLONIALITY VIA COMMODITY SELECTION: WHAT ABOUT VARIANCE?

How DOES COLONIALITY evolve? The answer to that question remains elusive despite decades of research (Ward and Zahavi 1973, Siegel-Causey and Kharitonov 1990, Hoogland 1995, Brown and Brown 1996, Danchin et al. 1998, Rolland et al. 1998). Scientists traditionally approached coloniality from an economic framework (Ward and Zahavi 1973, Witttenberger and Hunt 1985, Richner and Heeb 1995, Brown and Brown 1996). This research program weighed potential costs and benefits in an attempt to uncover the overriding advantages that produce coloniality. Recently, Danchin and Wagner (1997) suggested an abandonment of the economic approach and proposed commodity selection as a better conceptual framework for the study of coloniality. With commodity selection, benefits are irrelevant for colony formation and the subsequent evolution of coloniality. This framework shifted the focus from benefits of coloniality to mechanisms responsible for coloniality. Commodity selection, the synthesis of the hidden lek hypothesis and the performancebased conspecific attraction hypothesis, describes a behavior in which individuals select a commodity (e.g. habitat or mates) and, as a byproduct, aggregate at that location (Danchin and Wagner 1997, Wagner et al. 2000). For example, animals might prospect potential breeding habitats and choose to breed in favorable environments. Such a scenario could indirectly result in colonial breeding. Selecting suitable

Winter Resource Selection by Mule Deer on the Wyoming–Colorado Border Prior to Wind Energy Development

Abstract Areas identified as winter range are important seasonal habitats for mule deer (Odocoileus hemionus) because they can moderate overwinter mortality by providing thermal cover and forage. Therefore, identifying seasonally important resources is a conservation priority, especially when sensitive areas are proposed for development. We used data collected from global positioning system (GPS) collars fitted on female mule deer (n = 19; one location every 3 h) to identify resources important during winter (23 February 2011–30 April 2011; 1 November 2011–15 January 2012) in a region spanning southern Wyoming and northern Colorado that has been proposed for wind energy development. The study period included portions of two consecutive winters but were pooled for analysis. We used methods to account for GPS biases, fractal analyses to determine perceived spatial scale, and discrete choice models and conditional logistic regression to assess resource selection prior to development (i.e., baseline data). Resource selection by female mule deer revealed similar patterns between active (0600–1800 hours) and nonactive (2100–0300 hours) periods. Deer selected most strongly for proximity to rock outcrops and shrubland and average values of slope. Deer tended to avoid roads and grasslands; all other landscape features had minimal influence on resource selection (hazard ratios near, or overlapping, 1). Using the fixed-effects coefficient estimates, we developed two spatially explicit maps that depicted probability of mule deer occurrence across the landscape. Based on an independent validation sample, each map (active and nonactive) validated well with a greater percentage of locations occurring in the two highest probability of use bins. These maps offer guidance to managing mule deer populations, conserving important seasonal habitats, and mitigating development (e.g., wind energy) in areas identified as important to mule deer.

BREEDING RANGE EXPANSION BY CAVE SWALLOWS (PETROCHELIDON FULVA) IN TEXAS

Abstract The cave swallow (Petrochelidon fulva) was first discovered breeding in caves and sinkholes in Texas in 1915. Within the last 50 years, it has colonized new breeding sites in western and southern Texas, and colonization has been attributed to the presence of highway culverts and bridges. We examined published observations and breeding bird survey (BBS) data, and surveyed selected culverts in western and southeastern Texas to determine the rate and extent of colonization by cave swallows. From 1957 to 1999, the breeding range of the cave swallow increased by approximately 898%, with an average annual rate of increase of 6% per year. Based on BBS data, cave swallow populations are increasing 10.8% per year, and our survey indicated that cave swallows occupied >90% of the culverts surveyed in western Texas. Range expansion is likely to continue, and additional data are needed to determine how an expanding cave swallow population might affect local barn swallow populations.

Novel Nesting Behavior in Cave Swallows

Abstract The Cave Swallow (Petrochelidon fulva), first discovered breeding in Texas in 1915, originally was thought to be confined to sinkholes in central and western Texas. During our survey of bridges in Brazos County, Texas, we discovered Cave Swallows modify and use old Barn Swallow (Hirundo rustica) nests, a previously unreported behavior. The presence of Barn Swallows (or old Barn Swallow nests) may facilitate colonization of new areas by Cave Swallows.

Spatial ecology of female mule deer in an area proposed for wind energy development

ABSTRACT. Development for wind energy is increasing rapidly across the United States, particularly in Wyoming, despite a general lack of information on the potential interaction development could have on wildlife species. Therefore, knowledge of the space use and movement patterns of individuals can help define spatial distributions and management unit boundaries for populations prior to development. Such knowledge can also be used as baseline data from which to assess any future impacts on animal populations. We investigated the spatial ecology of female mule deer (Odocoileus hemionus; n = 18) equipped with global positioning system collars from 23 February 2011 to 15 January 2012 in an area along the Wyoming–Colorado border that has been proposed for wind energy development. The objectives of this study were to collect predevelopment baseline estimates of annual and seasonal home-range and core area size and fidelity, movement between seasonal ranges, changes in the use of elevation, and movement patterns at 2 temporal resolutions (i.e., within-season diel patterns and year-round diurnal and nocturnal movements by week). Annual size of home ranges averaged 2495 ha (SE = 121), whereas size of core areas averaged 310 ha (SE = 30). Seasonal site fidelity was substantial (81.1%, SE = 5.7) between successive cool-season ranges. Migration distances between cool- and warm-season home ranges were minimal (spring migration = 1319 m; autumn migration = 1342 m). Deer exhibited crepuscular movement patterns (peaks near 06:00 and 18:00) during the warm season but showed a diurnal movement pattern during the cool season (peak from 06:00 to 15:00). Partuition influenced movement during the warm season; movement was much reduced during a period from mid-June to mid-July Deer in this population appear to be year-round residents that exhibit strong seasonal and annual fidelity to previously established ranges and modify movement patterns in relation to general changes in environmental conditions (e.g., snow). These findings can be used to define seasonally important ranges and formulate boundaries and sizes of game management units. Understanding fine-scale temporal movement allows the development of strategies that could minimize disturbance to deer while allowing for development or recreation.

Annual Reproductive Success of Culvert-Dwelling Cliff Swallows in East-Central Texas

Abstract Most studies describing reproductive biology of an avian species provide some measure of annual reproductive success (ARS), frequently reported per nest or per egg. These measurements do not indicate the success of average females in the population. We report conventional measures of reproductive success along with ARS(b), number of broods successfully reared per female, and ARS(k), number of young successfully reared per female. We calculated ARS for four culvert-dwelling Cliff Swallow (Petrochelidon pyrrhonota) colonies in east-central Texas from 1982 to 1985 (n = 1805 nests) and compared our calculations of ARS with those reported for other regions. We analyzed differences in number of fledglings per female to estimate variation in ARS among years and among culverts. In east-central Texas, ARS differed significantly among years and among culverts. We attributed variation in ARS to predation and abiotic factors. Consistent reporting of ARS would facilitate comparisons among populations or species over multiple scales. Éxito Reproductivo Anual de Petrochelidon pyrrhonota que Forman Colonias en Puentes del Este-Central de Texas Resumen. La mayoría de los estudios que describen la biología reproductiva de especies de aves proveen alguna medida de éxito reproductivo anual (ERA), la cual, se reporta frecuentemente por nido o por huevo. Estas medidas no indican el éxito reproductivo de las hembras promedio de la población. Nosotros reportamos medidas convencionales de éxito reproductivo junto con el ERA(b), número de nidadas exitosamente criadas por hembra y ERA(k), número de juveniles exitosamente criados por hembra. Calculamos el ERA para cuatro colonias de Petrochelidon pyrrhonota que habitan puentes en el este-central de Texas desde 1982 hasta 1985 (n = 1805 nidos) y comparamos nuestros cálculos de ERA con aquellos reportados para otras regiones. Analizamos las diferencias en el número de pichones por hembra para estimar variaciones en el ERA entre años y entre puentes. En el este-central de Texas el ERA varió significativamente entre años y entre puentes. Atribuimos la variación en el ERA a depredación y factores abióticos. El informe consistente de valores de ERA facilitaría la comparación entre poblaciones y especies a través de múltiples escalas.